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Abstract Climate change poses a key threat to marine ecosystems and fisheries resources as well as to communities that depend on these systems for food and livelihoods. This paper reports on a community-based rapid vulnerability assessment (RVA) methodology developed and applied in eight small-scale fishing communities in the Benguela Current Large Marine Ecosystem region. This participatory methodology was designed to be applied in a workshop setting and draws on the observations, perceptions and local knowledge of fishers in order to better understand the extent to which their livelihoods are susceptible to various socio-ecological changes and their ability to respond to these changes. The paper highlights selected key findings and aims to demonstrate the type of information that can be elicited from an RVA. Although there were differences between the three countries involved in the study, findings suggest that key stressors are mainly associated with socio-economic and governance issues. Climate-related changes were seen to exacerbate existing vulnerabilities. Despite differences in spatial and temporal scales of data provided by scientists and fishers, changes in environmental conditions that could be attributed to climate change observed by fishers resonated with available science. Fishers identified a number of adaptation strategies that could address vulnerabilities and enhance resilience but require support from government and other stakeholders. Strengthening local organizations, rebuilding fisheries through local co-management plans, securing access rights, involving fishers in data collection and analysis, developing complementary livelihoods and addressing the broad socio-economic rights of communities were identified as necessary to address vulnerabilities. Participation in these community-level vulnerability assessments enhances understanding, builds capacity, generates knowledge for management, and allows communities to identify locally appropriate adaptation strategies. Highlights • A rapid vulnerability assessment (RVA) methodology was developed to assess climate change vulnerability in coastal communities in the BCLME region • Key stressors in coastal communities are mainly associated with socio-economic and governance changes and events. • Climate-related changes were seen to exacerbate vulnerability. • Despite scale differences climate-related changes experienced or perceived by fishers resonate with available science. • The RVA facilitates the identification of locally appropriate adaptation strategies to address vulnerabilities and enhance resilience. [ABSTRACT FROM AUTHOR]

Abstract Understanding and validating annual structures in fish otoliths are important for stock assessments and fisheries ecology. Biannual translucent zone formation has been demonstrated for 3–21 months old Namibian shallow-water hake Merluccius capensis. This paper addresses the hypothesis that the pattern continues in older fish. Otolith zone periodicity was studied for four cohorts hatched in July of 1996, 1998, 2002 and 2005, based on modal progression analysis (n = 1059). Edge analysis and marginal increment analysis were performed on otoliths representing eleven months of the year from port samples (n = 1153) from the years 2007–2015. Two to three translucent (T)-zones are formed on the hake otoliths each year, one or two between austral summer and autumn (January to April) and one in winter–spring (between July and October). Annual zones are usually the T2, T5, T8 zones (likely every third T-zone). Annual zones are not distinguishable from pseudo-annuli under the light microscope, and therefore otolith length measurements (OL) at each T-zone should be used as a guide for assigning age (9, 15 and 19 mm OL for ages 1, 2 and 3 respectively). Otolith T-zones are associated with both warm and cold periods, when they are presumably limited by temperature or dissolved oxygen concentration as well as food availability and feeding efficiency at both ends of their tolerance range. The most noticeable factor influencing the formation of translucent zones in otoliths is fish condition, not always linked with spawning (not always linked with high GSI). M. capensis otolith zonation is thus linked with their endogenous adaptation to the ecosystem, their fish physiology and also regulated by environmental variability. Highlights • At least two translucent (T) zones are formed on M. capensis otoliths per year, one in winter and one to two in summer • Age determination criteria should be updated for hake in the Benguela using measurements presented in this paper • Winter T-zones appear in August at coldest temperatures and highest dissolved oxygen (DO) concentrations • Summer T-zones occur December to April at warm temperatures and low DO concentrations and may occur more frequently • Translucent zone formation presence is associated with low fish condition [ABSTRACT FROM AUTHOR]

Rising Arctic temperatures are causing substantial declines in sea ice, altering ice retreat and formation in the Pacific Arctic and impacting marine communities. Despite the significant challenges facing the Pacific Arctic, there are still gaps in our understanding of the environmental impacts on pelagic communities, particularly sound scattering layers (SSLs), and their distributions in the southern Chukchi Sea (SCS), northern Chukchi Sea (NCS), and East Siberian Sea (ESS). This study utilized a wideband autonomous transceiver, net samplers, and optical instruments to explore SSLs in the Pacific Arctic, detailing their relationships with hydrographic properties. The findings indicated a greater vertical distribution of pelagic communities in the SCS than in the NCS and ESS. Significant differences in frequency spectra patterns were observed between the SCS and both the NCS and the ESS, though not between the NCS and the ESS. The correlations between the broadband acoustic and hydrographic values were generally weak to moderate. Elevated acoustic values in the SCS were linked to higher water temperature, dissolved oxygen, and chlorophyll and lower salinity. This study also revealed the behavioral properties of individual pelagic animals and identified Ctenophores and Copepods as the most abundant classes based on camera images and net samples. This research offers crucial insights into the distribution and interactions of pelagic communities with environmental factors, laying the groundwork for understanding climate change impacts. Additionally, this paper presents the first findings of frequency spectra from a broadband system in the Arctic Ocean. • Rapid decline of Arctic Sea ice causes a growing interest in fisheries resources. • The regional difference of SSL, the indicator of fisheries resources, was observed. • The frequency spectra of SSLs were significantly different across the Pacific Arctic. • Acoustic values of SSLs were closely related with essential environmental factors. • The results offer crucial insights into the pelagic communities in the Arctic Ocean. [ABSTRACT FROM AUTHOR]

The object of research - the Vistula Lagoon is one of the two lagoons on the Polish coast, which is of great importance not only from an economic point of view, but also an environmental one. The purpose of the paper is to provide calculations on the current water balance for the Vistula Lagoon, before and after construction of a canal through the Vistula Spit. This is important because the construction of a new connection between the Vistula Lagoon and the Baltic Sea can result in changes in the lagoon's water balance, which in turn cause changes in the Vistula Lagoon biotic and abiotic environment. In addition, we wish to update the estimate of the water exchange between the Vistula Lagoon and the Baltic Sea through the Strait of Baltiysk and to estimate the exchange through the Vistula Spit canal after it is fully open. The main works consisted of researching source materials from various state institutions, which allowed to calculate the water balance of the Vistula Lagoon and perform mathematical modeling. These data include the amount of precipitation and evaporation, the amount of inflow from the catchment, the amount of inflow from polders, underground supply, the amount of inflow and outflow through the Strait of Baltiysk. The largest portion of the water received by a coastal lagoon comes from the adjacent ocean. In this case, it is about 75%. In addition, an array of catchment sources yields 20% of the studied lagoon's water. The Strait of Baltiysk constitutes the main outflow pathway for water exiting the Vistula Lagoon – close to 98% of outflow. Simulations have shown that the construction of the Nowy Swiat ship canal will not alter the water balance in the Vistula Lagoon to a meaningful extent. The problems that may emerge include those related to changes in the local biotic and abiotic environment due at the construction stage or in the period that follows resulting from the disturbance of highly polluted lagoon floor deposits. Thus it may be argued that the new canal is desirable from an economic or flood control point of view, but not from an environmental point of view. • The exchange through the Strait of Baltiysk contributes 75% of the Vistula Lagoon water balance. • Construction of a canal will not significantly change the Lagoon's water balance. • A quantitative monitoring system for the entire Vistula Lagoon in needed. • Such monitoring system should be jointly implemented by Russia and Poland. [ABSTRACT FROM AUTHOR]

Using satellite maps this paper offers a complex analysis of chlorophyll & SST heterogeneity in the shelf seas around the southwest of the UK. The heterogeneity scaling follows a simple power law and is consequently parametrized by two parameters. It is shown that in most cases these two parameters vary only relatively little with time. The paper offers a detailed comparison of field heterogeneity between different regions. How much heterogeneity is in each region preserved in the annual median data is also determined. The paper explicitly demonstrates how one can use these results to calculate representative measurement area for in situ networks. [ABSTRACT FROM AUTHOR]

Abstract We provide an efficient tool for the processing of a large volume of data (big data) from a marine ecosystem and predicting its status, including its complex and nonlinear biological structure (biocomplexity) and its ability to remain alive or continue to exist (survivability). The Geoecological Information-Modeling System developed earlier by the authors of this paper is used for the first time as a basis for the development of the Sea Ecosystem Model that parameterizes the energy exchange between major trophic components of the sea with spatial resolution 1/6° × 1/6° taking into account natural and anthropogenic factors. In particular, the dependence of energy exchange processes on environmental factors is modeled with a minimum level of uncertainty. The biological components are modeled using traditional trophic balance equations, whose coefficients are determined from observational data. The simulation results for the Okhotsk Sea show the critical ecosystem states that prevail when the biocomplexity and survivability of this ecosystem reach dangerous levels. The prediction of the ecosystem status is carried out to 2100 with an accuracy of better than 79.9%. For this purpose, the complex model proposed recently by the same authors, entitled "nature-society system model", was used. Among the main results that have emerged is that the biocomplexity and survivability characteristics of this marine ecosystem will be stable over the next 100 years, regardless of the expected climate change. Highlights • A new tool for predicting the status of a marine system is proposed. • The critical system states are derived via its biocomplexity and survivability. • The Okhotsk Sea ecosystem will be stable over the next 100 years. [ABSTRACT FROM AUTHOR]

Abstract The dynamics of nutrients, phytoplankton, zooplankton and water clarity of the iconic Great Barrier Reef World Heritage Area (GBRWHA) are influenced by seasonal variation in coastal and oceanic conditions, and anthropogenic inputs. We use the 3-dimensional coupled catchment-hydrodynamic-sediment-wave-optical-biogeochemical eReefs model to hindcast nutrient and planktonic responses to changes in seasonal and annual variability over a six-year period (2011–2016). In this paper we present a comparison of the eReefs model conducted against a range of in situ observations that included 24 water quality moorings, 2 nutrient sampling programs (with a total of 18 stations) and time-series of taxon-specific plankton abundance. At 14 near-coastal stations the simulated chlorophyll a (Chl a), when compared with chlorophyll extractions from water samples, had an average root mean square (RMS) error of 0.30 mg m−3 and a Willmott index of 0.59. For the same sites, simulated turbidity, when compared with turbidity sensors, had a Willmott index of 0.58 and simulated nitrate + nitrite had a Willmott index of 0.41 when compared with tri-annual water samples. Comparison with a spatially-resolved statistical model of zooplankton based on >900 observations in the region showed similarities in the relationship and spatial distribution of simulated and observed biomass, where both show zooplankton biomass is greatest inshore, biomass is highest around shallow reef areas and in the southern and central GBRWHA, and greater in summer than winter. Additionally, we investigate planktonic and nutrient responses to climatic variation. The first two years of the simulation coincided with La Niña events that drive greater than average winds, rainfall and river discharge. Throughout all years, simulated Chl a increases from north to south and from outer to inner coastal regions. Dissolved inorganic nitrogen, primary production and phytoplankton biomass were higher during La Niña in inshore and mid-shelf waters, while offshore regions were similar in all years from 2011 to 2016. Simulated Secchi depth was deeper offshore and decreased from offshore to inner coastal regions and from north to south. The eReefs simulation contributes to the understanding at a high spatial and temporal resolution of where and how nutrients and plankton originate and interact within the Great Barrier Reef. Highlights • Use of a 3D-catchment-hydrodynamic-sediment-wave-optical-biogeochemical model • Model encompasses the 2300 km long Great Barrier Reef from coast to Coral Sea. • Comparison of observations with simulated plankton & nutrients • Observations include remote sensing, moorings and water samples. • Simulated nutrients and plankton show realistic seasonal and interannual variation. [ABSTRACT FROM AUTHOR]

Abstract This paper examines variations in gender-specific body growth, morphology and reproduction of the bearded goby (Sufflogobius bibarbatus) across the Namibian shelf, built on previous work on male reproductive modes. The results indicate a spatial variation in the size composition, condition factor and maturation of gobies across the shelf area. Low oxygen (<0.5 ml O 2 L−1) did not hinder reproduction in the bearded goby and off Walvis Bay, maturing and mature females and males were found mostly at the outer shelf edge (150–200 m depth). The histological analysis of gonads validates the macroscopic scale applied for assessing maturity, and the mean number of maturing oocytes was from 690 to 1060 g−1 body weight. Males were smallest in the central area (where oxygen levels are known to be lowest), and relative condition increased latitudinally from north to south. The bearded goby displays clear sexual size dimorphism (males larger than females), and there is evidence that supports previous findings suggesting that males display alternative reproductive tactics. Assumed territorial males were older than assumed sneaker males, and all morphological measurements, except eye diameter, were larger (absolutely and relatively) in territorial males compared to sneakers. The morphologic measurements of sneakers did not differ from those of females suggesting female mimicry by sneakers. The role of unclassified males was less clear. The findings are discussed in view of environmental variation and behavioural ecology. Highlights • Oxygen is a major limiting environmental factor in the sea. • Severe hypoxia occur in the Benguela upwelling ecosystem. • The Goboiid Sufflogobius bibarbatus is a fish found adapted to these environments. • It displays sexual size dimorphism, and alternative reproductive tactics in males. • Low oxygen reduce growth, but do not hinder reproduction. [ABSTRACT FROM AUTHOR]

Abstract Ten of the 15 seabird species that breed in the Benguela upwelling ecosystem, including six species that are endemic to it, are now classified as threatened or near-threatened in terms of Red List criteria. Both bottom-up (operating from lower in the food chain) and top-down (operating from higher in the food chain, or outside it) processes have influenced the seabirds. Historical harvests of eggs and guano caused a large decrease in numbers of African penguins Spheniscus demersus and altered their breeding habitat. More recently, food scarcity reduced the populations of several species that compete with fisheries for prey and was largely responsible for the recent collapse of penguins in South Africa. Predation, oiling and disturbance also have adversely affected seabirds and their relative impact may increase as species populations and sizes of colonies decrease. Co-ordinated management of the different factors diminishing populations will be necessary if the conservation status of seabirds in the Benguela ecosystem is to be improved. Highlights • Fifteen species of seabird breed in the Benguela ecosystem off southwestern Africa, of which seven are endemic to it and two more are endemic as races. Six of the endemic species have an unfavourable Red List classification. • The paper reviews bottom-up and top-down control of the Benguela's seabirds and shows that while top-down factors (including exploitation of seabirds and their products) were responsible for earlier large decreases of some species, recently food scarcity (bottom-up control) has caused big decreases of some species that compete with fisheries for prey. • Species breeding on the mainland are susceptible to human disturbance (top-down control). • For seabirds whose populations and colony sizes are decreasing the relative importance of top-down factors is likely to increase, so that coordinated management of all the threats to these species will be required to improve their conservation status. [ABSTRACT FROM AUTHOR]

Abstract The change in species dominance between anchovy and sardine that took place during the 1980s in the southern Benguela has been investigated previously using an Ecopath with Ecosim (EwE) model. The results from that model indicated that fishing pressure was unlikely to have been the driver of change. Instead, the findings indicated that changes within low trophic level groups such as the zooplankton affected prey availability for anchovy and sardine, leading to the shift in dominance. This paper applies the donor-driven Ecotran model to these same data for the southern Benguela ecosystem in the 1980s. The consumption matrix from the Ecopath model was converted to a production matrix, apportioning the production of prey groups in a constant proportion to their predators, rather than assuming the consumption of predator groups is taken in fixed proportions from their prey. This configuration allows donor-control of model ecosystem dynamics, appropriate when low trophic level groups affect the outcomes. The trophic structure for the Ecotran model was further amended to exclude “cannibalism”, and dissolved nutrient groups were added to allow for recycling. To test whether the donor-driven modelling affected model results, the same set of scenarios was applied using Ecotran models as were tested using the EwE model in previous research. Qualitative methods were used to compare the results of the two model techniques, as Ecotran scenarios represented static, steady-state solutions for the ecosystem state, whereas EwE scenarios represented dynamic solutions for the ecosystem state. These results indicate that for the majority of groups and scenarios the Ecotran model predicts the same direction of change as the EwE model when the 1980s ecosystem is used as a starting point. However there is more uncertainty in the direction of change predicted by the Ecotran model when it is applied to the 1990s state in an attempt to recreate the 1980s state, and thus more disagreements between the models. The results of the Ecotran model supported the conclusion from prior EwE analysis that the driver of change in anchovy and sardine dominance was likely changes in prey availability. The underlying cause of this shift in prey availability remains a question for further research. Highlights • Ecotran can be readily applied to ecosystems previously expressed as EwE models. • Anchovy-sardine abundance shifts are likely driven by prey availability. • Prey shift at meso- and microzooplankton levels are most likely the driver. [ABSTRACT FROM AUTHOR]

Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds. [ABSTRACT FROM AUTHOR]

This paper addresses the evolution of a mixed beach (Playa Granada, southern Spain) forced by an artificial nourishment project through the analysis of field observations and the modeling of hydro- and morphodynamics. The beach profile and coastline were periodically surveyed over a six-month period; a wave propagation model was calibrated by means of hydrodynamic measurements; four longshore sediment transport (LST) equations were tested through comparisons with bathymetric data; and the one-line model was applied between topographic surveys. The results indicate that severe coastline retreat (dry beach area loss > 208 m 2 /day) occurred during the 45 days following the intervention. This is mainly attributable to the morphology of the nourished coastline, the different characteristics of the sediment used for replenishment compared to natural sizes, and the occurrence of an intense westerly storm. The dry beach extension increased afterwards influenced by the westward LST due to the dominance of easterly waves. The Van Rijn formulation was found to provide the best fits to the observed volumetric changes, obtaining modeled/measured ratios of 93.1% and 77.4% for the two study beach profiles. The outputs of the one-line model based on the Van Rijn approach were also the best, with root-mean-square errors decreasing during the study period and lower than 4.6 m over the last 3 months. These results show that the joint application of a calibrated wave propagation model, the LST equation proposed by Van Rijn and the one-line model constitutes a management tool for predicting the evolution of these complex coastal settings. [ABSTRACT FROM AUTHOR]

Coastal upwelling and mud banks are two oceanographic processes concurrently operating along certain stretches of the southwest (Kerala) coast of India during the Southwest Monsoon period (June–September), facilitating significant enhancement in plankton biomass. Mud banks have scientific and societal attention from time immemorial, predominantly due to the large fisheries associated with them. In this paper, for the first time, the specific biophysical roles of these oceanographic processes have been discriminated, based on a focused 18 weekly/fortnightly time-series study (April to September 2014) in a mud bank-upwelling area (off Alappuzha, southwest coast of India). In conjunction with standard hydrographical and satellite remote sensing data, we utilised a FlowCAM to track the biophysical linkage in terms of plankton composition abundance and size structure at three locations (M1, M2 and M3) in the study area. During the Pre-Southwest Monsoon (April–May), the entire study area was warmer with low nitrate concentration in the surface waters, which caused lower biomass of autotrophs compared to the Southwest Monsoon (June–September). By the onset of the Southwest Monsoon (June), drastic hydrographical transformations took place in the study domain due to the Coastal upwelling, reflected as the surfacing of significantly cool, high nutrient and hypoxic waters. Concurrently, mud bank formed at location M2 due to the presence of relatively high-suspended sediments in the region, creating a localised calm environment conducive for fishing activities. In response to the hydrographical transformations in the entire study area during the Southwest Monsoon, the autotrophic plankton biomass and size structure experienced significant change. The micro-autotrophs biomass that was low during the Pre-Southwest Monsoon (av. 0.33 ± 0.2 mgC L − 1 at surface and av. 0.07 ± 0.04 mgC L − 1 at subsurface) noticeably increased during the Southwest Monsoon (av. 1.6 ± 0.4 mgC L − 1 at surface and av. 1.3 ± 0.2 mgC L − 1 at subsurface). The seasonal mean bio-volume of micro-autotrophs followed the same pattern in all three locations with the dominance of smaller individuals during the Pre-Southwest Monsoon (av. 55 ± 4.4 × 10 3 μm 3 individual − 1 at surface and av. 67.1 ± 38.4 × 10 3 μm 3 individual − 1 at subsurface). Relatively large phytoplankton dominated during the Southwest Monsoon (av. 77.3 ± 5.5 × 10 3 μm 3 individual − 1 at surface and av. 90.3 ± 4.9 × 10 3 μm 3 individual − 1 at subsurface). Similar spatial change in the plankton composition, biomass and size structure in all three locations suggested the dominant role of coastal upwelling, and not the mud bank, in shaping the dominant autotrophic plankton in the study domain. The nutrient enrichment in the region associated with the coastal upwelling facilitated the predominance of a classical short food chain capable of supporting large fish stocks. In addition to relatively calm mud bank, the hypoxic, cool upwelled waters that existed in the subsurface induce the fish stock to concentrate in the surface waters, making the relatively calm mud bank and adjoining areas a rich fishing ground for the native fishers. [ABSTRACT FROM AUTHOR]

Eutrophication and chemical pollution are typical threats to the ecosystem of the Gulf of Finland. This paper aims to make a comprehensive assessment of the environmental status of coastal habitats in the easternmost Gulf of Finland (Neva River estuary) by using different physical, chemical and biotic variables to find cost-effective indicators for further monitoring. During summers of 2014 and 2015 we measured water salinity, phosphorus (eutrophication marker), biomass of harmful filamentous macroalgae (coastline hypoxia inductor), sediment hazardous substances (trace metals, polycyclic aromatic hydrocarbons) and other concomitant characters at 12 sites in the gulf. Also, we analyzed responses of the phytoplankton and benthic organisms, including metal-tolerant and hydrocarbon-oxidizing bacteria, meio- and macrofauna, to these factors. We compared the indicative sensitivity and efficiency of several well-known biotic indices and methods, including a Saprobity system (basing on phytoplankton), Raffaelli and Mason index (meiobenthos), and two macrobenthic derived indices (Goodnight-Whitley Index and Benthic Quality Index). Also, we applied a new index – the embryo malformation frequency in benthic amphipods. To estimate the level of bottom hypoxia induced by the macroalgae blooms, we measured the algal cover and thickness of the algal mats. To verify our assessment, we tested correlations between all used variables. Biotic communities of these areas are subjected to high phosphorus and macroalgae blooms, toxic pollution, water salinity and other factors. We concluded that environmental state of coastal habitats at several southern sites (in Koporskaya Bay and near the developing port Bronka) and near port Primorsk in the north was bad, while the state of the rest of sites was moderate or good. The integrated approach for the assessment may be recommended for monitoring programs as an important tool for studying human-mediated and other effects on brackishwater coastal environments. [ABSTRACT FROM AUTHOR]

This paper analyses the relationships between the light absorption coefficients at 440 nm a p (440) for particles suspended in the surface waters of the southern Baltic Sea and the concentrations of some optically significant constituents in these waters. The analysis covers two main groups of particles: phytoplankton and non-algal. For this purpose we use the extensive database of optical measurements acquired from 2006 to 2013 during 40 cruises of r/v Oceania in various regions of the southern Baltic: open waters, coastal waters, the Gulf of Gdańsk, the Pomeranian Bay and river mouths. Expressions are derived for each of these regions to describe the seasonal variations of the dependence of the light absorption coefficients for phytoplankton a ph (440) and non-algal particles a NAP (440) on concentrations of chlorophyll a ( Tchla ) and suspended particulate matter in sea water (SPM). With a knowledge of these dependences, one can determine the overall absorption coefficient for all suspended particles in any part of the Baltic Sea in particular seasons from known Tchla and SPM concentrations using the relationship a p (440) = a ph (440) + a NAP (440) = f( Tchla , SPM). These dependences reflect the characteristics of a study area and season, and their application increases the accuracy of determination of the overall absorption properties of suspended particles and their main constituents as confirmed by statistical error reduction, e.g. standard error factor falls from 1.46 to 1.38. The relationships derived in this work can be applied in the local remote sensing algorithms used for monitoring the southern Baltic. [ABSTRACT FROM AUTHOR]

A rich dataset of time- and space-varying velocity measurements for a macrotidal estuary was used in the development of a vector-based formulation of bottom roughness in the Advanced Circulation (ADCIRC) model. The updates to the parallel code of ADCIRC to include directionally based drag coefficient are briefly discussed in the paper, followed by an application of the data assimilation (nudging analysis) to the lower St. Johns River (northeastern Florida) for parameter estimation of anisotropic Manning's n coefficient. The method produced converging estimates of Manning's n values for ebb (0.0290) and flood (0.0219) when initialized with uniform and isotropic setting of 0.0200. Modeled currents, water levels and flows were improved at observation locations where data were assimilated as well as at monitoring locations where data were not assimilated, such that the method increases model skill locally and non-locally with regard to the data locations. The methodology is readily transferrable to other circulation/estuary models, given pre-developed quality mesh/grid and adequate data available for assimilation. [ABSTRACT FROM AUTHOR]

The presence of kelp beds in the water column generates drag to flows and modifies hydrodynamic processes. In this paper we examine the modifications of tidal flows in the Hecate Strait by including an explicit representation of the kelp-induced drag in a three-dimensional numerical model. The model is evaluated against a theoretical solution and it agrees well with the theory. Model results show that kelp beds significantly change tidal circulation structures by damping tidal velocity by 40–80% in interiors of the beds, but enhancing tidal velocity by 15% along the edges. Comparing terms in momentum equations shows that the momentum flux caused by the kelp drag is able to become a dominant term with a magnitude comparable to that of the horizontal pressure gradient. Simulating the effects of kelp beds on particle trajectories shows that the drag due to kelp-beds decreases the dispersion rate of particles in the interiors of kelp forests, but increases the dispersion rate along the edges. Kelp beds form barriers along the edges and prevent particles from outside entering the interiors of kelp beds. The dispersion rate is in an inverse relationship to the kelp density in kelp-bed interiors, while in a positive relationship to the kelp density along edges. [ABSTRACT FROM AUTHOR]

This paper presents data on various parameters of primary production (chlorophyll concentration, carbon uptake, nitrogen uptake, phytoplankton groups) measured in 4 cruises in the Saudi Arabian waters of the Red Sea between 2012 and 2015. The results showed that while there was a tendency for an increase from north to south, the meridional distributions were distinguished by alternating high and low concentrations of chlorophyll, carbon uptake rates and cell densities of various phytoplankton groups, with the higher levels being associated with zonal currents and the lower values lying in between. These patterns of distributions lead us to conclude that the biological production in the Red Sea is influenced more by anticyclonic eddy, and less by meridional, circulations at any time of the year. Synthesizing the present results with earlier ones on the patterns of distributions of nutrients and the flow of Gulf of Aden Intermediate Water (GAIW), we also conclude that entrainment of GAIW in successive eddies is the cause for higher nutrients and biological production in the regions of eddy boundary currents. Data on size-fractionated carbon uptake and nitrogen uptake showed that the eddies in Red Sea favour the proliferation of producers across a range of size classes rather than one class. The amount of nutrients injected into the euphotic zone in the eddy boundary currents is probably not high enough to induce a definite shift in phytoplankton size classes, and the primary production still remains to a significant extent regenerated nutrient-driven. [ABSTRACT FROM AUTHOR]

In this paper we used a modelling approach integrating both physical and biological constraints to understand the biogeographical distribution of the great scallop Pecten maximus in the English Channel during its whole life cycle. A 3D bio-hydrodynamical model (ECO-MARS3D) providing environmental conditions was coupled to (i) a population dynamics model and (ii) an individual ecophysiological model (Dynamic Energy Budget model). We performed the coupling sequentially, which underlined the respective role of biological and physical factors in defining P. maximus distribution in the English Channel. Results show that larval dispersion by hydrodynamics explains most of the scallop distribution and enlighten the main known hotspots for the population, basically corresponding to the main fishing areas. The mechanistic description of individual bioenergetics shows that food availability and temperature control growth and reproduction and explain how populations may maintain themselves in particular locations. This last coupling leads to more realistic densities and distributions of adults in the English Channel. The results of this study improves our knowledge on the stock and distribution dynamics of P. maximus , and provides grounds for useful tools to support management strategies. [ABSTRACT FROM AUTHOR]

The paper contains a brief description of selected investigations carried out in the south Baltic coastal zone, with the particular focus on the history and recent activities conducted at the Coastal Research Station in Lubiatowo (CRS Lubiatowo), Poland. These activities comprise field investigations of nearshore hydrodynamic, lithodynamic, and morphodynamic processes. The study area is a sandy multi-bar shore with a mild slope, much exposed to the impact of waves approaching from NW-NE sector. The shore has a dissipative character which means that the wave energy is subject to gradual dissipation in the nearshore zone and only a small part of this energy is reflected by the shore. Due to the big wind fetch in N-NNE direction, the location of CRS Lubiatowo is favourable to registration of the maximum values of parameters of hydrodynamic and morphodynamic processes which occur in the Baltic during extreme storms. [ABSTRACT FROM AUTHOR]

In marine sciences, many fields display high variability over a large range of spatial and temporal scales, from seconds to thousands of years. The longer recorded time series, with an increasing sampling frequency, in this field are often nonlinear, nonstationary, multiscale and noisy. Their analysis faces new challenges and thus requires the implementation of adequate and specific methods. The objective of this paper is to highlight time series analysis methods already applied in econometrics, signal processing, health, etc. to the environmental marine domain, assess advantages and inconvenients and compare classical techniques with more recent ones. Temperature, turbidity and salinity are important quantities for ecosystem studies. The authors here consider the fluctuations of sea level, salinity, turbidity and temperature recorded from the MAREL Carnot system of Boulogne-sur-Mer (France), which is a moored buoy equipped with physico-chemical measuring devices, working in continuous and autonomous conditions. In order to perform adequate statistical and spectral analyses, it is necessary to know the nature of the considered time series. For this purpose, the stationarity of the series and the occurrence of unit-root are addressed with the Augmented–Dickey Fuller tests. As an example, the harmonic analysis is not relevant for temperature, turbidity and salinity due to the nonstationary condition, except for the nearly stationary sea level datasets. In order to consider the dominant frequencies associated to the dynamics, the large number of data provided by the sensors should enable the estimation of Fourier spectral analysis. Different power spectra show a complex variability and reveal an influence of environmental factors such as tides. However, the previous classical spectral analysis, namely the Blackman–Tukey method, requires not only linear and stationary data but also evenly-spaced data. Interpolating the time series introduces numerous artifacts to the data. The Lomb–Scargle algorithm is adapted to unevenly-spaced data and is used as an alternative. The limits of the method are also set out. It was found that beyond 50% of missing measures, few significant frequencies are detected, several seasonalities are no more visible, and even a whole range of high frequency disappears progressively. Furthermore, two time-frequency decomposition methods, namely wavelets and Hilbert–Huang Transformation (HHT), are applied for the analysis of the entire dataset. Using the Continuous Wavelet Transform (CWT), some properties of the time series are determined. Then, the inertial wave and several low-frequency tidal waves are identified by the application of the Empirical Mode Decomposition (EMD). Finally, EMD based Time Dependent Intrinsic Correlation (TDIC) analysis is applied to consider the correlation between two nonstationary time series. [ABSTRACT FROM AUTHOR]

Reliable statements about variability and change in marine ecosystems and their underlying causes are needed to report on their status and to guide management. Here we use the Framework on Ocean Observing (FOO) to begin developing ecosystem Essential Ocean Variables (eEOVs) for the Southern Ocean Observing System (SOOS). An eEOV is a defined biological or ecological quantity, which is derived from field observations, and which contributes significantly to assessments of Southern Ocean ecosystems. Here, assessments are concerned with estimating status and trends in ecosystem properties, attribution of trends to causes, and predicting future trajectories. eEOVs should be feasible to collect at appropriate spatial and temporal scales and are useful to the extent that they contribute to direct estimation of trends and/or attribution, and/or development of ecological (statistical or simulation) models to support assessments. In this paper we outline the rationale, including establishing a set of criteria, for selecting eEOVs for the SOOS and develop a list of candidate eEOVs for further evaluation. Other than habitat variables, nine types of eEOVs for Southern Ocean taxa are identified within three classes: state (magnitude, genetic/species, size spectrum), predator–prey (diet, foraging range), and autecology (phenology, reproductive rate, individual growth rate, detritus). Most candidates for the suite of Southern Ocean taxa relate to state or diet. Candidate autecological eEOVs have not been developed other than for marine mammals and birds. We consider some of the spatial and temporal issues that will influence the adoption and use of eEOVs in an observing system in the Southern Ocean, noting that existing operations and platforms potentially provide coverage of the four main sectors of the region — the East and West Pacific, Atlantic and Indian. Lastly, we discuss the importance of simulation modelling in helping with the design of the observing system in the long term. Regional boundary: south of 30°S. [ABSTRACT FROM AUTHOR]

This paper describes the use of resources and diet of nine resident fish species in the rocky intertidal zone of the Gulf of Cadiz and examines whether their populations are affected by trophic competition. A stomach content analysis of the nine species revealed that only one was herbivorous ( Parablennius sanguinolentus ), while the rest were mainly carnivorous ( Gobius bucchichi , Gobius cobitis , Gobius paganellus , Zebrus zebrus , Salaria pavo , Lepadogaster lepadogaster , Scorpaena porcus and Tripterygion tripteronotum ). The most frequently consumed prey were amphipods, isopods, polychaetes, decapods, chironomids, tanaidaceans, gastropods, copepods, cumaceans and ostracods. In most species, the occurrence of polychaetes and molluscs was higher in the cold season, whereas that of isopods, decapods, chironomids and fish increased in the warm season. In general, larger specimens consumed larger prey, with an increase in the occurrence of isopods, decapods and fish. An analysis of trophic niche breadth defined G. cobitis as generalist, G. bucchichi as opportunist and S. porcus as specialist, whereas the values obtained for the other species did not indicate a clearly defined strategy. Low diet overlap values and the segregation observed in several analyses indicated an adequate distribution of resources. [ABSTRACT FROM AUTHOR]

In this paper, we used multibeam bathymetry and backscatter, high-resolution seismic profiles, ROV video images and sediment samples to identify the principal morpho-sedimentary features and related megabenthic communities along the upper reach of the Gioia Canyon (depth < 600 m) and the surrounding shelf and slope areas. Interpretation of the multidisciplinary dataset was undertaken to evaluate the relationships between seafloor characteristics and faunal distribution along a submarine canyon in an active tectonic setting. The results from this study indicate that physical disturbance on the seafloor at the canyon head and surrounding shelf, related to high sedimentation rates and occasional turbidite flows, may limit the variability of megabenthic communities. Evidence of diffuse trawl marks over soft sedimentary bottoms indicates anthropogenic impact due to fishing activities, which could explain low abundances of megabenthic species observed locally. The canyon margins and flanks along the continental slope host octocorals Funiculina quadrangularis and Isidella elongata , species that are indicative of vulnerable marine ecosystems (VMEs) and relevant in terms of sustainable management priorities. At the Palmi Ridge, the occurrence of outcropping rocks and bottom currents related to the presence of Levantine Intermediate Waters, provide conditions for the development of hard-bottom assemblages, including the black coral Antipathella subpinnata and deep-sea sponges fields. [ABSTRACT FROM AUTHOR]

This paper presents data on inorganic nutrients obtained in several transects within Saudi Arabian waters of the Red Sea in 2012–2015. Increase in their concentrations from north to south is not monotonously linear but is punctuated by regions of high concentrations alternating with those of low concentrations, regardless of the type of nutrient (N, P or Si), season and location. Such a type of distribution could be only explained in terms of eddy circulations within the Red Sea basin. The enrichment with nutrients of the boundary currents of the eddies could be explained partly by entrainment of Gulf of Aden Intermediate Water in the eddies and the mixing of the latter with the underlying Red Sea Deep Water, and partly by a higher biological productivity in the peripheries of the eddies. These results have two major implications for our understanding of biogeochemical cycles in the Red Sea. The first is that the eddy-associated injection of nutrients into the euphotic zone could cause higher levels of production over a substantial spread of the Red Sea. The second is that the anticyclonic eddies may function as traps of nutrients and in that event, their peripheries and centers may function as independent mesocosms. [ABSTRACT FROM AUTHOR]

In this paper we investigated, for two years and with a bi-monthly frequency, how physical, chemical, and biological processes affect the marine carbonate system in a coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, northern Adriatic Sea, Mediterranean Sea). By combining synoptic measurements of the carbonate system with in situ determinations of the primary production ( 14 C incorporation technique) and secondary prokaryotic carbon production ( 3 H-leucine incorporation) along a river–sea gradient, we showed that the conservative mixing between river endmember and off-shore waters was the main driver of the dissolved inorganic carbon (DIC) distribution and seasonal variation. However, during spring and summer seasons also the influence of biological uptake and release of DIC was significant. In the surface water of June 2012, the spreading and persistence of nutrient-rich freshwater stimulated the primary production (3.21 μg C L − 1 h − 1 ) and net biological DIC decrease (− 100 μmol kg − 1 ), reducing the dissolved CO 2 concentration and increasing the pH T . Below the pycnocline of August 2012, instead, an elevated bacterial carbon production rate (0.92 μg C L − 1 h − 1 ) was related with net DIC increase (92 μmol kg − 1 ), low dissolved oxygen concentration, and strong pH T reduction, suggesting the predominance of bacterial heterotrophic respiration over primary production. The flux of carbon dioxide estimated at the air–sea interface exerted a low influence on the seasonal variation of the carbonate system. A complex temporal and spatial dynamic of the air–sea CO 2 exchange was also detected, due to the combined effects of seawater temperature, river discharge, and water circulation. On annual scale the system was a sink of atmospheric CO 2 . However, in summer and during elevated riverine discharges, the area close to the river's mouth acted as a source of carbon dioxide. Also the wind speed was crucial in controlling the air–sea CO 2 exchange, with strong Bora events (a typical ENE wind of the Gulf of Trieste) that drastically increased the absorption (− 32.2 mmol m − 2 day − 1 ) or the release (5.34 mmol m − 2 day − 1 ) of carbon dioxide. [ABSTRACT FROM AUTHOR]

In spite of recent advances, biogeochemical models are still unable to represent the full complexity of natural ecosystems. Their formulations are mainly based on empirical laws involving many parameters. Improving biogeochemical models therefore requires to properly characterize model uncertainties and their consequences. Subsequently, this paper investigates the potential of using random processes to simulate some uncertainties of the 1/4° coupled Physical–Biogeochemical NEMO/PISCES model of the North Atlantic ocean. Starting from a deterministic simulation performed with the original PISCES formulation, we propose a generic method based on AR(1) random processes to generate perturbations with temporal and spatial correlations. These perturbations are introduced into the model formulations to simulate 2 classes of uncertainties: the uncertainties on biogeochemical parameters and the uncertainties induced by unresolved scales in the presence of non-linear processes. Using these stochastic parameterizations, a probabilistic version of PISCES is designed and a 60-member ensemble simulation is performed. With respect to the simulation of chlorophyll, the relevance of the probabilistic configuration and the impacts of these stochastic parameterizations are assessed. In particular, it is shown that the ensemble simulation is in good agreement with the SeaWIFS ocean color data. Using these observations, the statistical consistency (reliability) of the ensemble is evaluated with rank histograms. Finally, the benefits expected from the probabilistic description of uncertainties (model error) are discussed in the context of future ocean color data assimilation. [ABSTRACT FROM AUTHOR]

The Changjiang (Yangtze River) Estuary plays an important role in the land–ocean interactions of East Asia, particularly in regard to the fate of land-derived materials and their impact on marine ecosystems in the Northwest Pacific Ocean. The 12 papers included in this special issue describe results from the MEcoPAM Study, an IMBER-China project, which occurred in 2011–2015. This project used a multi-disciplinary approach to understand ecosystem function of the Changjiang Estuary in response to multiple stressors (i.e. combined external forcings). The results presented here show that human activities in the watersheds have greatly changed the flux and variation of dissolved and particulate materials from the river. Further interactions between the Changjiang Watersheds and the East China Sea can dramatically modify the pathways of biogeochemistry and food web dynamics of the estuary and adjacent coastal environment at seasonal and inter-annual scales. [ABSTRACT FROM AUTHOR]

The tidal residual current may play an important role in the mean flow in the Changjiang Bank region, in addition to other residual currents, such as the Taiwan Warm Current, the Yellow Sea Coastal Current, and the Yellow Sea Warm Current. In this paper, a detailed structure of the tidal residual current, in particular the meso-scale eddies, in the Changjiang Bank region is observed from model simulations, and its role in the mean flow is quantified using the well-validated Finite Volume Coastal Ocean Model. The tidal residual current in the Changjiang Bank region consists of two components: an anticyclonic regional-scale tidal residual circulation around the edge of the Changjiang Bank and some cyclonic meso-scale tidal residual eddies across the Changjiang Bank. The meso-scale tidal residual eddies occur across the Changjiang Bank and contribute to the regional-scale tidal residual circulation offshore at the northwest boundary and on the northeast edge of the Changjiang Bank, southeastward along the 50 m isobath. Tidal rectification is the major mechanism causing the tidal residual current to flow along the isobaths. Both components of the tidal residual current have significant effects on the mean flow. A comparison between the tidal residual current and the mean flow indicates that the contribution of the tidal residual current to the mean flow is greater than 50%. [ABSTRACT FROM AUTHOR]

The south eastern Mediterranean is characterized by antiestuarine circulation which leads to extreme oligotrophic conditions. The Nile river that used to transport fresh water and nutrients into the basin was dammed in 1964 which led to a drastic reduction of fresh water fluxes, and later, changes in Egyptian agriculture and diet led to increased nutrient fluxes. In this paper we present the results of simulations with a biogeochemical model of the south eastern Mediterranean. Four experiments were conducted: (1) present day without riverine inputs; (2) Nile before damming (pre-1964); (3) post-damming 1995 Nile; and (4) fresh water and nutrient discharges of Israeli coastal streams. The present day input simulation (control run) successfully reproduced measured nutrient concentrations, with the exception of simulated chlorophyll concentrations which were slightly higher than observed. The pre-1964 Nile simulation showed a salinity reduction of 2 psu near the Egyptian coast and 0.5 psu along the Israeli coast, as well as elevated chlorophyll a concentrations mostly east of the Nile delta and north to Cyprus. The spring bloom extended from its present peak during February–March to a peak during February–May. The 1995 Nile simulation showed increased chlorophyll a concentrations close to the Egyptian coast. The Israeli coastal stream simulation showed that the effect of the Israeli coastal stream winter flow on chlorophyll converged to control concentrations within about one month, demonstrating the stability and sensitivity of the model to external forcing. The results of this study demonstrate the significance of fresh water fluxes in maintaining marine productivity, which may have large scale effects on the marine ecosystem. [ABSTRACT FROM AUTHOR]

The Gulf of Naples is a coastal area in the south-eastern Tyrrhenian Sea (western Mediterranean). Zones of great environmental and touristic value coexist in this area with one of the largest seaports in the Mediterranean Sea, industrial settlements and many other pollution sources. In such an environment, water renewal mechanisms are crucial for maintaining the ecological status of the coastal waters. In this paper, we focus on the water exchange between the interior of the Gulf and the neighbouring open Tyrrhenian Sea. The surface dynamics of the Gulf have been investigated based on measurements carried out with a high-frequency (HF) radar system. The vertical component of the current field has been provided by the Regional Ocean Modelling System (ROMS) model of ocean circulation. We present the results of a one-year-long analysis of data and simulation results relative to the year 2009. Inshore/offshore exchanges were assessed by looking at the zonal component of the surface and subsurface current field across a transect representing a sort of threshold between the interior of the Gulf and the open sea. This also allows for the reconstruction of the short-term origin of waters found inside the Gulf in the different forcing and circulation conditions. [ABSTRACT FROM AUTHOR]

In this paper, we apply an established methodology for estimating Net Anthropogenic Nitrogen Inputs (NANI) to India and its major watersheds. Our primary goal here is to provide initial estimates of major nitrogen inputs of NANI for India, at the country level and for major Indian watersheds, including data sources and parameter estimates, making some assumptions as needed in areas of limited data availability. Despite data limitations, we believe that it is clear that the main anthropogenic N source is agricultural fertilizer, which is being produced and applied at a growing rate, followed by N fixation associated with rice, leguminous crops, and sugar cane. While India appears to be a net exporter of N in food/feed as reported elsewhere ( Lassaletta et al., 2013b ), the balance of N associated with exports and imports of protein in food and feedstuffs is sensitive to protein content and somewhat uncertain. While correlating watershed N inputs with riverine N fluxes is problematic due in part to limited available riverine data, we have assembled some data for comparative purposes. We also suggest possible improvements in methods for future studies, and the potential for estimating riverine N fluxes to coastal waters. [ABSTRACT FROM AUTHOR]

The Yellow and East China Seas (YECS) has been known to exhibit interannual variability in both physical and biological aspects, in relation with El Niño–Southern Oscillation (ENSO). This paper investigates the interannual variability of summer sea surface salinity (SSS) in the YECS and its linkage with ENSO, using a global ocean general circulation model (OGCM) with a regional focus on the YECS. The OGCM experiment reveals that the dominant interannual variability of the SSS in the YECS is attributed to a variability of the Changjiang river discharge (CRD). The variability of the CRD is linked to ENSO-related precipitation over the Changjiang river; when El Niño events occur in winter, precipitation over the Changjiang river increases in the rainy season of the following years. The increased precipitation in El Niño years results from enhanced southwesterly moisture flux from the South China Sea into southern China. Our finding suggests that ENSO-related precipitation in southern China contributes to the dominant interannual variability of the summer SSS in the YECS by modulating CRD. [ABSTRACT FROM AUTHOR]

In this paper we study the hypoxia dynamics in a fjord-like gulf, the Amvrakikos Gulf, in the Mediterranean Sea and highlight the factors which control the development of hypoxia. Bimonthly physicochemical data were collected in order to describe the hypoxic conditions and a three-dimensional model was used to describe the hydrodynamic circulation and explain the variations in hypoxic conditions. According to our results, the horizontal intrusion of well oxygenated open seawater can lead to the oxygenation of the deepest water in this semi-enclosed gulf. The key factor in determining the success of this horizontal intrusion is the density difference between the gulf's deepest area and the open sea outside the gulf. When the well oxygenated open seawater is denser than the bottom water in the gulf, it inflows into the gulf near the bottom and slowly re-oxygenates the isolated deep waters through mixing and diffusion, as the water travels eastward. However, when the gulf's deep water is denser than the open sea's water, the inflow stops. This, in combination with the eutrophic conditions which characterize the Amvrakikos, causes the re-establishment of hypoxic/anoxic conditions. [ABSTRACT FROM AUTHOR]

Anthropogenic inputs of nutrient phosphorus (P) and nitrogen (N) to the Eastern Mediterranean Sea (EMS) increased significantly after 1950. Nonetheless, the EMS remained ultra-oligotrophic, with eutrophication only affecting a restricted number of nearshore areas. To better understand this apparent contradiction, we reconstructed the external inputs of reactive P and N to the EMS for the period 1950 to 2000. Although the inputs associated with atmospheric deposition and river discharge more than doubled, the inflow of surface water from the Western Mediterranean Sea (WMS) remained the dominant source of nutrient P and N to the EMS during the second half of the 20th century. The combined external input of reactive P rose by 24% from 1950 to 1985, followed by a slight decline. In contrast, the external reactive N input increased continuously from 1950 to 2000, with a 62% higher input in 2000 compared to 1950. When imposing the reconstructed inputs to the dynamic model of P and N cycling in the EMS developed in the companion paper, a maximum increase of primary production of only 16% is predicted. According to the model, integrated over the period 1950–2000, outflow of Levantine Intermediate Water (LIW) to the WMS exported the equivalent of about one third of the P supplied in excess of the 1950 input, while another one third was translocated to the Eastern Mediterranean Deep Water (EMDW). Together, both mechanisms efficiently counteracted enhanced P input to the EMS, by drawing nutrient P away from primary producers in the surface waters. Furthermore, between 1950 and 2000, inorganic and organic dissolved N:P ratios increased in all water masses. Thus, the EMS became even more P limited because of anthropogenic nutrient inputs. A model simulation incorporating the circulation changes accompanying the Eastern Mediterranean Transient (EMT) between 1987 and 2000 yielded a 4% increase of EMS primary productivity relative to the baseline scenario. [ABSTRACT FROM AUTHOR]

Underwater noise is now classed as pollution in accordance with the Marine Strategy Framework Directive. Noise from shipping is a major contributor to the ambient noise levels in ocean, particularly at low (< 300 Hz) frequencies. This paper studies patterns and seasonal variations of underwater noise in the Celtic Sea by using a coupled ocean model (POLCOMS) and an acoustic model (HARCAM) in the year 2010. Two sources of sound are considered: (i) representing a typical large cargo ship and (ii) noise from pile-driving activity. In summer, when the source of sound is on the onshore side of the front, the sound energy is mostly concentrated in the near-bottom layer. In winter, the sound from the same source is distributed more evenly in the vertical. The difference between the sound level in summer and winter at 10 m depth is as high as 20 dB at a distance of 40 km. When the source of sound is on the seaward side of the front, the sound level is nearly uniform in the vertical. The transmission loss is also greater (~ 16 dB) in the summer than in the winter for shallow source while it is up to ~ 20 dB for deep source at 30 km. [ABSTRACT FROM AUTHOR]

The multidisciplinary IDEADOS project funded by the Spanish Government was developed between 2009 and 2012 aiming to determine the relationships between environmental conditions and the nekto-benthic slope communities in two areas of the western Mediterranean, north and south of the Balearic Islands, with different geomorphologic and hydrodynamic characteristics. In this paper we describe the background and goals of this project, its study area and the sampling strategy applied, as well as the main conclusions reached in a final workshop. This volume is a compendium of the main contributions presented at this workshop, which have been peer-reviewed and can represent the state of the art of the complex interactions between the pelagic domain and the slope benthic communities, within the context of the hydrodynamics and oligotrophy of the Balearic Islands, and considering different temporal scales and organization levels. [ABSTRACT FROM AUTHOR]

This paper reports on detailed studies of the relationship between the inherent optical properties (IOPs) of suspended particulate matter populations occurring in southern Baltic Sea waters, and the basic biogeochemical and morphological quantities enabling these populations to be generally characterized. Specifically, these IOPs are the spectral absorption coefficients by all particulate matter, phytoplankton pigments and detritus, the spectral scattering and backscattering coefficients by particles, and the backscattering ratio. The biogeochemical properties of suspended matter populations are characterized by measuring concentrations of suspended particulate matter (SPM), particulate organic matter (POM) and particulate inorganic matter (PIM), as well as concentrations of various phytoplankton pigments, including chlorophyll a (Chl a). We also take particle size distributions (PSDs) into account. This diverse empirical material is used to describe how the typical relationships between the IOPs of suspended matter and the concentrations of the main water constituents (SPM or Chl a) can be influenced by differences in the general composition and size distributions of the suspended matter. We statistically describe the possible impact on these relationships of the variability of composition ratios, such as POM/SPM and Chl a /SPM, as well as the impact of the variability of certain characteristics calculated on the basis of PSDs: the average particle diameter weighted by the particle's projected area (D A), the average apparent density of particles (ρ a), the average intracellular concentration of chlorophyll a (c i), and the corresponding products of these quantities. We also demonstrate the significant variability of the specific IOPs (SIOPs) by attempting to determine them in the classical way for our southern Baltic data, and we give a possible interpretation of this variability. On the basis of these analyses, we derive new, multicomponent IOP parameterizations that are functions of several variables. These new parameterizations enable the IOPs of suspended matter to be characterized and predicted with better accuracy than with the often-used standard one-component relationships. • the optically complex waters of the southern Baltic Sea, • detailed measurements of optical and biogeochemical properties of suspended matter, • influence of particle composition and size distributions on optical properties, • interpretation of the variability of the specific inherent optical properties, • new, multicomponent parameterizations of inherent optical properties. [ABSTRACT FROM AUTHOR]

The South Shetland Islands, including King George Island (KGI), are located in the northern hydrographic zone on the West side of the Antarctic Peninsula (Northern WAP), which is washed mainly by the Antarctic Circumpolar Current (ACC). Continuous vertical mixing of the water column by strong currents, violent tidal water exchanges in deep fjords and frequent strong winds do not favour the seasonal appearance of large phytoplankton blooms. In contrast, the southern WAP is bound by the continental shelf, and is under the influence of the weaker Antarctic Peninsula Coastal Current (APCC), maintaining seasonal winter sea ice, which provides a shallow mixed layer, which in turn supports high levels of biological production in summer. During the 2009 / 2010 summer, however, a distinctive bloom event (chl-a > 20 μgL−1) was documented for in Admiralty Bay (AB), the largest and deepest fjord in KGI. It commenced in early summer (29 December 2009) at the edge of melting sea ice which had persisted since the preceding cold winter of 2009. The phytoplankton group dynamics, determined using photosynthetic pigment data, and associated changes in nutrient concentration during the bloom, have been described in this paper. The area where the phytoplankton bloom developed coincided with the surface of the brash sea ice cover. The sequence and size of biological and chemical changes recorded within the fjord during the bloom resembled the recurring ice edge blooms which occur in the southern WAP, although they had a much shorter lifespan (< two weeks), which may have been due to the slow SE winds and related surface water movement direction, which hindered vertical mixing and kept the surface water within the fjord. • A distinctive diatom bloom was documented after sea ice melting in Admiralty Bay. • The massive bloom entailed changes in phytoplankton assemblages composition. • The concentration of chl-a has reached an unusually high level. • The phosphates have depleted locally to the values limiting primary production. • The environmental changes during the bloom were similar to those in the southern WAP. [ABSTRACT FROM AUTHOR]

Particles located at the interface between the surface ocean layer and the top of the mesopelagic domain are the initial vector of the biological pump yet, their nature is still largely unknown. During the MOBYDICK cruise in the vicinity of the Kerguelen Islands (Indian sector of the Southern Ocean) we deployed a recently available device that concentrates and collects deep particles over a predetermined layer of water. In this paper, we present a detailed description of the collected particles and individual planktonic cells, including their taxonomy, carbon and lipid content, as well as cell viability, in order to characterize the particle stocks present at depth. The cruise was carried out at the end of the summer bloom, a period characterized by declining stocks of biogenic material associated with various mortality processes of planktonic organisms. Unexpectedly, the majority of the collected particles consisted of single empty diatom frustules, while fecal pellets and aggregates accounted for only a minor fraction. Distinct mortality processes, from parasitic infection to mesozooplankton grazing, and distinct silicification degrees as well as different life stages could be identified in relation to diatom taxa suggesting the occurrence of several export modes to intermediate and deep layers within the diatom community. We observed a dominant contribution of single cell diatoms (93 ± 6%) to the deep particle stocks but a very small contribution of intact diatom cells (~0.3%) to C content in the intermediate layer (125–500 m), together with a very small fecal pellet contribution, that was dominated by the minipellet size-class. Taxonomical analyses revealed distinct communities west of Kerguelen in the HNLC area compared to the island's fertilized plateau and its eastern flank. Differences in silicification degrees as well as distinct mortality/export processes linked to surface nutrient depletion and trophic interactions (such as parasitic infection or grazing by phaeodarians) were identified in the upper layer, leading to distinct contributions of major diatom taxa to deep suspended particles. • There is a dominant contribution of single cell diatoms to the deep particle stocks. • There is a very small fecal pellet contribution at depth by the end of summer, dominated by minipellets. • Distinct mortality/export processes in the upper layer control the contribution of major diatom taxa to deep suspended particles. [ABSTRACT FROM AUTHOR]

Nutrient dynamics play an important role in mangroves and adjacent coastal ecosystems. This paper discusses the spatiotemporal variation of physicochemical factors in two monsoons and intermonsoons and their influence on chlorophyll a and the dissolved inorganic nutrient concentrations in selected creeks. The present study focused on dense mangrove cover creeks (Waddi Khuddi (WK) and Dabbo (DC)), sparse mangrove cover creek (Hajamro (HC)), and no mangrove to mixed terrestrial and agricultural vegetation (Khobar (KC)) along with the Indus River and adjacent NE Arabian Sea. Silicate (SiO 3 2–) was the most abundant nutrient, and its concentration increased from the northeast to the southwest monsoon and decreased during the fall intermonsoon. Erosion of the riverbank catchment area, weathering, and sand mining are the major sources of elevated SiO 3 2–. The highest concentration of nitrate (NO 3 –) was found in the main river channel (KC) throughout the year, with maximum concentration (37.42 ± 5.05 μM) in the river (KC) during the rainy season (SW monsoon) due to the agricultural runoff that resulted in an increase in chlorophyll a. The concentration of nitrite (NO 2 –) was high in the creek (DC) with mangroves and agricultural runoff input. The concentration of phosphate (PO 4 3–) was high in mangrove-dominated creeks (WK and DC), suggesting litterfall as a major source of PO 4 3− from the creeks. The river with no mangrove cover (KC) indicated that PO 4 3– was a limiting factor. In the case of DSi:DIN ratios, SiO 3 2–was not limited throughout the sampling period for primary production. The chlorophyll a concentration increased from upstream to downstream in the river and was positively correlated with SiO 3 2– and NO 3 –, resulting in the dominance of diatoms during the SW monsoon. The study confirms that natural sources (river/terrestrial runoff and geomorphological factors) and anthropogenic factors (application of fertilizers, manure, construction of dams, and industrialization) significantly influenced the nutrients and chlorophyll a , both spatially and temporally. On a global scale, SiO 3 2– concentrations in the Indus River during the southwest monsoon were lower than those in the Himalayan rivers (Brahmaputra, Ganges, Huanghe, and Yangtze Rivers). The NO 3 – concentration is comparable with that of Narmada, Tapti, and Pangani Rivers but lower than that for rivers originating from the Himalayas. Nutrient enrichment and eutrophication in coastal waters were mainly caused by urbanization and population increase, which affect the higher trophic level productivity and fish abundance in the coastal and shelf areas. Therefore, an integrated approach for the management and monitoring of upstream river systems is required for a better future. • The river discharge influenced the nutrients, chlorophyll a , TSM and salinity. • Groundwater showed elevated silicate concentrations. • Mangrove-dominated creeks were not limited by phosphate. • Light and turbidity play an important role in chlorophyll a concentration. • The delta has a strong tidal influence that keeps the system well mixed. [ABSTRACT FROM AUTHOR]

Spatial variability of 7Be activity in both particulate and dissolved phases in the Black Sea was studied using field observations from the 95th cruise of R/V Professor Vodyanitsky in the summer of 2017. The total (particulate + dissolved) 7Be activity varied spatially from 2.8 to 8.3 Bq m−3 and averaged to 5.3 ± 1.9 Bq m−3. The particulate fraction of 7Be activity varied spatially between 5% and 13%, with an average value of 8% ± 2%. This paper provides an analysis of the influence of atmospheric precipitation, mixed layer depth, total suspended matter concentration (TSM), seawater temperature and salinity on the spatial variability of 7Ве activity. It is shown that the variability of the TSM might determine the spatial heterogeneity of total 7Be activity in the study area. Quantitative estimates of the distribution coefficient (K d) of 7Be for the dissolved and particulate phases were obtained, and the functional dependence of K d on the TSM was established. The average K d value was determined to be (1.6 ± 0.3) × 102 m3 kg−1. K d decreased with an increase in TSM. The obtained estimates suggested that the average 7Be sinking rate on the particulate matter was (1.3 ± 0.7) × 10−5 m s−1. Sinking particles removed approximately 7% of total 7Be activity from the surface layer offshore and reached 29% on the Black Sea shelf. The influence of the TSM, its sinking rate, vertical exchange intensity, and bathymetry on the 7Be sinking flux in the surface mixed layer (SML) were also investigated. A statistically significant correlation was established for both the particle sinking rate and TSM: an increase in the sinking rate and TSM led to an increase in the contribution of the sinking process to the total 7Be flux from SML. • The particulate fraction of 7Be activity varied spatially from 5% to 13% • The total 7Be activity was significantly negatively correlated with TSM • Lower K d -7Be values were found with increasing TSM • The mean sinking rate of 7Ве on particle matter is (1.3 ± 0.7) × 10−5 m s−1 • Sinking particles removed ~7% of 7Be offshore and up to 29% on a shelf [ABSTRACT FROM AUTHOR]

The paper describes the community composition of phytoplankton in the eastern Arabian Sea (EAS) during winter monsoon (WM, January–February 2018), encompassing the entire eastern part of the Arabian Sea basin (~6–22°N and 77–67°E) with high-resolution sampling (7 transects, 56 sites), from coastal to offshore regions. The phytoplankton pigment concentrations estimated by high-performance liquid chromatography were interpreted using 'CHEMTAX' (Mackey et al., 1996) to determine relative abundance and contribution of phytoplankton functional groups at the class level. A distinct spatial heterogeneity was observed in the distribution of phytoplankton groups in the coastal and offshore regions of the northern as well as southern part of the EAS. The basin-scale column integrated chlorophyll a (Chl a) concentration in the upper 100 m was higher (16–118 mg m−2) in the northeastern Arabian Sea (NEAS) as against 9–79 mg m−2 in the southeastern Arabian Sea (SEAS). The chromatographic analysis revealed the dominance of diatoms in the coastal waters of the EAS basin. A closer evaluation of the hydrodynamics and nutrient chemistry of the offshore regions revealed that entrainment of sub-halocline nutrients into the sunlit water column through convective mixing supported the dominant cyanobacterial population in the NEAS. In the warm oligotrophic waters of the SEAS, the substantially high NH 4 + concentration indicates that the dominant prochlorophytes were sustained by the regenerated production. The dominance of large phytoplankton like diatoms indicates a herbivorous control in the food chain in coastal waters of the EAS. Offshore waters are characterised by large proportions of pico-nano plankton along with considerable micro phytoplankton, which suggests a mixotrophic ecosystem. The statistical analysis showed that the silicate (Si/N ratio) concentration played a major role in controlling the diatom abundance in the coastal areas of the north (south) EAS while temperature and salinity together with nutrients structured the phytoplankton assemblage in the offshore waters during WM. • First hi-res study on phytoplankton community in entire eastern Arabian Sea (EAS). • Silicate (Si/N ratio) controls diatom abundance in north (south) coastal EAS. • Significant role of salinity in determining distribution of prochlorophytes. • Abundance of pico-nano plankton in offshore EAS indicate mixotrophic condition. [ABSTRACT FROM AUTHOR]

In situ incubations of sediment with overlying water provide valuable and consistent information about benthic fluxes and processes at the sediment-water interface. In this paper, we describe our experiences and a variety of applications from the last 14 years and 308 deployments with the Gothenburg benthic chamber lander systems. We give examples of how we use sensor measurements for chamber leakage control, in situ chamber volume determination, control of syringe sampling times, sediment resuspension and stirring quality. We present examples of incubation data for in situ measurements of benthic fluxes of oxygen, dissolved inorganic carbon, nutrients, metals and gases made with our chamber landers, as well as manipulative injection experiments to study nitrogen cycling (injections of 15N nitrate), phosphate retention (injections of marl suspension) and targeted sediment resuspension. Our main goal is to demonstrate the possibilities that benthic chamber lander systems offer to measure solute fluxes and study processes at the sediment-water interface. Based on our experience, we recommend procedures to be used in order to obtain high quality data with benthic chamber landers. • Experience learned with the Gothenburg benthic chamber lander systems • Sensor measurements for incubation quality control • Examples of incubation data for in situ measurements of benthic fluxes • Manipulative injection experiments and targeted sediment resuspension • Recommendations for procedures to use with benthic chamber landers [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) are strong synoptic systems which induce strong sea surface currents. This paper first cross-checks a detailed surface current response to specific TCs Rammasun (2014), Kalmaegi (2014) and Sarika (2016) based on buoy/mooring observations as well as a three-dimensional numerical model (three-dimensional version of the Price-Weller-Pinkel model, 3DPWP) and a one-dimensional semi-analytical model which simplifies the driving forcing into wind stress and Coriolis force, then estimates the impact of all possible tropical cyclones using the semi-analytical model. The results show that the sea surface current response to the kinetic energy input of TCs, which is dependent on the TC configurations (translation speed, size and intensity) and the environmental configurations (Coriolis frequency and upper ocean stratification), can be represented by two simple parameters, namely the TC nondimensional translation speed (S) and the TC wind force parameter (V ~ c) or TC wind energy parameter (E ~). S represents a combined effect of TC translation speed, size and Coriolis frequency, determines the structure of surface current response. V ~ c or E ~ represents a combined effect of TC intensity, mixed layer depth and Coriolis frequency, determines the intensity of surface current response or wind energy input into surface currents. Ekman-like divergence dominates the sea surface current response when S is small (0 < S ≤ 0.4), an inertial oscillation in the lee that bias to the right rear part of a TC dominates when S is medium (0.4 < S ≤ 5), and an impulse with forward (backward) current on the right (left) side of the track dominates when S is large (S > 5). The response pattern with S > 5 was rarely studied before. The three values range of S take up ~30.36%, ~69.36% and ~0.28% of all recorded TCs during 2001–2017, which explains why the second response pattern with 0.4 < S ≤ 5 is usually observed while the third response pattern with S > 5 has been rarely studied before. Besides, the surface rightward bias is greatest at S = 2.5 (S = 1.45) for current speed (kinetic energy input rate). V ~ c (E ~) determine the amplitude of current speed (wind energy input into currents). This work provides a simple and easy-to-use method to estimate the surface current response pattern to TCs when TCs and associated environmental configurations are given, which may help to improve the parameterization of TCs in regional and climate modeling. It also suggests that S is a better index than TC translation speed to classify TCs when studying the oceanic response. • Sea surface current response patterns to tropical cyclones (TCs) are classified • Complicated response can be simplified into the function of two parameters • A better index than TC translation speed is proposed in classification • The classification includes a rarely observed and studied pattern • The classification may improve parameterization of TCs in climate modeling [ABSTRACT FROM AUTHOR]

The Penghu archipelago locates near the Tropic of Cancer, guarding the southern entrance of the Taiwan Strait (TWS). Since the archipelago is usually surrounded by warm waters from the Kuroshio branch and the South China Sea, the marine ecosystem in the waters surrounding the archipelago is mainly tropical. However, this area may be invaded by cold water, which can cause serious ecological disasters. Among the few rare events ever documented, the cold event in early 2008 represented a typical case in this regard. In this paper, we investigated this event using in situ measurements and remote sensing data. Our analyses show that during the destructive snow and ice storm of early 2008, strong cold winds persisted for ~40 days over the TWS area, with a mean prevailing wind speed of about 15 m/s, and the water temperature in the strait dropped sharply, especially along the mainland coast. On the other side of the strait, the Penghu area experienced extremely low temperatures, leading to a cold event. Note that the time of temperature reduction in Penghu was earlier than the time of temperature reduction in the area farther north along the coast of Taiwan. This indicates that a cross-strait outbreak of the mainland coastal cold-water (MCCW) caused the cold event, and thus triggered the cold disaster. The outbreak resulted from the combined effect of favorable background hydrographic conditions, persistent strong northeasterly, strong mainland coastal current (MCC), and the interaction of current and waves with the bottom topography of the Taiwan Bank (TWB). Remotely generated coastal trapped waves (CTWs) may also play a role. • A rare cold event occurred at Penghu waters in early 2008. • A cross-strait outbreak of the mainland coastal cold-water caused the cold event. • The outbreak resulted from the combined effect of several factors. • Remotely generated coastal trapped waves may also play a role. [ABSTRACT FROM AUTHOR]

The traditional view of the circulation in the Tasman Sea includes a coherent, quasi-zonal, eastward flow towards the northern tip of New Zealand that is widely referred to as the Tasman Front. This flow was first suggested in the 1960s by oceanographers reasoning that the source of volume transport "feeding" the East Auckland Current, around northern New Zealand and extending down the east coast, must be off eastern Australia. The first reported in situ measurements of the Tasman Front included hand-drawn temperature sections that highlighted features that are not supported by observations. Here, we objectively map the original data, showing that the published reports of strong, sub-surface, north-south temperature gradients were unjustified. In the absence of additional observations, we can't be sure of the context of those original measurements - so we have objectively "searched" fields in a recent 25-year ocean reanalysis to identify scenarios that are consistent with the observations. We suggest that the most likely interpretation of the original data, is that they measured an eddy field - or a series of discontinuous streams across the central Tasman Sea. We also analyse data from surface drifting buoys to show that water traversing the Tasman Sea may take several different paths. We conclude that a continuous, zonal, eastward flow across the Tasman Sea is less common than widely-accepted conceptual models imply. Instead, we suggest that the eastward flow between Australia and northern New Zealand is perhaps better described as an "eastern extension of the EAC" - since this doesn't imply the presence of a front, and doesn't preclude a broad flow. For clarity, we also suggest that the southern branch of the EAC, known as the EAC extension, should be referred to as the "southern extension of the EAC". • The traditional view of the circulation in the Tasman Sea includes a feature called the Tasman Front. • In this paper, we revisit the early observations that were the basis for the "discovery" of the front and re-interpret those observations with the benefit of recent data and more modern tools. • We conclude that a continuous, zonal, eastward flow across the Tasman Sea is less common than widely-accepted conceptual models imply. • Instead, we find that the flow between Australia and New Zealand follows multiple paths, and is much broader than the label "Tasman Front" suggests. • We recommend that the eastward flow between Australia and northern New Zealand is perhaps better described as an "eastern extension of the EAC" - since this doesn't imply the presence of a front, and doesn't preclude a broad flow. [ABSTRACT FROM AUTHOR]

Wind-driven coastal upwelling along the eastern boundary currents sustains the ecosystem productivity in these systems by transporting deep nutrient-rich waters to the euphotic zone where photosynthesis can occur, generating one of the most productive ecosystems in the world. One of the most pressing concerns in oceanography is how coastal upwelling systems might respond to climate change. These systems are affected by two mechanisms associated with climate change which are opposing each other: the surface warming that increases the stratification of the water column and, as the Bakun hypothesis states, the intensification of coastal alongshore winds that could enhance the upwelling. The question is which of these mechanisms will dominate the coastal upwelling dynamics. This paper addresses this question for the coastal upwelling system along the western coast of the Baja California Peninsula, which comprises the southern part of the California Current System. A regional physical-biogeochemical coupled model, nested to a global circulation model (GFDL-CM3), is used to explore the response of primary production to future climate-change scenarios (RCP6.0 and RCP8.5) in this region. The results toward the year 2050 project an increase in chlorophyll concentration during spring in both scenarios. During summer, when the highest temperatures are observed, an increase in chlorophyll is projected only within a narrow zone along the coast and a decrease in chlorophyll out of that narrow zone due to enhanced stratification in open ocean in the RCP6.0 scenario. In the RCP8.5 scenario, the strip with enhanced chlorophyll becomes wider due to stronger alongshore winds which enhance the nutrient supply into the upper levels over the continental shelf. • A physical-biogeochemical ocean model was nested to a general circulation model. • Downscaled climate change scenarios were obtained for Baja California, Mexico. • The two most extreme climate-change scenarios (RCP6.0 and RCP8.5) were diagnosed. • Coastal upwelling shows intensification along Baja California by the year 2050. [ABSTRACT FROM AUTHOR]