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Six species of cetaceans have been found to occur in the Chukchi Sea adjacent to the Pacific walrus rookery at Cape Vankarem: the gray whale, the bowhead whale, the humpback whale, the killer whale, the beluga whale, and the fin whale. The humpback whale is noted to have become abundant in the Chukchi Sea in the summer in recent years. The coastal mortality of cetaceans in a 100-km section in the western part of the distribution range of both gray and bowhead whales has been established to average 1.66 and 0.3 whales per year, respectively. Mostly young animals of 1–2 years of age appear to die, the main cause of death of which is predation by killer whales. The most common whales in that area in the summer–autumn period are humpback whales, which at the same time form significant concentrations in the coastal waters during the accumulation of the main food items. Both bowhead and gray whales are much less frequent, found rather irregularly, while despite the relative scarcity of encounters, these species account for the lion's share of all dead cetaceans. [ABSTRACT FROM AUTHOR]

The ecological patterns of the formation of the avifauna and bird populations on Iturup Island have been analyzed. Route censuses were used along transects with unlimited width. As many as 116 bird species have been registered; 36% of them are ubiquitous, 34% are local, and the other 26% are highly local. Seventy-one species were shown to nest. The taxonomic structure of the avifauna, represented by species from 15 orders, corresponded to the zonal and landscape features of the island areas located at the eastern margins of northern Eurasia. Passeriformes (37%), Charadriiformes (22%), Anseriformes (9%), and Procellariiformes (8%) prevailed. The zoogeographic peculiarity of the local avifauna was the combination of elements of the Far East island, Pacific, Siberian, and Chinese faunal complexes, some Siberian–American and widespread species, and Japanese island endemics. The avifauna around Iturup Island, formed by a system of general zonal-landscape and altitudinal-belt patterns, combines the ecological groups of marine and terrestrial species, including mountain ones (n = 9). The local avifauna includes 41 species in coastal marine habitats vs. 55 species in forests, 37 species in light forests, and 46 species in tall grasses, with the population density being 607, 785, 968, and 518 individuals/km2, respectively. The similarity coefficients were 19–48% for the populations of forest habitats vs. 22% for light forests and 20–37% for tall grasses, while they were 21–52% for the sea coast and adjacent water areas. The populations of terrestrial habitats are dominated by the oriental turtle-dove, Pacific swift, Siberian rubythroat, Japanese bush-warbler, marsh tit, coal tit, Eurasian nutcracker, oriental greenfinch, Eurasian siskin, long-tailed rosefinch, masked bunting, and gray bunting. The populations of the coast and adjacent sea area are dominated by Temminck's cormorant, the rufous-necked stint, slaty-backed gull, black-tailed gull, and black-backed wagtail. In open sea areas, the most common species are the white-winged scoter, black-footed and Laysan albatrosses, northern fulmar, and short-tailed shearwater. [ABSTRACT FROM AUTHOR]

The capacity of many macroalgae to rapidly absorb soluble inorganic nutrients and convert them into primary biomass provides opportunities for their use in the bioremediation of nutrient-enriched waters. Marine-based macroalgal cultivation has the potential to target diffuse source nutrient discharges and produce valuable bioproducts such as fertiliser, soil conditioning agents and agricultural feed additives and phycocolloids. Whilst macroalgal diversity offers benefits for improving and maintaining healthy marine ecosystems, it also presents a challenge for determining the best candidate species for cultivation as a nutrient biofilter and, ultimately, a source of bioproducts. We developed and applied a multi-criteria selection model to identify likely candidate macroalgal species for cultivation in Queensland's coastal waters for biofiltration and bioproduct development, focusing on native species and product development for the agronomical and horticultural sectors. From a species database of 1380 macroalgal species, candidates were initially selected based on their regional abundance, distribution and morphological characteristics considered amenable to in-situ cultivation and harvesting. From a resulting shortlist of 17 species, five systematic literature searches were applied to identify biofilter potential, bioproduct potential and current cultivation status. Of the shortlisted species, Ulva lactuca, Gracilaria edulis and Hypnea cervicornis ranked most highly in the multi-criteria analysis, with several other species showing good potential, but requiring further investment in understanding key biological processes and the development of cultivation protocols. [ABSTRACT FROM AUTHOR]

Transferability of species distribution models (SDMs) is vital for guiding biological conversation in the changing marine ecosystems, whereas most SDMs have remained insufficiently tested in terms of transferences. Particularly, the roles of biotic interactions in shaping ecological niches had less been considered when predictive models are transferred into a new circumstance. Therefore, using silver croaker (Pennahia argentata) and slender lizardfish (Saurida elongata), two keystone predators in the coastal systems as examples, this study examined how the consideration of abiotic and biotic factors as well as spatial autocorrelation would improve the transferability of prevalent SDMs. We collected the data of species abundance and hydrological variables from coastal waters of Shandong Peninsula, China, and developed a framework to evaluate the interpolation performance and spatial transferability of SDMs with respect to different modelling algorithms and combinations of covariates. The covariates tested included (1) abiotic environmental variables only; (2) biotic variables of prey availability only; (3) both abiotic and biotic variables; and (4) spatial autocorrelation in addition to other variables. Generally, our results showed that including abiotic and biotic variables simultaneously could improve the model transferability, whereas biotic models exhibited greater uncertainty and overestimation in spatial transferences when delineating suitable habitats. Besides, models accounting for spatial autocorrelation yielded more accurate forecasts for slender lizardfish's abundance, and were less limited by geographic distance in transference. Regarding the model algorithms, GLM slightly outperformed GAM and RF overall, while RF showed more robust spatial extrapolations in many cases. Our transferability evaluations offer the opportunity to extend the use of biotic signals and spatial autocorrelation to improve the forecasts of habitat suitability, which would be informative for guiding marine conservation actions. [ABSTRACT FROM AUTHOR]

The handling of boundary conditions (BCs) is a key issue for the development of dynamical downscaling techniques in which nearshore wave models require the definition of the sea conditions at the offshore boundaries. This study addresses the implications of using simplified BCs represented by bulk or partitioned wave parameters with respect to using the complete information from directional wave spectra. As a large-scale model, we used WAVEWATCH III (WW3) running over the Mediterranean Sea providing the wave BCs for the small-scale SWAN model. One year of measured directional wave spectra from three deepwater buoys allowed the assessment of the WW3 model accuracy. The nested SWAN model simulations propagated the wave field over three nearshore areas. The accuracy of SWAN simulations was assessed through the comparison of computed results with wave measurements from nearshore buoys. Being the wave conditions dominated by unimodal seas, modest differences of error metrics are found between the datasets forced by different types of BCs. Conversely, focusing the attention on multimodal seas, an accurate definition of wave BCs achieved by the use of the directional wave spectra or, in alternative, by the reconstruction of wave spectra from partitioned wave parameters becomes crucial for nearshore wave predictions. [ABSTRACT FROM AUTHOR]

Coccolithophorid Emiliania huxleyi was isolated to clonal culture from plankton of coastal waters of the Black Sea in February, 2023. Algal virus strain EhV-SS2 affecting this algal species was isolated from coastal waters in May, 2023. By means of scanning electron microscopy, it was shown that viral particles were 124–174 nm in diameter with an icosahedral symmetry. Supercapsid was detected in this strain and its titer was determined (2.5 × 105 virions/mL). The effect of algal virus on E. huxleyi growth and efficiency of PS II (Fv/Fm) at different levels of biogenic elements in the medium was investigated. Throughout the latent period of algal virus (0–101 h), we observed a decrease in the Fv/Fm ratio in the algae as compared with control values. Within time interval from 101 to 168 h, first cells lysed by the virus were revealed in the culture by means of light and scanning electron microscopy. Over the period from 168 to 264 h, lysis intensified and its rate on full f/2 medium was five times greater than in the case of nitrogen or phosphorus deficit. The rate of cell lysis on seawater lacking nutrient elements was two times lower than on the full medium. By the end of the experiment (in 264 h), infected culture displayed functionally active cells sheeted with coccoliths and without them. The percentage of the latter on f/2 medium was 95%, whereas in the case of nitrogen and phosphorus deficit their proportion was small. [ABSTRACT FROM AUTHOR]

The article "Unleashing the power of remote sensing data in aquatic research: Guidelines for optimal utilization" published in Limnology & Oceanography Letters discusses the importance of remote sensing data in lake studies, focusing on the estimation of chlorophyll a as a water quality indicator. It highlights the complexities of utilizing remote sensing data in limnological studies, emphasizing the need for careful product selection, atmospheric correction, and validation processes. The article provides recommendations for optimal utilization of remote sensing data in aquatic research, including choosing the right products, processes, and strategies for improving data quality and collaboration between aquatic sciences and remote sensing communities. [Extracted from the article]

Water masses are carriers of anthropogenic fingerprints in the ocean interior, with their property changes manifesting oceanic thermodynamic responses to climate change. Yet, delimiting ocean water masses remains challenging in either observational atlas or climate models. This study analyzes the distribution of Indian Ocean seawater in the density–spicity space and uses volumetric maxima and minima between σ = 27.1 and 27.4 kg m−3 to track the cores and boundaries of intermediate water masses, respectively. In addition to the well-known Antarctic Intermediate Water (AAIW) and Red Sea–Persian Gulf Intermediate Water (RS-PGIW), two other water masses are identified by the new approach. One is the Indian-AAIW (I-AAIW), as a mixture of the AAIW and the Indonesian Throughflow water, existing in the South Equatorial Current and the Agulhas Current system. The other [equatorial Indian Intermediate Water (EIIW)] exits in the equatorial Indian Ocean and Bay of Bengal, sourced from the RS-PGIW and overlying fresh waters. These waters are corroborated by nutrient and dissolved oxygen data. Around half (26 out of 51) of phase 6 of the Coupled Model Intercomparison Project (CMIP6) models can reasonably simulate these intermediate water masses. Compared with the observed water masses, the intermediate water masses in models are of a smaller thickness and the RS-PGIW is colder and fresher. The former arises from a warm bias in the thermocline, whereas the latter is likely linked to insufficient ventilation in the Red Sea and Persian Gulf in models owing to coarse grid resolution and a surface cold bias. Significance Statement: Oceanic water masses are important for understanding climate change. Yet, the definition of water masses is controversial. Here, we use volumetric minima in the density–spicity space to track the boundaries of intermediate (27.1–27.4 kg m−3) water masses in the Indian Ocean. We identify four water masses: AAIW, I-AAIW, EIIW, and RS-PGIW. We delineate the geographical location of each water mass, including two newly identified water masses (I-AAIW and EIIW). We also examined the performance of 51 CMIP6 models in simulating these water masses and found that 26 models can reasonably simulate the distribution of these water masses. There are two systematic model biases emerging from these models. The intermediate water masses in models are of a thinner thickness arising from a warm bias in the thermocline, and the RS-PGIW is colder and fresher owing to insufficient ventilation in the Red Sea and Persian Gulf. These results provide a useful benchmark for understanding water masses in a changing climate and constraining climate models. [ABSTRACT FROM AUTHOR]

Rates of ecosystem metabolic properties, such as plankton community respiration, can be used as an assessment of the eutrophication state of a waterbody and are the primary biogeochemical rates causing oxygen depletion in coastal waters. However, given the additional labor involved in measuring biogeochemical rate processes, few monitoring programs regularly measure these properties, and thus, few long-term monitoring records of plankton respiration exist. An 8-year, biweekly plankton community respiration rate time series was analyzed as part of a monitoring program situated in the lower Patuxent River estuary, a tributary of Chesapeake Bay. We found that particulate nutrients (nitrogen and phosphorus) were the most highly correlated covariates with respiration rate. Additionally, statistical and kinetic models including variables both water temperature and particulate nitrogen were able to explain 74% of the variability in respiration. Over the long-term record, both particulate nutrients and respiration rate were elevated when measured at higher tides. Separate measurements of respiration rate during 10 consecutive days and during high and low tide on three separate days also support the enhancement of respiration with high tide. The enhancement was likely due to the import of particulate nutrients from the highly productive mid-bay region. This analysis of the longest consistently measured community respiration rate dataset in Chesapeake Bay has implications for how to interpret long-term records of measurements made at fixed locations in estuaries. [ABSTRACT FROM AUTHOR]

Oxygen depletion in coastal waters is increasing globally due primarily to eutrophication and warming. Hypoxia responses to nutrient loading and climate change have been extensively studied in large systems like the Chesapeake Bay and the Baltic Sea, while fewer studies have investigated smaller, shallower hypoxic zones. Thus, an improved understanding of the interactions of eutrophication and warming on hypoxia expansion (or reduction) in the wide variety of different estuarine environments is needed. We examined interannual controls on oxygen depletion in the Patuxent River estuary, a eutrophic sub-estuary of Chesapeake Bay where seasonal hypoxia develops annually. We conducted a spatial and temporal analysis of dissolved oxygen (DO) trends, timing, and several metrics of depletion over a long-term record (1985–2021). We found an internally generated hypoxic zone that initiates in the middle estuary, spreading upstream and downstream as the summer progresses, and that hypoxic volume days (HVD) have been increasing (0.11 per year, p = 0.03) over the record despite reduced watershed nitrogen loads and stable phosphorus loads. River flow and temperature have been increasing and are major drivers of increased HVD, with river flow explaining 40% of the interannual variation in HVD (temperature has increased 0.03 and 0.06 °C per year in summer and fall, respectively). Apparent oxygen utilization (AOU) is increasing in bottom waters in the fall, consistent with increasing trends of both water temperature and stratification strength. HVD was negatively related (r2 = 0.34, slope = −0.59*HVD) to the biomass of benthic invertebrates in the middle region of the estuary, suggesting that benthic forage for higher trophic levels will be limited by sustained hypoxia. These results indicate that current and future climate variability plays an important role in regulating oxygen depletion in the Patuxent River estuary, which reinforces the need to factor climate change into strategies for the restoration and management of estuaries. [ABSTRACT FROM AUTHOR]

Fresh submarine groundwater discharge (FSGD) can deliver significant fluxes of water and solutes from land to sea. In the Arctic, which accounts for ∼34% of coastlines globally, direct observations and knowledge of FSGD are scarce. Through integration of observations and process‐based models, we found that regardless of ice‐bonded permafrost depth at the shore, summer SGD flow dynamics along portions of the Beaufort Sea coast of Alaska are similar to those in lower latitudes. Calculated summer FSGD fluxes in the Arctic are generally higher relative to low latitudes. The FSGD organic carbon and nitrogen fluxes are likely larger than summer riverine input. The FSGD also has very high CO2 making it a potentially significant source of inorganic carbon. Thus, the biogeochemistry of Arctic coastal waters is potentially influenced by groundwater inputs during summer. These water and solute fluxes will likely increase as coastal permafrost across the Arctic thaws. Plain Language Summary: Groundwater flows from land to sea, transporting freshwater, organic matter, nutrients, and other solutes that impact coastal ecosystems. However, along coasts of the rapidly‐warming Arctic, there is limited knowledge regarding how much fresh groundwater enters the ocean. Using field observations and numerical models, we show that groundwater flowing from tundra in northern coastal Alaska carries large amounts of freshwater, organic matter, and carbon dioxide to the Arctic lagoons during summer. These inputs are likely significant to coastal biogeochemical cycling and marine food webs. Groundwater discharge and the associated transport of dissolved materials are expected to increase due to longer periods of above‐zero temperatures that thaw frozen soils below the tundra. Key Points: Summer fresh submarine groundwater discharge (FSGD) to the Alaskan Beaufort Sea is only 3%–7% of rivers but carries as much organic matterSummer FSGD delivers a median of 116 (interquartile range: 35–405) and 6 (2–21) kg/d per km dissolved organic carbon and nitrogenFresh groundwater at the beach of Simpson Lagoon (SL) has a median PCO2 of ∼33,000 μatm implying substantial CO2 flux [ABSTRACT FROM AUTHOR]

The ocean supplies large quantities of thermal energy to tidewater glaciers, but the mechanisms behind the heat delivery are not fully understood. To examine heat flux dynamics in glacial fjords, we run an 8‐year realistic numerical simulation of Milne Fiord, validated with observations. We leverage the duration and spatial resolution of the simulation to calculate ice melt, offshore density variations, average fjord temperature, and heat fluxes at different locations along‐fjord. Correlations between these quantities reveal that heat fluxes near the grounding line (<5 km) are linked to buoyancy‐driven circulation while offshore forcing is linked to heat fluxes along the remainder of the fjord. Comparison to a simulation with constant offshore boundary conditions reveals that offshore forcing enhances the exchange between the coastal shelf and the fjord, increasing glacier melt rates by 18%. Including offshore forcing into numerical and box models of glacial fjords is essential for accurate melting predictions. Plain Language Summary: In high latitude coastal regions, glaciers can flow into the ocean. These glaciers, called tidewater glaciers, are therefore exposed to the warming ocean which can drive submarine melting and glacier retreat. Since most tidewater glaciers terminate in fjords, understanding the mechanisms that regulate the exchange of heat between the ice and the ocean in glacial fjords is important for accurate estimates of glacier melt rates and retreat. In this study we recreate Milne Fiord in a numerical model to study these mechanisms. First, we find that the heat transport near the glacier is regulated by the freshwater released at the glacier face. Second, we find that further than 5 km from the glacier, offshore density variations are responsible for the heat exchange, with a net effect of increasing the exchange between the fjord and the open ocean, which enhances the melting of the tidewater glacier. Key Points: 8‐year high‐resolution realistic numerical model of Milne Fiord, validated with observationsHeat fluxes are linked to offshore density variations, except within 5 km of the grounding line where they are linked to buoyancy forcingOffshore density variations act to enhance coastal shelf‐fjord exchange, increasing tidewater glacier melt rates by 18% [ABSTRACT FROM AUTHOR]

Severe convection, responsible for hazards such as tornadoes, flash floods, and hail, is usually preceded by abundant convective available potential energy (CAPE). In this work, we use a Lagrangian approach to study the buildup of anomalously large values of CAPE from 2012 to 2013 in various regions. Nearly all extreme values of CAPE arise from surface fluxes underneath a layer of convective inhibition (the CIN layer) over several diurnal cycles, but the origin of the CIN layer and the diurnal cycle of surface fluxes differ around the world. In some regions, such as North America and Europe, the air above the boundary layer must be much warmer than usual to form this CIN layer, whereas in other regions, especially the Middle East and central Africa, a CIN layer is common. Additionally, high CAPE occurrences that are over land (those in the Americas, Europe, Africa, and Southeast Asia) tend to lose their CIN layers before the time of maximum CAPE due to large diurnal cycles of sensible heating, whereas those that occur over coastal waters (in the Middle East, Northern Australia, South Asia, and the Mediterranean) usually retain substantial convective inhibition. Uniquely, CAPE in Southeast Australia often builds up due to cooling aloft rather than to boundary layer warming. These results show that one hoping to understand or predict CAPE patterns must understand a variety of mechanisms acting in different regions. Plain Language Summary: The energy available to power severe storms that cause events such as tornadoes and hailstorms is known as convective available potential energy (CAPE). Therefore, these events are usually preceded by the buildup of anomalously large amounts of CAPE. Here, we study the processes by which CAPE accumulates in various parts of the world. In nearly all regions, warming and moistening of near‐surface air provides this energy, demonstrating the importance of surface fluxes. However, other characteristics of CAPE accumulation differ around the world, meaning that one hoping to understand how large CAPE values arise must consider specific regions. This work is a step toward understanding where and how frequently severe convective events occur, and if these events will change in the future. Key Points: Worldwide, accumulation of CAPE is usually caused by surface enthalpy flux mostly through latent heatingBuildup of CAPE requires a layer of convective inhibition, which in some regions is rare and in others is commonThe CIN accompanying CAPE maxima over water often never decays due to a lack of daytime surface sensible heating [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are widespread in oceans worldwide, posing a significant threat to aquatic ecosystems. The abundance of these particles in water is related to population density and urban development, functioning as a sink for MPs. However, the pollution levels due to the accumulation of MPs in the estuarine in Amazonian mangrove areas remain unknown. Here, we show that population density and fishing activities influence the distribution of MP pollution in these waters. We found the highest abundance of MPs in the inner (1.03 items/m3) and outer (0.82 items/m3) portions of the estuary, corresponding to the areas with the highest population density and fishing activity, respectively. The main morphological characteristics of MPs are fibers (89.8%), blue color (55.2%), and size of 1000–2000 μm (31.7%). The risk analysis showed a low level of danger, suggesting that the potential impact on the ecosystem is still small. Our results demonstrate that the presence of human populations and their fishing activities significantly influence the accumulation of MPs in the estuarine waters on the Amazon coast. Based on our findings, more sophisticated analysis using MPs' spatial distribution models can be associated with hydrodynamic processes, aiming to define pollution hotspots and support the mitigation of their emerging negative effects. In addition, monitoring and generating valuable information are the main targets for developing comprehensive strategies to preserve biodiversity and sustainability in the Amazon coastal zone. [ABSTRACT FROM AUTHOR]

Typhoon waves possess significant destructive potential, and their numerical simulation relies on accurate sea surface wind fields. An evaluation of different combinations of the radial air pressure distribution coefficient B and the radius of maximum wind speed (R max) in the Holland wind field (HWF) model was conducted to determine the optimal configuration. The HWF and the ERA5 wind field (EWF) were used as input wind fields to drive the typhoon wave model for China's coastal waters. Validation results indicated that neither wind field accurately reflected real conditions; therefore, a hybrid wind field (HBWF) was created by combining HWF and EWF using weighting coefficients that vary with the radius of wind speed to enhance accuracy. Simulation results showed that the HBWF improved the accuracy of significant wave heights (SWHs), with a mean relative error of 25.29%, compared to 32.48% for HWF and 27.94% for EWF. Additionally, HBWF also demonstrated the best performance in terms of root mean square error (RMSE) and consistency index. Overall, the HBWF enhances the simulation accuracy of typhoon waves in China's coastal waters. [ABSTRACT FROM AUTHOR]

Freshwater inputs originating from terrestrial streams and gullies that discharge into quiescent, semi-enclosed coastal regions (such as estuaries, tidal inlets or lagoons), typically provide point sources of nutrients (e.g. nitrates, phosphates) and/or contaminants (e.g. pesticides, pathogens) that may have a deleterious impact on water quality. Many of these sheltered coastal regions also increasingly support aquaculture operations (e.g. finfish, shellfish, or seaweed farms), which can therefore be directly impacted by nutrient and contaminant inputs. Dynamically, these terrestrial freshwater inflows behave as surface buoyant jets or plumes within the coastal saline or brackish receiving waters, due to the salinity-induced density gradients. As such, the presence of infrastructure associated with aquaculture operations in sheltered coastal waters can provide obstruction to the propagation characteristics and residence times for these surface freshwater flows. Consequently, an improved physical understanding of the flow-structure interaction is clearly crucial to assessing the potential contamination risk of aquaculture products. The aim of the current study is therefore to explore, through scaled laboratory experiments within a channel-basin facility, the impact of physical obstruction induced by a vertical grid structure on the flow evolution of a 2D – 3D expanding, surface buoyant jet. Two grid obstructions with different solidity ratios are tested, along with surface gravity currents of different density excesses and freshwater inflows to infer the influence of different parametric conditions on the propagation, blockage and mixing characteristics of the surface current in the vicinity of the grid obstruction. Measurements of the velocity structure and thickness of the expanding surface plume are obtained by ultrasonic velocity profilers, while the density excess in the evolving plume is measured by micro-conductivity probes. Dye visualization results also show that, in the presence of the grid obstruction, the generation of shear-induced billows at the lower interface of the expanding surface current is largely blocked and a local deepening of the fresh-salt water interface in the immediate vicinity of the grid obstruction is observed. In this sense, the obstruction imposed by aquaculture infrastructure in coastal domains can have a considerable influence of the local turbulent mixing and vertical transfer of substances (e.g. nutrients and contaminants), but is likely to have relatively minimal impact in the final dispersion of the surface plume. [ABSTRACT FROM AUTHOR]

Phosphate treatment at the Kpémé plant uses hydrocycloning with seawater, which produces phosphate sludge wastes discharged into the sea without any prior treatment. This waste is highly enriched in trace elements and is the source of water and coastal sediment pollution. The objective of this study is to highlight the pollutant load of the different phases of phosphate mud mining waste and their possible impact on the marine environment of the Togolese coast and certain neighboring countries, depending on their density. The methodology consists of a classification using a mini hydrocyclone Galaxi–Tower and a geochemical characterization of the phases of these sludgy mining wastes. A study of the bulk density of the phases obtained shows that the apatite-rich phase is denser than the clay-rich phase. Clay-rich phases will be transported over longer distances than apatite-rich phases, in accordance with the sea environment conditions prevailing on the coast. The clay-rich phase has a higher degree of acidity and redox potential than the apatite-rich phase. These phosphate sludgy wastes and the various phases are enriched in Cr, Cd, Cu, Co, Zn, Ni and Hg compared with the earth's crust. On the other hand, the light phase is more enriched in trace elements than the apatite-rich phase. The light phase has a higher apparent partition coefficient for all elements than the apatite-rich phase, except for Cd and Zn. In the dissolved solutions of clay-rich phases, Fe, Zn and Hg contents are higher than in apatite-rich phases. In contrast, Al, Cr, Cd, Cu and Ni contents are higher in apatite-rich phases than in clay-rich phases. Article Highlights: Separation of phosphate sludge waste phases according to density in seawater using a mini hydrocyclone Galaxi-Tower Assessment of trace element load of the particles constituting this sludgy phosphate waste and each separated phase Demonstration of trace element level in dissolved solution of phases during their possible transit in marine environment [ABSTRACT FROM AUTHOR]

Background: Subtropical coral reefs are comparatively understudied compared to tropical coral reef ecosystems, yet also host a diverse and abundant array of marine life and provide substantial socio-economic benefits to communities. Research into the impacts of ocean warming on subtropical coral reefs has increased over the past two decades due to increase frequency and intensity of bleaching and degradation of these ecosystems. Understanding the extent of research effort and type of evidence assessing the response of subtropical corals and reefs to ocean warming provides valuable insight into global patterns in research efforts allowing critical knowledge gaps to be identified. A comprehensive understanding the impact of ocean warming on these systems will underpin our ability to predict and respond to future changes on subtropical coral reefs. Here, a systematic-map approach is used to identify recent research effort, from 2010 to 2023, and highlight patterns in the type, scale, and location of research conducted and as well as identify the availability of data and evidence reported. Methods: Primary literature was identified by searching Scopus and Science Citation Index Expanded through Web of Science Core Collection databases. The methodologies provided in a previously published systematic map protocol were applied, and 90 primary research publications were subsequently identified. Data extraction from the identified literature included bibliometric data, discipline and type of research, type of data reported and how it was recorded, and data availability. Findings: The identified literature consisted primarily of experimental (49%) and observational (39%) studies. The majority of the primary literature investigated corals in the ecoregions of Southern China (13%), Western Mediterranean (10%) and across a total of seven ecoregions grouped within Oceania (29%). Stressors reported in the literature as drivers of ocean warming reflect the standardisation of methods applied in reporting of events within the literature. Standardised metrics related to degree heating weeks (DHW) and marine heatwaves (MHW) have been reported when assessing the occurrence and severity of drivers, and are increasing in recent years, particularly in Australia. Finally, the need for increased research effort across much of the subtropics is evident, particularly for understudied regions such as the Western Indian Ocean where there are far fewer studies than other similar subtropical coral reef ecosystems. Conclusions: Climatic change, increasing ocean temperatures, and the impacts to subtropical and temperate coral reefs are of increasing concern to policy makers and researchers alike. This systematic map provides a broad overview of research topics and effort around the globe since 2010 and identifies areas where more research effort is urgently needed. Our study has identified major research clusters in Asia, Australia, the Mediterranean, and North America and gaps of research in regions such as the East Indian Oceans. Of the research conducted to date approximately one third reports on evidence related to marine protected areas and the vast majority of evidence is from close/territorial sea locations, providing important knowledge base for management of these areas. Of the 17 studies reporting on specific extreme events (rather than experimental studies which is the majority of evidence identified here) 13 have been published since 2019, with the majority reporting on events occurring in 2019/20 indicating a trend of increasing evidence in recent years (a total of 7 studies from 2010 to 2013, compared to over 10 studies published annually since 2019 up to mid-2023). [ABSTRACT FROM AUTHOR]

A hyperspectral reflectance database was acquired for the Baltic Sea submerged aquatic vegetation (SAV) and bare substrates by using Ramses (TriOS) radiometers capturing the spectral data within the visible (VIS) and near infrared (NIR) spectral range. The target samples included the most dominant and characteristic SAV species in the Baltic Sea, as well as several bare substrate types and beach cast communities. Target samples were measured within the 350 to 900 nm wavelength range under sun light conditions without the water column influence i.e. samples were taken out of the water. Such library is expected to provide insight into the spectral properties of various SAV species and substrates occurring in the coastal waters of the temperate geographic regions facilitating development of algorithms for differentiation and mapping various SAV communities. Additionally, measured reflectance spectra can be used as spectral endmembers in physical models and classification algorithms for coastal vegetation mapping and quantification. Data are openly available at PANGAE online repository https://doi.pangaea.de/10.1594/PANGAEA.971518 (Vahtmäe et al., 2024). [ABSTRACT FROM AUTHOR]

Prokaryotic communities play a dominant role in driving biogeochemical cycling in marine ecosystems. How short‐term temperature increase impacts prokaryotes in subtropical coastal waters is still largely unknown. Here, 14 field experiments were conducted to investigate the response of prokaryotes in subtropical coastal waters to temperature increases of 3°C and 6°C, encompassing a range of ambient temperatures from 17°C to 31°C. We found that responses of prokaryotic growth, grazing pressure, community, and transcriptomes to increased temperatures were largely affected by ambient temperatures. Increased temperatures enhanced the growth rate and grazing pressure of heterotrophic prokaryotes when ambient temperatures were below 26–28°C. The increased temperatures had greater negative effects on the grazing rate compared to the growth rate; therefore, the abundance of heterotrophic prokaryotes generally increased after temperature increase across all temperature regimes. Metatranscriptomics analysis showed that at an ambient temperature of 30°C, genes involved in the adenosine triphosphate synthase were significantly downregulated by the increased temperature. This could be a major factor contributing to the decreased prokaryotic growth rate. In comparison, autotrophic prokaryotes (Synechococcus) exhibited better performance in response to elevated temperatures, thriving up to 35°C, beyond which their growth rate experienced a dramatic decline. When exposing to extremely high temperatures, genes involved in photosynthesis significantly decreased. These findings highlight the differential ecological impacts of temperature increase on prokaryotic communities, varying across different ambient temperatures and taxa in subtropical coastal waters. [ABSTRACT FROM AUTHOR]

This article investigates the simultaneously developing pure turbulent mixed convective regime and compares the hydrodynamic and thermal features of both buoyancy-assisted and opposed flows in a vertical tube. Two-dimensional (2D) axisymmetric steady-state simulations were carried out for Reynolds number, 5,000–20,000; Grashof number, 1.25 × 106 to 108; and Richardson number, 0.05–0.25 for a length-to-diameter ratio of 150 with uniform heat flux boundary condition and water as the working fluid. Three Reynolds-averaged-Navier–Stokes turbulence models were compared and then the most suitable model was used for the simulations. At a given Richardson number, the friction factor and Nusselt number are lower in the case of buoyancy-assisting flow compared to buoyancy-opposing flows. Similar friction factors and heat transfer trends were obtained at a given Grashof number. At varying Grashof numbers and Richardson numbers keeping the Reynolds number constant, no discernible variations were observed for both flows. The entry length was also examined, and it has been found that the hydrodynamic and thermal entry lengths are restricted to a length-to-diameter ratio of 25 and 20 for assisting and opposing flows, respectively. Correlations were developed for both flows to quantify the friction factor, Colburn factor, and Nusselt number in terms of the Reynolds number. [ABSTRACT FROM AUTHOR]

Distribution patterns of benthic dinoflagellates that are widely observed in tropical and temperate waters and have toxic potential are changing in response to ocean climate change. Although there have been no outbreaks associated with the genus Coolia affecting humans, it is crucial to understand their changing distribution and clearly identify the species in the study area to prepare for potential toxic events. In this study, five strains of Coolia species were isolated from macroalgae samples collected from Jeju Island and the eastern coastal waters of Korea. Through morphological and molecular analysis of these isolates, one strain was identified as Coolia palmyrensis , marking the first report of this species in Korea, and four strains as C. malayensis. One of the C. malayensis strains was isolated in Pohang on the eastern coast of Korea, where it had not been previously reported. From 2021 to 2023, monitoring of Jeju Island using a quantitative polymerase chain reaction (PCR) assay revealed that C. palmyrensis cells occurred mostly in autumn, with a maximum density of 242 cells g-1, and overwintering populations were observed in 2023. However, C. malayensis cells were not observed in this area. Additionally, C. malayensis was observed in Pohang and Ulsan, located further north than Jeju Island with maximum cell densities of 537 and 201 cells g-1, respectively. These data and our decade of monitoring experience confirmed the introduction and establishment of C. palmyrensis and habitat shift of C. malayensis in Korean coastal waters. This study provides advances for understanding of the relationships between climate-driven alterations and biogeographic distribution of these species. [ABSTRACT FROM AUTHOR]

Little is known about the role of remote and sparsely populated Arctic coastal zones in the microplastic cycle. Distribution of microplastics was studied in the Svalbard fjords in June – July 2022 with the main goal of assessing rivers' role in the fate of microplastic in Arctic coastal waters. Surface microplastics (0 – 20 cm depth, 500 – 5000 µm size) were sampled with a neuston net in triplicate per study site in parallel with sampling of subsurface microplastics with a pump system (1.5 m depth, 100 – 5000 µm size). The central part of Isfjorden and its several branches covering populated and unpopulated fjords were studied; the sampling was conducted during an intense riverine discharge in all studied sites. Maximum abundance of surface microplastics (71,400 items/km2 or 0.19 iterms/m3, 0.19 mg/m3) was found along the river plume border in the middle of populated Adventfjorden indicating importance of both local sources and surface hydrodynamics in the formation of microplastics accumulation hotspots. All other unpopulated fjords were free of the floating on the sea surface microplastics as river discharge prevented transport of microplastics inside the fjords. The highest concentration of subsurface microplastics was found in the central part of Isfjorden and the lowest – in river plume waters, which also indicates the removal of microplastics from the inner part of fjords during an intensive river discharge. Our results may suggest that Arctic rivers flowing through unpopulated areas bring clean water and thereby reduce level of microplastic pollution in the coastal waters. In contrast to the rest of the world's ocean, rivers are not the main source of microplastic pollution in the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Coastal waters are currently receiving anthropogenic impacts from the mainland that caused the natural conditions to change to higher nutrient content. This study was conducted to examine the spatial and temporal dynamics of trophic status and how zone location and rainfall category affect the distribution of trophic status. Water quality data were collected for 6 months with different rainfall intensities at 16 observation stations. Trophic status was determined using the TRIX index which combines biological, physical, and chemical water variables. Rainfall had no significant effect on the TRIX index with a p-value of 0.223 (> 0.05), but the distance from the land had a significant effect with a p-value of (< 2e-16). In coastal waters in the 1st zone, the average TRIX value was 5.93 ± 0.23 (high trophic status/eutrophy that tends to be very high/hypertrophy), in the 2nd zone was 5.49 ± 0.21 (high trophic status/moderate trophy), in the 3rd zone was 5.23 ± 0.25 (high trophic status/eutrophy that is slightly low) and in the 4th zone was 4.47 ± 0.47 (moderate trophic status/mesotrophy). Based on PCA analysis and correlation for water quality data, Index TRIX had a strong positive correlation with phosphate (0.92), TSS (0.91), chlorophyll-a (0.089), temperature (0.88), nitrate (0.83), and moderate positive correlation with turbidity (0.68). In addition, the TRIX index had a strong negative correlation with salinity (-0.85), a moderate negative correlation with TDS (-0.77) and DO (-0.62), and a weak correlation with pH (-0.09). There has been eutrophication in coastal areas, especially in the near shoreline zone and tends to decrease at more distant locations. It is necessary to manage anthropogenic waste based on quality standards to ensure that coastal waters are healthy and support sustainable ecosystems. [ABSTRACT FROM AUTHOR]

The editorial discusses the significant transformations in coastal and estuarine ecological environments due to hydrodynamic variability. It emphasizes the importance of understanding hydrodynamic processes through advanced methodologies like remote sensing and numerical modeling to unravel ecological changes. The editorial presents six papers that highlight research on ecological environment changes in response to hydrodynamic variability, covering topics such as dissolved oxygen patterns, boundary current transitions, hypoxia/anoxia evolution, geochemical behavior in sediments, remote sensing estimation of nitrogen concentration, and coastal water darkening. These studies underscore the need for advanced technologies and long-term data to manage and protect vulnerable coastal ecosystems in the face of climate change. [Extracted from the article]

The impact of freshwater sources like surface river runoff and submarine groundwater discharge (SGD) on coastal waters is currently in focus of intense debate and investigation. One of the ongoing challenges in SGD research is the characterization and quantification of the freshwater endmember contributions to the subsurface mixing zone and their influences on element balance and biogeochemical transformations. Long-term investigations of the sediment porewater composition provide characterization and understanding of the physical, hydrological and biogeochemical processes controlling the substance exchanges. In this study, we focus on the hydrochemical and stable isotope (δ2H, δ18O) compositions of sediment porewaters along the coastline of a southern Baltic Sea peatland. Coastal surface water and groundwater dynamics were monitored at two coastal sites using 5-m-long stationary lances over a 5-year period.The vertical compositional gradients were used to extrapolate to zero-salinity (ZS) components applying a binary mixing model on the salinity and water isotope composition. The results characterize a subterranean estuary (STE) with three potential mixing endmembers: two fresh groundwaters and the brackish Baltic Sea. Tritium–helium (3H–3He) porewater dating gave ages of more than about 20 years for the freshwater components. The ZS components were compared with other SGD sites along the southern Baltic Sea and North Sea and highlight the importance of local SGD studies for a proper groundwater endmember characterization as basis to understand hydrological and biogeochemical developments at the land–ocean continuum in times of current climate change. [ABSTRACT FROM AUTHOR]

\nIMPACT STATEMENTPrevious studies have achieved success in obtaining cultured juveniles of the sea urchin Salmacis sphaeroides, but few have reported their reproduction potential and development rates. This comprehensive study examined the spawning potential of broodstock and described embryonic, larval and juvenile development. The broodstock consisted of wild-caught specimens from Singapore’s coastal waters that were regularly provided a mixed animal-plant diet comprising 3 g prawn and 3 g corn. Gametes were obtained using 0.5 M of potassium chloride (KCl) injection into the coelomic cavity. Fertilization rates of the 32 spawning attempts varied from 42.9% to 100%. Hatched larvae were subsequently reared with a density of 0.5 larvae ml−1 in 50 µm filtered seawater at 28°C and fed 20,000 cells ml−1 of Tisochrysis lutea once every 2 days. Despite the presence of natural biofilms as settlement cues, the settlement rates in culture were very low and variable (2.08–9.78%). The majority of juvenile S. sphaeroides from F1 and F2 generations was sexually mature at ≥35 mm in test diameter, and the sex ratios were female-biased, ranging from 1:1.14 to 1:8. Findings from this study open up new opportunities for developing tropical sea urchin cultures under controlled rearing systems that can guarantee production. Salmacis sphaeroides metamorphosis was induced using natural biofilms but had poor settlement ratesRecommendation to induce spawning only in adult Salmacis sphaeroides that are at ≤35 mm in test diameter and at least 10 months oldFemale-biased sex ratios of lab-grown F1 and F2 generationsSalmacis sphaeroides metamorphosis was induced using natural biofilms but had poor settlement ratesRecommendation to induce spawning only in adult Salmacis sphaeroides that are at ≤35 mm in test diameter and at least 10 months oldFemale-biased sex ratios of lab-grown F1 and F2 generations [ABSTRACT FROM AUTHOR]

Background: Aquaculture and salmon farming can cause environmental problems due to the pollution of the surrounding waters with nutrients, solid wastes and chemicals, such as antibiotics, which are used for disease control in the aquaculture facilities. Increasing antibiotic resistance in human-impacted environments, such as coastal waters with aquaculture activity, is linked to the widespread use of antibiotics, even at sub-lethal concentrations. In Chile, the world's second largest producer of salmon, aquaculture is considered the primary source of antibiotics residues in the coastal waters of northern Patagonia. Here, we evaluated whether the structure and diversity of marine bacterial community, the richness of antibiotic resistance bacteria and the frequency of antibiotic resistance genes increase in communities from the surface seawater of an area with salmon farming activities, in comparison with communities from an area without major anthropogenic disturbance. Results: The taxonomic structure of bacterial community was significantly different between areas with and without aquaculture production. Growth of the culturable fraction under controlled laboratory conditions showed that, in comparison with the undisturbed area, the bacterial community from salmon farms displayed a higher frequency of colonies resistant to the antibiotics used by the salmon industry. A higher adaptation to antibiotics was revealed by a greater proportion of multi-resistant bacteria isolated from the surface seawater of the salmon farming area. Furthermore, metagenomics data revealed a significant higher abundance of antibiotic resistant genes conferring resistance to 11 antibiotic families in the community from salmon farms, indicating that the proportion of bacteria carrying the resistance determinants was overall higher in salmon farms than in the undisturbed site. Conclusions: Our results revealed an association between bacterial communities and antibiotic resistance from surface seawater of a coastal area of Chile. Although the total bacterial community may appear comparable between sites, the cultivation technique allowed to expose a higher prevalence of antibiotic resistant bacteria in the salmon farming area. Moreover, we demonstrated that metagenomics (culture-independent) and phenotypic (culture-dependent) methods are complementary to evaluate the bacterial communities' risk for antibiotic resistance, and that a human—influenced environment (such as salmon farms) can potentiate bacteria to adapt to environmental stresses, such as antibiotics. [ABSTRACT FROM AUTHOR]

Diazotrophic cyanobacteria can fix nitrogen gas (N2) but are usually scarce in nitrogen-limited coastal waters, which poses an apparent ecological paradox. One hypothesis is that high salinities (> 10 g/L NaCl) may inhibit cyanobacterial N2 fixation. However, here we show that N2 fixation in a unicellular coastal cyanobacterium exclusively depends on sodium ions and is inhibited at low NaCl concentrations (< 4 g/L). In the absence of Na+, cells of Cyanothece sp. ATCC 51142 (recently reclassified as Crocosphaera subtropica) upregulate the expression of nifHDK genes and synthesise a higher amount of nitrogenase, but do not fix N2 and do not grow. We find that the loss of N2-fixing ability in the absence of Na+ is due to insufficient ATP supply. Additional experiments suggest that N2 fixation in this organism is driven by sodium energetics and mixed-acid fermentation, rather than proton energetics and aerobic respiration, even though cells were cultured aerobically. Further work is needed to clarify the underlying mechanisms and whether our findings are relevant to other coastal cyanobacteria. High salinities are thought to inhibit nitrogen fixation by cyanobacteria in coastal waters. In contrast, Tang et al. show that nitrogen fixation in a coastal cyanobacterium requires sodium ions and is apparently driven by sodium energetics and mixed-acid fermentation. [ABSTRACT FROM AUTHOR]

Caulerpa is a genus of green macroalgae that lives in tropical and subtropical coastal waters. It is an intriguing organism because, despite having plant-like structures, it is one giant cell – which, next to multiple nuclei, chloroplasts, and mitochondria, also contains endo- and epiphytic bacteria. The role of these bacteria is unknown, but they might impact the growth and development of the host, adaptation to environmental parameters, and, hence, the ecological success of these algae. We hypothesised that increased sulphide concentrations would trigger a significant shift in the microbial community composition associated with C. prolifera rhizoids, favouring sulphide-oxidizing bacteria. To test this hypothesis, we conducted a mesocosm experiment incubating C. prolifera in sediments with different sulphide concentrations and analysed the algal photosynthesis, growth, and microbiome composition. While photosynthesis was not affected, the Caulerpa weight-based growth rate decreased linearly with increasing sulphide concentration. To analyse the microbiome, we extracted DNA and RNA from the fronds, rhizoids, and the accompanying sediments and performed 16S amplicon sequencing. The microbiome of the fronds was unaffected in both the DNA and RNA samples. However, an increase in sulphide concentration coincided with a decrease in the relative abundance of sulphate-reducing bacteria associated with Caulerpa rhizoids, particularly from the family Desulfocapsaceae. In the RNA samples, potential sulphide oxidisers of the rhizoid-associated members of the Beggiatoaceae were detected. Our results suggest that the rhizobiome of Caulerpa plays a significant role in its adaptation to sulphide-rich environments, offering new insights into the complex interactions within marine holobionts. [ABSTRACT FROM AUTHOR]

Southern Ocean phytoplankton form the base of the Antarctic food web, influencing higher trophic levels through biomass and community structure. We examined phytoplankton distribution and abundance in the Indian Sector of the Southern Ocean during austral summer as part a multidisciplinary ecosystem survey: Trends in Euphausiids off Mawson, Predators and Oceanography (TEMPO, 2021). Sampling covered six meridional transects from 55-80°E, and from 62°S or 63°S to the ice edge. To determine phytoplankton groups, CHEMTAX analysis was undertaken on pigments measured using HPLC. Diatoms were the dominant component of phytoplankton communities, explaining 56% of variation in chlorophyll a (Chl a), with haptophytes also being a major component. Prior to sampling the sea ice had retreated in a south-westerly direction, leading to shorter ice-free periods in the west (< 44 days, ≤65°E) compared to east (> 44 days, ≥70°E), inducing a strong seasonal effect. The east was nutrient limited, indicated by low-iron forms of haptophytes, and higher silicate:nitrate drawdown ratios (5.1 east vs 4.3 west), pheophytin a (phaeo) concentrations (30.0 vs 18.4 mg m-2) and phaeo:Chl a ratios (1.06 vs 0.53). Biological influences were evident at northern stations between 75-80°E, where krill "super-swarms" and feeding whales were observed. Here, diatoms were depleted from surface waters likely due to krill grazing, as indicated by high phaeo:Chl a ratios (> 0.75), and continued presence of haptophytes, associated with inefficient filtering or selective grazing by krill. Oceanographic influences included deeper mixed layers reducing diatom biomass, and a bloom to the north of the southern Antarctic Circumpolar Current Front in the western survey area thought to be sinking as waters flowed from west to east. Haptophytes were influenced by the Antarctic Slope Front with high-iron forms prevalent to the south only, showing limited iron transfer from coastal waters. Cryptophytes were associated with meltwater, and greens (chlorophytes + prasinophytes) were prevalent below the mixed layer. The interplay of seasonal, biological and oceanographic influences on phytoplankton populations during TEMPO had parallels with processes observed in the BROKE and BROKE-West voyages conducted 25 and 15 years earlier, respectively. Our research consolidates understanding of the krill ecosystem to ensure sustainable management in East Antarctic waters. [ABSTRACT FROM AUTHOR]

Stationary in situ measurements conducted in close proximity to the shoreline present unique challenges. The shallow depth, automated profiling and accessibility for maintenance, particularly in the context of biofouling, are key considerations. The WInch for Long-term MOnitoring (WILMO), a solution designed to meet these requirements, is therefore presented. The fully automated system keeps the sensitive devices outside of the water until a profiling cycle is initiated, reducing the available settling time for species on the surface of the sensors. The design leverages common hardware and is structured in distinct units. This feature facilitates the interchangeability of individual hardware components and the implementation of a unifying software system capable of simultaneously managing all elements of WILMO. Using wireless broadband communications, WILMO can be fully controlled remotely, allowing for adjustments to the setup and monitoring of system functionality through a special web interface. The data are transmitted to a server with adjustable frequency and a post processing tool prepares them for analysis. The system underwent rigorous testing and demonstrated effective performance in northern Bali, Indonesia, between March and December 2022, gathering physical and biogeochemical time series data. The consistency of the data is validated through comparison with other instruments to ensure data quality. The results obtained are employed to ascertain the suitability of the special flow velocity sensor in this context. WILMO is a demonstrably reliable device, easily manageable and perfectly suited for long-term coastal monitoring. [ABSTRACT FROM AUTHOR]

Coastal waters require monitoring of chlorophyll-a concentration (Chl-a) in a wide range of Chl-a from a few mg/m3 to hundreds of mg/m3, which is of interest to the fisheries industry, evaluation of climate change effects, ecological modeling and detection of Harmful Algal Blooms (HABs). Monitoring can be carried out from the Visible Infrared Imaging Radiometer Suite (VIIRS) and Ocean and Land Colour Instrument (OLCI) Ocean Color (OC) satellite sensors, which are currently on orbit and are expected to be the main operational OC sensors at least for the next decade. A Neural Network (NN) algorithm, which uses VIIRS M3-M5 reflectance bands and an I1 imaging band, was developed to estimate Chl-a in the Chesapeake Bay, for the whole range of Chl-a from clear waters in the Lower Bay to extreme bloom conditions in the Upper Bay and the Potomac River, where Chl-a can be used for bloom detection. The NN algorithm demonstrated a significant improvement in the Chl-a retrieval capabilities in comparison with other algorithms, which utilize only reflectance bands. OLCI NIR/red 709/665 nm bands red edge 2010 algorithm denoted as RE10 was also explored with several atmospheric corrections from EUMETSAT, NOAA and NASA. Good consistency between the two types of algorithms is shown for the bloom conditions and the whole range of waters in the Chesapeake Bay (with RE10 switch to OC4 for lower Chl-a) and these algorithms are recommended for the combined VIIRS-OLCI product for the estimation of Chl-a and bloom monitoring. The algorithms were expanded to the waters in Long Island Sound, demonstrating good performance. [ABSTRACT FROM AUTHOR]

The Agulhas Current is a globally important western boundary current that influences numerous processes (e.g., upwelling, biogeochemical fluxes and distribution of marine taxa) in the southwestern Indian Ocean. The oceanographic processes of the Agulhas Current are well understood, but precisely how they influence coastal ecosystem productivity remains to be elucidated. In the present foundational study, we characterized the bacterial (16S rRNA gene) and phytoplankton (chloroplast 16S rRNA, rbcL, and eukaryotic 18S rRNA genes) community structures of the Agulhas Current system using a metabarcoding approach. All four markers provided consistent data on the bacterial and phytoplankton communities in the Agulhas Current and coastal sites. The study revealed distinct, conserved communities and similar patterns of dominance by taxa adapted to oligotrophic conditions within the Agulhas Current, sampled 2 yr apart. By contrast, there was significant variability in taxonomic diversity and abundance of phytoplankton communities in the adjacent coastal waters that could be linked to localized upwelling. While the Agulhas Current bacterial and phytoplankton communities were diverse and represented many functional groups, the coastal sites were more diatom‐dominated and included genera typically associated with upwelling, for example, Thalassiosira spp. Based on their relative abundance profiles, phytoplankton communities were more responsive to environmental variability than bacteria and may therefore prove more useful in linking ecosystem dynamics to environmental variability in marine systems. [ABSTRACT FROM AUTHOR]

The expansion of transient and permanent coastal benthic anoxia is one of the most severe problems for the coastal ocean globally. We report frequent, hidden hypoxia in the bottom 5 cm of the water column of a coastal site in the central Baltic Sea by continuous high‐resolution profiling of oxygen (O2) directly above the sediment surface. This hypoxia stood in stark contrast to 30‐yr O2 monitoring records at this site that suggest apparent continuous well‐oxygenated conditions. In situ measurements showed highly dynamic conditions in the bottom 30 cm recording frequent gradual and abrupt changes between normoxic (> 63 μmol L−1) and hypoxic (< 63 μmol L−1) conditions that would remain undetectable by conventional bottom water O2 monitoring. The temporal variability of these "hidden" hypoxia is tied to the dynamic current field and to changes in O2 consumption following resuspension events. Our observations suggest that transient benthic hypoxia is much more common than routine monitoring data indicate. [ABSTRACT FROM AUTHOR]

Environmental conditions have a significant influence on the physiological processes that regulate the reproduction of fish. However, there is less information on this subject for chondrichthyans, and particularly for males. This study describes the spermatogenic cycle of the narrownose smooth hound shark Mustelus schmitti related to sex steroid plasma levels and the potential influences of photoperiod and temperature as reproductive cues. A total of 70 males were caught bi-monthly for over a year in the coastal waters of Argentina. Testicular samples were taken for histological characterization and blood samples were taken for the measurement of testosterone (T) and progesterone (P4) plasma levels from each male. Bottom temperature was recorded at each sampling point and the daily photoperiod was estimated from Julian Day Calendar. Histological assessment revealed that the complete cycle of spermatogenesis in M. schmitti lasts just over a year, with the onset of the new spermatogenic cycle (spermatocyte formation) overlapping with the end (spermiation and filling of the seminiferous ducts) of the previous cycle. This particular phase was associated with the peak in T plasma levels, which was found to be significantly explained by the increase in photoperiod in spring. The rise in temperature above 15–16 °C at the end of spring was significantly associated with a reduction in T plasma levels. Additionally, an elevation in P4 plasma levels was observed after the photoperiod increase phase. Males would be ready to mate from mid-spring, following female parturition and just before ovulation/pregnancy. [ABSTRACT FROM AUTHOR]

In this study, an acoustic Doppler current profiler (ADCP) operating at 600 kHz was installed on an ocean data buoy in the Qigu waters, Taiwan, to gather real-time sound echo intensity data. These data were then correlated with turbidity measurements obtained by a turbidimeter mounted on the buoy's mooring line at a water depth of 13 m. The data buoy operated from 6 June to 16 August 2017. During this period, turbidity measurements were recorded from 6 to 21 June 2017. This study established a calibration between the sound echo intensity measured by the ADCP and the turbidity measured using the turbidimeter; a strong linear correlation was discovered between these two variables. This correlation enabled the conversion of echo intensity data into a continuous time series of turbidity measurements, facilitating real-time and long-term monitoring of coastal water turbidity through the deployment of a buoy equipped with an ADCP. The relationships between turbidity and environmental factors such as rainfall, tides, current speeds, and wave activity over an extended period were then investigated. The results revealed that stronger tides and currents in the Qigu waters often lead to higher turbidity, suggesting that these two factors are the primary driving forces for sediment transport in the Qigu waters. Additionally, sampling of water in the Qigu area revealed sediment particles of size ranging from 2 to 120 μm. [ABSTRACT FROM AUTHOR]

Coastal environments, which are crucial for economic and strategic reasons, heavily rely on accurate bathymetry for safe navigation and resource monitoring. Recent advancements in through-water photogrammetry have shown promise in mapping shallow waters efficiently. However, robust uncertainty modeling methods for these techniques, especially in challenging coastal environments, are lacking. This study introduces a novel likelihood-based approach for through-water photogrammetry, focusing on uncertainties associated with camera pose—a key factor affecting depth mapping accuracy. Our methodology incorporates probabilistic modeling and stereo-photogrammetric triangulation to provide realistic estimates of uncertainty in Water Column Depth (WCD) and Water–Air Interface (WAI) height. Using simulated scenarios for both drone and airborne surveys, we demonstrate that viewing geometry and camera pose quality significantly influence resulting uncertainties, often overshadowing the impact of depth itself. Our results reveal the superior performance of the likelihood ratio statistic in scenarios involving high attitude noise, high flight altitude, and complex viewing geometries. Notably, drone-based applications show particular promise, achieving decimeter-level WCD precision and WAI height estimations comparable to high-quality GNSS measurements when using large samples. These findings highlight the potential of drone-based surveys in producing more accurate bathymetric charts for shallow coastal waters. This research contributes to the refinement of uncertainty quantification in bathymetric charting and sets a foundation for future advancements in through-water surveying methodologies. [ABSTRACT FROM AUTHOR]

Atmospheric correction, the removal of the atmospheric signal from a satellite image, still poses a challenge over optically complex coastal water. Here, we present the first atmospheric correction validation study performed in optically complex Norwegian fjords. We compare in situ reflectance measurements and chlorophyll-a concentrations from Western Norwegian fjords with atmospherically corrected Sentinel-3 Ocean and Land Colour Instrument observations and chlorophyll-a retrievals. Measurements were taken in Hardangerfjord, Bjørnafjord and Møkstrafjord during a bright green coccolithophore bloom in May 2022, and during a period of no apparent discoloration in April 2023. Coccolithophore blooms generally peak in the blue region (490 nm), but spectra measured in this bloom peaked in the green region (559 nm), possibly due to absorption by colored dissolved organic matter (aCDOM(440) = 0.18 ± 0.01 m−1) or due to high cell counts (up to 15 million cells/L). We tested a wide range of atmospheric correction algorithms, including ACOLITE, BAC, C2RCC, iCOR, L2gen, POLYMER and the SNAP Rayleigh correction. Surprisingly, atmospheric correction algorithms generally performed better during the bloom (average MAE = 1.25) rather than in the less scattering water in the following year (average MAE = 4.67), possibly because the high water-leaving radiances due to the high backscattering by coccolithophores outweighed the adjacency effect. However, atmospheric correction algorithms consistently underestimated water-leaving reflectance in the bloom. In non-bloom matchups, most atmospheric correction algorithms overestimated the water-leaving reflectance. POLYMER appears unsuitable for use over coccolithophore blooms but performed well in non-bloom matchups. Neither BAC, used in the official Level-2 OLCI products, nor C2RCC performed well in the bloom. Nine chlorophyll-a retrieval algorithms, including two algorithms based on neural nets, four based on red and near-infrared bands and three maximum band-ratio algorithms, were also tested. Most chlorophyll-a retrieval algorithms did not perform well in either year, although several did perform within the 70% accuracy threshold for case-2 waters. A red-edge algorithm performed best in the coccolithophore blooms, while a maximum band-ratio algorithm performed best in the following year. [ABSTRACT FROM AUTHOR]

Sentinel-2/MSI and Landsat-8/OLI sensors enable the mapping of ocean color-related bio-optical parameters of surface coastal and inland waters. While many algorithms have been developed to estimate the Chlorophyll-a concentration, Chl-a, and the suspended particulate matter, SPM, from OLI and MSI data, the absorption by colored dissolved organic matter, acdom, a key parameter to monitor the concentration of dissolved organic matter, has received less attention. Herein we present an inverse model (hereafter referred to as AquaCDOM) for estimating acdom at the wavelength 412 nm (acdom (412)), within the surface layer of coastal waters, from measurements of ocean remote sensing reflectance, Rrs (λ), for these two high spatial resolution (around 20 m) sensors. Combined with a water class-based approach, several empirical algorithms were tested on a mixed dataset of synthetic and in situ data collected from global coastal waters. The selection of the final algorithms was performed with an independent validation dataset, using in situ, synthetic, and satellite Rrs (λ) measurements, but also by testing their respective sensitivity to typical noise introduced by atmospheric correction algorithms. It was found that the proposed algorithms could estimate acdom (412) with a median absolute percentage difference of ~30% and a median bias of 0.002 m−1 from the in situ and synthetic datasets. While similar performances have been shown with two other algorithms based on different methodological developments, we have shown that AquaCDOM is much less sensitive to atmospheric correction uncertainties, mainly due to the use of band ratios in its formulation. After the application of the top-of-atmosphere gains and of the same atmospheric correction algorithm, excellent agreement has been found between the OLI- and MSI-derived acdom (412) values for various coastal areas, enabling the application of these algorithms for time series analysis. An example application of our algorithms for the time series analysis of acdom (412) is provided for a coastal transect in the south of Vietnam. [ABSTRACT FROM AUTHOR]

Extracting water information from remote-sensing images is of great research significance for applications such as water resource protection and flood monitoring. Current water extraction methods aggregated richer multi-level features to enhance the output results. In fact, there is a difference in the requirements for the water body and the water boundary. Indiscriminate multi-feature fusion can lead to perturbation and competition of information between these two types of features during the optimization. Consequently, models cannot accurately locate the internal vacancies within the water body with the external boundary. Therefore, this paper proposes a water feature extraction network with spatial partitioning and feature decoupling. To ensure that the water features are extracted with deep semantic features and stable spatial information before decoupling, we first design a chunked multi-scale feature aggregation module (CMFAM) to construct a context path for obtaining deep semantic information. Then, an information interaction module (IIM) is designed to exchange information between two spatial paths with two fixed resolution intervals and the two paths through. During decoding, a feature decoupling module (FDM) is developed to utilize internal flow prediction to acquire the main body features, and erasing techniques are employed to obtain boundary features. Therefore, the deep features of the water body and the detailed boundary information are supplemented, strengthening the decoupled body and boundary features. Furthermore, the integrated expansion recoupling module (IERM) module is designed for the recoupling stage. The IERM expands the water body and boundary features using expansion and adaptively compensates the transition region between the water body and boundary through information guidance. Finally, multi-level constraints are combined to realize the supervision of the decoupled features. Thus, the water body and boundaries can be extracted more accurately. A comparative validation analysis is conducted on the public datasets, including the gaofen image dataset (GID) and the gaofen2020 challenge dataset (GF2020). By comparing with seven SOTAs, the results show that the proposed method achieves the best results, with IOUs of 91.22 and 78.93, especially in the localization of water bodies and boundaries. By applying the proposed method in different scenarios, the results show the stable capability of the proposed method for extracting water with various shapes and areas. [ABSTRACT FROM AUTHOR]

The monitoring of coastal waters using satellite data, from sensors such as Sentinel-3 OLCI, has become a vital tool in the management of these water environments, especially when it comes to improving our understanding of the effects of climate change on these regions. In this study, the latest Level-2 water products derived from different OLCI Sentinel-3 processors were validated against a comprehensive in situ dataset from the NW Baltic Sea proper region through a matchup analysis. The products validated were those of the regionally adapted Case-2 Regional Coast Colour (C2RCC) OLCI processor (v1.0 and v2.1), as well as the latest standard Level-2 OLCI Case-2 (neural network) products from Sentinel-3's processing baseline, listed as follows: Baseline Collection 003 (BC003), including "CHL_NN", "TSM_NN", and "ADG443_NN". These products have not yet been validated to such an extent in the region. Furthermore, the effect of the current EUMETSAT system vicarious calibration (SVC) on the Level-2 water products was also validated. The results showed that the system vicarious calibration (SVC) reduces the reliability of the Level-2 OLCI products. For example, the application of these SVC gains to the OLCI data for the regionally adapted v2.1 C2RCC products resulted in RMSD increases of 36% for "conc_tsm"; 118% for "conc_chl"; 33% for "iop_agelb"; 50% for "iop_adg"; and 10% for "kd_z90max" using a ±3 h validation window. This is the first time the effects of these SVC gains on the Level-2 OLCI water products has been isolated and quantified in the study region. The findings indicate that the current EUMETSAT SVC gains should be applied and interpreted with caution in the region of study at present. A key outcome of the paper recommends the development of a regionally specific SVC against AERONET-OC data in order to improve the Level-2 water product retrieval in the region. The results of this study are important for end users and the water authorities making use of the satellite water products in the Baltic Sea region. [ABSTRACT FROM AUTHOR]

Animal movement and population connectivity are key areas of uncertainty in efforts to understand and predict the spread of infectious disease. The emergence of highly pathogenic avian influenza (HPAI) in South America poses a significant threat to globally significant populations of colonial breeding marine predators in the South Atlantic. Yet, there is a poor understanding of which species or migratory pathways may facilitate disease spread. Compiling one of the largest available animal tracking datasets in the South Atlantic, we examine connectivity and inter‐population mixing for colonial breeding marine predators tagged at the Falkland Islands. We reveal extensive connectivity for three regionally dominant and gregarious species over the Patagonian Shelf. Black‐browed albatrosses (BBA), South American fur seals (SAFS) and Magellanic penguins (MAG) used coastal waters along the Atlantic coast of South America (Argentina and Uruguay). These behaviours were recorded at or in close proximity to breeding colonies and haul‐out areas with dense aggregations of marine predators. Transit times to and from the Falkland Islands to the continental coast ranged from 0.2–70 days, with 84% of animals making this transit within 4 days ‐ a conservative estimate for HPAI infectious period. Our findings demonstrate BBA, SAFS and MAG connectivity between the Falkland Islands and mainland South America over an expansive spatial network and numerous pathways, which has implications for infectious disease persistence, transmission and spread. This information is vital in supporting HPAI disease surveillance, risk assessment and marine management efforts across the region. [ABSTRACT FROM AUTHOR]

Understanding species distribution across habitats and environmental variables is important to inform area-based management. However, observational data are often lacking, particularly from developing countries, hindering effective conservation design. One such data-poor area is the Gulf of Guinea, an understudied and biodiverse region where coastal waters play a critical role in coastal livelihoods. Here, we describe the results of the largest national-scale Baited Remote Underwater Video Systems (BRUVS) survey in the region, aiming to understand the effects of several environmental variables on fish community composition and diversity. From 2018 to 2020, we successfully deployed 417 benthic BRUVS in the coastal waters of the São Tomé and Príncipe (STP) archipelago. Species richness and relative abundance were higher in deeper waters, on steeper slopes, and in rocky reef habitats. Nevertheless, maerl and sand habitats also hosted unique, and economically important species. Our results potentially indicate historical impacts of fishing in the archipelago, especially in São Tomé Island, where observed fishing effort is higher. Indeed, abundance of large predatory fish was low in both islands and abundance of species targeted by artisanal fisheries was lower in São Tomé than in Príncipe. Our results provide crucial information supporting the designation and future monitoring of marine protected areas in STP. [ABSTRACT FROM AUTHOR]

Lakshmanan, R.; Saravanan, R.; Kalidas, C.; Rajendran, P.; Babu, A.M.; Asha, P.S., and Joshi, K.K., 2024. Occurrence of the non-native mauve stinger, Pelagia cf. noctiluca, in coastal waters off Cape Comorin, southern Bay of Bengal. Journal of Coastal Research, 40(6), 1103–1110. Charlotte (North Carolina), ISSN 0749-0208. During a jellyfish survey in the southern Bay of Bengal, India, four scyphozoan jellyfish from the family Pelagiidae (Order: Semaeostomeae) were observed. The observed specimens were found at a depth of 1 to 2 m off the coast of Arockiapuram (8°05′ N, 77°11′ E), Cape Comorin (now Kanyakumari). The underwater photographic and video documentation with live colouration enabled the identification of the collected specimens as mauve stingers, Pelagia noctiluca (Forskal, 1775). The observed specimens have pink- or mauve-coloured hemispherical umbrellas with eight marginal tentacles that are transversely wrinkled and eight pear-shaped rhopalia. In general, P. noctiluca has a common distribution along the Atlantic Ocean, the Mediterranean Sea, and the Pacific Ocean; however, recordings of this species in Indian waters are considered rare and out of its documented distribution area. It has been reported earlier from Indian waters, and the nearest known distribution is from the Gulf of Mannar, Bay of Bengal. This species shows an invasive distribution in the warmer tropical environments due to its wide range of temperature tolerance. The species can be considered "invasive" as the periodic occurrence of large abundances in coastal waters occurs when this typically offshore species is advected shoreward in years when population densities appear to be exceptionally high. Consequently, it is problematic at the very periphery of its "natural range," thus differing from truly invasive species that have been introduced into a new area. The findings in this study suggest that specific hydrodynamic conditions may transport the permanent offshore population of P. noctiluca inshore, resulting in non-native outbreaks on shores. The study sheds light on the presence of the non-native oceanic mauve stinger in the Cape Comorin coastal waters in the Bay of Bengal, which alters the fisheries and tourism industries because it has a negative interaction with human recreational and coastal fishing activities. [ABSTRACT FROM AUTHOR]

Sumangala, D.; Abhinav, G.; Nagamani, P.V., and Warrior, H., 2024. Enhanced upwelling dynamics simulation in the Bay of Bengal: Integrating ANNs into hydrodynamic models. Journal of Coastal Research, 40(6), 1125–1136. Charlotte (North Carolina), ISSN 0749-0208. The Bay of Bengal exhibits a unique upwelling pattern, which is most pronounced during the summer monsoon months. This phenomenon is driven by a combination of open-ocean processes and seasonally reversing winds, leading to the transport of cooler, nutrient-rich waters to the coastal areas. The upwelling process is crucial for the marine ecosystem, supporting a diverse range of organisms that thrive in colder temperatures. To accurately capture the upwelling dynamics in the Bay of Bengal, a combination of the Delft3D model and an artificial neural network (ANN) was employed. The Delft3D model alone was unable to adequately represent the upwelling phenomenon, particularly the vertical velocity component (w). The incorporation of an ANN into the Delft3D framework significantly improved the accuracy of vertical velocity predictions. This modification provided a better capacity to forecast velocities in the Bay of Bengal, with a correlation of up to 0.92 (0.97) for the u (v) velocity components. The findings of this study highlight the importance of incorporating ANNs into hydrodynamic models to accurately represent complex processes such as upwelling. This approach provides a more comprehensive understanding of these critical processes, enabling better management and conservation of marine ecosystems. [ABSTRACT FROM AUTHOR]

False killer whales, striped dolphins, and Pacific white-sided dolphins have been targeted by dolphin fisheries in the coastal waters off Japan. Annual catch quotas are allocated on the basis of past abundance estimates, but those estimates were unpublished or more than 30 years old. Here, we reanalyzed the line-transect data collected from the sighting survey on the Pacific coast of Japan from 1985 to 2021 and estimated the past and latest abundances of those three species using a standard distance sampling approach. The surveys were conducted as part of the JAFRACSS-SC (Japan Fisheries and Education Agency Cetacean Sighting Survey-Small Cetacean Survey Program). This program mainly targets other fishery-targeted cetacean species and, thus, covers only a part of the above three species' distribution ranges. As a result, we obtained the latest abundance estimates of 4105 false killer whales, 84,657 striped dolphins, and 28,052 white-sided dolphins. Considering the current estimates represent only a part of the entire population size and that annual catch records did not largely exceed potential biological removals calculated based on these abundances, the current harvest level will not lead to a severe depletion or extinction for these three species. [ABSTRACT FROM AUTHOR]