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The recycling of scarce nutrient resources in the sunlit open ocean is crucial to ecosystem function. Nitrification directs ammonium (NH4+) derived from organic matter decomposition towards the regeneration of nitrate (NO3-), an important resource for photosynthetic primary producers. However, the technical challenge of making nitrification rate measurements in oligotrophic conditions combined with the remote nature of these environments means that data availability, and the understanding that provides, is limited. This study reports nitrite (NO2-) regeneration rate (RNO2 – the first product of nitrification derived from NH4+ oxidation) over a 13 000 km transect within the photic zone of the Atlantic Ocean. These measurements, at relatively high resolution (order 300 km), permit the examination of interactions between RNO2 and environmental conditions that may warrant explicit development in model descriptions. At all locations we report measurable RNO2 with significant variability between and within Atlantic provinces. Statistical analysis indicated significant correlative structure between RNO2 and ecosystem variables, explaining ∼65 % of the data variability. Differences between sampling depths were of the same magnitude as or greater than horizontally resolved differences, identifying distinct biogeochemical niches between depth horizons. The best overall match between RNO2 and environmental variables combined chlorophyll-a concentration, light-phase duration, and silicate concentration (representing a short-term tracer of water column physical instability). On this basis we hypothesize that RNO2 is related to the short-term autotrophic production and heterotrophic decomposition of dissolved organic nitrogen (DON), which regenerates NH4+ and supports NH4+ oxidation. However, this did not explain the observation that RNO2 in the deep euphotic zone was significantly greater in the Southern Hemisphere compared to the Northern Hemisphere. We present the complimentary hypothesis that observations reflect the difference in DON concentration supplied by lateral transport into the gyre interior from the Atlantic's eastern boundary upwelling ecosystems.

Human activities are changing the Arctic environment at an unprecedented rate resulting in rapid warming, freshening, sea ice retreat and ocean acidification of the Arctic Ocean. Trace gases such as nitrous oxide (N2O) and methane (CH4) play important roles in both the atmospheric reactivity and radiative budget of the Arctic and thus have a high potential to influence the region’s climate. However, little is known about how these rapid physical and chemical changes will impact the emissions of major climate-relevant trace gases from the Arctic Ocean. The combined consequences of these stressors present a complex combination of environmental changes which might impact on trace gas production and their subsequent release to the Arctic atmosphere. Here we present our current understanding of nitrous oxide and methane cycling in the Arctic Ocean and its relevance for regional and global atmosphere and climate and offer our thoughts on how this might change over coming decades. Supplementary Information The online version contains supplementary material available at 10.1007/s13280-021-01633-8.

Dimethyl sulphide (DMS) and carbon monoxide (CO) are climate-relevant trace gases that play key roles in the radiative budget of the Arctic atmosphere. Under global warming, Arctic sea ice retreats at an unprecedented rate, altering light penetration and biological communities, and potentially affect DMS and CO cycling in the Arctic Ocean. This could have socio-economic implications in and beyond the Arctic region. However, little is known about CO production pathways and emissions in this region and the future development of DMS and CO cycling. Here we summarize the current understanding and assess potential future changes of DMS and CO cycling in relation to changes in sea ice coverage, light penetration, bacterial and microalgal communities, pH and physical properties. We suggest that production of DMS and CO might increase with ice melting, increasing light availability and shifting phytoplankton community. Among others, policy measures should facilitate large-scale process studies, coordinated long term observations and modelling efforts to improve our current understanding of the cycling and emissions of DMS and CO in the Arctic Ocean and of global consequences.

In response to an increasing demand for bespoke or tailored regional ocean modelling configurations, we outline fundamental principles and practices that can expedite the process to generate new configurations. The paper develops the principle of reproducibility and advocates adherence by presenting benefits to the community and user. The elements of this principle are reproducible workflows and standardised assessment, with additional effort over existing working practices being balanced against the added value generated. The paper then decomposes the complex build process, for a new regional ocean configuration, into stages and presents guidance, advice and insight for each component. This advice is compiled from across the NEMO (Nucleus for European Modelling of the Ocean) user community and sets out principles and practises that encompass regional ocean modelling with any model. With detailed and region-specific worked examples in Sects. 3 and 4, the linked companion repositories and DOIs all target NEMOv4. The aim of this review and perspective paper is to broaden the user community skill base and to accelerate development of new configurations in order to increase the time available for exploiting the configurations.

The north sea is a highly productive area, both biologically and for a variety of economic activities. It is also undergoing great change; anthropogenic usage is changing with Oil and gas activities ramping down whilst offshore wind installations are increasing, all against the increasing impact of climate change. For oil and gas structures there is an active debate as to the positive or negative ecosystem effects of different decom​missioning strategies for structures (e.g. removal, topp​ling). Whilst the effect of different options have been ​extensively studied at the level of individual structures, it is necessary to consider them in a basin wide context and ​in combination with the effect of other contemporary pressures.Here we use coupled physics-biogeochemistry models (GOTM-ERSEM, FVCOM-ERSEM and FVCOM-PyLAG with specific adaptions for man-made structures to understand the possible scope and magnitude of effects on the north sea ecosystem for different decommissioning scenarios of oil and gas structures (removal, toppling, leaving intact). Specifically we look at the utilisation of structures by colonising organisms, the effects of trawling exclusion, and changes to connectivity. We also consider these with the addition of other man made structures (shipwrecks and wind farms) and under a future climate scenario.

The recycling of scarce nutrient resources in the sunlit open ocean is crucial to ecosystem function. Ammonium oxidation, the first stage of the nitrification process, directs ammonium derived from organic matter decomposition towards the regeneration nitrate, an important resource for photosynthetic primary producers. However, the technical challenge of making nitrification rate measurements in oligotrophic conditions combined with the remote nature of these marine systems means that data availability, and the understanding that provides, is limited. This study reports rate measurements of ammonium oxidation over a 13, 000 km transect within the photic zone of the Atlantic Ocean. These measurements, at relatively fine resolution (order 300 km), permit the examination of interactions with environmental conditions that may warrant explicit development and inclusion in model descriptions. At all locations we report measurable rates with significant variability between and within Atlantic provinces. This adds to evidence that nitrification is an important component of pelagic nitrogen cycling which modifies the inorganic nitrogen inventory of the sunlit ocean. Particular features of interest included a significant hemispheric difference in ammonium oxidation rate and elevated rates associated with mesoscale eddy features. Statistical analysis of potential links between ammonium oxidation rate and routinely measured ecosystem variables indicated significant correlative structure, explaining ~65 % of the data variability. Differences between sampling depths were of the same magnitude or greater than horizontally resolved differences along the transect length, identifying distinct biogeochemical niches between depth horizons. Principle component analysis demonstrated that the best overall match between ammonium oxidation rate and environmental variables involved a combination of chlorophyll-a concentration, the duration of the light phase and silicate concentration (which we argue to be a short-term tracer of physical instability). Results allude to an association between ammonium oxidation and potentially short-term product(s) of photosynthetic activity and subsequent degradation. Approximately 35 % of data variability was not explained, which may include descriptions of DOM pool dynamics.

Nitrous oxide (N2O) is important to the global radiative budget of the atmosphere and contributes to the depletion of stratospheric ozone. Globally the ocean represents a large net flux of N2O to the atmosphere but the direction of this flux varies regionally. Our understanding of N2O production and consumption processes in the ocean remains incomplete. Traditional understanding tells us that anaerobic denitrification, the reduction of NO3− to N2 with N2O as an intermediate step, is the sole biological means of reducing N2O, a process known to occur in anoxic environments only. Here we present experimental evidence of N2O removal under fully oxygenated conditions, coupled with observations of bacterial communities with novel, atypical gene sequences for N2O reduction. The focus of this work was on the high latitude Atlantic Ocean where we show bacterial consumption sufficient to account for oceanic N2O depletion and the occurrence of regional sinks for atmospheric N2O.

Background Numerous man-made structures (MMS) have been installed in various parts of the ocean (e.g. oil and gas structures, offshore wind installations). Many are now at, or nearing, the end of their intended life. Currently, we only have a limited understanding of decommissioning effects. In many locations, such as the North Sea, regulations restrict decommissioning options to complete removal, with little consideration of alternative management options might offer. To generate a reliable evidence-base to inform the decision-making processes pertaining to marine MMS management, we propose a wide-encompassing systematic map of published research on the ecosystem effects (including ecosystem services) of marine MMS while in place and following cessation of operations (i.e. including effects of alternative decommissioning options). This map is undertaken as part of the UKRI DREAMS project which aims to develop a system to show the relative effects of implementing different decommissioning strategies in the North Sea. Method For the purpose of this map, we will keep our focus global, in order to subsequently draw comparisons between marine regions. The proposed map will aim to answer the following two primary questions: 1. What published evidence exists for the effects of marine man-made structures while in place on the marine ecosystem? 2. What published evidence exists for the effects of the decommissioning of marine man-made structures on the marine ecosystem? The map will follow the Collaboration for Environmental Evidence Guidelines and Standards for Evidence Synthesis in Environmental Management. Searches will be run primarily in English in at least 13 databases and 4 websites. Returns will be screened at title/abstract level and at full-text against pre-defined criteria. Relevant meta-data will be extracted for each study included. Results will be used to build a database of evidence, which will be made freely available. This map, expected to be large, will improve our knowledge of the available evidence for the ecosystem effects of MMS in the global marine environment. It will subsequently inform the production of multiple systematic-reviews and meta-analyses.

Results from a 1D setup of the European Regional Seas Ecosystem Model (ERSEM) biogeochemical model were compared with new observations collected under the UK Shelf Seas Biogeochemistry (SSB) programme to assess model performance and clarify elements of shelf-sea benthic biogeochemistry and carbon cycling. Observations from two contrasting sites (muddy and sandy) in the Celtic Sea in otherwise comparable hydrographic conditions were considered, with the focus on the benthic system. A standard model parameterisation with site-specific light and nutrient adjustments was used, along with modifications to the within-seabed diffusivity to accommodate the modelling of permeable (sandy) sediments. Differences between modelled and observed quantities of organic carbon in the bed were interpreted to suggest that a large part (>90%) of the observed benthic organic carbon is biologically relatively inactive. Evidence on the rate at which this inactive fraction is produced will constitute important information to quantify offshore carbon sequestration. Total oxygen uptake and oxic layer depths were within the range of the measured values. Modelled depth average pore water concentrations of ammonium, phosphate and silicate were typically 5–20% of observed values at the muddy site due to an underestimate of concentrations associated with the deeper sediment layers. Model agreement for these nutrients was better at the sandy site, which had lower pore water concentrations, especially deeper in the sediment. Comparison of pore water nitrate with observations had added uncertainty, as the results from process studies at the sites indicated the dominance of the anammox pathway for nitrogen removal; a pathway that is not included in the model. Macrofaunal biomasses were overestimated, although a model run with increased macrofaunal background mortality rates decreased macrofaunal biomass and improved agreement with observations. The decrease in macrofaunal biomass was compensated by an increase in meiofaunal biomass such that total oxygen demand remained within the observed range. The permeable sediment modification reproduced some of the observed behaviour of oxygen penetration depth at the sandy site. It is suggested that future development in ERSEM benthic modelling should focus on: (1) mixing and degradation rates of benthic organic matter, (2) validation of benthic faunal biomass against large scale spatial datasets, (3) incorporation of anammox in the benthic nitrogen cycle, and (4) further developments to represent permeable sediment processes. Electronic supplementary material The online version of this article (doi:10.1007/s10533-017-0367-0) contains supplementary material, which is available to authorized users.

Carbon capture with offshore storage may take place at various geographical locations, characterized by diverse physical and biogeochemical properties and dynamics of the overlying water. In order to ensure storage integrity, baseline conditions must be carefully assessed for each potential storage area, which will allow design and deployment of optimal monitoring and sampling programs and establish appropriate site-specific criteria for anomaly detection, to allow timely reaction and necessary remedial measures. Within this paper, we assess applicability of using outputs of coupled hydrodynamic-biogeochemical models for the selection of appropriate variables to describe baseline variability and, consequently, strategies for the following monitoring. Via application of multivariate linear regression we identify combinations of modelled variables that best predict variability in pCO2 at a location corresponding to the potential storage site at Goldeneye Field in the Central North Sea. Although some variable pairs better predict pCO2 variability, we focus on a combination of oxygen saturation and silicate, as variables that can potentially be frequently and accurately monitored over long periods. In this work we employ highly simplified leakage scenarios to highlight the accuracy of baseline characterization and implications for establishment of thresholds for anomaly detection in highly dynamic marine environments. We conclude that hydrodynamic-biogeochemical models are invaluable tools for informing cost-effective monitoring strategies regarding the optimal number and combination of parameters surveyed and for establishing appropriate anomaly criteria for each potential storage location.

Benthic macrofauna, as an element of rich and diverse benthic communities of the shelf seas, play a key role in marine biogeochemical cycles and support a wide range of ecosystem services. To better understand how macrofauna affects mass and energy fluxes within the seabed and between the bed and the pelagic, it is fundamental to characterise their structural and dynamic response to the quantity, quality and timing of food supply. To do so, we have combined long-term time-series of pelagic productivity and macrofaunal abundance with a model of benthic food web to: (1) estimate the characteristic response time scales of major groups of benthic macrofauna to food availability, (2) relate these to carbon fluxes within sediments and across the benthic-pelagic boundary, and (3) explore the mechanisms responsible. The model was designed as a canonical representation of the benthic system, retaining the key pathways that connect benthic macrofauna to pelagic environment, but aggregating variables and groups that were not explicitly observed. Both observations and model simulations revealed pronounced differences between deposit and suspension feeders in their rate of response to phytoplankton blooms: deposit feeders showed a dampened response lagging 26-125 days behind the peak in pelagic production, while suspension feeders responded rapidly, within only 5-7 days. The model parametrisation obtained during calibration relates this to differences in feeding modes, in (trophic) proximity to primary production and in rates of ingestion and losses. Specifically, suspension feeders are predicted to act as a gateway to pelagic productivity, controlling the quantity of organic carbon reaching sediment-dwelling fauna.

This paper describes the utility of developing marine system models to aid the efficient and regulatory compliant development of offshore carbon storage, maximising containment assurance by well-planned monitoring strategies. Using examples from several model systems, we show that marine models allow us to characterize the chemical perturbations arising from hypothetical release scenarios whilst concurrently quantifying the natural variability of the system with respect to the same chemical signatures. Consequently models can identify a range of potential leakage anomaly detection criteria, identifying the most sensitive discriminators applicable to a given site or season. Further, using models as in-silico testbeds we can devise the most cost-efficient deployment of sensors to maximise detection of CO2 leakage. Modelling studies can also contribute to the required risk assessments, by quantifying potential impact from hypothetical release scenarios. Finally, given this demonstrable potential we discuss the challenges to ensuring model systems are available, fit for purpose and transferable to CCS operations across the globe.

The European Regional Seas Ecosystem Model (ERSEM) is one of the most established ecosystem models for the lower trophic levels of the marine food web in the scientific literature. Since its original development in the early nineties it has evolved significantly from a coastal ecosystem model for the North Sea to a generic tool for ecosystem simulations from shelf seas to the global ocean. The current model release contains all essential elements for the pelagic and benthic parts of the marine ecosystem, including the microbial food web, the carbonate system, and calcification. Its distribution is accompanied by a testing framework enabling the analysis of individual parts of the model. Here we provide a detailed mathematical description of all ERSEM components along with case studies of mesocosm-type simulations, water column implementations, and a brief example of a full-scale application for the north-western European shelf. Validation against in situ data demonstrates the capability of the model to represent the marine ecosystem in contrasting environments.

The response of nutrient and chlorophyll fields to climate change by the end of the twenty-first century was evaluated in the Gulf of Finland (Baltic Sea) using comparison of a hindcast simulation for 1997–2006 and future climate forcing, assuming an A1B greenhouse gas emission scenario and business-as-usual riverine nutrient load for 2090–2099. The comparison of simulated oxygen, phosphate and nitrate levels from the hindcast model with the measurements indicated a good performance of the 3D ecosystem model, except for overestimated near-bottom layer nitrates. The mean chlorophyll level was slightly overestimated by the model, whereas the variability in the surface layer chlorophyll level was well reproduced. Future projection simulations indicate no considerable changes in the upper layer oxygen concentrations compared with the hindcast simulation and observations, but deeper near-bottom layers were projected to become anoxic, causing an increase in phosphate and a decrease in nitrate concentrations in these layers. The increase in surface layer phosphate and the decrease in nitrate concentrations lead to an increase in summer cyanobacteria blooms and an increase in nitrogen fixation, which therefore led to an increase in the annual mean chlorophyll content in the upper layer.

Regulations pertaining to carbon dioxide capture with offshore storage (CCS) require an understanding of the potential localised environmental impacts and demonstrably suitable monitoring practices. This study uses a marine ecosystem model to examine a comprehensive range of hypothetical CO2 leakage scenarios, quantifying both impact and recovery time within the benthic system. Whilst significant mortalities and long recovery times were projected for the larger and longer term scenarios, shorter-term or low level exposures lead to reduced projected impacts. This suggests that efficient monitoring and leak mitigation strategies, coupled with appropriate selection of storage sites can effectively limit concerns regarding localised environmental impacts from CCS. The feedbacks and interactions between physiological and ecological responses simulated reveal that benthic responses to CO2 leakage could be complex. This type of modelling investigation can aid the understanding of impact potential, the role of benthic community recovery and inform the design of baseline and monitoring surveys.

A combination of numerical modeling results with measurement and satellite imagery data was used during the biologically active period for the determination of the coastal zone extent in the central and eastern Gulf of Finland. Adopting the approach that the coastal zone can be identified by the spatial distribution of biotic parameters, spatial variations and gradients of chlorophyll a (chl-a) concentrations were analyzed. The results showed that chl-a concentrations vary in a wide range over the biologically active period. During heavy blooms, the coastal zone may appear occasionally and depend on the spatial distribution of the bloom. On average, clear limits of the coastal zone could be defined for the central and eastern Gulf of Finland. In the central Gulf of Finland, water and material exchange are rather intensive, and the coastal zone is narrower than in the eastern Gulf. In the easternmost part of the Gulf of Finland, chl-a concentrations were permanently high in an area of about 100 km width due to the discharge of the Neva River. The study has shown that gradients of chl-a spatial distribution can be applied for determining limits of the coastal zone extent. The standardized gradient of zero is shown to be a threshold separating the coastal zone (standardized gradients > 0) from the open sea (standardized gradients < 0).

The mean spatial distributions of phytoplankton and inorganic nitrogen (IN) in Narva Bay (southeastern Gulf of Finland) during a single biologically active period were studied by means of numerical modelling. The model implemented is three-dimensional ecohydrodynamic model MIKE 3. Model validation gave reasonable justification for studying the mean spatial distributions of IN and phytoplankton in Narva Bay. Results showed that mean inorganic nitrogen concentration in Narva Bay was highest near the river mouth (0.015 to about 0.03 gN/m3), while phytoplankton concentration was relatively low there. Another area of elevated IN concentration was found at the southern coast of Narva Bay some 30 km to the west from the river mouth, where high phytoplankton concentration persisted during summer. In general, coastal waters enriched with inorganic nitrogen (IN > 0.006 gN/m3) formed a narrow belt of approximately 3–8 km wide that extended from the middle of the eastern coast and along the entire southern coast of Narva Bay. According to phytoplankton distribution the coastal waters can be characterized with concentrations exceeding 0.45 gC/m3. The results allow to the separation of the Narva Bay coastal area into zones with different trophic status and nutrients origin: (a) the river mouth area with high IN and low phytoplankton concentration due to intensive hydrodynamic processes, (b) the area to the right of the river mouth with high phytoplankton concentration due to river IN discharge, (c) the southwestern coastal part of the bay enriched with nutrients due to upwelling, and (d) the area between upwelling zone and the river mouth influenced by both upwelling and river discharge.

A coupled three-dimensional hydrodynamic–ecological model was used for the assessment of water quality in Narva Bay during one biologically active season. Narva Bay is located in the south-eastern Gulf of Finland. Narva River with a catchment’s area covering part of Russia and Estonia discharges water and nutrients to Narva Bay. The ecological model includes phytoplankton carbon, nitrogen and phosphorus, chlorophyll a, zooplankton, detritus carbon, nitrogen and phosphorus, inorganic nitrogen, inorganic phosphorus and dissolved oxygen as state variables. Both the hydrodynamic and ecosystem models were validated using a limited number of measurements. The hydrodynamic model validation included comparison of time series of currents and temperature and salinity profiles. The ecological model results were compared with the monitoring data of phytoplankton biomass, total nitrogen and phosphorus and dissolved oxygen. The comparison of hydrodynamic parameters, phytoplankton biomass, surface layer total phosphorus and dissolved oxygen and near-bottom layer total nitrogen was reasonable. Time series of spatially mean values and standard deviations of selected parameters were calculated for the whole Narva Bay. Combining model results and monitoring data, the characteristic concentrations of phytoplankton biomass, total nitrogen and phosphorus and near-bottom dissolved oxygen were estimated. Phytoplankton biomass and total phosphorus showed seasonal variations, of 0.6–1.1 and 0.022–0.032 mg/l, respectively, during spring bloom, 0.1–0.3 and 0.015–0.025 mg/l in summer and 0.2–0.6 and 0.017–0.035 mg/l during autumn bloom. Total nitrogen and near-bottom oxygen concentrations were rather steady, being 0.25–0.35 and 2–6 mg/l, respectively. The total nitrogen and phosphorus concentrations show that according to the classification of Estonian coastal waters, Narva Bay water belongs to a good water quality class.

A coupled hydrodynamic-biogeochemical model was implemented in order to estimate the effects of Major Baltic Inflows on the near-bottom hydrophysical and biogeochemical conditions in the northern Baltic Proper and the western Gulf of Finland during the period 1991-2009. We compared results of a realistic reference run to the results of an experimental run where Major Baltic Inflows were suppressed. Further to the expected overall decrease in bottom salinity, this modelling experiment confirms that in the absence of strong saltwater inflows the deep areas of the Baltic Proper would become more anoxic, while in the shallower areas (western Gulf of Finland) near-bottom average conditions improve. Our experiment revealed that typical estuarine circulation results in the sporadic emergence of short-lasting events of near- bottom anoxia in the western Gulf of Finland due to transport of water masses from the Baltic Proper. Extrapolating our results beyond the modelled period, we speculate that the further deepening of the halocline in the Baltic Proper is likely to prevent inflows of anoxic water to the Gulf of Finland and in the longer term would lead to improvement in near-bottom conditions in the Baltic Proper. Our results reaffirm the importance of accurate representation of salinity dynamics in coupled Baltic Sea models serving as a basis for credible hindcast and future projection simulations of biogeochemical conditions., JRC.H.1-Water Resources

The hydrodynamic model GETM coupled with the ecosystem model ERGOM was applied to the Baltic Sea area for the period 1991–2010. The first part of the modeled period is characterized by considerable socioeconomic changes in the area that are generally considered favorable for the status of coastal marine ecosystems due to a decrease in external nutrient loads. Model results were used to describe and analyze changes in salinity, nutrient (nitrate and phosphate) and oxygen dynamics in the central part of the Gulf of Finland, the most eutrophied sub-basin of the Baltic Sea, over the last two decades. Model validation showed very good agreement between modeled and measured parameters in the Gulf. In the surface layer nitrates were slightly underestimated, while phosphates were overestimated during the second half of the modeled period. Near-bottom parameters were generally accurately reproduced. Model results show that in fact the eutrophication status of the Gulf of Finland has worsened during the last two decades, especially during the latter part of the modeled period. This is reflected in an increased frequency of anoxic events and consecutive high phosphate loading and decrease of near-bottom nitrate concentrations. Stronger stratification favors anoxic conditions in the near-bottom, while a decrease in salinity induced by mixing processes allows for oxygenation of deep areas. However, the effect of these mixing events is short-term and deep water quickly returns to the anoxic state.

Direct and indirect effects of changing meteorological conditions include alterations in nutrient cycling, timing and extent of algal blooms, species composition and oxygen dynamics of the Baltic coastal ecosystems. In this study the one-dimensional water column model GOTM coupled with a modified version of the biogeochemical model ERGOM was implemented to study the effects of changes in meteorological forcing associated with climate change on dynamics of nutrients, phytoplankton and dissolved oxygen in the central part of the Gulf of Finland. The modeling period from 1997 to 2008 (11 years) was chosen. Initial distributions of salinity, temperature and biogeochemical parameters from available measurement data were prescribed. As a reference run representing the present conditions of the ecosystem, model results with real atmospheric forcing were used. The model results were validated using observational data from the HELCOM monitoring program. The first three years of the simulation were used as a spin-up period. For the rest of the period modeled ecosystem sensitivity to variations in wind speed, air temperature, cloud cover and precipitation were analyzed separately and in a combination. The ranges of variations were chosen in agreement with recent publications on the assessment of climate change in the Baltic Sea region. Results have shown that increase in precipitation does not have any remarkable effect on the ecosystem. Increase in wind speed intensifies water mixing thus providing more nutrients for phytoplankton, but also slightly decreases water temperature. Change in cloud cover negatively affects phytoplankton growth due to decrease in light availability during biologically active period. Increased air temperature influences phytoplankton growth rates, leading to enhanced sedimentation of organic matter and near-bottom oxygen consumption. The scenario which combined all the previous, showed similar results as change in air temperature only, but slightly closer to the reference run due to action of wind speed and cloud cover. The study has shown that regardless of known limitations of one-dimensional models, they are a valuable tool in the investigation of marine ecosystem properties and their sensitivity to changes in the forcing parameters., JRC.DDG.H.3-Global environement monitoring

Two different approaches in defining coastal zone extent exist. One of them sets fixed boundaries to the coastal zone, and, thus, is easily adopted by decision-makers. Another approach follows distribution of a set of contiguous ecosystems, and is more accordant with the ecosystem-based management of the coastal zone. Ecological approach requires comprehensive research of the system in focus. However, managers usually need more general tools which allow a first-order assessment of ecosystem structure and functioning. This work demonstrates how results of ecohydrodynamic model can be used by managers in the assessment of coastal ecosystem status and proposes mapping of characteristic coastal zone regions for management purposes.

Hydrostatic and non-hydrostatic versions of the hydrodynamic model MIKE 3 were used to hindcast hydrophysical fields in the Baltic Sea for the period 1 April-1 November 1996. The model results were compared with observed sea level at Helsinki station and with temperature and salinity measured at monitoring stations in the Gulf of Finland and the Baltic Proper for the period 1 June-1 November 1996. The comparison was quite good for the sea level and the differences between the results of two model versions were insignificant for temperature and salinity stratification. In general, the results were better for the Baltic Proper than for the Gulf of Finland.