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A rapid increase in population size along with expansion in hotel investment have been identified as key drivers of marine pollution in Zanzibar coastal waters. A validated high-resolution hydrodynamic tracer model was used to estimate the dispersal and impact range of pollutants from the main hotel areas along the western coastline of Unguja Island. The model showed the highest impact of pollutants from land during the northeast monsoon season due to the weakening of the main current. Marine protected areas with short distances to hotel areas and weak tidal currents were more likely to be impacted by pollutants from land than the more remote areas with higher flushing in agreement with water quality and seagrass health measurements. Cumulative effects of pollutants instead of single sources are important to consider for integrated wastewater treatment plans and management strategies to reduce pollution for the protection of biodiversity and guide future monitoring.

The Greenland ice sheet is melting, and the rate of ice loss has increased 6-fold since the 1980s. At the same time, the Arctic sea ice extent is decreasing. Meltwater runoff and sea ice reduction both influence light and nutrient availability in the coastal ocean, with implications for the timing, distribution, and magnitude of phytoplankton production. However, the integrated effect of both glacial and sea ice melt is highly variable in time and space, making it challenging to quantify. In this study, we evaluate the relative importance of these processes for the primary productivity of Disko Bay, west Greenland, one of the most important areas for biodiversity and fisheries around Greenland. We use a high-resolution 3D coupled hydrodynamic–biogeochemical model for 2004–2018 validated against in situ observations and remote sensing products. The model-estimated net primary production (NPP) varied between 90–147 gC m−2 yr−1 during 2004–2018, a period with variable freshwater discharges and sea ice cover. NPP correlated negatively with sea ice cover and positively with freshwater discharge. Freshwater discharge had a strong local effect within ∼ 25 km of the source-sustaining productive hot spots during summer. When considering the annual NPP at bay scale, sea ice cover was the most important controlling factor. In scenarios with no sea ice in spring, the model predicted a ∼ 30 % increase in annual production compared to a situation with high sea ice cover. Our study indicates that decreasing ice cover and more freshwater discharge can work synergistically and will likely increase primary productivity of the coastal ocean around Greenland.

The North Sea and the Baltic Sea, including Danish coastal waters, have experienced a drastic decline in eelgrass Zostera marina coverage during the past century. Around 1900, eelgrass meadows covered about 6700 km of Danish coastal waters while the current potential distribution area is only about one third of this. In some areas, the potential distribution area is far from realized, and restoration efforts are needed to assist recovery. Such efforts are challenging, and resource-demanding and careful site selection is, therefore, important. In the present study, we aim to identify the connectivity of eelgrass populations as a basis for guiding site selection for restoration. We developed a coupled biophysical model to study eelgrass dispersal in the Kattegat. Partly submerged particles simulated the dispersal of reproductive eelgrass shoots containing seeds during the flowering season July–September. We then used network analysis to identify the potential connectivity between populations. We evaluated connectivity based on In-strength, Betweenness and Eigenvector centrality metrics and identified key areas in the Kattegat such as the central part of Aalborg Bay, to be considered to restore the network of Z. marina patches. The study proves the potentials of combining hydrodynamic models and network analysis to support marine conservation and planning, and highlights the importance of collaboration between ecologists, oceanographers, and practitioners in this endeavour., This research has been funded from the European Union's Horizon 2020 research and innovation programme under grant agreement No 869300 ″FutureMARES. AO was supported by a contract financed through the call for postdoctoral fellowships of the Government of the Balearic Islands, program “Vicenç Mut” 2020.

In the Baltic Sea, rainbow trout Oncorhynchus mykiss is the most common species used in marine aquaculture, but further increase in production is problematic due to environmental legal regulations, especially in the coastal zone. A solution could be to place the fish farms offshore and use mussel mitigation cultures to extract nutrients released from the fish farms. We used 3D ecological modeling to identify suitable locations for mussel mitigation cultures in relation to nutrient pollution from a fish farm in the inner Danish waters. The model results showed that potential mussel harvest depended on the food flux following a saturation curve with a maximum yield of 2100 to 2600 t wet weight and then stabilized at around 2100 to 2600 t wet weight of mussels. A single mussel farm (36 ha) can potentially remove 17-31% of the released nitrogen from the fish farm. Mussel farms located inside or a few km outside the coastal areas receiving the highest nutrient inputs from the fish farm were found to be the most suitable among the tested sites. In contrast, co-location with the fish farm was not advisable due to the negative benthic impact below the farms. However, it is up to the managers to decide which positive and negative effects should receive the most attention, given the present need for protection of water bodies and habitats and in relation to other activities in the area. This study demonstrates that modeling can support management decisions with respect to site selection of aquaculture and provide the needed data on far-field and local environmental effects from integrated aquaculture. In the Baltic Sea, rainbow trout Oncorhynchus mykiss is the most common species used in marine aquaculture, but further increase in production is problematic due to environmental legal regulations, especially in the coastal zone. A solution could be to place the fish farms offshore and use mussel mitigation cultures to extract nutrients released from the fish farms. We used 3D ecological modeling to identify suitable locations for mussel mitigation cultures in relation to nutrient pollution from a fish farm in the inner Danish waters. The model results showed that potential mussel harvest depended on the food flux following a saturation curve with a maximum yield of 2100 to 2600 t wet weight and then stabilized at around 2100 to 2600 t wet weight of mussels. A single mussel farm (36 ha) can potentially remove 17-31% of the released nitrogen from the fish farm. Mussel farms located inside or a few km outside the coastal areas receiving the highest nutrient inputs from the fish farm were found to be the most suitable among the tested sites. In contrast, co-location with the fish farm was not advisable due to the negative benthic impact below the farms. However, it is up to the managers to decide which positive and negative effects should receive the most attention, given the present need for protection of water bodies and habitats and in relation to other activities in the area. This study demonstrates that modeling can support management decisions with respect to site selection of aquaculture and provide the needed data on far-field and local environmental effects from integrated aquaculture.

Longline mussel farming has been proposed as a tool to remove nutrients and counteract the negative effects of eutrophication in coastal waters. In this study, we use coupled 3D hydrodynamic and ecological modelling in combination with measurements from a full-scale mitigation farm to assess the environmental effects of mitigation cultures in Skive Fjord, Denmark, a shallow eutrophic estuary. The results show that mitigation cultures decrease chl a concentration and increase Secchi depth especially in the surroundings of the farms but also on a basin scale. Fecal production by the mussels increases sedimentation below the farms but reduces ambient sedimentation, resulting in a net decrease in sedimentation of organic material on a basin scale. Comparisons with nutrient load reduction scenarios indicate that nutrient removal by mitigation cultures have a higher short-term impact on water quality parameters (chl a, Secchi depth and sedimentation) than nutrient removal using land-based measures.

Larval dispersal is dependent on multiple physical and biotic factors, and is a key driver of population connectivity. Connectivity is believed to be important in determining how species will cope in a changing climate by allowing species’ ranges to expand or constrict in response to environmental shifts. The Limfjorden in Denmark contains a large mussel fishery from the species Mytilus sp. based on wild populations and mussel farms. It is believed that climate change will produce changes in the species biology that will affect their dispersal and connectivity. In the following study, we address these changes using an individual-based approach. We couple a 3D physical model system with an agent-based model (ABM) in order to answer whether climate change effects on mussel larvae will affect the dispersal and the structure of the connectivity in the Limfjorden. We produced scenarios changing the pelagic larval duration (PLD), spawning time, and larval presence after events of hypoxia. Recruitment and self-recruitment of larvae in the different areas was investigated in depth. The results show no significant difference of the spawning and PLD scenarios except for the lowest PLD. Severe events of hypoxia could potentially lead to isolation of the southeastern areas of the fiord. Overall, this well-connected system is very stable to changes. These results are of fundamental importance for the future management and conservation of the mussel fisheries and wild mussel populations in a changing climate.

Fishery of blue mussels Mytilus edulis constitutes a very important economic activity in Denmark, whereas mussel farming on long-lines or nets is a new, growing sector. Spawning from natural mussel beds takes place during early summer, and larvae disperse via water currents before settling on the bottom or on spat collectors in the farms. In the present study, we coupled a 3D physical model system (FlexSem) with an agent-based model in order to examine the connectivity of this marine system in terms of mussel larval dispersal and settling potential. To address this question, we (1) estimated the dispersal and connectivity between 17 areas in the Limfjorden, (2) identified the main donor and receiver areas of mussel larvae and (3) identified possible dispersal barriers. The results show that the central narrow strait in the Limfjorden was the main donor area in all the studied years, and that the adjacent eastern areas were the main receiver areas. Towards the inner basins of the Limfjorden, isolation increased and limited connectivity was observed. The results from the cluster analysis grouped the Limfjorden into 3 to 5 clusters, but there was still some exchange of simulated larvae observed among these clusters. Analysis of molecular markers revealed no genetic differentiation between areas and supports the model results, indicating that despite distinguishable hydrographic boundaries, the mussel populations in the Limfjorden are well connected. This study demonstrates how connectivity modeling can be used to support site selection processes in aquaculture.

European legislation requires monitoring of toxic algae in marine areas where shellfish are harvested for consumption. Monitoring assumes the existence of homogeneous water bodies, the definition of which have important implications for stakeholders and consumers. Yet, the definition of homogeneous water bodies remains unclear. Here we present a methodology to divide coastal and estuarine waters into homogeneous water bodies to monitor toxic algae. The proposed method is mainly based on water transport, and secondarily on oceanographic characteristics; salinity and sea surface height. We apply the methodology to the Limfjord in Denmark and demonstrate its usefulness in areas with a complicated coastal morphology. The oceanographic descriptors applied in the method are standard outputs from coastal hydrodynamical models. Provided that validated and high resolution model output is available for a given area, the technique is thus adaptable to other morphologically and oceanographically complicated estuarine and coastal areas where toxic algae monitoring is necessary.

Mass mortality of blue mussels occurs every summer due to hypoxia in eutrophic estuaries and the oxygen consumption of decaying mussels is suspected to accelerate the hypoxia. In the present study, the solution of transplanting 3600 and 6000 t-WW of mussels from donor areas with frequent hypoxia to more suitable growth areas was tested as a tool to mitigate hypoxia in the Limfjorden. The environmental effects in the donor area were estimated by a 3D ecological model in FlexSem. Model results showed that hypoxia mitigation was most efficient at water depths of 3–5 m with highest changes in mussel biomass and oxygen levels close the ecosystem hypoxia threshold of 3.4 mg l−1. Mussel biomass soon recovered from the fishing pressure during summer due to the better oxygen conditions. These effects led to reduced Chl a concentrations and increased Secchi depths in the model. Negative effects of dredging on Secchi depth and oxygen levels were short-lived, locally and exceeded by the positive effects during the following summer period. In conclusion, mussel transplantation can prevent mass mortalities and limit the extent of the hypoxic events and the associated negative environmental effects, which is important knowledge for the management of eutrophic systems.

Mussel dredging causes resuspension of sediment particles that reduce water clarity and potentially leads to reduced eelgrass growth. In order to study the impact of resuspension from mussel dredging on light conditions in the water column, field experiments were conducted at two sites in the Limfjorden. Light loggers were placed in two circular arrays around the dredge area. Vertical profiles of current velocity were measured by an ADCP and the sediment particle size composition was obtained from sediment core samples. The field data was used to force, calibrate and validate a sediment transport model developed in the FlexSem model system. Changes in sediment concentrations during and after mussel dredging were modeled for the two sites and for seven scenarios. We found that the distance and direction of the plume in the model was in good agreement with light logger data. The plume duration was less than 1 h, and the impact range was between 260–540 m. The scenarios showed that fishing intensity and current speeds were most important for shaping the sediment plumes. Changes in suspended sediment concentrations were 0.62–1.79 mg l −1 on median average and 1.22–11.61 mg l −1 for the upper quantile of the plume, which were on the same order of magnitude as background values in the Limfjorden. The amount of fishing days during the eelgrass growth season was 6–8% in Lovns Bredning and 16–35% in Løgstør Bredning and less than 1–2% of the total area was dredged per season. Even though there are substantial changes in the light conditions from the sediment plumes, the overall spatio-temporal impact in the study area is considered low. We recommend that management plans in other areas could sustain a shellfish fishery by limiting fishing intensity and frequency near eelgrass beds. The presented approach combines observational data, sediment transport modeling and reported fishing activity. It is a step forward within sediment transport modeling and could be incorporated into environmental impact assessments. The results have recently been used as scientific background for recommendations to improve the management plans according to the Danish Mussel Policy and relevant EU Directives.

The aim of the study was to investigate the relative importance of bottom-up and top-down forcing on trophic cascades in the pelagic food-web and the implications for water quality indicators (summer phytoplankton biomass and winter nutrients) in relation to management. The 3D ecological model ERGOM was validated and applied in a local set-up of the Kattegat, Denmark, using the off-line Flexsem framework. The model scenarios were conducted by changing the forcing by ± 20% of nutrient inputs (bottom-up) and mesozooplankton mortality (top-down), and both types of forcing combined. The model results showed that cascading effects operated differently depending on the forcing type. In the single-forcing bottom-up scenarios, the cascade directions were in the same direction as the forcing. For scenarios involving top-down, there was a skipped-level-transmission in the trophic responses that was either attenuated or amplified at different trophic levels. On a seasonal scale, bottom-up forcing showed strongest response during winter-spring for DIN and Chl a concentrations, whereas top-down forcing had the highest cascade strength during summer for Chl a concentrations and microzooplankton biomass. On annual basis, the system was more bottom-up than top-down controlled. Microzooplankton was found to play an important role in the pelagic food web as mediator of nutrient and energy fluxes. This study demonstrated that the best scenario for improved water quality was a combined reduction in nutrient input and mesozooplankton mortality calling for the need of an integrated management of marine areas exploited by human activities.

Mussel aquaculture in the Danish fjord Limfjorden has the largest potential in relation to production volume, economic potential and sustainability. Spawning of the blue mussel Mytilus edulis takes place in the natural mussel beds during spring. The resultant larvae are then spread by the water currents to other areas before settling on the bottom, or on the long-lines in the mussel farms. The farms should be located in areas with a high and stable year-to-year recruitment of mussel larvae and be climate ready, taking changes in future distributions of larvae into account. In the following study, we used a 3D ecosystem modelling tool to estimate the mussel larval distribution on fine spatial and temporal scales in a local set-up of the Limfjorden. We coupled a 3D physical Limfjord model with an agent based model (ABM) using the Flexsem system, where the larvae were defined by several biological parameters. Preliminary results show that there is a high proportion of larval self-recruitment in the system. This is the case in all areas except for Nissum Bredning and Hjarbæk Fjord. Kås Bredning seem to be the main donor area, and Skive Bredning the main receiver area. Connectivity results can be explained by the current circulation patterns in the area. The model provided maps of mussel larvae distribution and will be used for site-selection processes of mussel farming in the fjord. These results are of fundamental importance for the development of mussel farming as a measure to mitigate eutrophication.

Akvakulturproduktionen af regnbueørred ønskes forøget i de indre danske farvande ifølge Fødevarepakken. Havbrugene er planlagt til at ligge uden for 1 sømilsgrænsen for at begrænse de negative miljøeffekter af de kystnære vandområder. Havbrugene er planlagt til at producere ca. 2.200 tons fisk per år svarende til en ekstra udledning på 100 t-N og 13 t-P per farm. Vi anvendte en 3D model, Flexsem, til at beregne de rumlige og sæsonmæssige effekter af 2 potentielle havbrug beliggende i området øst for Samsø. Vandkvalitet (DIN og primærproduktion) blev mest påvirket i det åbne havområde omkring havbrugene, og ændringer var ikke synlige, efter at produktionsperioden sluttede i november. Det organiske stof i sedimentet blev forøget under havbrugene pga. udsynkning af foderrester og fiskefækalier og nåede ikke at blive omsat inden den næste fiskeproduktionsperiode i området med lav resuspension. Omkring 20% af de udledte næringsstoffer fra havbrugene blev transporteret ind i de kystnære vandområder beskyttet af EU vandrammedirektivet, men der var ikke tydelige ændringer i vandkvalitet. Den ekstra næringsstofudledning fra havbrug vil dog modvirke de nødvendige reduktioner fra landbaserede kilder for at opnå en god økologisk tilstand. Hvis flere havbrug skal implementeres i de indre danske farvande, vil det kræve en detaljeret rumlig planlægning, en optimering af havbrug design og en næringsstofkompensation fra marine virkemidler, fx muslingefarme. Det i gangværende BONUS OPTIMUS projekt har til formål at optimere produktionen af miljømuslinger ift. næringsstoffjernelse ved høstning, udvælge egnede områder for miljømuslingerne og teste anvendelse af muslingerne som fiskefoder.

The multiple hydrodynamic and ecological processes characterizing estuarine systems make ecological modelling an essential tool for ecosystem-based management by increasing the understanding of the complex interactions and by quantifying the effects of various natural and anthropogenic pressures. The modelling technique used is dominated by computational simple box model approaches with a low spatial resolution and coupled 3D hydrodynamic-ecological models with high computational requirements. In this paper we present a novel concept (Flexsem) which combines the computational simplicity and condensed hydrodynamics from box models with a high spatial resolution characterizing coupled 3D models. The modelling framework Flexsem is a fast, flexible and user-friendly tool specifically targeted towards scientific and management challenges of the complex biogeochemical processes in coastal zone ecosystems. We use Flexsem to simulate the physical conditions in a typical Danish estuary, Horsens Fjord utilizing unstructured computational meshes to vary the complexity of grid geometry and resolution. The results showed that the model was able to reproduce the physical conditions in the estuary and provide reliable estimates for the tracer residence time.

Knowledge about the interior temperatures of the polar caps on Mars is crucial for the understanding of stratigraphy and dynamics of the polar caps. The insolation and thereby the temperatures of the surface are strongly influenced by factors including obliquity, conductivity, and albedo. Basal temperatures are mainly determined by surface temperature, cap thickness, thermal conductivity, and areothermal (Areo, Greek for Mars) heat flux. This paper presents a model for the northern polar cap on Mars, where temperature profiles are determined as a function of orbital parameters (obliquity and eccentricity), thermal conductivity, areothermal heat flux, and cap thickness. Furthermore we will look at the thermal behavior of the upper layer (∼100 m) of a martian ice cap. There is strong evidence that the northern polar cap consists mainly of H 2 O ice. In the model we will treat the cap as that of H 2 O ice with a high dust content and the possibility for solid CO 2 or CO 2 clathrates. The temperature model shows that the ice is most likely flowing and that the flow rate oscillates with a time lag of 30–70 Kyrs compared to the surface temperature obliquity oscillation. The possibility for measuring the areothermal heat flux by measuring the temperature in the upper 2 m of the ice cap is not very good, but measurements of temperatures through the top 2 m of the ice could provide valuable information on the conductivity of the ice and thereby the constituents of the Mars ice cap.

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approximately 10(6) km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young--preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approximately 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason--providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.

DNA-binding transcription factors bind to promoters that carry their binding sites. Transcription factors therefore function as nodes in gene regulatory networks. In the present work we used a bioinformatic approach to search for transcription factors that might function as nodes in gene regulatory networks during the differentiation of the small intestinal epithelial cell. In addition we have searched for connections between transcription factors and the villus metabolome. Transcriptome data were generated from mouse small intestinal villus, crypt, and fetal intestinal epithelial cells. Metabolome data were generated from crypt and villus cells. Our results show that genes that are upregulated during fetal to adult and crypt to villus differentiation have an overrepresentation of potential hepatocyte nuclear factor (HNF)-4 binding sites in their promoters. Moreover, metabolome analyses by magic angle spinning1H nuclear magnetic resonance spectroscopy showed that the villus epithelial cells contain higher concentrations of lipid carbon chains than the crypt cells. These findings suggest a model where the HNF-4 transcription factor influences the villus metabolome by regulating genes that are involved in lipid metabolism. Our approach also identifies transcription factors of importance for crypt functions such as DNA replication (E2F) and stem cell maintenance (c-Myc).

The inner Danish waters have experienced from a drastic decline in eelgrass Zostera marina coverage during the last decades. In 1901 eelgrass meadows covered ca. 15% of all Danish marine waters, which in 1930 was reduced to less than 8% due to the wasting disease. Currently the eelgrass distribution is very limited and restoration efforts are being planned to recover eelgrass in the coastal areas of Denmark. In the present study, we developed a hydrodynamic model within the FlexSem framework coupled to an Individual-Based model, to study eelgrass dispersal in the Kattegat Sea. Floating particles simulated the dispersal of eelgrass reproductive shoots containing seeds during the flowering season July-September. We then use the graph theory approach to analyze the connectivity and identify key areas for eelgrass restoration. Our results identify fragile nodes and edges in the network, keystone areas and important sites to restore the network of patches. This study shows the possibilities of using such approach and the importance of collaborative work between researchers and practitioners in order to understand these complex systems and restore eelgrass beds in coastal areas.

Eutrophication is one of the largest threats to the Baltic Sea manifested by algal blooms, turbid waters, loss of submerged vegetation and hypoxic and anoxic conditions at the sea bottom in large areas. It is well known that marine suspension-feeders possess a significant capacity for clearing the water column of particles. The potential of using bivalves such as blue mussels to mitigate effects of eutrophication in the coastal zone has been proved to be cost-effective in Danish waters. However, it is still a challenge to optimize mussel farms and mussel production and thereby further reduce costs in order to compete with other mitigation measures. The farm design and locations need to be adapted to different environmental conditions in order to handle e.g. high predation pressure, low salinity, exposure to high wind, waves or ice coverage, but also in terms of efficient mussel larvae settling on the long-lines. Spawning takes place in the natural mussel beds in May-June and the resultant larvae are spread by the water currents to other areas before settling on the bottom or on the long-lines in the mussel farms. In the following study, we used 3D ecosystem modelling to estimate the mussel larval distribution on fine spatial and temporal scales in a local set-up of the Limfjorden. We coupled a 3D physical Limfjord model with an agent based model (ABM) using the Flexsem system, where mussel larvae were defined by several biological parameters. The model provided maps of mussel larvae distribution and will be used for site-selection processes of mussel farming in the Limfjorden. These results are of fundamental importance for the development of mussel farming as a measure to mitigate eutrophication.

Mussel fishery in Denmark is heavily regulated and controlled in Natura2000 areas under the Danish mussel policy. Restrictions such as gear size and weight, quotas and limit in the amount of area impacted have been established in order to protect key ecosystem components such as macroalgae and benthic organisms. For eelgrass, no tolerance is accepted, fishery is restricted below 5m depth in the eelgrass zone, and a buffer zone of 300m is established around the eelgrass where no fishery is allowed to take place. In order to assess the potential indirect effects of dredging operations such as: i) reduction of light availability to the eelgrass beds due to sediment resuspension during and after dredging ii) smothering and burial of eelgrass seedling and beds from transport and sedimentation coming from sediment plumes, two sets of experiments were conducted in the Limfjorden in two different broads and with different fishery intensity. A range of water quality parameters was measured such as: light intensity, suspended particulate matter concentration, sedimentation, turbidity, oxygen and chlorophyll concentrations were measured under natural condition versus various fishing intensity at different distance from the fished areas.Field data showed that the resuspended material signal from mussel seed fishery activity is highly dependent on the current direction and the fishing practice. Collected data was used to calibrate a sediment transport module in the Flexsem model developed for the Limfjorden. The model describes the transport of different size fractions of sediment particles under different fishing scenarios and will be used as a new tool for managing fisheries and help to decide on an appropriate buffer zone to protect the existing eelgrass beds from indirect impacts from mussel seed fisheries.

Aquaculture production of rainbow trout is planned to increase offshore in the inner Danish waters and the expected release to the environment is 100 t-nitrogen (N) and 12.8 t-phosphorus (P) per farm annually. We applied 3D modelling to estimate spatial- and temporal effects of two potential future offshore fish farms on water quality, sediment fluxes and nutrient transports in the Samsø Belt area. The model results showed that water quality (mainly dissolved inorganic nitrogen and primary production) was affected in open waters during the production period leaving no traces one month after the production period. Changes in bottom water oxygen levels and Secchi depths were not considered important for the system. Sediment organic content and nutrient fluxes increased from reference conditions locally below the fish cages. The sediment did not recover from the impact between the production periods, especially at the site with lowest resuspension. There was a gross transport of nutrients into the coastal water areas corresponding to 21% (N) and 16% (P) of the farm inputs, but this only resulted in minor changes of water quality. However, the additional nutrient enrichment counteracts the required nutrient reductions from other sources with the aim to improve the ecological status. Likewise, far-field nutrient transports was shown to reach several protected Natura 2000 sites. Future implementation of fish farms in the area requires detailed spatial planning, optimisation of farm design and nutrient compensation by marine measures, e.g. blue mussel farming.