Sensitivity of the N. AEGEAN SEA ecosystem to Black Sea Water inputs

The effect of Black Sea Water (BSW) inputs on the North Aegean Sea productivity and food web dynamics was investigated, by means of sensitivity simulations, investigating the effect of the inflowing BSW, in terms of inorganic nutrients and dissolved organic matter. The model used has been successfully applied in the area in the past and extensively presented. Considering the importance of the microbial loop in the ecosystem functioning, the role of the dissolved organics and in order to achieve a more realistic representation of the Dissolved Organic Matter pool, the bacteria sub-model was appropriately revised. The importance of the microbial loop is highlighted by the carbon fluxes where almost 50% of carbon is channelled within it. The impact of dissolved organic matter (DOM) (in the inflowing to the Aegean Sea, BSW) appears to be stronger than the impact of dissolved inorganic nutrients, showing a more extended effect over the N Aegean. Bacterial production and biomass is more strongly affected in the simulations by modified DOM, unlike phytoplankton biomass and production, which are more dependent on the inflowing nutrients and particularly phosphorus (inorganic and dissolved organic). In the phytoplankton composition, the dinoflagellates appear to be mostly affected, being favoured by higher nutrient availability at the expense of all other groups, particularly picoplankton, indicating a shift to a more classical food chain

Effects of Nutrient Management Scenarios on Marine Eutrophication Indicators: A Pan-European, Multi-Model Assessment in Support of the Marine Strategy Framework Directive

A novel pan-European marine model ensemble was established, covering nearly all seas under the regulation of the Marine Strategy Framework Directive (MSFD), with the aim of providing a consistent assessment of the potential impacts of riverine nutrient reduction scenarios on marine eutrophication indicators. For each sea region, up to five coupled biogeochemical models from institutes all over Europe were brought together for the first time. All model systems followed a harmonised scenario approach and ran two simulations, which varied only in the riverine nutrient inputs. The load reductions were evaluated with the catchment model GREEN and represented the impacts due to improved management of agriculture and wastewater treatment in all European river systems. The model ensemble, comprising 15 members, was used to assess changes to the core eutrophication indicators as defined within MSFD Descriptor 5. In nearly all marine regions, riverine load reductions led to reduced nutrient concentrations in the marine environment. However, regionally the nutrient input reductions led to an increase in the non-limiting nutrient in the water, especially in the case of phosphate concentrations in the Black Sea. Further core eutrophication indicators, such as chlorophyll-a, bottom oxygen and the Trophic Index TRIX, improved nearly everywhere, but the changes were less pronounced than for the inorganic nutrients. The model ensemble displayed strong consistency and robustness, as most if not all models indicated improvements in the same areas. There were substantial differences between the individual seas in the speed of response to the reduced nutrient loads. In the North Sea ensemble, a stable plateau was reached after only three years, while the simulation period of eight years was too short to obtain steady model results in the Baltic Sea. The ensemble exercise confirmed the importance of improved management of agriculture and wastewater treatments in the river catchments to reduce marine eutrophication. Several shortcomings were identified, the outcome of different approaches to compute the mean change was estimated and potential improvements are discussed to enhance policy support. Applying a model ensemble enabled us to obtain highly robust and consistent model results, substantially decreasing uncertainties in the scenario outcom

Modelling the mediterranean pelagic ecosystem using the POSEIDON ecological model. Part II: Biological dynamics

A three-dimensional coupled hydrodynamic/biogeochemical numerical model, currently in operation as part of the POSEIDON forecasting system, was implemented in the Mediterranean Sea. The model was assessed regarding its efficacy in representing the main biogeochemical components and seasonal dynamics of the Mediterranean planktonic system. Model outputs were compared with available historical data in a proposed objective eco-regionalisation of the Mediterranean basin, based on productivity. The simulated production (primary, bacterial) and planktonic biomass (phytoplankton, zooplankton and bacteria), as well as particulate and dissolved organic carbon, were found consistent with observational estimates in different areas of the Mediterranean Sea, following large scale productivity gradients. Although some limitations of the model were identified, the observed variability of the phytoplanktonic community structure was reasonably well-reproduced, simulating a dominant microbial food web with an intermittent development of the classical food web. The generic POSEIDON ecosystem model skill assessment provides a benchmark for future model improvement, highlighting the need to expand the range of biological variables sampled for further model calibration and validation. © 2020 Elsevier Lt

Modelling the Mediterranean pelagic ecosystem using the POSEIDON ecological model. Part I: Nutrients and chlorophyll-a dynamics

Ecosystem models are recognized as valuable tools to understand marine ecosystem dynamics and address management questions, requiring an integrated approach of physical and biotic processes. In the present study, a three-dimensional basin scale Mediterranean hydrodynamic/biogeochemical model, currently operational as part of the POSEIDON forecasting system, was extensively validated against available in-situ and satellite data. The generic POSEIDON ecosystem model skill was objectively assessed, in capturing the observed seasonal variability of the main chemical ecosystem components within the planktonic food web. A cluster K-means analysis was applied to obtain an objective `biogeography' of the Mediterranean Sea, allowing a more efficient validation of model outputs against observational data. The model presented a reasonable skill in reproducing the seasonal cycle and observed patterns of the Mediterranean inorganic nutrients and chlorophyll-a, characterized by a prominent west-to-east gradient and their increase in areas receiving lateral nutrient inputs. Despite some model deviations, validation results have demonstrated the capability of the model to represent the Mediterranean ecosystem, ranging from oligotrophic open ocean to mesotrophic conditions in productive coastal areas

Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the singular evolutive interpolated Kalman (SEIK) filter, the ensemble variant of the singular evolutive extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α. © 2016 Elsevier B.V.

Microplastics in the Mediterranean: Variability From Observations and Model Analysis

In this study, the abundance and properties (size, shape, and polymer type) of microplastics (MPs) in sea surface water samples, collected during two sampling campaigns over 2018–2019, in four coastal areas of the Mediterranean Sea (Saronikos Gulf, LIgurian Sea, Gulf of Lion, and Gabes Gulf) were investigated. Coupled hydrodynamic/particle drift model simulations with basin-scale Mediterranean and high resolution nested models were used to provide a better understanding on the variability of the abundance/size of MPs, originating from wastewater and river runoff, in the four areas. Different size classes of MPs were considered in the model, taking into account biofouling induced sinking, as a possible mechanism of MPs removal from the surface. The Gabes Gulf showed the highest mean MPs abundance (0.073–0.310 items/m2), followed by Ligurian Sea (0.061–0.134 items/m2), Saronikos Gulf (0.047–0.080 items/m2), and Gulf of Lion (0.029–0.032 items/m2). Overall, the observed MPs abundance and size distribution was reasonably well reproduced by the model in the four different areas, except an overestimation of small size contribution in Saronikos Gulf. The basin-scale simulation revealed a strong decrease of smaller size MPs in offshore areas, due to biofouling induced sinking, with larger (floating) MPs being able to travel longer distances in the open sea. A significant impact of waves drift and advection of MPs from non-local sources was identified from model simulations, particularly in the Gulfs of Lion and Gabes, having a stronger effect on larger microplastics. In Gabes Gulf, most MPs originated from offshore areas, being mainly (floating) larger size classes, as suggested by the observed quite small contribution of <1 mm particles. The MPs observed abundance distribution in each area could be partly explained by the adopted sources distribution. The modeling tools proposed in this study provide useful insight to gain a better understanding on MPs dynamics in the marine environment and assess the current status of plastic pollution on basin and regional scale to further develop environmental management action for the mitigation of plastic pollution in the Mediterranean Sea. Copyright © 2022 Tsiaras, Costa, Morgana, Gambardella, Piazza, Faimali, Minetti, Zeri, Thyssen, Ben Ismail, Hatzonikolakis, Kalaroni and Garaventa

A new space technology for ocean observation: the SMOS mission

Capability for sea surface salinity observation was an important gap in ocean remote sensing in the last few decades of the 20th century. New technological developments during the 1990s at the European Space Agency led to the proposal of SMOS (Soil Moisture and Ocean Salinity), an Earth explorer opportunity mission based on the use of a microwave interferometric radiometer, MIRAS (Microwave Imaging Radiometer with Aperture Synthesis). SMOS, the first satellite ever addressing the observation of ocean salinity from space, was successfully launched in November 2009. The determination of salinity from the MIRAS radiometric measurements at 1.4 GHz is a complex procedure that requires high performance from the instrument and accurate modelling of several physical processes that impact on the microwave emission of the ocean’s surface. This paper introduces SMOS in the ocean remote sensing context, and summarizes the MIRAS principles of operation and the SMOS salinity retrieval approach. It describes the Spanish SMOS high-level data processing centre (CP34) and the SMOS Barcelona Expert Centre on Radiometric Calibration and Ocean Salinity (SMOS-BEC), and presents a preliminary validation of global sea surface salinity maps operationally produced by CP34.Peer ReviewedPostprint (published version

International education journal : IEJ

Capability for sea surface salinity observation was an important gap in ocean remote sensing in the last few decades of the 20th century. New technological developments during the 1990s at the European Space Agency led to the proposal of SMOS (Soil Moisture and Ocean Salinity), an Earth explorer opportunity mission based on the use of a microwave interferometric radiometer, MIRAS (Microwave Imaging Radiometer with Aperture Synthesis). SMOS, the first satellite ever addressing the observation of ocean salinity from space, was successfully launched in November 2009. The determination of salinity from the MIRAS radiometric measurements at 1.4 GHz is a complex procedure that requires high performance from the instrument and accurate modelling of several physical processes that impact on the microwave emission of the ocean’s surface. This paper introduces SMOS in the ocean remote sensing context, and summarizes the MIRAS principles of operation and the SMOS salinity retrieval approach. It describes the Spanish SMOS high-level data processing centre (CP34) and the SMOS Barcelona Expert Centre on Radiometric Calibration and Ocean Salinity (SMOS-BEC), and presents a preliminary validation of global sea surface salinity maps operationally produced by CP34.Peer ReviewedPostprint (published version

A new space technology for ocean observation: the SMOS mission

Capability for sea surface salinity observation was an important gap in ocean remote sensing in the last few decades of the 20th century. New technological developments during the 1990s at the European Space Agency led to the proposal of SMOS (Soil Moisture and Ocean Salinity), an Earth explorer opportunity mission based on the use of a microwave interferometric radiometer, MIRAS (Microwave Imaging Radiometer with Aperture Synthesis). SMOS, the first satellite ever addressing the observation of ocean salinity from space, was successfully launched in November 2009. The determination of salinity from the MIRAS radiometric measurements at 1.4 GHz is a complex procedure that requires high performance from the instrument and accurate modelling of several physical processes that impact on the microwave emission of the ocean’s surface. This paper introduces SMOS in the ocean remote sensing context, and summarizes the MIRAS principles of operation and the SMOS salinity retrieval approach. It describes the Spanish SMOS high-level data processing centre (CP34) and the SMOS Barcelona Expert Centre on Radiometric Calibration and Ocean Salinity (SMOS-BEC), and presents a preliminary validation of global sea surface salinity maps operationally produced by CP34.Peer Reviewe