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Despite the ubiquitous and persistent presence of microplastic (MP) in marine ecosystems, knowledge of its potential harmful ecological effects is low. In this work, we assessed the risk of floating MP (1 μm–5 mm) to marine ecosystems by comparing ambient concentrations in the global ocean with available ecotoxicity data. The integration of twenty-three species-specific effect threshold concentration data in a species sensitivity distribution yielded a median unacceptable level of 1.21 ∗ 105 MP m−³ (95% CI: 7.99 ∗ 103–1.49 ∗ 106 MP m−³). We found that in 2010 for 0.17% of the surface layer (0–5 m) of the global ocean a threatening risk would occur. By 2050 and 2100, this fraction increases to 0.52% and 1.62%, respectively, according to the worst-case predicted future plastic discharge into the ocean. Our results reveal a spatial and multidecadal variability of MP-related risk at the global ocean surface. For example, we have identified the Mediterranean Sea and the Yellow Sea as hotspots of marine microplastic risks already now and even more pronounced in future decades.

Phytoplankton is a diverse group of photosynthesizing organisms which account for approximately fifty percent of the primary production on Earth. Increasing our knowledge on phytoplankton dynamics (and plankton in general) is therefore of major importance. In the present research, we aimed to reveal the spatiotemporal dynamics of the phyto- and zooplankton community in the Eastern English Channel, Southern Bight of the North Sea and the Thames estuary. To do so, we organized a JERICO-NEXT Lifewatch cruise in May 2017 on board of the RV Simon Stevin and sampled 44 stations, involving five research institutions from France (CNRS-LOG,), The Netherlands (RWS, NIOZ) and Belgium (UGENT, VLIZ). To quantify the biomass of the phytoplankton community we used a unique combination of three flow cytometers and two Fast Repetition Rate Fluorometerss that were coupled to the underway ferrybox system. These observations were complemented with Water Insight Spectrometer and water profile data (by means of a CTD) and samples for zooplankton, pigment and nutrient analysis. A dedicated data workshop was organized with all partners to conduct a joint analysis on both the biotic and abiotic data. A first exploration of the data, by means of regression-based models and multivariate statistics, suggested that mainly nutrient discharges from the rivers influence the plankton structure. Furthermore, water turbidity is controlling photosynthetic activity and horizontal and vertical variations of photosynthetic properties can be discriminated.

Fishing effort in the Vietnamese coastal ecosystem has rapidly increased from the 1990s to the 2000s, with unknown consequences for local ecosystem structure and functioning. Using ecosystem models that integrate fisheries and food webs we found profound differences in the production of six functional groups, the food web efficiency, and eight functional food web indices between the 1990s (low fishing intensity) and the 2000s (high fishing intensity). The functional attributes (e.g. consumption) of high trophic levels (e.g. predators) were lower in the 2000s than in the 1990s while primary production did not vary, causing food web efficiency to decrease up to 40% with time for these groups. The opposite was found for lower trophic levels (e.g. zooplankton): the functional attributes and food web efficiency increased with time (22 and 10% for the functional attributes and food web efficiency, respectively). Total system throughput, a functional food web index, was about 10% higher in the 1990s than in the 2000s, indicating a reduction of the system size and activity with time. The network analyses further indicated that the Vietnamese coastal ecosystem in the 1990s was more developed (higher ascendancy and capacity), more stable (higher overhead) and more mature (higher ratio of ascendancy and capacity) than in the 2000s. In the 1990s the recovery time of the ecosystem was shorter than in 2000s, as indicated by a higher Finn's cycling index in the 1990s (7.8 and 6.5% in 1990s and 2000s, respectively). Overall, our results demonstrate that the Vietnamese coastal ecosystem has experienced profound changes between the 1990s and 2000s, and emphasise the need for a closer inspection of the ecological impact of fishing.

A complex chemical cocktail, with unknown composition and concentrations, is present in marine waters. Although the awareness of the vulnerability of marine ecosystems to pollution-induced changes increased, the ecotoxicological effects of chemical pollutants on marine ecosystems are poorly understood. Even in intensively monitored regions such as the North Sea, current knowledge of the ecotoxicological effects of chemicals is limited to few (priority) substances and few (model) species (discussed in chapter I). To partly address this knowledge gap, in the present work, using phytoplankton, it is assessed how marine ecosystems respond to the presence of organic chemicals. By analyzing existing data and performing laboratory experiments, ecotoxicological effects of organic chemicals to marine organisms and ecosystem functions are quantified. Specific aims of this work are: (1) to infer spatiotemporal trends of concentrations of organic chemicals; (2) to investigate the impact of primary and secondary emissions on the spatiotemporal trends of organic chemicals; (3) to examine the partitioning of organic chemicals in different environmental compartments; (4) to assess the potential ecotoxicological effect of realistic mixtures of organic chemicals along environmental gradients; and (5) to quantify the relative contribution of organic chemicals to the phytoplankton growth dynamics. Spatiotemporal trends of polychlorinated biphenyl (PCB) concentrations are inferred based on an extensive set of concentrations monitored between 1991 and 2010 in sediments of the Belgian Coastal Zone (BCZ) and the Western Scheldt estuary in chapter II. The time trends unravel two to three-fold PCB concentration decreases in the BCZ during the last 20 years. In the Western Scheldt estuary, time trends are spatially heterogeneous and not significantly decreasing. These results demonstrate that international efforts to cut down emissions of PCBs have been effective to reduce concentrations in open water ecosystems like the BCZ but had little effect in the urbanized and industrialized area of the Scheldt estuary. Most likely, estuaries are subject to secondary emissions from historical pollution. In chapter III, trends found for the BCZ (chapter II) are confirmed at larger spatiotemporal scales. In chapter III multidecadal field observations (1979–2012) in the North Sea and Celtic Sea are analyzed to infer spatiotemporal concentration trends of PCBs in mussels (Mytilus edulis) and in sediments. Decreasing interannual PCB concentrations are found in North Sea sediments and mussels. PCB concentrations in sediments show, less than PCB levels in mussels, decreasing interannual trends. In addition in chapter III, interannual changes of PCB concentrations are separated from seasonal variability. By doing so, superimposed to the generally decreasing interannual trends, seasonally variable PCB concentrations are observed. These seasonal variations are tightly coupled with seasonally variable chlorophyll a concentrations and organic carbon concentrations. Indeed, the timing of phytoplankton blooms in spring and autumn corresponds to the annual maxima of the organic carbon content and the PCB concentrations in sediments. These results demonstrate the role of seasonal phytoplankton dynamics (biological pump) in the environmental fate of PCBs at large spatiotemporal scales.The latter is a novel result since the working of the biological pump was never assessed before based on field data collected at the scale of a regional sea in multiple decades. Despite the generally decreasing spatiotemporal trends of PCBs that are found in chapter II and III, it is not clear whether current concentrations (still) pose a risk to marine ecosystems. In chapter IV, the spatiotemporal trends inferred in chapter III are used to assess the ecological risk of PCBs in North Sea and Celtic Sea sediments and mussels. To do so, PCB concentrations are compared with environmental assessment criteria (EAC). It is found that the potential ecotoxicological risk of PCBs change considerably over time and in space. Risk quotients (RQs) of PCBs in marine sediments primarily depend on the location of the monitoring site, i.e. the closer to the coast, the higher the RQ. Especially in summer, when PCB concentrations in sediments are high, PCBs present in marine coastal sediments may pose an environmental risk. By contrast, RQs in mussel depend first on the interannual changes of PCB concentrations. At present, in the Celtic Sea, RQs in mussels are below the value of 1, suggesting no potential environmental risk. In the North Sea, however, PCBS in mussels may still exceed the prescribed environmental quality criteria. Overall, the results shown in chapter IV demonstrate that the spatiotemporal variability in PCB concentrations should be considered in future environmental risk assessments. Comparing concentrations of chemicals with quality thresholds (as in chapter IV) only suggest a potential ecological risk. Therefore, in case if risk quotients exceed the value of 1, additional assessments are recommended. Considering the results obtained in chapter IV, in chapter V, additional experimental studies are performed in which a marine diatom is exposed to a realistic mixture of organic contaminants. To do so, passive samplers are used to achieve exposure to realistic mixtures of organic chemicals close to ambient concentrations. The main conclusion is that organic chemicals present in Belgian marine waters do not affect the intrinsic growth rate of Phaeodactylum tricornutum. In this context, caution is needed when extrapolating these results to field conditions. In the present research, results were obtained under laboratory controlled conditions with one single species and thus neglecting possible species interactions. Therefore, prior to extrapolating these results to other diatoms and other groups of phytoplankton species, it is suggested to assess the validity of the results in a mesocosm experiment (including multiple species and different trophic levels) or under field conditions. In addition, in chapter V, the relative contribution of organic chemicals to the growth of a marine diatom is examined. Natural drivers such as nutrients regime, light intensity and temperature explain about 85% of the observed variability in the experimental data. Although the methodology used in chapter V is a standard way to assess toxicity of chemicals, it is not realistic to use just one algal species to represent ecotoxicological effects of an entire phytoplankton community. Therefore in chapter VI, an ecosystem model is used to assess the potential adverse effects of organic contaminants on the total primary production. To do so, we model phytoplankton dynamics using four classical drivers (light and nutrient availability, temperature and zooplankton grazing) and test whether extending this model with a POP-induced phytoplankton growth limitation term improves model fit. As inclusion of monitored concentrations of PCBs and pesticides did not lead to a better model fit, it is suggested that POP-induced growth limitation of marine phytoplankton in the North Sea and the Kattegat is small compared to the limitations caused by the classical drivers. The inferred contribution of POPs to phytoplankton growth limitation is about 1% in Belgian coastal waters, but in the Kattegat POPs explain about 10% of the phytoplankton growth limitation. These results suggest that there are regional differences in the contribution of POPs to the phytoplankton growth limitation. The validity of these conclusions should be further assessed for other substances, other species and higher trophic levels.

We developed a model for the coastal marine ecosystem of Vietnam to evaluate interactions between fisheries and the food web, using fisheries data from 2000 to 2005. Comparing the maximum trophic level of fish estimated by the model (4.195) and the mean trophic level of the catch (3.712) indicates that fisheries have been harvesting high trophic level species. Using the model, we found that maintaining the fishing effort at the 2000-2005 level puts the coastal marine resources at risk as the biomasses of ten out of twelve stocks decline by 5-20% in a 15 years period. A 20% fishing effort reduction of fish and shrimp trawling or gillnet and purse seine fishing still resulted in 10% biomass reductions of several key functional groups. Reducing fishing effort for all fisheries by 10% increased the biomass of almost all groups in the ecosystem up to 14% (large demersal fish). Meeting social and economic, but not ecological constraints required an increase from 4 to 8.5-fold in fishing effort and resulted in the collapses of sea turtle, tuna, small pelagic fish and cephalopods. When only meeting ecological constraints, fishing efforts reduced for four out of the eight fisheries, e.g. a 95% reduction was recommended for the gillnet fishery. A trade-off scenario indicated that achieving economic, social and ecological goals was possible by fourfold increase of traditional small-scale fisheries (e.g. handline), combined with 20-65% reductions of fish trawl and purse seine fisheries.

Marine habitat suitability models typically predict the potential distribution of organisms based on basic abiotic variables such as salinity, oxygen concentrations, temperature fluctuations (Gogina & Zettler, 2010) or sediment class information (Degraer et al., 2008; Willems et al., 2008). Recently, Dachs & Méjanelle (2010) claimed that the modification of biota composition due to marine pollution is a factor to be taken into account in marine habitat suitability models. Although the anthropogenic pressure on the environment has been exponentially increasing during the last six decades (Dachs & Méjanelle, 2010), the global effect of human inputs on oceanic phytoplankton remains unknown (Echeveste et al., 2010). A limited number of studies have assessed the impact of anthropogenic stressors on phytoplankton in marine environments at a global level (Faust et al., 2003; Magnusson et al.,2008). In order to fill this knowledge gap, this research tries to determine to what extent pollution data can be used to predict the occurrence of the phytoplanktonic organisms compared to basic abiotic variables. Here we explored this issue by developing classification trees relating physical-chemical variables with the occurrence of the potential harmful toxic algae Odontella sinensis.

In this paper we analyse the effects of soft budget constraints in an international context. Firstly, we show that soft budget constraints in an exporting country lead to higher levels of trade protection in the recipient country. Secondly, the model predicts that protectionist trade policy helps to harden budget softness in the exporting country. We therefore argue that, when industrial policy fails to enforce financial discipline, trade policy can take over this role. Finally, we discuss potential implications of our model for EU-policy with respect to Central and Eastern European Countries. ispartof: DTEW Research Report 0117 pages:1-36 status: published