Relative contribution of multiple stressors on copepod density and diversity dynamics in the Belgian part of the North Sea

The effect of multiple stressors on marine ecosystems is poorly understood. To partially bridge this knowledge gap we investigated the relative contribution of environmental variables to density and diversity dynamics of the zooplankton community in the Belgian part of the North Sea. We applied multimodel inference on generalized additive models to quantify the relative contribution of chlorophyll a, temperature, nutrients, salinity and anthropogenic chemicals (i.e. polychlorinated biphenyls and polycyclic aromatic hydrocarbons) to the dynamics of calanoid copepod species in the Belgian part of the North Sea. Temperature was the only predictor consistently showing a high importance in all models predicting the abundances of the selected copepod species. The relative contribution of other predictors was species-dependent. Anthropogenic chemicals were important predictors for three out of six species indicating that chemical mixtures at low concentrations should not be left unattended when performing risk assessments in a natural environment

Potential health risks via consumption of six edible shellfish species collected from Piura - Peru

Scallops and their potential predators were collected in Sechura Bay and in front of the Illescas Reserved Zone (north Peru), during El Nino-Southern Oscillation (ENSO) 2016, and analyzed for the metals chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb). This study showed that similar to 20% of the molluscs exceeded the maximum residual levels (MRLs) for human consumption in inorganic As, while similar to 30% of the crustaceans did. For Cd, around 10% and 40% of the molluscs and the crustaceans were above the MRLs, respectively. The cephalopod Octopus mimus exhibited As concentrations, but not Cd concentrations, that exceeded the MRLs. Cr, Ni, Cu, Zn and Pb in muscle exhibited generally concentrations below the MRLs. Integrated risk indices were estimated to determine if there is a health risk for consumption. Target hazard quotients (THQs) and total hazard indices (HIs) were mostly < 1, implying no human health risk. Provisional tolerable weekly intake (PTWI) for Cd was exceeded in Bursa ventricosa at Illescas Reserved Zone. Target cancer risks (TRs) for inorganic As were always higher than the threshold (1 x 10(-6)), therefore an actual cancer risk is present

Preliminary description of a hillslope-storage Boussinesq model for subsurface and overland flow

The Boussinesq model for subsurface flow in an idealized sloping aquifer has recently been extended to hillslopes of arbitrary geometry by incorporating the width function w(s) into the governing equation, were x is the distance along the length of the hillslopes. The resulting mathematical model can be simplified if three higher order terms containing (1/w)w’(x) are dropped. In this preliminary report we describe the model along with some characteristic hillslopes that will be used to test it and develop it further

Multimodel inference to quantify the relative importance of abiotic factors in the population dynamics of marine zooplankton

The effect of multiple stressors on marine ecosystems remains poorly understood and most of the knowledge available is related to phytoplankton. To partly address this knowledge gap, we tested if combining multimodel inference with generalized additive modelling could quantify the relative contribution of environmental variables on the population dynamics of a zooplankton species in the Belgian part of the North Sea. Hence, we have quantified the relative contribution of oceanographic variables (e.g. water temperature, salinity, nutrient concentrations, and chlorophyll a concentrations) and anthropogenic chemicals (i.e. polychlorinated biphenyls) to the density of Acartia clausi. We found that models with water temperature and chlorophyll a concentration explained ca. 73% of the population density of the marine copepod. Multimodel inference in combination with regression-based models are a generic way to disentangle and quantify multiple stressor-induced changes in marine ecosystems. Future–oriented simulations of copepod densities suggested increased copepod densities under predicted environmental changes

The influence of a berm and a vertical wall above swl on the reduction of wave overtopping

The Eurotop Manual, based on the TAW guidelines, recognizes the reducing effect of a vertical wall or a berm on wave overtopping over an impermeable slope. Nevertheless, these reduction factors are only introduced in the formula for breaking waves. Furthermore, the berms for which reduction factors are proposed are mainly located below the SWL. In this paper, the reducing effect of a berm above SWL, a vertical wall and the combination of both are investigated. Reduction factors have been deducted, and are introduced in the existing overtopping formulae for an impermeable slope

Seasonal and spatial fatty acid profiling of the calanoid copepods <i>Temora longicornis</i> and <i>Acartia clausi</i> linked to environmental stressors in the North Sea

The Belgian part of the North Sea (BPNS) is subjected to multiple environmental stressors. The impact of these stressors includes the modulation of fatty acid (FA) composition of the zooplankton. This study recorded temporal and spatial patterns of the FA profiles of two dominant calanoid copepods within the BPNS: Temora longicornis (Müller, 1785) and Acartia clausi (Giesbrecht, 1889). By means of distance-based linear modelling and by applying multi model inference to generalized additive models, environmental stressors were linked to patterns of the FA profiles of these species. The FA profiles of A. clausi and T. longicornis showed distinct intraspecific, spatial and temporal differences within the BPNS. Temperature and algal food quality (marked by the ratio of silicate concentration to dissolved inorganic nitrogen concentration, SiO4/DIN) were the most important drivers of seasonal fluctuations in the DHA/EPA ratio of both species. DHA/EPA ratio can be used as marker for stress in copepods in the BPNS in order to have a quick indication of food quality changes at the basis of the food web