Increased food availability at offshore wind farms affects trophic ecology of plaice Pleuronectes platessa.

Offshore wind farms (OWFs) and their associated cables, foundations and scour protection are often constructed in soft-sediment environments. This introduction of hard substrate has been shown to have similar effects as artificial reefs by providing food resources and offering increased habitat complexity, thereby aggregating fish around the turbines and foundations. However, as most studies have focused their efforts on fish species that are typically associated with reef structures, knowledge on how soft sediment species are affected by OWFs is still largely lacking. In this study, we analysed the trophic ecology and condition of plaice, a flatfish species of commercial interest, in relation to a Belgian OWF. The combination of a stomach and intestine content analysis with the use of biomarkers (i.e. fatty acids and stable isotopes) identified a clear shift in diet with increased occurrences of typical hard-substrate prey species for fish in the vicinity of the foundations and this both on the short and the long term. Despite some condition indices suggesting that the hard substrate provides increased food availability, no clear increases of overall plaice condition or fecundity were found. Samples from within the wind farm, however, contained larger fish and had a higher abundance of females compared to control areas, potentially indicating a refuge effect caused by the cessation of fisheries activities within the OWF. These results suggest that soft-sediment species can potentially benefit from the presence of an OWF, which could lead to fish production. However, more research is still needed to further elucidate the behavioral ecology of plaice within OWFs to make inferences on how they can impact fish populations on a larger spatial scale.

Faunal and environmental drivers of carbon and nitrogen cycling along a permeability gradient in shallow North Sea sediments.

Ecosystem functions are driven by abiotic and biotic factors, but due to high collinearity of both, it is often difficult to disentangle the drivers of these ecosystem functions. We studied sedimentological and faunal controls of benthic organic matter mineralization, a crucial ecosystem process provided for by sediments of shelf seas. Subtidal benthic habitats representative of the wide permeability gradient found in the Belgian Part of the North Sea (Northeast Atlantic Shelf) were characterized in terms of sediment descriptors, macrofauna, and sediment biogeochemistry was estimated. Our results confirmed a strong correlation between sediment characteristics and macrofauna, and estimated sediment biogeochemical process rates were clearly linked to both. Results of variance partitioning and statistical modelling showed that oxic mineralization and nitrification were mainly regulated by faunal activities whereas anoxic mineralization was regulated by sediment properties, with permeability as a decisive factor. Both biotic and abiotic factors were needed to explain variability in oxygen consumption and total mineralization estimates, suggesting that macrofaunal activities have different effects across habitats. The statistical models were a useful tool to interpret the impact of anthropogenic activities in the study area and represent a step towards predicting the effects of human activities on crucial ecosystem functions.

Quantifying and addressing the prevalence and bias of study designs in the environmental and social sciences.

Building trust in science and evidence-based decision-making depends heavily on the credibility of studies and their findings. Researchers employ many different study designs that vary in their risk of bias to evaluate the true effect of interventions or impacts. Here, we empirically quantify, on a large scale, the prevalence of different study designs and the magnitude of bias in their estimates. Randomised designs and controlled observational designs with pre-intervention sampling were used by just 23% of intervention studies in biodiversity conservation, and 36% of intervention studies in social science. We demonstrate, through pairwise within-study comparisons across 49 environmental datasets, that these types of designs usually give less biased estimates than simpler observational designs. We propose a model-based approach to combine study estimates that may suffer from different levels of study design bias, discuss the implications for evidence synthesis, and how to facilitate the use of more credible study designs.

Isolation and characterisation of 14 novel microsatellite markers through Next Generation Sequencing for the commercial Atlantic seabob shrimp Xiphopenaeus kroyeri.

Assessing population genetic structure is a crucial step to support fisheries and conservation management. DNA microsatellite molecular markers are a widely used tool in population genotyping. In the present study, we characterised and developed 14 novel polymorphic microsatellite markers for a decapod crustacean, the Atlantic seabob shrimp Xiphopenaeus kroyeri (Heller, 1862), through rapid and cost-effective Illumina shotgun sequencing and a Galaxy-based bioinformatic pipeline. We genotyped 60 individuals from 2 populations with the newly developed microsatellites, resulting in the detection of 3 to 29 alleles per locus. Four loci deviated from Hardy-Weinberg equilibrium. Cross-amplification in a cryptic congeneric species was successful for eight loci (57%). The microsatellite loci developed in this study will be highly relevant for genetic and evolutionary studies of X. kroyeri, and for the stock management of this commercially exploited species.

Similar diversity-disturbance responses to different physical impacts: three cases of small-scale biodiversity increase in the Belgian part of the North Sea.

Human activities at sea are still increasing. As biodiversity is a central topic in the management of our seas, it is important to understand how diversity responds to different disturbances related with physical impacts. We investigated the effects of three impacts, i.e. sand extraction, dredge disposal and offshore wind energy exploitation, on the soft-bottom macrobenthic assemblages in the Belgian part of the North Sea. We found similar diversity-disturbance responses, mainly related to the fact that different impacts caused similar environmental changes. We observed a sediment refinement which triggered a shift towards a heterogenic, dynamic (transitional) soft-bottom macrobenthic assemblage, with several species typically associated with muddy sands. This led to a local unexpected biodiversity increase in the impacted area. On a wider regional scale, the ever increasing human impacts might lead to a homogenization of the sediment, resulting in a more uniform, yet less diverse benthic ecosystem.