Annelies De Backer

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.

Behaviour and time allocation of the mud shrimp, Corophium volutator, during the tidal cycle: a laboratory study

Despite the numerous ecological and behavioural studies, relatively little is known about the behavioural dynamics of Corophium volutator during the tidal cycle. In the present study, the behaviour of C. volutator was observed in the laboratory in a tide-simulated aquarium, and time allocation of the different activities was quantified. Overall, the surface activity was low and showed a steep decline after submersion. A clear tide-based cyclic pattern was found, with a boost of activity immediately after first submersion, continuing during submersion, and shifting over a period with decreasing activity towards almost total inactivity at the end of emersion.

Assessing the impact degree and areal degradation extent of the benthic ecosystem caused by different human activities.

How sustainable are human activities and at what pace do they impact the ecosystem? An ongoing debate urging for uniform assessments. The EU Nature Directives (Marine Strategy Framework, Habitat and Water Framework Directives) provide good bases for scientifically sound assessments. However, they all have different assessment criteria, hampering the objective comparison of the impact degree and the areal extent of degradation caused by human activities. In this study, we applied a harmonized and uniform set of biodiversity indicators, as defined for MSFD-Descriptor 1 with respect to the benthic ecosystem in the Belgian North Sea. We assessed the impact of dredge disposal and aggregate extraction, two activities only allowed in dedicated zones, and compared this to the impact of the more widespread fishery activity. At certain pressure thresholds (e.g. volume disposed, volume and frequency of extraction, number of trawls), all activities caused a decrease in benthic habitat quality. However, for each activity the thresholds and the areal extent of degradation were quite different dependent on the benthic habitat type in which the activity took place. Such detailed insights on pressure footprints are necessary, to allow for an integrated evaluation of the biodiversity status across multiple activities within different marine regions.

Long-term trends in soft-bottom fauna based on 30 years biodiversity monitoring systems

From 1984 onwards, several locations (outside direct human impact) were yearly sampled for macrobenthos, epibenthos and demersal fish in autumn. This provided a unique dataset to study natural variability over time within the soft-bottom ecosystem. Both coastal and offshore assemblages of each ecosystem component were sampled, which permitted to detect if the coastal and offshore area changed differently over time within one ecosystem component. Furthermore, these long-term data enabled to identify whether the different ecosystem components showed similar or different trends over time. Observed changes were linked to physical and climate-related environmental variables.

Chapter 9 sediment characterization of intertidal mudflats using remote sensing

Abstract In this paper an automated method for hyperspectral image classification is proposed. The method is based on a linear transformation of each spectrum in the hyperspectral cube. Different sediment types and land covers were classified using two dimensions of the transformed data space. The methodology is applied to hyperspectral images of the IJzermonding mudflat, acquired by the Compact Airborne Spectrographic Imager (CASI) in 2001 and 2003. Comparable classification results were obtained using a standard classification method employed in hyperspectral image processing. The similarity between classification results was 82 and 65% for the images of 2001 and 2003, respectively. The superiority of the proposed user-friendly method lies in its autonomy, reliability and objectivity. The proposed method uses the underlying statistical information of the data set, while the standard method is mainly based on expert knowledge.