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Newsletter December 2017

Hope for recovery. The current status of the soil fauna in the seabed-protected zones of the Flemish Banks.

In the future, some zones in our part of the North Sea will be protected against seabed disturbance, with the aim of restoring the local benthic communities. But what does the seabed in those areas look like now? And what about the status of the fauna living there? ILVO and RBINS examined the seabed protected zones and see potential for recovery.

soil fauna

In the Marine Spatial Plan, two seabed protected areas have been defined within the Natura 2000 area "Flemish Banks" (Vlaamse Banken in Dutch). These will be safeguarded in the future from activities that disrupt or damage the seabed. One area is located in the coastal zone, where mainly mud and sand and a biologically valuable benthic community can be found. The other area is further away from the coast, in a zone with gravel that accommodates a fragile community. To evaluate the effects of the protection in the future, the current state of the seabed and the ecology in both areas was investigated in detail. The assignment fits within the agreements concerning the fishing measures set out in the Belgian Marine Spatial Plan (MRP) and the obligations arising from the European Marine Strategy Framework Directive (MSFD).

The methodology for sampling was tailored to the type of substrate in each zone. In the coastal zone (zone 1 of the MRP), sediment characteristics and fauna were described based on Van Veen grab samples. The gravel zone (zone 3 of the MRP) was mapped using multi-beam technology. Both the soil fauna and the fauna that live attached to the stones were sampled with a combination of techniques (Hamon grab, Gilson dredge). The results show that the coastal zone is characterized by an Abra alba community with a high species diversity, density and biomass. The MSFD indicators score well, despite the relatively high fishing pressure in the area. The diversity of species and density does decrease with increasing fishing pressure, which suggests that the fauna will evolve to a better condition if the seabed disturbance is reduced. The ecological situation in the gravel zone is less good: typical species expected to live on hard substrates, such as sponges, bryozoans, mussels and soft corals, are found. However, the most fragile species were not found in the area, and mussels and soft corals (dead man's fingers) occurred as small, stunted colonies. In this zone a rich gravel zone was observed in one channel, while in two other channels the gravel was irregularly distributed. In this area, there is clear potential for the recovery of fragile species in the case of the exclusion of seabed disturbance.

This study forms the baseline for potential recovery when the protective measures come into effect. The impact of the fisheries measures will be monitored through a monitoring program. In the gravel zone (zone 3) all seabed disturbing techniques will be completely excluded; in the coastal zone (zone 1) shrimp fisheries will still be able to continue to a limited extent, but only with a beam trawl equipped with roller shoes (wheels replacing the shoes).

Project: Analysis of the current status of the soil fauna in the soil protection zones of the Flemish Banks.
Funding: Federal Public Service Health, Food Chain Safety and Environment
Partner: RBINS - OD Nature
Contact: Gert.VanHoey@ilvo.vlaanderen.be