Trawl marks on the the seafloor
We use hydroacoustic methods (e.g. sonar) to investigate the influence of bottom-contact fisheries on the seabed, and the sediment composition and structure. The backscatter strength of the acoustic signal provides information about the condition of the seabed. This allows us to identify where trawls have been dragged across the seabed. Initial results from the project show that the detectable structures on the seabed disappear after only a few months. The sediments seem to level out again relatively quickly, moved by ocean currents.
Autonomous Reef Monitoring Structures
One Method to analyze benthic communities are Autonomous Reef Monitoring Structures (ARMS). These standardized 3D structures mimic the complex structure of sea bottom habitats (e.g. reefs). The stacked PVC plates offer an attachment substrate for larvae, incrusting invertebrates and hiding spaces for small animals. We deploy the ARMS while diving and attach them with steel rods to the seafloor next to reef structures to evaluate the response of cryptic, often overlooked reef communities to the different management practices (e.g differences in fishing pressure). In 2021, we deployed 49 ARMS at 10 different stations at the Sylt Outer Reef and Borkum Reef Ground. We will fetch the first ARMS in June 2022 from the seabed and investigate which organisms settled on the individual PVC plates.
Baited Remote Underwater Videostations
The development and test of new non-invasive sampling methods is an important part of MGF-Nordsee. The use of baited remote underwater videostations (BRUV) provides unique insights into the underwater world of the North Sea.
In the first year of the project, many interesting recordings have already been captured in the Natura 2000 areas, which help to determine the biodiversity in the areas.