Habitats and Biotopes in the German Baltic Sea

Abstract

To maintain or enhance biodiversity and sea floor integrity, mapping benthic habitats is a mandatory requirement in compliance with the Marine Strategy Framework Directive (MSFD). The EU Commission Decision distinguishes between Broad Habitat Types (BHTs) and Other Habitat Types (OHTs). At the regional level, biotopes in the Baltic Sea region are classified according to the HELCOM underwater biotope and habitat classification (HUB). In this study, the habitats and their benthic communities were mapped for the entire German Baltic Sea at a high spatial resolution of 1 km. In two nature conservation areas of the Exclusive Economic Zone (EEZ) as well as selected focus areas in the coastal waters, the resolution we provide is even more detailed at 50 × 50 m. Hydroacoustic data recording and benthological surveys (using bottom grabs, underwater towing camera technology, and diver sampling) helped identify biotopes in high resolution. Based on these data, together with additional data acquired since 2010 (a total of over 7000 stations and transect sections), we were able to spatially delineate benthic biotopes and their communities via predictive habitat modelling. The results are provided as full-coverage maps each for BHT, OHT, and HUB (9 classes of BHTs, 5 classes of OHTs, and 84 classes of HUB) with a level of spatial detail that does not yet exist for the Baltic Sea, and they form an essential basis for future monitoring, status assessments, and protection and management measures.

Baseline Inventory of Benthic Macrofauna in German Marine Protected Areas (2020–2022) before Closure for Bottom-Contact Fishing

“…Blue mussel Mytilus edulis and infaunal bivalve species like sand gaper Mya arenaria were among characteristic taxa for KR MPA, confirming the habitat distribution reported in [50]. Also, in accordance with Marx et al [50], muddy sediment at RB MPA was dominated by the Baltic tellin M. balthica, whereas blue mussels were common in mixed and sand substrate. Mytilus edulis as well as Gammarus salinus associated with benthic vegetation were typical macrofauna species for AG.…”

“…Characteristic species in the FB MPA apart from A. islandica included infaunal polychaete species like Aricidea suecica and Levinsenia gracilis, as well as Diastylis rathkei, Varicorbula gibba and Abra alba, in line with Schiewer [32], Gogina et al [34] and Marx et al [50]. Blue mussel Mytilus edulis and infaunal bivalve species like sand gaper Mya arenaria were among characteristic taxa for KR MPA, confirming the habitat distribution reported in [50]. Also, in accordance with Marx et al [50], muddy sediment at RB MPA was dominated by the Baltic tellin M. balthica, whereas blue mussels were common in mixed and sand substrate.…”

“…Multivariate analysis for the Baltic Sea macrofauna suggested less distinct and therefore more similar community structure between the five MPAs compared to those in the North Sea. This is likely due to the inclusion of multiple habitats and biotopes with patchy distribution in each of the German Baltic Sea MPAs [ 50 ], and due to less distinct boundaries and gradual ecological transitions along environmental gradients between the adjacent communities. In agreement with previously reported increasing variability towards the entrance to the North Sea [ 33 , 34 ], our results showed gradually increasing similarity within the Baltic Sea MPAs with decreasing salinity from west to east.…”

“…In agreement with previously reported increasing variability towards the entrance to the North Sea [ 33 , 34 ], our results showed gradually increasing similarity within the Baltic Sea MPAs with decreasing salinity from west to east. The FB MPA had the lowest mean similarity of 38.8% among the Baltic Sea MPAs as it includes stations from broad habitat types ranging from circa- and infralittoral mixed sediment (hard substrate) to sand and mud [ 50 ]. Characteristic species in the FB MPA apart from A. islandica included infaunal polychaete species like Aricidea suecica and Levinsenia gracilis, as well as Diastylis rathkei, Varicorbula gibba and Abra alba , in line with Schiewer [ 32 ], Gogina et al [ 34 ] and Marx et al [ 50 ].…”

“…Macrofauna communities of the Western Baltic Sea and the North Sea have high exposure to natural and anthropogenic stressors [ 18 , 40 ] and especially to bottom-contact fishing [ 41 , 42 , 43 , 44 , 45 , 46 ]. Historically, in both regions, macrofauna monitoring and assessment are well-covered by established programs, such as projects in MPAs funded by the Federal Agency for Nature Conservation (BfN) like LABEL [ 47 , 48 ], CLUSTER and LEGRA [ 49 ], the project ATLAS (funded by the State Agency for Environment, Nature Conservation and Geology Mecklenburg-Vorpommern (LUNG MV) [ 50 ]), as well as long-term research studies (e.g., [ 18 , 51 ]).…”