Abteilung Aquatische Ökologie

Der Übergangsbereich zwischen Wasser und Land beherbergt vielfältige Lebensräume und zahlreiche Arten: Die dort vorhandene Biodiversität ist besonders hoch und über die blaugrüne Grenze hinweg laufen zahlreiche ökologische Prozesse ab und Stoffe werden ausgetauscht. Der Mensch hat die blaugrünen Lebensräume schon immer genutzt, ja manche verdanken ihre Entstehung dem Menschen. Auch in Zukunft wird der Mensch blaugrüne Landschaftselemente vielfältig nutzen, aber auch vonihnen abhängig sein, sei dies zur Wasserrückhaltung unter dem Klimawandel oder für die Erholung.

Aim: Seagrass meadows represent a key marine ecosystem owing to the significant biodiversity they host. Protection actions are often implemented without considering connectivity between habitats. In this article, we project and prioritise Mediterranean seagrass habitats (Posidonia oceanica and Cymodocea nodosa) based on their potential as sources/retention and stepping stones for dispersal propagules of the associated biotic communities. We use this information to identify gaps in the protection of highly ranked habitats.
Location: Mediterranean Sea.
Methods: We related seagrass observations with marine environmental predictors to run species distribution models and infer the distribution of Mediterranean seagrasses. We then used a network-based approach (CONEFOR) to rank patches of seagrass suitable areas based on their contribution to the seascape in terms of patch area, potential as source/retention of propagules and stepping stone. Finally, by overlaying our ranking with the spatial distribution of marine protected areas (MPAs), we identified potential gaps in the protection of important seagrass habitats across the Mediterranean and its basins.
Results: Most of the identified patches of seagrass suitable areas are not included in MPAs, only reaching a maximum protection coverage of ~50% in the Northwestern Mediterranean. Relatively few patches contribute disproportionately to connectivity, but top-ranked habitat patches are not included within the existing MPAs network, both at the Mediterranean scale and for most basins. The largest gaps for the source/sink role are in the Aegean and Ionian Sea, and largest gaps for the stepping stone role are in the Adriatic, Ionian and Tyrrhenian Sea.
Main Conclusions: Our results suggest that the current MPAs network fails to protect highly relevant patches of seagrass suitable areas in most of the Mediterranean basins. However, this gap could be filled by a few well-placed MPAs. Overall, we provide novel insights for the identification of key habitats and planning novel coastal MPAs in the region.

Millipedes are thought to depend on their gut microbiome for processing plant-litter-cellulose through fermentation, similar to many other arthropods. However, this hypothesis lacks sufficient evidence. To investigate this, we used inhibitors to disrupt the gut microbiota of juvenile Epibolus pulchripes (tropical, CH₄-emitting) and Glomeris connexa (temperate, non-CH₄-emitting) and isotopic labelling. Feeding the millipedes sterile or antibiotics-treated litter reduced faecal production and microbial load without major impacts on survival or weight. Bacterial diversity remained similar, with Bacteroidota dominant in E. pulchripes and Pseudomonadota in G. connexa. Sodium-2-bromoethanesulfonate treatment halted CH₄ emissions in E. pulchripes, but it resumed after returning to normal feeding. Employing ¹³C-labeled leaf litter and RNA-SIP revealed a slow and gradual prokaryote labelling, indicating a significant density shift only by day 21. Surprisingly, labelling of the fungal biomass was somewhat quicker. Our findings suggest that fermentation by the gut microbiota is likely not essential for the millipede’s nutrition.

Biodiversity loss is increasing worldwide, necessitating effective approaches to counteract negative trends. Here, we assessed aquatic macroinvertebrate biodiversity in two river catchments in Switzerland; one significantly degraded and associated with urbanisation and instream barriers, and one in a near-natural condition. Contrary to our expectations, environmental heterogeneity was lower in the near-natural stream, with enhanced productivity in the degraded system resulting in a greater range of environmental conditions. At face value, commonly employed alpha, beta and gamma biodiversity metrics suggested both catchments constituted healthy systems, with greater richness or comparable values recorded in the degraded system relative to the near-natural one. Further, functional metrics considered to be early indicators for anthropogenic disturbance, demonstrated no anticipated differences between degraded and near-natural catchments. However, investigating the identity of the taxa unique to each river system showed that anthropogenic degradation led to replacement of specialist, sensitive species indicative of pristine rivers, by generalist, pollution tolerant species. These replacements reflect a major alteration in community composition in the degraded system compared with the near-natural system. Total nitrogen and fine sediment were important in distinguishing the respective communities. We urge caution in biodiversity studies that employ numerical biodiversity metrics alone. Assessing just one aspect of diversity, such as richness, is not sufficient to track biodiversity changes associated with environmental stress. We advocate that biodiversity monitoring for conservation and management purposes must go beyond traditional richness biodiversity metrics, to include indices that incorporate detailed nuances of biotic communities that relates to taxon identity.