Introducing the Ecological Aspects

Abstract

Combined results from both the BACOSA and SECOS projects highlight structure and function of aquatic Baltic Sea ecosystems in a gradient from land to open Sea.

Coastal lagoons differ highly not only in their hydrological and nutrient regimes: Lagoons with dense submerged vegetation display higher biomass and species richness at all trophic levels and reveal higher trophic transfer efficiency than more eutrophicated lagoons with sparse vegetation. In the Darß-Zingst Bodden chain, high-resolution and long-term data identify the importance of extreme, but rarely occurring events for changes in abiotic and biotic parameters, such as oxygen depletion under the ice cover or Major Baltic Inflows. The Vitter Bodden is characterized by dense submerged vegetation and high food web connectivity, but low recycling, redundancy and short trophic pathways indicate that this system might be close to the “tipping point” and at risk for drastic changes.

Based on aggregated data, benthic faunal communities and their traits in the offshore waters are mapped and hot spots of functional aspects are identified, supporting projections of marine ecosystem features. We compare bioturbation values measured directly with those captured by corresponding indices, in an attempt to highlight this functional aspect of the benthos. Seasonal dynamics of plankton communities differ markedly between Belt Sea and Baltic Proper. Our data show how understanding of short-term anomalies and long-term variability is important for assessing implications of climate change. Long-term data sets in the pelagic and benthic realm play therefore a crucial role in assessing the state of the marine systems and changes, such as regime shifts and longer growing seasons.

Long-term monitoring data from inner and outer coastal waters identify six possible phytoplankton blooming types and different spatio-temporal limitation regimes, revealing rather stable intra-annual patterns, but almost no long-term trends. This indicates a high system resilience, which may be favourable to sustain a certain ecosystem state, but unfavourable if such systems need to be restored.