WP2: Ecological Networks uses field contrasts and experimental facilities to analyze the effects of biodiversity change on the structure and interaction strength of ecological networks in salt marshes. We study networks of plants, microbial communities, benthos/soil fauna under different scenarios for temperature and/or flooding and/or pollutants. In field contrasts in all three Wadden Sea countries we investigate differences between patches dominated by the native Salicornia europaea and the non-native Spartina anglica. We also look at the difference between species rich areas (grazed by livestock) and areas with lower species richness (non-grazed areas). Preliminary results indicate that grazing has a positive impact on plant diversity, but a negative impact on detritivore invertebrates. Controlled in-situ warming experiments, such as the MERIT research facility, provide valuable insights into how temperature rise alters structural and functional interactions within salt marsh ecosystems. Previous results indicate that warming exerts only minor effects on general plant parameters, however a slight shift of root biomass towards deeper soil layers was observed in the high marsh. Also, first insights into the effects of warming on methane fluxes and microbial communities indicate differences between the elevational zones and temperature scenarios. A large-scale mesocosm experiment at AWI (Sylt) focused on interactions between two dominant salt marsh species of the pioneer zone (Salicornia europaea agg. and Spartina anglica), microbial communities and the bioturbating ragworm Hediste diversicolor under stress conditions induced by (marine) heatwaves. The analysis of the collected data within MERIT and the mesocosm experiment is ongoing and is expected to provide new insights into how salt marsh communities may respond and adapt to future climate change.

Participating Researchers
Prof. Dr. Kai Jensen, Universität Hamburg
Dr. Viktoria Unger, Universität Hamburg
Jacqueline Bruhy, Universität Hamburg
Prof. Dr. Chris Smit, Rijksuniversiteit Groningen
Dr. Maarten van Hardenbroek, Rijksuniversiteit Groningen
Farah Kootstra, Rijksuniversiteit Groningen
Dr. Andreas Waser, AWI Sylt
Ditte van de Merwe, AWI Sylt