PhD defence Suzanne Poiesz

Livestream

Suzanne Poiesz (ConsEco/NIOZ)

Promotores: Prof. T. van der Heide, Prof. K. Soetaert (UU); copromotor: Dr H.W. van der Veer (NIOZ)

Deep dive into the Wadden Sea

A divers approach to better understand spatial and temporal variability in the Wadden Sea fish food web

This dissertation explores the spatial and temporal variability of the Wadden Sea fish food web using multiple approaches. The current food web spans various trophic levels, from algae consumers to top predators. Stomach content analysis shows a mix of opportunistic feeders and specialist fish species, many of which rely on a few key prey species. The significant diet overlap among species suggests possible intra- and interspecific competition. Spatial differences in stomach content composition point to local variability in predator and prey abundance. However, bulk stable isotope analysis revealed strong spatial correlation in the trophic positions of most fish, indicating a broadly consistent food web structure across the Wadden Sea. An analysis of historical stomach content data found no significant changes in the trophic position of individual fish species in the western Dutch Wadden Sea over the past 80 years (1930–2019). This reflects long-term trophic stability at the species level. Nevertheless, the food web structure at the community level fluctuated annually, driven by changes in species composition and relative abundances. Despite this species-level stability, at the community level, trophic structure varied due to interannual fluctuations in species composition and year-to year fluctuations in the relative abundance of the various fish species. At the ecosystem level the trophic role of the fish community has been degraded due to the decrease in total fish biomass in the area.

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