PhD ceremony Ms. E.M. van der Zee: Soft-bottom intertidal ecosystems shaped by ecosystem engineers. Consequences for trophic structure

PhD ceremony: Ms. E.M. van der Zee

Dissertation: Soft-bottom intertidal ecosystems shaped by ecosystem engineers. Consequences for trophic structure

Promotor(s): prof. T. Piersma

Faculty: Mathematics and Natural Sciences

Ecosystem engineers are species that strongly change their environment. By doing so, they can affect the abundance and distribution of other species. With field surveys and experiments, Elsbeth van der Zee studied the effects of ecosystem engineers on the community of species in soft-bottom intertidal coastal areas. She found that the presence of ecosystem engineers such as reef-building bivalves (i.e. mussels and oysters), seagrass and crabs, strongly changed the number of species and the composition of the foodweb in these areas both in space and time. Specifically, by providing structure and by stabilizing the sediment, reef-building bivalves can influence multiple foodweb levels and these effects can range up to 100s of meters beyond reef boundaries. In addition, ecosystem engineering effects of reef-building bivalves in combination with other type of interactions such as predation and competition, strongly structure the population of other bivalve species in these areas such as cockles. Furthermore, colonizing seagrass patches that accumulate silt, and burrowing crabs that create large intertidal pools in this accumulated silt layer, dramatically alter food web structure and its temporal development (>10y). Overall, the findings of this study underline the importance of ecosystem engineers in structuring soft-bottom intertidal communities over large areas and long timescales.