Intermediate report for a pilot assessment for EU MSFD descriptor D4 food webs for Kattegat

The objective is to evaluate the current state of the food web and provide a foundation for future operational food web assessments under the EU MSFD. Marine food webs are complex networks of trophic interactions that reflect ecological structure and ecosystem functioning. Understanding their dynamics is essential for assessing Good Environmental Status (GES) under Descriptor D4, which requires evaluating the diversity, abundance, size structure, and productivity of trophic guilds.

Given the challenges of indicator development and data availability, the pilot utilizes a suite of ecological indicators derived from the EwE model and Ecological Network Analysis (ENA) to operationalize the D4 assessment criteria. Key findings show a regime shift in the Kattegat ecosystem from a pelagic-dominated to a benthic-dominated system, occurring between 1982 and 2008, in line with previous findings by Lindegren et al. (2012). This shift is reflected in changes to modelled biomass trends, spatial distributions, and multiple food web indicators.

Important trends include a decline in cod and other pelagic species, a rise in plaice, seals, and benthic organisms, and alterations in trophic efficiency, biomass ratios, diversity indices, and system structure metrics such as Average Mutual Information (AMI) and Path Length. The spatial Ecospace component complements the temporal analysis by visualizing changes in biomass and indicator distribution across the Kattegat, although these outputs remain preliminary due to the model still being under development and validation.