10.18453/rosdok_id00005054 Steinkopf, Markus Markus Steinkopf http://d-nb.info/gnd/1387145258 https://orcid.org/0000-0003-2370-4441 Universität Rostock 2024 500 Natural sciences 570 Life science 590 Zoological sciences 2024 en https://purl.uni-rostock.de/rosdok/id00005054 urn:nbn:de:gbv:28-rosdok_id00005054-9 The collapse of seabird or fish populations often signals disruptions in ecosystems altered by stressors. This dissertation compares food webs in the Elbe and Oder estuaries and the Baltic Sea to illustrate how stressors like eutrophication and turbidity affect food web structures. Stressed food webs elongate, causing energy loss at higher levels, which can lead to population collapse. Changes in nitrogen sources and the rise of microbial systems at the base of the food web are key factors in this trophic lengthening.