Site: Plum Island Ecosystems LTER

Long-term nutrient enrichment causes S. alterniflora habitat to collapse into the creek, limiting access to high-marsh invertebrates. Fish use more energy to access the high marsh which reduces trophic efficiency. In addition, these cracks also create crevasses where fish predators, such as American eel, can hide and feed on mummichog.
Courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science (ian.umces.edu/symbols/).
Credit: Figure 7 in: Nelson, J.A., Johnson, D.S., Deegan, L.A. et al. Feedbacks Between Nutrient Enrichment and Geomorphology Alter Bottom-Up Control on Food Webs. Ecosystems 22, 229–242 (2019). https://doi.org/10.1007/s10021-018-0265-x

For the first six years of an ongoing 13-year nitrate addition experiment in tidal creeks, benthic algae, invertebrate prey, and a small fish, the mummichog, showed a classic positive bottom-up response to added nutrients. However, after six years, creek banks began to collapse and mummichog abundance in fertilized creeks declined relative to reference sites, likely because the changing shape of creek channels cut off access to food resources on the marsh platform. Amphipods in fertilized creeks also developed a much higher incidence of trematode parasites, which made them more vulnerable to predation.