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Predators regulate communities through top-down control in many ecosys-tems. Because most studies of top-down control last less than a year and focuson only a subset of the community, they may miss predator effects that mani-fest at longer timescales or across whole food webs. In southeastern US saltmarshes, short-term and small-scale experiments indicate that nektonic preda-tors (e.g., blue crab, fish, terrapins) facilitate the foundational grass, Spartinaalterniflora, by consuming herbivorous snails and crabs. To test both hownekton affect marsh processes when the entire animal community is present,and how prior results scale over time, we conducted a 3-year nekton exclusionexperiment in a Georgia salt marsh using replicated 19.6 m 2 plots. Our nektonexclusions increased densities of plant-grazing snails and juveniledeposit-feeding fiddler crab and, in Year 2, reduced predation on tethered juve-nile snails, indicating that nektonic predators control these key macroinver-tebrates. However, in Year 3, densities of mesopredatory benthic mud crabsincreased threefold in nekton exclusions, erasing the tethered snails' predationrefuge. Nekton exclusion had no effect on Spartina biomass, likely because theobserved mesopredator release suppressed grazing snail densities and elevateddensities of fiddler crabs, whose burrowing alleviates soil stresses. Structuralequation modeling supported the hypotheses that nektonic predators andmesopredators control invertebrate communities, with nektonic predators hav-ing stronger total effects on Spartina than mud crabs by controlling densitiesof species that both suppress (grazers) and facilitate (fiddler crabs) plantgrowth. These findings highlight that salt marshes can be resilient to multiyearreductions in nektonic predators if mesopredators are present and thatmultiple pathways of trophic control manifest in different ways over time tomediate community dynamics. These results highlight that larger scale andlonger-term experiments can illuminate community dynamics not previouslyunderstood, even in well-studied ecosystems such as salt marshes.

Morton, J.P., Hensel, M.S., DeLaMater, D.S., Angelini, C., Atkins, R., Prince, K., Williams, S.L., Boyd, A.D., Parsons, J., Resetarits, E.J., Smith, C.S., Valdez, S., Monnet, E., Farhan, R., Mobilian, C., Smith, D., Craft, C.B., Byers, J., Alber, M., Pennings, S.C. and Silliman, B.R. 2024. Mesopredator release moderates trophic control of plant biomass in a Georgia salt marsh. (DOI: 10.1002/ecy.4452)