Discharge and nutrients interact to determine trophic structure in a wetland: Evidence from a landscape-scale manipulation

Limnology and Oceanography
By: , and 

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Abstract

Identifying drivers of consumer biomass patterns and community structure is complex for managed freshwater ecosystems that are sensitive to nutrients and drought. In the Florida Everglades, flow restoration is expected to reintroduce discharge across an expansive wetland, yet most research on consumers has focused on water depth and dry disturbances. Low-velocity flow can mediate nutrient availability for basal food resources, but its scaled-up effects on consumer communities remain largely untested. We quantified consumer responses to a landscape-scale flow manipulation that created discharge variability along a 2.5-km path of interconnected shallow sloughs. Over 4 yr, we repeatedly sampled macroinvertebrates, small fishes, and large predatory fishes (standard length > 8 cm) in 26 sloughs—some along a flow path experiencing pulsed water releases and others in two non-flowing reference areas. We tested the effects of antecedent discharge on consumer biomass while accounting for local nutrient concentrations (total phosphorus). Discharge increased biomass across all consumer groups, particularly in oligotrophic sloughs. Conversely, eutrophic sloughs demonstrated stronger top-down effects on small fishes and macroinvertebrates, with discharge primarily benefiting large predatory fishes. Nutrient gradients preferentially increased large fishes and caused macroinvertebrate community shifts favoring herbivorous and possibly predation-resistant taxa. Structural equation modeling similarly indicated bottom-up support from discharge but stronger top-down control in nutrient-rich sloughs. These findings demonstrate that discharge and total phosphorus interactively produce distinct consumer biomass patterns. Flow restoration in oligotrophic Everglades sloughs is hypothesized to enhance aquatic consumer biomass across trophic levels, revealing an ecological benefit to slow-flowing ecosystems not previously recognized.

Suggested Citation

Fernandez, M., Trexler, J.C., Saunders, C.J., Harvey, J., and Dorn, N.J., 2025, Discharge and nutrients interact to determine trophic structure in a wetland: Evidence from a landscape-scale manipulation: Limnology and Oceanography, v. 70, no. 11, p. 3355-3369, https://doi.org/10.1002/lno.70211.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Discharge and nutrients interact to determine trophic structure in a wetland: Evidence from a landscape-scale manipulation
Series title Limnology and Oceanography
DOI 10.1002/lno.70211
Volume 70
Issue 11
Publication Date September 24, 2025
Year Published 2025
Language English
Publisher Association for the Sciences of Limnology and Oceanography
Contributing office(s) WMA - Earth System Processes Division
Description 15 p.
First page 3355
Last page 3369
Country United States
State Florida
Other Geospatial Water Conservation Area 3B of the Florida Everglades
Additional publication details