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EFFECTS OF WATER FLOW ON A WETLAND MACROINVERTEBRATE COMMUNITY
Title
EFFECTS OF WATER FLOW ON A WETLAND MACROINVERTEBRATE COMMUNITY.
Creator
Hansen, Chris, Dorn, Nathan, Florida Atlantic University, Department of Environmental Sciences, Charles E. Schmidt College of Science
Abstract/Description
Macroinvertebrates make up a large fraction of secondary production in wetlands and are strongly influenced by hydrologic alterations. However, little is known of the effect flow has on macroinvertebrate production and community composition in wetlands. Reintroducing measurable water velocities (1-5 cm/s) to the oligotrophic (phosphoruslimited) Everglades has the potential to affect macroinvertebrate production and community structure by increasing the supply of phosphorus (P) to periphyton,...
Show moreMacroinvertebrates make up a large fraction of secondary production in wetlands and are strongly influenced by hydrologic alterations. However, little is known of the effect flow has on macroinvertebrate production and community composition in wetlands. Reintroducing measurable water velocities (1-5 cm/s) to the oligotrophic (phosphoruslimited) Everglades has the potential to affect macroinvertebrate production and community structure by increasing the supply of phosphorus (P) to periphyton, changing basal food quality, and physically altering the habitat. In Chapter 2, I investigated the potential effects of flow-mediated nutrient-loading on the growth rate of herbivorous grazers, apple snails (Pomacea maculata), by growing periphyton on standard substrates, in four sloughs within a landscape-scale flow addition experiment; two sloughs received elevated flow velocities (2.9-5.2 cm/s) and two control sloughs (0.3-0.4 cm/s). Snails fed periphyton from the flowing sloughs gained more than 3.7-fold greater total mass than snails fed periphyton from the control sloughs. The highest velocity slough produced the greatest snail growth. Snail growth was correlated with P accumulation and C:P ratios in the periphyton. Water column nutrients were low and the water column TP differences among sloughs could not fully explain differences in periphyton nutrients or snail growth. Increasing flow above background conditions by as little as 2.4 cm/s in this oligotrophic wetland altered periphyton food quality by flow loading, which subsequently increased growth rates of primary consumers. In Chapter 3, I investigated potential changes in macroinvertebrate standing stock biomass and community composition caused by flow by conducting two sweep net surveys. Surveys were conducted within two groups of sloughs, flow sloughs (6 sloughs) and control sloughs (12 sloughs), within the same landscape-scale flow addition experiment as the growth experiment. Surveys were conducted from January to March in 2018 and 2021. Biomass was compared between the flow sloughs and control sloughs using generalized linear models. Community composition was analyzed at the slough level using Bray-Curtis similarity. Biomass of macroinvertebrates was similar among transects in 2018 but higher in the flow sloughs in 2021 with the highest biomasses further from the L67A (velocities <2cm/s). The two highest flowing sloughs (typically >3cm/s) had a different community composition from the other 16 sloughs in both 2018 and 2021 with a predator resistant non-native snail appearing in 2021. The results of the surveys show an increase in macroinvertebrate production in the flow sloughs possibly related to increased nutritional value of food, however, with higher biomass further from the L67A and the invasion of a predator resistant snail at the high flow sloughs, it also appears that there is increased top-down pressure on the macroinvertebrates at the sloughs closer to the L67A (were cover from predation has been reduced). The overall results of these studies indicate flow produces more nutritional food for herbivorous macroinvertebrates and increases standing stock biomass but can change the community composition when periphyton cover is reduced.
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Date Issued
2021
PURL
http://purl.flvc.org/fau/fd/FA00013873
Subject Headings
Wetland ecology, Everglades (Fla.), Invertebrate communities
Format
Document (PDF)