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EFFECTS OF WATER FLOW ON A WETLAND MACROINVERTEBRATE COMMUNITY

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Date Issued:
2021
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, 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.
Title: EFFECTS OF WATER FLOW ON A WETLAND MACROINVERTEBRATE COMMUNITY.
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Name(s): Hansen, Chris, author
Dorn, Nathan, Thesis advisor
Florida Atlantic University, Degree grantor
Department of Environmental Sciences
Charles E. Schmidt College of Science
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Date Created: 2021
Date Issued: 2021
Publisher: Florida Atlantic University
Place of Publication: Boca Raton, Fla.
Physical Form: application/pdf
Extent: 100 p.
Language(s): English
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, 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.
Identifier: FA00013873 (IID)
Degree granted: Thesis (MS)--Florida Atlantic University, 2021.
Collection: FAU Electronic Theses and Dissertations Collection
Note(s): Includes bibliography.
Subject(s): Wetland ecology
Everglades (Fla.)
Invertebrate communities
Persistent Link to This Record: http://purl.flvc.org/fau/fd/FA00013873
Use and Reproduction: Copyright © is held by the author with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Host Institution: FAU
Is Part of Series: Florida Atlantic University Digital Library Collections.