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Climate and watershed land use as drivers of change in phytoplankton community structure and ecosystem function

Hayes, Nicole M
http://orcid.org/0000-0002-5664-9939
http://rave.ohiolink.edu/etdc/view?acc_num=miami1434464484

Abstract Details

2015, Doctor of Philosophy, Miami University, Ecology, Evolution and Environmental Biology.
The goal of my dissertation was to understand how phytoplankton, specifically cyanobacteria respond to the individual and interactive effects of land use change and climate change. Chapter 1: Climate and land use interactively affect lake phytoplankton nutrient limitation status. Climate change models predict more frequent and intense summer droughts and precipitation events, which could modify the rates and ratios at which nitrogen (N) and phosphorus (P) enter lakes. However, watershed land use also determines nutrient run off. I found that phytoplankton in lakes with forested watersheds were consistently N-limited. While, phytoplankton in lakes with agricultural watersheds were typically P-limited, they switched to N-limitation during drought. This interaction suggests that droughts would increase the incidence of N-limitation and likely impair valuable ecosystem services. Chapter 2: Increased light and gizzard shad excretion maintain high phytoplankton biomass in a eutrophic reservoir despite watershed management. Conservation tillage aims to control soil and fertilizer loss from agricultural fields with the added benefit of reducing nutrient run-off into nearby lakes. With a 20 year dataset I found that chlorophyll increased following conservation tillage as a result of decreased light limitation (less sediment) and increased internal nutrient cycling by a dominant detritivorous fish. Chapter 3: Phytoplankton community composition, reservoir morphometry, and nutrient concentrations predict microcystin concentrations. Cyanobacteria toxins are a primary concern of eutrophication management but efforts to predict toxin concentrations have implicated numerous physical and chemical variables. I found that shallow reservoirs with high internal nutrient cycling had elevated toxins, implicating lake morphometry as a driver of water quality. Chapter 4: Abundant nitrogen not nitrogen limitation promotes cyanobacteria and microcystin. The importance of nitrogen limitation versus abundant nitrogen in promoting cyanobacteria is contested in the literature. In a mesocosm study I tested the importance of N:P supply ratio by manipulating light, P supply, and the N:P supply ratio and measuring cyanobacteria biomass, nitrogen fixation, and microcystin production. I found that all three variables were elevated when primary production was highest, under high light/high P supply/high N:P supply ratio suggesting that the most nutrient and light rich conditions favor cyanobacteria.
Michael Vanni, J (Advisor)
Maria Gonzalez, J (Committee Member)
Thomas Crist, O (Committee Member)
Martin Stevens, H (Committee Member)
Rachael Morgan-Kiss, M (Committee Member)
121 p.
Aquatic Sciences; Biogeochemistry; Ecology; Limnology
climate change; land use; cyanobacteria; phytoplankton; nitrogen fixation; microcystin; toxin production; nutrient limitation; ecosystem process

Recommended Citations

Citations

  • Hayes, N. M. (2015). Climate and watershed land use as drivers of change in phytoplankton community structure and ecosystem function [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1434464484

    APA Style (7th edition)

  • Hayes, Nicole. Climate and watershed land use as drivers of change in phytoplankton community structure and ecosystem function. 2015. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1434464484.

    MLA Style (8th edition)

  • Hayes, Nicole. "Climate and watershed land use as drivers of change in phytoplankton community structure and ecosystem function." Doctoral dissertation, Miami University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1434464484

    Chicago Manual of Style (17th edition)

miami1434464484
354
© 2015, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.