Date Approved

12-2019

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Alan Steinman

Second Advisor

Erica Young

Third Advisor

Mark Luttenton

Academic Year

2019/2020

Abstract

Macrophytes and their epiphytic algal communities are integral for optimizing littoral ecosystem functioning in lakes. Epiphytic algae’s placement on the plant’s surface can reduce light and nutrient availability (i.e., nitrogen and phosphorus) for the host macrophyte. Macrophyte and epiphytic algal proximity complicates these primary producer group interactions and responses to bioavailable nutrients in the water column or porewater. For example, epiphytic algae may have a competitive advantage over surface water nutrients compared to macrophytes, which may have a competitive advantage over porewater nutrients via root systems.

Muskegon Lake’s industrial history and designation as an Area of Concern prompted shoreline restoration, where macrophyte surveys were conducted pre- (2009-2010) and post- (2011-2012) restoration. For my thesis, I continued the macrophyte survey in 2018 to determine restoration impacts on the macrophyte community. An epiphytic algal survey also was included to evaluate interactions with their host macrophyte (Vallisneria americana) and to determine algal community structure variation across habitats. To further evaluate V. americana-epiphytic algal interactions, I examined both primary producer groups responses to source of nutrient enrichment (sediment porewater and/or surface water).

Fluctuations in hydrologic and meteorological conditions among all survey years, largely due to water levels, obscured restoration-induced macrophyte changes and slowed ecosystem improvement. By 2018, however, we had seen an increase in restored habitat quality compared to the reference habitat based on Coefficient of Conservatism values and macrophyte biomass and density increases. My results also indicated a negative impact of epiphytic algal biomass and density on V. americana in Muskegon Lake and the mesocosm experiment. During the experiment, water column nutrient enrichment induced phytoplankton accumulation, reducing light and subsequent macrophyte and epiphytic algal biomass. Porewater nutrient enrichment helped alleviate the negative influence of phytoplankton biomass on macrophyte and epiphytic algal biomass when the water column was enriched.

These studies reinforced the importance of environmental variation and biological interactions in influencing macrophyte community structure. Managers can use this knowledge to choose restoration locations that will enhance macrophyte success: intermediate light and hydrologic exposure will help mitigate epiphytic algal growth, and shallow slope could help increase habitat resiliency to climactic scale environmental shifts.

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