Date Awarded
2023
Document Type
Thesis
Degree Name
Master of Science (M.Sc.)
Department
Virginia Institute of Marine Science
Advisor
Christopher J Patrick
Committee Member
David S Johnson
Committee Member
Robert J Latour
Committee Member
Rochelle D Seitz
Abstract
Foundation species, such as seagrasses, provide many ecosystem functions in coastal habitats and support diverse food webs. However, environmental changes and human impacts to coastal ecosystems worldwide are threatening these biogenic habitats. When these changes cause shifts in the identity of foundation species, whole food webs dependent on those habitats can be altered. Seagrass meadows in Chesapeake Bay are an ideal study system to investigate these shifts, because the identity of the dominant seagrass in the lower Bay is currently shifting due to climate change. As water temperatures have risen, the once dominant species, Zostera marina, has been declining, while Ruppia maritima has been expanding. We performed quantitative surveys on epifaunal, infaunal, and nektonic communities of meadows with different seagrass species composition to examine how the structure and function of faunal communities differ between these two seagrass species. We found that seagrass bed type impacted epifaunal, infaunal, and nektonic abundance, biomass, secondary production, and diversity differently depending on trophic level. Epifaunal abundance was higher in Ruppia beds, but evenness was higher in Zostera beds. Furthermore, while epifauna biomass and secondary production per unit plant biomass was higher in Ruppia beds, biomass did not differ per unit area and secondary production was comparatively higher in Zostera beds suggesting that shifts to larger fauna and higher Zostera plant biomass per unit area offsets the increased abundance of small fauna in comparatively low biomass Ruppia beds. And while species composition of deep dwelling infauna differed by bed type, we observed few differences in infaunal abundance, biomass, and production between bed types. Based on current bay wide seagrass coverage, Ruppia has approximately 28.6% less gigagrams standing biomass of epifauna and infauna and 22.2% less gigagrams secondary production than Zostera. Moreover, in the water column, nektonic abundance, biomass, and richness all increased with the proportion of Zostera coverage relative to Ruppia coverage. We interpret these patterns to show that replacement of Zostera by Ruppia in Chesapeake Bay will reduce overall biomass and production of invertebrates and mobile fauna and shift invertebrate size distributions to smaller species. Overall, this study advances our understanding of how the shift in seagrass species occurring in Chesapeake Bay impacts the food web and serves as a case study for predicting how changes in the identity of foundation may affect community structure in other estuaries.
DOI
https://dx.doi.org/10.25773/v5-k1g0-ph59
Rights
© The Author
Recommended Citation
Alvaro, Lauren Elizabeth, "Changing Foundation Species In The Chesapeake Bay: Implications For Faunal Communities Of Two Dominant Seagrass Species" (2023). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1697552658.
https://dx.doi.org/10.25773/v5-k1g0-ph59
