Date on Master's Thesis/Doctoral Dissertation

12-2025

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Mehring, Andrew

Committee Member

Eason, Perri

Committee Member

Gaughan, Andrea

Committee Member

Kolmann, Matt

Committee Member

Yanoviak, Steve

Author's Keywords

remote sensing; climate change; sediment oxygen demand; elemental cycling

Abstract

As evidenced by their historic losses due to anthropogenic activities, wetlands are undervalued ecosystems that provide numerous ecosystem services, from recreational opportunities to carbon (C) storage. However, these wetlands are also the largest natural source of atmospheric methane (CH4). Additionally, small water bodies (< 10,000 m2) are disproportionately large emitters relative to larger lakes and reservoirs. As construction and restoration efforts proceed, it is crucial to identify wetlands that need restoration and to understand the factors driving both greenhouse gas (GHG) fluxes and the C balance of these systems. This dissertation investigates the drivers of greenhouse gas fluxes in small ponds and identifies regional hotspots of GHG emissions from these ponds. My initial study investigated how sediment organic matter (SOM) mediates the effects of Chironomus riparius larvae on GHG fluxes in wetland sediments. I constructed artificial sediment cores and compared their results with field-collected cores. I found that, while chironomids had a moderate effect on CH4 fluxes, this effect was not mediated by sediment OM or environmental variables; instead, it was overpowered by sediment OM and environmental variables. However, in the field collected cores, chironomid number was a significant predictor of CH4 fluxes. This study demonstrates that chironomids do not have a substantial effect on N2O fluxes as previously reported, and that sediment OM is crucial to consider when accounting for macroinvertebrate effects. In my second study, I investigated drivers of GHG fluxes from small ponds through sediment and water sampling. I identified that duckweed, a ubiquitous floating plant found globally, is a significant driver of GHG fluxes from these water bodies. This result was true for CH4 fluxes, but not for CO2 fluxes. This result could be because we found that duckweed-covered water bodies do not store a significant amount of C compared to open bodies of water, and that the higher decomposition rate in duckweed-covered ponds outweighs duckweed's photosynthesis. For the third study, I investigated how multispectral satellites can estimate chlorophyll a (chl-a) concentrations in small water bodies and how atmospheric effects obscure this signal. We used field and laboratory sampling to compare two atmospheric correction methodologies, ACOLITE and RAdCor, for chl-a retrieval. We found that both ACOLITE and RAdCor had similar retrieval of chl-a by utilizing the normalized difference chlorophyll index (NDCI). We also found that the surrounding landscape significantly predicted the residuals of both models, and pond NDCI was overestimated when external NDCI was high and underestimated when pond NDCI was low.

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