SPATIAL AND TEMPORAL HETEROGENEITY OF ORGANIC-MATTER DECOMPOSITION IN A SMALL EUTROPHIC LAKE

Organic-matter decomposition (OMD) in lakes is critical to biogeochemical cycling, nutrient availability, water quality, and overall ecosystem health. OMD within and among lake habitats remains little researched compared to stream and river systems. Our study aims to identify the within- and among-habitat seasonal drivers of OMD. Briefly, we conducted a field-based experiment to assess how seasonality, within lake habitats, and nutrients influence the decomposition of litter from the emergent macrophyte Schoenoplectus acutus in a small eutrophic dimictic lake in southeast Michigan (USA). We also used the standardized cotton-strip decomposition assay that is more readily comparable to other systems. Among the inlet, outlet, littoral, intermediate (2m), and pelagic (10m) habitats, the decomposition rate of cotton strips from November 14, 2023, to August 16, 2024, has consistently been the fastest in the pelagic sites.  We attribute this result to warmer bottom waters during ice-on caused by inverse stratification, and nutrient-rich cold-anoxic hypolimnetic waters during the spring and summer.  The decomposition rate of the macrophyte was slower than the cotton strips, and the pelagic site had the slowest rate among habitats for the winter season (November 14, 2023, to March 18, 2024). Overall, our results highlight that nutrient availability in anoxic waters can overcome the temperature dependency of OMD in lakes.

Presentation Preference: Oral

Primary Presenter: Ryan Andrews, Oakland University (ryanandrews@oakland.edu)

Authors:

Ryan Andrews, Oakland University  (ryanandrews@oakland.edu)

Nicole Wagner, Oakland University  (nicolewagner@oakland.edu)

David Costello, Kent State University  (dcostel3@kent.edu)

Hailee Mersino, Oakland University  (hmersino@oakland.edu)

Iman Al-Nsour, Oakland University  (imanalnsour@oakland.edu)

Olivia Sowa, Oakland University  (oliviasowa@oakland.edu)

Scott Tiegs, Oakland University  (tiegs@oakland.edu)