Document Type

Honors Project - Open Access

Abstract

Lakes are an important part of the global carbon cycle. Carbon from terrestrial sources washes into lakes where it can be processed and then emitted to the atmosphere, buried in sediments, or make its way downstream to an ocean. During rain events, precipitation can flush dissolved organic carbon (DOC)-enriched water from the upper soil layers into lakes. As climate change causes increased precipitation totals and precipitation events in the upper Midwest, this may cause increased DOC in lakes. Increased DOC in lakes leads to increased microbial respiration, contributing to increased greenhouse gas release from lakes. Thus, it is important to understand the effects of DOC on lake ecosystems. Here, I use long-term data and newly collected data from a set of lakes in Michigan and Wisconsin to analyze how precipitation affects DOC in lakes to better understand how changing precipitation patterns could affect the carbon cycle in lakes. I found that increased total annual precipitation leads to increased dissolved organic carbon within lakes. The lag period between when a precipitation event occurs and when the DOC-enriched water enters the lakes was less than 2 weeks in this study. Wet years generally have higher DOC than dry years. Furthermore, DOC and lake water color have a positive relationship at all depths within lakes, but there are some lakes where this relationship is weaker and the effect of DOC on water color decreases with depth. This relationship does not change with high or low precipitation years. My results suggest that climate-driven changes in local precipitation regimes could lead to shifts in lake 1 DOC-loading with potential implications for lake respiration, lake community ecology, and landscape-level carbon storage.

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