CAREER: Understanding heterogeneity in lake biogeochemistry across time and space

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Freshwater aquatic ecosystems, which include lakes, ponds, and reservoirs, provide important services to society, including power generation, recreational opportunities, and the provisioning of clean drinking water. Additionally, freshwater aquatic ecosystems are a major component of the global carbon cycle. Lakes emit a substantial amount of carbon dioxide to the atmosphere, which is derived from a combination of internal organic matter breakdown and external inputs of inorganic carbon from surrounding watersheds. Dissolved oxygen, which is consumed as organisms break down organic matter, is declining in lakes around the world, threatening the ability of these ecosystems to support the current diversity and biomass of organisms they harbor. Past attempts to understand coupled carbon dioxide and dissolved oxygen dynamics in lakes have not accounted for seasonal variation in light intensity and temperature or water column heterogeneity, both of which influence gross fluxes of both gasses. This project seeks to understand how heterogeneity in environmental conditions, in both time and space, impacts carbon and oxygen balance in aquatic ecosystems, and thus improve our understanding of the role lakes play in the global carbon cycle. Together, the integrated research and education plan of this project will provide educational and training opportunities to a wide range of students and early career scientists through improved course materials, a large workshop, and local outreach efforts. This project will also leverage datasets that exist at many organizations and institutions, and the insights gained via the process of compiling and harmonizing diverse data sets will be translatable to many other networks and research efforts. Finally, outreach to citizen-scientists and lake associations around the world will leverage the power of comparative network science to understand individual lake conditions in a global context.Lakes often exhibit substantial and dynamic structural heterogeneity, largely driven by thermal stratification. This project focuses on the production and consumption of carbon dioxide and dissolved oxygen in lakes, and how heterogeneity in time and space regulate the dynamics of these critical biogeochemical fluxes. Lakes are globally important hot-spots of carbon cycling, venting about as much carbon dioxide to the atmosphere as is taken up by the world’s oceans. Theoretically, carbon dioxide and dissolved oxygen are stoichiometrically coupled via metabolic processes, but departures from expectations based on stoichiometry and partial pressure in the atmosphere regularly occur in aquatic ecosystems. Understanding what causes these departures may provide insights into underlying biogeochemical processing in lakes, and may enable more accurate predictions of continental-scale carbon dioxide emissions from lakes. This project aims to combine high-frequency sensor observations, manually collected data, long-term data sets and ecosystem modeling to understand the dynamics of lake carbon dioxide and dissolved oxygen across large environmental gradients. Data will be obtained and harmonized from diverse sources such as the National Ecological Observatory Network (NEON) and collaborating scientists and organizations in the Global Lake Ecological Observatory Network (GLEON).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.