A COMPARISON OF DIATOM RELATIVE ABUNDANCE AND TOTAL PHOSPHORUS CONCENTRATIONS IN OHIO’S INLAND LAKES

Lakes are vital for life; specifically, they serve as freshwater resources, sites of recreation, and habitats for various organisms. Globally, lacustrine environments have been impacted by nutrient input from humans. In Ohio, many inland lakes have been particularly impacted via agricultural runoff. Determining past water quality and nutrient levels in nutrient-enriched lakes helps inform lake restoration efforts seeking to alleviate the negative effects of nutrient enrichment by providing valuable baseline data. Diatoms, algae sensitive to environmental change, can serve as indicators of aquatic ecosystems' health. This project employs diatoms as a proxy for nutrient (e.g., phosphorus) enrichment in lakes throughout Ohio, focusing on the relative abundance (RA) of small species of Stephanodiscus (e.g., S. parvus and S. hantzschii), which are associated with nutrient-enriched waters. Typically, higher RAs of small Stephanodiscus will indicate higher total phosphorus (TP) concentrations in lakes. To create a model that conveys the diatom abundance data, surface sediment samples were retrieved from 10 lakes throughout Ohio and were processed to isolate diatom frustules (shells) onto slides. Between 400 and 500 diatom valves were counted for each sample, and valves of Stephanodiscus species were identified to the genus or species level. The RA of small Stephanodiscus valves to other valves was then calculated for each lake and compared to previously obtained TP values. This data serves as the framework for the creation of a statistical model that will be employed as a proxy for phosphorus in sediment cores collected in the state of Ohio. It is expected that in examining lake sediment cores that extend back to the periods before industrial farming, the diatom abundance from older sections of the core will more closely resemble modern lakes that are not enriched. Using this proxy to better understand changes in nutrient concentration in Ohio’s lakes can help us understand how and why aquatic systems change throughout time because, while understanding modern water quality is important, establishing water quality baselines is necessary for effective restoration. The results of this study will be shared with environmental agencies and local community organizations to help inform future restoration projects.