EMPLOYING DIATOM-BASED ENVIRONMENTAL RECONSTRUCTIONS TO UNDERSTAND CHANGING NUTRIENT LOADS IN OHIO’S INLAND LAKES

In Ohio, lacustrine ecosystems have been adversely impacted by agriculture and mining practices since the Industrial Revolution. Due to their abundance, environmental sensitivity, and high preservation potential, diatoms can offer a suite of information regarding the historical conditions of their environments and can therefore be used to reconstruct environmental change. Previous efforts to restore Ohio’s inland lakes have been informed solely by water quality data from the last few decades. Unlike modern water quality data, diatom-based environmental reconstructions can be employed to determine a lake’s natural— pre-industrial— conditions. For this study, I analyzed modern diatom assemblages from six inland Ohio lakes and grouped individual diatoms into morphological taxonomic units (mOTUs) based on frustule (shell) morphology. Because diatoms are known to be particularly sensitive to changes in total phosphorus (TP) concentrations and pH, the lakes chosen for this study represent a wide range of pH (pH 6.04 – 9.03) and TP (76.2 – 451.5 ppb) values. I created a training set by comparing modern water quality data from the six lakes to the relative abundances of the mOTUs to determine which mOTUs show preference for specific parameter ranges. Once I supplement this training set with data from 26 additional lakes, I will apply the training set to historical diatom assemblage data collected from lake sediment cores, to estimate the natural conditions of eight lakes. Knowledge of the natural water quality of a lake can be used to determine the extent to which lake chemistry has been perturbed by human activity, as well as the state to which polluted lakes can reasonably be restored.