WATER QUALITY AND OSTRACODES: TRACKING CHANGES IN ROAD SALT AND NITRATE IN A NORTHEAST OHIO WATERSHED

Road salt runoff is a significant environmental issue in the Midwest and often contributes to changes in surface water chemistry that impact local flora and fauna. A study was conducted to observe this variation in hydrochemistry along the flow path of Tinkers Creek, the largest tributary of the Cuyahoga River in Northeast Ohio. Its headwaters begin near Herrick Fen, a nearly pristine fen wetland home to a wide variety of plants and animals. Of particular interest are the many species of ostracodes, microscopic crustaceans with bivalved calcite shells. Ostracodes are indicators of groundwater-surface water interactions, as their species distributions are heavily dependent upon the hydrologic characteristics of their habitats.

Within the fen several distinct microhabitats were observed in sites marked by the occurrence of groundwater recharge, discharge, or a combination of the two. Ostracode assemblages were highly diverse in the fen, and sodium chloride and nitrate levels were low, as expected for an unpolluted freshwater ecosystem. In areas of perennial groundwater discharge, water temperatures were generally cool at the surface (11^o C) and species such as Cavernocypris wardi, Cypridopsis okeechobei, and Microdarwinula sp. A were present. In locations where groundwater seepage was occurring along with surface water recharge, the temperature of the surface water varied depending upon the air temperature. Species assemblages included Candona compressa, Darwinula stevensoni, Cypridopsis vidua, Physocypria globula, and Scottia browniana. At the headwaters of Tinkers Creek, surface water temperatures again mimicked the air temperatures, and ostracodes such as Physocypria globula, Cypridopsis vidua, and Cypria opthalmica were found. As Tinkers Creek was sampled along its flow path downstream to its eventual discharge into the Cuyahoga River, increased sodium chloride and nitrate levels were observed. These hydrochemical changes at the sampling locations were accompanied by changes in the ostracode species assemblages and reductions in their species richness. Ilyocypris bradyi, Physocypria globula, Candona elliptica, Cypria opthalmica, and Heterocypris sp. (juvenile) were the ostracodes observed farther downstream, although most sites were predominantly inhabited by I. bradyi.