SEDIMENT AND WATER QUALITY DETERMINATION OF THE OTTER CREEK WATERSHED

The Otter Creek Watershed is an area draining 124 square miles spanning across Clay, Parke, and Vigo counties of Indiana into the Wabash River. It has been considered significantly impaired by Escherichia coli since IDEM’s 2009 research. This study sought to determine the level of E. coli contamination, phosphorus concentrations, and possible contamination of heavy metals in the water and sediment. The presence of E. coli can be an indication of other harmful pathogens that can infect both land and aquatic life. Heavy metal and phosphorus concentrations can disrupt the ecology of the watershed by causing harmful effects to aquatic life, and possible eutrophication, respectively. Physiological and pathological effects that impair growth, survival, and reproduction of aquatic organisms can be caused by elevated metal concentrations.

Water and sediment samples were collected from twelve sites for eight weeks and analyzed using Coliscan Easygel kits, UV-visible spectrophotometry, and inductively coupled plasma optical emission spectrometry. Eight of our twelve sample sites exceeded the recommended geometric mean of 125 CFU/ 100mL for E. coli in the water. Evidence of increased E. coli during rainfall suggests that runoff and nonpoint sources are significant contributors. Only two samples out of ninety-six exceeded the 0.1 mg/L recommended limit of phosphorus in the water, and harmful algal blooms were not present at any of the sites during sampling. Weak acid extractable metal concentrations in sediments ranged from 1.39 µg/g to 425.41 µg/g for Zn, from 0.97 µg/g to 152.85 µg/g for Ba, from 10.92 µg/g to 89.21 µg/g for Sr, from 165.23 µg/g to 162,233 µg/g for Fe and from 30.12 µg/g to 33,043 µg/g for Al. Generally, the abundance of metals increased from the headwaters to the mouth of the watershed. The Otter Creek Watershed is unsafe for recreational use due to the impairment of E. coli. Additional biological sampling is needed to assess how metals are influencing the aquatic organisms.