The Peconic River had many mass depletions in its fish population. These depletions resulted from an inadequate amount of oxygen in the water for a long time, which suffocated the fish. Studies show that the scarce oxygen levels were affected by rising water temperatures, algal blooms, and excessive nitrogen, biochemical oxygen demand (BOD), and sediment oxygen demand (SOD). Mass kills that happened in the river are now known as “fish kills”, which has occurred repeatedly during the life of the river. The last fish kill was in 2015. In this study, the CO1 gene which is found in nucleotide pairs 5904 to 7444 in sections of mtDNA is compared to a database of gene sequences to determine the identity of each sample. Using data from last year, our goal is to observe how the presence of aquatic macroinvertebrates act as indicators of overall water quality. We expect to observe a stable or slight rise in biodiversity of invertebrates due to reduced damage caused by human impacts.