Assessment of Middle Creek stream (Snyder County, PA) using Water Quality Index (WQI) and Diatom metrics

Water quality Index (WQI) in combination with diatom community metrics were used to provide single values to express the overall quality of water based on a number of measurable parameters. WQI, Pollution Tolerance Index (PTI) and Bray-Curtis Index of similarity were all measured during the period between June 26th and July 14th in an effort to assess the water quality of Middle Creek (MC) (Snyder, CO., PA). MC is a 2nd order tributary stream flowing into Penns Creek before joining the Susquehanna River. In this study, eleven sites were selected between the head waters and its confluence with Penns Creek. MC has two main branches in its upper reaches, each branch with a manmade reservoir. 3 sites were selected on each branch with one site upstream, the other site downstream and the third site on the reservoir. Five sites (A, B, C, D and E) were selected on the main stem from the confluence with Penns Creek to the confluence of the two headwater branches. For the WQI, all sites were sampled three times during the first week, twice the second week and once a week for the remaining two weeks. Diatom communities were samples by placing diatometers at each site and allowing them to incubate in situ for three weeks. Each diatometer had five microscope slides, each of which was mounted to form a permanent slide and then examined at 1000X using a Nikon E 200. A minimum of 300 cells was identified to species on each slide (~1500 cells per diatometer). The resulting relative abundances were used to generate a Pollution Tolerance Index (PTI) for each site and to compare the diatom communities using a Bray-Curtis Similarity Index. Physical properties were measured in the field and grab-samples were tested for PO43-, NO2-, NH3, NO3-, Na+, NH4, K+, Mg2+, and Ca2+ in addition to BOD5, COD and TSS. The results showed and average WQI for the first week of 90.35 confirming that the water was in good condition and could overcome discharge of runoff with nutrients chemicals. KE (conductivity), TDS, and ORP generally decreased gradually from site A toward the headwaters, while Temperature (To) and pH increased. The two most headwater sites G and I on each branch are characterized by cold water, lower pH and higher KE, TDS and ORP compared to the lakes. To and Ca2+ in these two sites showed an effect of high base flow. Out of a scale of 0 to 4, with 4 being the most resistant to organic pollution, PTI range for MC was between 2.82 to 3.00, meaning moderately sensitive to organic pollution. BCI for all stream sites showed high to very high similarities. However, when Cocconeis species were removed, the sites ranged only from very low to high illustrating the complete dominance by a single genus.