Health Assessment of a Pennsylvania Limestone Spring Using Macroinvertebrates and Sediment Levels: Urban and Agricultural Proximity Do Not Always Result in Impairment

The health of Little Cedar Creek, a stream running through popular recreational parks in the third largest city in Pennsylvania, USA (Allentown), was declared “impaired by sediment” by the Pennsylvania Department of Environmental Protection, requiring remediation steps by local government. This designation was based on a modeling analysis using a Geographic Information System (GIS) platform. The present study is the first quantitative in-person analysis of the ecology of this creek using macroinvertebrates, sediment, and basic water chemistry parameters over a three-year period at seven sites within the stream reach. While the macroinvertebrate community has some impairment, including the invasive New Zealand mud snail, the stream is limestone-influenced. Therefore, a lower Shannon-Wiener diversity index, the preponderance of dipteran larvae, lack of stoneflies, and low macroinvertebrate diversity in general is to be expected. The study sites were not dominated by small-sized sediment, and macroinvertebrate indices were not negatively correlated with the proportion of fine pebbles and smaller (<8 mm) sediment. Therefore, it appears that if there is a consistent pollution source, it is likely not sediment-derived, or else flooding regularly clears smaller sediment. Most notable in our results was the large degree of variation among sites and among years, even at the same sites. Our results caution that, while GIS-based mathematical modeling can highlight potentially threatened areas, in-person evaluations of the sites should evaluate these hypotheses. The current study provides a baseline report to enable future monitoring of this urban stream.