Non-point source pollution from fertilizer runoff has had a significant impact on the quality of the waterways in the U.S. through its effects on biotic and abiotic factors. Increased nitrogen and phosphorus levels in streams can lead to habitat degradation and decline in water quality which can cause long-term, negative impacts on aquatic life, including macroinvertebrates. Increased nutrient levels are known to significantly influence stream biodiversity and previous studies also suggest that nutrient enrichment is directly related to the presence of filamentous bacteria (Leptothrix spp. and Sphaerotilus spp.) on macroinvertebrates. The presence of these filamentous bacteria in streams has the potential to be used as a bioindicator for water quality. The objectives of this study are to (1) investigate differences in the density and biomass of macroinvertebrates in nutrient enriched and non-enriched streams in western New York and (2) determine if there is a relationship between nutrient concentration and bacterial coverage on different insect orders. Three enriched and three non-enriched streams were sampled seasonally for macroinvertebrates and nutrient concentrations and the presence and percentage of bacteria was recorded. In addition, microcosm experiments will be performed to determine which nutrient is the main contributor towards the growth of Leptothrix spp. and its effects on Odonata and Ephemeroptera.
Results/Conclusions
Initial results show that the non-enriched streams have higher total macroinvertebrate richness as well as insect species richness compared to the nutrient enriched streams (p < 0.05). Using the Shannon-Weiner Diversity Index, our non-enriched streams were marginally more diverse than the enriched streams (p = 0.055). Through our sampling, we found that the bacteria are only present on aquatic insects and are generally found on the orders Coleoptera, Ephemeroptera, Plecoptera, and Trichoptera. Trichoptera, particularly in the family Hydropsychidae, has significantly more individuals with bacteria compared to the other orders (p < 0.05). Our results so far show no difference in the amount of bacteria present in the nutrient enriched streams compared to the non-enriched; however, there was a marginally nonsignificant difference in seasonal differences with Fall exhibiting greater bacterial coverage than Summer (p = 0.07). Continued sampling may provide more insight on seasonal differences. These results so far highlight the negative implications associated with agricultural runoff and stream macroinvertebrates. Results from our microcosm experiment may also provide information on which nutrient is the driver for bacterial growth and could be useful during rapid bioassessment procedures regarding stream health.