Cattle access affects periphyton community structure in Tennessee farm ponds.

Cattle farming is vital to the economy of the United States. Frequently, cattle are given access to ponds and streams for water. The relative impacts of cattle access in natural water sources on the periphyton community have been rarely investigated. Periphyton is the basis of the aquatic food web, and community composition can serve as a bioindicator of pollution. Thus, my objectives were to quantify the effects of cattle access in aquatic lentic systems on periphyton community structure and biovolume, identify taxa that were associated with cattle access, and identify abiotic mechanisms that might be driving assemblage changes. I conducted my research in 4 cattle-access (CA) and 4 no-access (NA) farm ponds on the University of Tennessee Plateau Research and Education Center from May 2005 – April 2006. Periphyton community composition and water quality were measured every 2 weeks using standard environmental monitoring procedures. I documented 181 new periphyton taxonomic records (7 phyla, 52 families, and 132 genera) in Cumberland County, Tennessee. Periphyton species richness was greatest in NA ponds. Mean biovolume of pollution-sensitive diatoms (e.g., Achnanthidium minutissimum, Cymbella sp., Eunotia sp., Fragilaria crotonensis and Tabellaria fenestrata) was greater in NA ponds. In contrast, pollution-tolerant diatoms (e.g., Gomphonema sp. and Navicula sp.) and non-diatoms (e.g., Oscillatoria sp. and Scenedesmus sp.) were more abundant in CA ponds. Turbidity, pH, conductivity, and concentrations of the total Kjeldahl nitrogen, total phosphorus, potassium, periphyton phosphorus, silicon, iron, magnesium and aluminum were greater in CA ponds. Thus, changes in water quality associated with cattle-access likely mediated changes in the periphyton community. Considering that changes in periphyton community composition can destabilize higher trophic levels, I recommend that cattle farmers take advantage of USDA conservation programs that provide funds for fencing cattle from watersheds and developing alternate water sources. My results also provide evidence that monitoring the periphyton community is a reliable technique to detect water pollution from cattle.