Differential riparian responses to wild pigs, Sus scrofa, in the Gulf Coastal Plain

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Elizabeth A. Bradley and Graeme Lockaby, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL

Background/Question/Methods:
Wild pigs (Sus scrofa) are an extremely prolific and destructive invasive species in the United States, reportedly worth $1.5 billion in damages and control costs annually. Around half of the nation's wild pigs reside in the Southeast, where their preferential habitat selection, diet, and behavior pose a significant threat to riparian ecosystems. Wild pigs alter numerous chemical and geophysical processes, such as modifying soil chemistry, nutrient cycling, and water quality. These alterations to natural processes can have cascading impacts on the biodiversity and ecological function of riparian ecosystems. However, current literature on this topic is scarce and understanding of their impacts on system types is limited. Redwater (eutrophic) and blackwater (oligotrophic) systems are two of the most distinct stream ecosystem types globally. Redwater streams are high gradient, productive systems characterized by their high nutrient availability and sediment loads. In contrast, blackwater streams are low gradient less productive systems associated with low nutrient availability and vulnerability to nutrient loading. This project aims to determine differential stream system responses to wild pig invasions through the evaluation of biogeochemical analyses of eutrophic and oligotrophic systems in the Gulf Coastal Plain prior-to and post wild pig removal.
Results/Conclusions:
Our preliminary data indicate that E. coli and fecal coliform levels are significantly higher in redwater streams. The increased bacteria levels may be due to redwater streams' higher gradient and greater capacity to carry sediment and other substances. The mean E.coli levels were greater in redwater streams (M=1226.44cfu) than in blackwater streams (M=60.71cfu), (t=3.156, p-value=0.0037). Like the mean E.coli levels, mean fecal coliform levels were greater in redwater streams (M=4009.297cfu) than in blackwater streams (M=2456.83cfu) (t=2.780 and p=0.008). Following this trend, further analyses are being conducted comparing other water quality metrics (like TSS, pH, temperature, and nutrient levels) between the two regions. We are also exploring relationships between E.coli, fecal coliform, and other water quality metrics.