Swine (Sus scrofa Linnaeus) are an invasive species with a negative impact on native terrestrial plant and animal diversity. Further, in its native range, excessive population size has been perceived as a potential problem. The effects of swine on aquatic organisms remain poorly documented. We investigated the effect of an unmanaged population of feral and free ranging swine upon aquatic habitat, invertebrates and microbes in a coastal plain stream in Louisiana. Sampling was conducted twice yearly, spring and fall, from August 2002 through April 2004, at five sites within the Mill Creek watershed. We measured stream characteristics, carbon and nitrogen, biochemical oxygen demand, fecal coliform counts and heterotrophic plate counts. We collected invertebrates from woody debris, microbes from the water column and identified both to the lowest practical taxon. Invertebrate, microbial, habitat and swine relationships were assessed with detrended and canonical correspondence analysis. Swine activity ...

The fungus Aspergillus flavus infects corn, peanut, and cottonseed, and contaminates seeds with acutely poisonous and carcinogenic aflatoxin. Aflatoxin contamination is a perennial threat in tropical and subtropical climates. Nonaflatoxin-producing isolates (atoxigenic) are deployed in fields to mitigate aflatoxin contamination. The biocontrol competitively excludes toxigenic A. flavus via direct replacement and thigmoregulated (touch) toxin inhibition mechanisms. To understand the broad-spectrum toxin inhibition, toxigenic isolates representing different mating types and sclerotia sizes were individually cocultured with different atoxigenic biocontrol isolates. To determine whether more inhibitory isolates had a competitive advantage to displace or touch inhibit toxigenic isolates, biomass accumulation rates were determined for each isolate. Finally, to determine whether atoxigenic isolates could inhibit aflatoxin production without touch, atoxigenic isolates were grown separated from a single toxigenic isolate by a membrane. Atoxigenic isolates 17, Af36, and K49 had superior abilities to inhibit toxin production. Small (<400 µm) sclerotial, Mat1-1 isolates were not as completely inhibited as others by most atoxigenic isolates. As expected for both direct replacement and touch inhibition, the fastest-growing atoxigenic isolates inhibited aflatoxin production the most, except for atoxigenic Af36 and K49. Aflatoxin production was inhibited when toxigenic and atoxigenic isolates were grown separately, especially by slow-growing atoxigenic Af36 and K49. Additionally, fungus-free filtrates from atoxigenic cultures inhibited aflatoxin production. Toxin production inhibition without direct contact revealed secretion of diffusible chemicals as an additional biocontrol mechanism. Biocontrol formulations should be improved by identifying isolates with broad-spectrum, high-inhibition capabilities and production of secreted inhibitory chemicals.