Graduate Student Seed Grant Projects

The effect of livestock antibiotics on leaf breakdown and shredder function


Carl Wepking, Kevin Eliason and Matt Hedin, Biological Sciences; Faculty Mentor: Michael Strickland

Increased antibiotic resistance of human bacterial pathogens has brought all uses of antibiotics under scrutiny. Livestock antibiotics account for approximately four-fifths of all antibiotics sold in the United States. Additionally, antibiotics and antibiotic residues have been detected in livestock manure, potentially providing a pathway for large quantities of antibiotics to enter the environment. Pasture soils are likely the initial point of entry for these antibiotics, and study of this setting is ongoing. However, livestock antibiotics have also been found in streams, and little research has been conducted on the potential effects on stream microbial community composition and the ecosystem level processes they regulate. In smaller streams leaves provide a substantial energy source for the system. Aquatic microbial communities are integral to leaf breakdown and make up the main diet of macroinvertebrate “shredders.”

Through investigation of how antibiotics can affect microbial communities, their ability to break down leaves, and the effect of microbial community alterations on macroinvertebrate feeding efficiency, we hope to determine the effect of antibiotics on stream ecosystem functioning. Also, mounting evidence indicates that alteration of an organism’s microbiome can have overarching impacts on an organism’s well-being. As antibiotic inputs can affect an organism’s microbiome, investigating the changes in microbial community structure between invertebrates exposed to antibiotics and those unexposed should help to reveal impacts of antibiotics on macroinvertebrate function. Finally, as increased abundance of antibiotic resistance genes allows for greater uptake of these genes by pathogens of human concern, quantifying alterations to these pools of genes has serious human health implications.