Author: Ariana  Chiapella,  Postdoctoral Associate (1990)

Description:
Invasive species have had cascading impacts on freshwater ecosystems around the globe. The consequences of invasions ripple across food webs, and often include severed trophic connections and loss of native species. Dreissenid mussels, for example, have negatively impacted pelagic fish communities in lakes across North America. These filter-feeders shunt nutrients away from the pelagic zone to the nearshore benthic zone, and thus cut off the energy supply to the open water food web. Zebra mussels were first discovered in Lake Champlain in 1993, with seemingly minor impacts to the food web. However, a quagga mussel invasion is imminent. Given they have a greater depth range and filtering rate than zebra mussels, quagga mussels may have more serious consequences if open-water forage fish (alewife and rainbow smelt) rely on pelagic energy sources. We tested the hypothesis that pelagic carbon is the primary source of energy to Lake Champlain’s forage fish by using stable isotope, stomach content, and fatty acid analyses to map the food web’s carbon energy pathways. We determined that alewife and rainbow smelt – which are important prey species for native and stocked lake trout and Atlantic salmon – primarily rely on pelagic energy sources. If quagga mussels do in fact sever the pelagic energy pathway in Lake Champlain, the salmonid fisheries may be at risk, and managers may have to consider adjusting piscivore stocking rates to preserve the current structure and integrity of the food web.

Category: Scientific Program Abstract > Special Session > SS36 Tracing change in food webs: current and emergent methods to determine impacts of anthropogenic change on ecosystem structure and function