PARENT SESSION
Contributed Oral Session 56: Aquatic Ecology: Communities
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 513 C, Level 5, Palais des congrès de Montréal

Linkages between climate, land use, hydrology, and amphibians in the ecological network of the Mississippi River.

Sadinski, Walt^*,1, Bourassa, Sam², Meyer, Leah ¹, Roth, Mark¹, Jones, Perry ³, ¹ U.S. Geological Survey, La Crosse, WI, U.S.² University of Wisconsin, La Crosse, La Crosse, WI, U.S.³ U.S. Geological Survey, Moundsview, MN

ABSTRACT- The floodplain of the Mississippi River is home to remarkable biodiversity. Two hundred and forty-one species of fish, 37 species of mussels, 45 species of amphibians, 50 species of mammals, and 40% of all migratory birds in the U.S. live in the floodplain. Yet this biodiversity is largely a function of conditions across the larger landscape of the middle U.S. at multiple scales of space and time. The floodplain is linked to these conditions primarily via climate and the network of streams and rivers that drain the upper landscape and empty into the Mississippi River. The importance of these linkages was evident in relationships between climate, hydrology, land cover/use, and amphibians living in the floodplain during 2004. Rain events across the landscape caused flooding in the Upper Mississippi River during May and June. This flooding interrupted the breeding activities of Bufo americanus, Hyla versicolor, H. chrysoscelis, Acris crepitans blanchardi, and Rana clamitans via deep and flowing water at breeding sites. Floodwaters also carried herbicides that had been applied on row crops across the region. We used Enzyme-linked Immunosorbent Assays to measure concentrations of triazines (herbicides) in the water at 60 sites (46 breeding sites of amphibians) we sampled in the floodplain from April to August, including a subset of 30 sites that we sampled up to six times. We compared these concentrations with the hydrograph for the Mississippi River and with physical linkages of sampling sites to areas where triazines were used. The mean concentration of triazines at sampling sites was 0.65 ppb (s.e. = ± 0.070) and increased with water levels. Concentrations were higher in areas with direct linkages to row crops where these compounds were applied. Up to 13 species of amphibians were exposed to the triazines we measured. Atrazine, which has been shown to cause gonadal abnormalities in amphibians, was one of those triazines. Thus, storms, land use, and hydrological connectivity across the greater landscape ultimately interrupted breeding and exposed amphibians in the floodplain to potentially toxic levels of herbicides. These observations demonstrate how biodiversity in the floodplain of the Mississippi River has to be considered in a broad context of linkages across scales.

Key words: climate, amphibians, hydrology, linkages