Fish-mediated nutrient and energy exchange between a Lake Superior coastalwetland and its adjacent bay

Little has been done to quantify fluxes of organisms, nutrients, and energy between fresh-water coastal habitats and adjacent offshore waters or to ev aluate the ecological implications of these exchanges on a whole-lake basis . To test the hypothesis that fish-mediated transport might play an importa nt role in the flux of nutrients and energy between coastal wetlands and ad jacent lake waters, net carbon, nitrogen, phosphorus, and energy fluxes wer e estimated in forage fish between a Lake Superior coastal wetland and an a djacent bay. This was accomplished by sampling fish at the inlet/outlet of Bark Bay Slough for 1 week per ice-free month in 1995. Average carbon, nitr ogen, and phosphorus content of the 20 species analyzed was 45.1, 11.3, and 2.45% of dry-weight, respectively. Estimates of organism, nutrient, and en ergy movement revealed a net export from the slough to the adjacent Bark Ba y, due largely to emigration of YOY yellow perch, Perca flavescens (> 40,00 0 individuals), YOY northern pike, Esox lucius (> 600 individuals), and yea rling emerald shiner, Notropis atherinoides (> 8,000 individuals) in July a nd July, and YOY brown bullhead, Ameiurus nebulosus (> 500 individuals) in October. Since these fish movements resulted in relatively small fluxes of nutrients (1,376 g carbon, 335 g nitrogen, 73 g phosphorus) and energy (65, 100 kJ) from the wetland to the lake, the most significant influence of for age fish emigration on Lake Superior may be through subsequent trophic inte ractions in nearshore habitats. However, assessment of the significance of the nutrient and energy results awaits a more complete budget for these eco systems.