The Distribution of Amphipods in Southeastern Minnesota and Their Relation to Water Quality and Land Use

The distribution of the amphipods Gammarus pseudolimnaeus and Hyalella azteca was determined from 97 designated trout streams in Minnesota, along with temperature, conductivity, and nitrate levels. Streams were classified into 4 land use/geology groups. G. pseudolimnaeus was found in 11 counties and at 123 of 168 sites in 83 of the 97 streams sampled. Hyalella azteca was found in 7 counties at 26 sites m 21 streams. Spearman rank correlations showed a high degree of correlation between nitrate (range: 0-11 mg N/L), conductivity (range: 325-870 μS/cm), and geology. The relative abundance of G. pseudolimnaeus was negatively correlated with nitrate, geology groups, and H. azteca relative abundance; G. pseudolimnaeus was most common in low-order streams originating from diffuse springs, and H. Azteca was more common in larger streams. The distribution of G. pseudolimnaeus with its strong correlation to geology may be largely influenced by land use and it may be a good long-term indicator of water quality