US Long-Term Ecological Research Network
Invertebrate Collection
We used modified Hester-Dendy colonization substrates to sample benthic invertebrate communities. Each sampling device consisted of a 3"x3" top plate, alternating layers of course and fine mesh, a 'choreboy' commercial scrubbing puff, alternating layers of coarse (6.35 mm) and fine (3.18 mm) black plastic mesh, and a 3"x3" bottom plate (see NTL-LTER website for further description). Two Hester-Dendy samplers were set at a depth of one meter on each of three substrate types (cobble, sand and silt) within each lake for four weeks. Within each lake, areas of different substrate types were identified using WI-DNR depth contour lake maps, and substrate type was verified by direct observation. Different substrates were sampled to account for invertebrate associations with specific substrate characteristics.

All benthic invertebrates were removed from the colonization samplers, preserved in 70% ethanol, identified and enumerated. Aquatic insects were identified to family and other invertebrate were classified to order using standard taxonomic keys, e.g., Hilsenhoff (1981), Thorp and Covich (1991), Merritt and Cummins (1998). Invertebrate information from all sites was pooled to create a single invertebrate sample from each lake. From these data, estimates of invertebrate abundance, richness and evenness were calculated for each lake. Abundance estimates reflect the average number of individuals per Hester-Dendy in each lake. Richness was the cumulative number of taxa found at each site.

Lake order was used to examine the variation of the lake attributes and invertebrate assemblage characteristics along the lake landscape position gradient. Lake order is a method of classifying lakes based on the type and strength of linkages between lakes and stream networks, and has been used as a surrogate measure for lake landscape position (Riera et al. 2000). Riera and colleagues (2000) developed a numbered system to differentiate lakes without permanent inlets or outlets (seepage lakes, negative lake order), from those having inlets and outlets (drainage lakes, positive lake order). The lakes that we selected for this study were previously assigned an order from analyses of maps by Riera and colleagues (2000).


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