Effects of Habitat Complexity on Macroinvertebrate Colonization of Artificial Substrates in North Temperate Lakes

Abstract

The purpose of this study was to determine the effects of substrate complexity on community structure of macroinvertebrates in littoral zones of lakes. Artificial substrates were used to simulate characteristics of structures commonly placed on the lake bed along shorelines. Cement balls in a wire basket simulated rock riprap, whereas concrete patio blocks simulated retaining walls; the samplers had nearly equal surface areas. Samplers were placed in the littoral zones of 3 dissimilar lakes in Wisconsin, and in front of 3 types of shorelines: rock riprap, vertical retaining wall, and natural shorelines. Colonization periods were 40-45 d starting immediately after ice-out. Significantly greater numbers of organisms colonized basket samplers (1947 ± 155 / m² mean ± 1 SE) than block samplers (951 ± 73 / m²). Taxa richness was significantly higher on baskets (31 ± 1) versus blocks (22 ± 1). Hydra, Turbellaria, Oligochaeta, Crustacea, Ephemeroptera, and Odonata were significantly more abundant on baskets than on blocks. Mollusca, Hydrachnida, and Chironomidae showed a strong trend toward greater abundance on baskets. Only Trichoptera was equally abundant on both samplers. Neither abundance nor richness differed significantly among shoreline types, but a trend of higher values for both variables was observed along rock riprap. The results were consistent with the hypothesis that the more complex, 3-dimensional artificial substrate, with its greater substrate heterogeneity, surface complexity, and interstitial space, will support a more diverse and abundant macroinvertebrate community in lakes compared to the less complex, 2-dimensional artificial substrate. Shoreline management practices that reduce habitat complexity may reduce local invertebrate diversity.