Habitat Preference of Aquatic Macroinvertebrates in an East Texas Sandy Stream

Abstract

I identified the habitat types available to manoinvertebrate colonization in an east Texas sandy stream and then described differences in colonization of those habitat types.Six habitat types were identified in Harmon Creek: aquatic macrophytes (Hydrocotyle umbellara, Justicia ovata, Altemanfhaphiloxeroides), coarse woody debris (CWD), leaf packs, submersed roots extending from riparian trees, submerged macrophytes (Najus grcadalupemis) growing on bedrock (Najas/bedrock), and benthic sand.One-way analysis of variance showed signiricant differences in macroinvertebrate density among habitat types.The greatest density was found on macrophytes (815.8 organisms/m2) followed by CWD (679.7 organisms/m2).The third greatest densities were found on leaf packs (516.1 organisms/m2) and roots (492.5 organisms/m3, which were not sisnificantly different from one another.Lowest densities were collected from Najus/lxdmck (218.6 organisms/m2) and benthic sand (2163 organisms/m2).Coarse woody debris also showed sisnificant differences in macroinvertebrate density with degree of wood decay.Wood with loose bark, and well-decayed wood with many interstitial spaces had the greatest density of macroinvertebrates.Macroinvertebrate richness was highest in leaf packs.which contained 46 genera of rnacroinvertebrates, and thdowest richness occurred on Najas/lxdmck, which contained 24 genera. INTRODUCI'IONHabitat utilization by macroinvertebrates is an important component of the ecology of lotic environments.Previous investigations have shown that streams with stable cobble substrates often have different habitat use by macroinvertebrates than do streams with less stable sandy substrates (Benke et al. 1984, Smock et al. 1985. Phillips 1993).In sandy streams woody debris is often very important as habitat for aquatic macroinvertebrates because sand does not provide a stable enough environment for many species (Benke et al. 1984, Smock et al. 1985).Additionally, woody debris is used as food by xylophagous invertebrates, and it provides substrate for the growth of biofilm which many invertebrates feed upon (Anderson et al. 1978, Anderson 1989, Steedman and Anderson 1985, Phillips and Kilambi 1994, Phillips 1995).Other types of habitats can add stability to lotic systems.Aquatic macrophytes can add both a stable habitat and a food source for many aquatic macroinvertebrates (Botts and Cowell 1994, Beckett et al. 1992, Cattaneo 1983, Schnunm et al. 1987, Cyr and Downin, 1988).Losee and Wetzel (1988) concluded that submersed macrophytes provided approximately ten times more surface area for macroinvertebrate colonization than the total benthic area of Lawrence Lake in Michigan.Leaf packs are a primary food source and serve as habitat for many aquatic macroinvertebrates (