Seasonal Variations in Water Chemistry and Diversity of the Phytophilic Macroinvertebrates of Three Swamp Communities in Southeastern Louisiana

Abstract

The McElroy Swamp in Ascension Parish, Louisiana, consisted of variety of habitats, three of which were sampled. Each of the three stations was distinct from the others in terms of both physico-chemical features and faunal characteristics. Significantly different communities existed in spite of the close proximity of one station to another. The cooler, shaded, temporary waters of the mixed hardwoods swamp exhibited relatively stable chemical regime. The macroinvertebrates were those of pro- tected situations with minimal variations in water conditions. Hydrozoans, hemip- terans, coleopterans, chironomids and culicids characterized this habitat. The permanent waters of the cypress swamp were more exposed to sunlight. Oxygen saturation, carbon dioxide, and related factors were largely controlled by the dense aquatic plant community. Chemical characteristics of these waters were more variable than the mixed swamp. There was an abundance of some species of water mites, backswimmers, odonates, and the mosquito Culex. The dead cypress swamp was unprotected from sun and wind. A dense growth of aquatic vegetation offered an abundance of food and substrates for benthic invertebrates. However, variations in physico-chemical factors were extreme. Chironomid and naidid abundance was highly variable. Gastropods, caddisflies, mayflies, and dipterans, particularly biting midges, characterized this habitat. A swamp, as defined by Penfound (1952), is a woody com- munity occurring in an area where the soil is usually saturated or covered with surface water for one or more months of the growing season. Swamplands characterize low-lying areas and although they are extremely abundant, especially in the Gulf States, they have been almost completely neglected in terms of their limnology and aquatic invertebrate communities. KruIl and Hubert (1973) and Matta (1974) published reports on the invertebrate fauna of two swamp habitats. However, their reports contain little in-