The impact of small chironomid grazers on epiphytic algal abundance and dispersion

Abstract

1. A combination of field and laboratory experiments was used to assess the impact of chironomid grazers on taxonomic composition, abundance and dispersion of epiphytic algal assemblages. 2. In the laboratory, Psectrocladius sp. reduced the biovolume of algal spedes preferred as food and increased the degree of clumping of non-preferred spedes. Thienemanniella cf. fusca had both positive and negative effects (depending on the algal spedes) on the biovolumes of algal spedes preferred as food and increased the degree of clumping of non-preferred spedes. 3. In field exclosures, no effect of removal of chironomid larvae from the grazer ' assemblage could be detected in autumn or winter experiments. A third, longer removal experiment, conducted in summer, resulted in increased biovolumes of edible Cosmarium spp. and Aphanocapsa spp., preferred foods of chironomid larvae. Biovolumes of Lyngbya sp., Bulbochaete spp. and Oedogonium spp., filamentous taxa used extensively in larval case construction, also increased. Chironomid larvae had no effect on total algal biovolume or biovolume of large unicellular algae. 4. Chironomid larvae can influence epiphytic algal assemblages through selective • • grazing by redudng the biovolumes of preferred foods and through case-building activity by redudng the biovolumes of construction materials. 25

Recommendations for sampling littoral diatoms in lakes for ecological status assessments

“…Diatoms are an important component of the diet of a range of grazers (Round, 1981), especially chironomid larvae (Botts, 1993) and thus grazers can alter the floristic assemblage of the diatom community (Allan, 1995). The effect of grazers is hard to quantify and few studies have attempted to examine the effect of grazers on phytobenthos communities in standing waters (Aberle et al, 2005).…”

Seasonal dynamics of aufwuchs Naididae (Oligochaeta) on Phragmites australis in a eutrophic lake

“…MUller, 1994MUller, , 1995, indicating that algal biomass may have been limited by grazing at this time. Invertebrate grazing on algae is a central process in aufwuchs and has been reported not only to alter algal community composition (Botts, 1993), but also to limit algal biomass (e.g. Cattaneo, 1983;Hann, 1991;Kairesalo, 1984;Kairesalo & Koskimies, 1987).…”

INCORPORATION OF FRESHWATER RHODOPHYTA INTO THE CASES OF CHIRONOMID LARVAE (CHIRONOMIDAE, DIPTERA) FROM NORTH AMERICA1

“…and Oedogonium sp. (Botts 1993). In both habitats, the biomass of the algal filaments decreased significantly during the period of active case building.…”