Macroinvertebrate communities and biofilm chlorophyll on woody debris in two Canadian oligotrophic lakes
Bowen, Kelly L.; Kaushik, Narinder K.; Gordon, Andrew M.
published: Mar 9, 1998
ArtNo. ESP141014103008, Price: 29.00 €
Wood-associated macroinvertebrates and biofilm chlorophyll-a were investigated in Scott Lake and Mykiss Lake in Algonquin Provincial Park, Ontario, Canada. Invertebrate communities on littoral submerged coarse woody debris (CWD) were compared with those on experimentally introduced substrates consisting of fresh branches, which were monitored for one year. The most abundant invertebrates were Chironomidae (Diptera), followed by Naididae (Oligochaeta), Polycentropidae (Trichoptera), and Heptageniidae (Ephemeroptera). Collector and scraper taxa dominated, highlighting the importance of the surface biofilm as a food source. Invertebrate community composition changed slightly as the wood decomposed, with Trichoptera, Elmidae (Coleoptera) and xylophagous chironomids such as Stenochironomus spp. becoming more abundant on microbially conditioned CWD. Mean invertebrate densities on the introduced substrates were 2,827 and 4,827·m Scott and Mykiss, respectively, while corresponding values on natural CWD were only 922 and 1,249· m-2 Mean invertebrate biomass on the introduced substrates were 387 mg·m -2 in Scott and 698 in Mykiss, while corresponding values for natural CWD were 134 and 302 mg m-2 Invertebrate density and taxa richness on the introduced wood was highest on white cedar (Thuja occidentalis), intermediate on eastern hemlock (Tsuga canadensis) and lowest on sugar maple (Acer saccharum), probably because of differences in bark microhabitat and availability of biofilm. Chlorophyll-a also tended to be highest on cedar substrates, intermediate on hemlock and lowest on maple, with mean values of 10.3, 8.3 and 4.7 mg·m-2, respectively. The higher mean chlorophyll-a content on the natural CWD (22.5 mg m-2) may have resulted from longer submergence time, lower invertebrate grazing pressure, or differences in methodology.