Two preservative treatments traditionally used in aquatic sciences, formalin (4%) and ethanol (70%), were compared for their effects on biomass estimations. The effects of both preservatives on wet weight, dry weight, and ash-free dry weight were determined for samples preserved for 10, 21, and 90 days. The effects were studied in four different macrofauna species commonly found in German estuaries: Heteromastus filiformis (Capitellidae, Polychaeta), Hediste diversicolor (Nereididae, Polychaeta), Corophium sp. (Amphipoda, Crustaceae), and Gammarus spp. (Amphipoda, Crustacea). The biomass estimates of preserved samples were compared with those of unpreserved samples. In all four species the loss in wet weight, dry weight, and ash-free dry weight was most pronounced within the first 10 days, and an additional weight loss was recorded between days 10 and 21. However, there was no further loss in weight for samples kept for as long as 90 days in the preservatives. In general, crustaceans exhibited higher weight loss than polychaetes, and smaller species (H. filiformis and Corophium sp.) showed higher weight loss and a higher variability than larger species. As our main result, significant differences between the two preservative treatments did never occur. Our results contradict some earlier investigations on this matter where formalin has been reported to be superior to alcoholic preservatives because weight loss was less pronounced than in ethanol. Factors affecting biomass estimates are discussed and we conclude that, for the macrofauna groups tested, the use of the toxic formalin solution is not justified when the major intent is biomass estimation.

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During the past 30 y, periphyton has been recognized as a key component in the benthos of lake littoral zones. However, the role of meiofauna-sized organisms living in the periphyton and mechanisms regulating and influencing those communities largely have been neglected, and the process of community development and colonization pathways of periphytic meiofauna are unknown in lakes. We studied these processes on littoral hard substrates in an oligotrophic lake. We manipulated the access of meiofauna to artificial hard substrates for a period of 57 d in a field experiment. In one treatment, the direct colonization pathway via active crawling was prohibited by elevating substrates into the water column. Development of the meiofaunal community was compared between elevated and nonelevated (control) treatments. In addition, relationships among the meiofaunal communities on the substrates in the field experiment and those in sediment traps and on natural hard substrates were examined. Periphyton biomass (chlorophyll a, total organic matter) and inorganic matter increased significantly in both experimental treatments throughout the experiment. Meiofauna colonized the substrates quickly and reached maximum densities of 107 ind./cm 2. The initial colonization phase (2-8 d) was characterized by a great variation in meiofaunal community structure; rotifers and crustaceans were the most abundant groups. Communities became less variable during the experiment and resembled natural communities on hard substrates at the end of the experiment. In general, development of meiofaunal abundance and periphyton biomass was rapid and proceeded similarly in both treatments. Our results show that colonization of littoral hard substrates can be driven by water-column transport of meiofauna and point to the importance of this pathway for dispersal and colonization of hard substrates by meiofauna.