Elemental composition of two coexisting Daphnia species during the seasonal course of population development in Lake Constance

Abstract

In 1986 and 1987 the seasonal course of population density, life history traits and biomass composition (CHN-elemental and ash) of two coexisting Daphnia species from L. Constance (Überlinger See) were studied. The two daphnids are morphologically similar, but demonstrate different seasonal variation of behaviour (i.e. diurnal vertical migration). With the exception of nitrogen content, the mean biomass composition of adults and that of eggs were significantly different: the dry biomass of eggs (adults) contained on average 55.6 (46.1) % C, 7.9 (6.5) % H, 9.7 (9.7) % N, and 10.0 (23.8) % ash. These values were similar to those of other daphnids; it may be concluded that the average daphnid composition is not species specific, but is determined mainly by the position in the life cycle and by the nutritional state of the animal. A distinct seasonal variation in the elemental composition of the biomass of adult daphnids was observed. It related significantly to the concentration of food, as indicated by the epilimnetic chlorophyll-a concentrations and by Secchi depth. From the amplitude of seasonal variation of elemental composition and from the shape of relationships between the elemental composition of daphnids and their food, it can be concluded that in summer the non-migrating D. galeata lives under stronger food limitation than the migrating H. hyalina. In spring, there were no differences in the biomass composition of either species. In summer, the adult fcmales of D. galeata contained significantly less carbon, and hydrogen than those of D. hyalina. In most parameters of biomass (i.e. biomass composition of adults) and of life history (i.e. clutch size, mean adult weight), D. galeata displayed higher coefficients of variation. A tendency in D. galeata to have peaks of population development carlier in the season and in D. hyalina to have them towards autumn was observed. These contrasting responses of the populations development, the seasonal variability of the biomass composition seem to support the view of Geller (1986) who called D. galeata and D. hyalina "exploitative" and "conservative" strategists respectively.

Seasonal changes of trophic transfer efficiencies in a plankton food web derived from biomass size distributions and network analysis

“…This result is in agreement with the idea that herbivores are food limited during summer in Lake Constance. Direct evidence for a severe food limitation during the clear-water phase and in summer is available for several species of rotifers from the egg ratio, and for daphnids from the clutch size, length-weight relationship, and age structure of the population (Geller, 1989) as well as from their elemental composition (Berberovic, 1990). Ciliates are most probably also food limited from the clear-water phase onwards .…”

Biofloc Technology (BFT): A Tool for Water Quality Management in Aquaculture

“…They could supply a high amount of protein into the biofloc cultures. Berberovic [60] evaluated the elemental composition (CHN) of two Daphnia species, reporting the following: C, 46.1%; H, 6.5%; N, 9.7%; and ash, 23.8%, which permit to estimate a protein content of 60.6%. This group of organisms was reported in biofloc system by Emerenciano et al [61].…”

The size distribution of plankton biomass in a large lake and its seasonal variability

“…Otherwise (e.g. for filamentous species), classification was done Latja and Salonen 1978;Berberovic 1990 Original data were converted to DW by DW = 0.25 x FW. The C content of DW was estimated by assuming that protein contribute 70% and fat 20% to total DW (Kausch and Zimmermann 1976) and that the C content of protein is 53% and of fat 78% [Gnaiger and Bitterlich 1984; i.e.…”