Relation between nematode communities and trophic state in southern Swedish lakes

Abstract

The aim of this study was to examine whether littoral nematode community patterns are shaped by lake trophic state. It was hypothesized that trophic level is associated negatively with the proportion of omnivores and positively with the percentages of bacterial feeders, but not at all with the diversity, abundance, and biomass of freshwater nematodes. Sediment samples were taken at littoral sites of eight southern Swedish lakes of different trophy in spring and autumn 2007. Trophic level was found to strongly influence species richness, as oligotrophic and mesotrophic lakes supported the greatest species numbers, whereas nematode abundance, biomass, and Shannon index were unaffected. Furthermore, our results indicated effects on the nematode community's trophic structure, with a larger proportion of predatory nematodes in oligotrophic and mesotrophic lakes but no differences in the other feeding types (bacteria, algae and suction feeders, omnivorous species). Multivariate analysis indicated a shift in species compositions along the threshold from mesotrophic to eutrophic conditions, with the presence of Tobrilus gracilis, Monhystera paludicola, Brevitobrilus stefanskii, and Ethmolaimus pratensis related to the latter. Nematode communities in oligotrophic and mesotrophic lakes were characterized by a similar species composition, with pronounced occurrences of Eumonhystera longicaudatula, Semitobrilus cf. pellucidus, Prodesmodora circulata, and Rhabdolaimus terrestris. Overall, the results suggested that lake trophic state is a major factor structuring littoral nematode communities, although intra-lake variations might be of importance as well.

Temporal changes in periphytic meiofauna in lakes of different trophic states

“…With increasing trophic state meiofaunal abundance and production showed a unimodally shaped curve, since the average values were highest in the mesotrophic lake. Whereas several studies of macroinvertebrates and zooplankton reported that these populations were positively related to lake trophy (McCauley, and Kalff 1981;Hanson, and Peters 1984;Rasmussen, and Kalff 1987), this cannot be claimed for sedimentdwelling meiofauna based on the rare data describing these organisms (Särkkä 1996;Ristau, and Traunspurger 2011). Especially in the profundal zone, the trophic state can even negatively affect meiofaunal densities due to the lower oxygen concentrations (Prejs 1977).…”

“…Males, females, and juveniles were treated separately. If length and width data for nematode juveniles were not specified in the literature, biomass was assumed to be a quarter of the adult biomass (Ristau, and Traunspurger 2011).…”

“…Overall, empirical models predict that with increasing trophic state primary production and hence also the abundance and biomass of zooplankton will increase (Hanson, and Peters 1984;Rasmussen, and Kalff 1987). The rare data on littoral meiofaunal communities so far did not confirm this result gained for zooplankton (Ristau, and Traunspurger 2011). In profundal sediments, the trophic state actually negatively affected meiofaunal densities through the related changes in oxygen concentration (Prejs 1977).…”

Short-term effects of nutrient enrichment on river biofilm: N–NO3 − uptake rate and response of meiofauna

“…Studies of lacustrine meiofauna have shown that the density of lacustrine rotifers can increase with the increasing phosphorus concentrations in lake habitats (Särkkä, 1992;Wu et al, 2004;Ristau & Traunspurger, 2011) and in microcosm sediments (Ristau et al, 2012). Ristau et al (2012) propose that the observed responses are indirectly linked to a nutrient-induced change in the availability of food (e.g.…”

Quantitative Assessment of Epiphytic and Benthic Meioinvertebrate Fauna in Various Types of Standing Water

“…The greatest number of species was found in mesotrophic and oligotrophic lakes, while the abundance and biomass remained at a similar level. Overall, the results suggest that the trophic state of the lake is an important factor shaping the structure of nematodes in the littoral lakes [18].…”