Trophic Characterization, Pelagic Food Web Structure and Comparison of Two Mesotrophic Lakes in Brandenburg (Germany)

Abstract

We conducted comprehensive field investigations to characterise the trophic status and food web structure of Großer Vätersee (GV) and Kleiner Vätersee (KV), two stratified lakes in the Baltic lake region of northeastern Germany. The lakes will be used as manipulation (GV) and reference (KV) ecosystems in food web studies. Both lakes are mesotrophic to slightly eutrophic with mean epilimnetic total phosphorus (P) concentrations of 24 and 21 μg L–1 in GV and KV, respectively. Mean phytoplankton biomass was 0.9 and 0.5 cm3 m–3 in GV and KV. During summer, the algal community of both lakes was dominated by cyanobacterial picoplankton and Ceratium spp. Filamentous cyanobacteria (mostly Planktothrix sp.) prevailed in a deep chlorophyll maximum found within the chemocline of both lakes. Bacterial biomass in the epilimnion of GV usually ranged between 1 and 3 cm3 m–3. Mean ciliate abundance was 13 ind. mL –1 in GV and 14 ind. mL–1 in KV. While Oligotricha dominated in GV, Scuticociliata were found most frequently in KV. Mean annual crustacean biomass was high in both lakes (GV 2.5 cm3 m–3, KV 1.2 cm3 m–3); Eudiaptomus gracilis, E. graciloides and Daphnia spp. were the most prominent species. Total fish biomass of both lakes was dominated by roach (GV 52%; KV 57%) and perch (GV 24%; KV 34%) Vaucheria dichotoma and Chara spp. dominated the macrophyte community in GV; Chara spp. dominated in KV. The slightly more eutrophic character of GV was most likely a result of greater P accumulation in the sediments due to external loading, which resulted in greater hypolimnetic P concentrations throughout the summer in GV. However, on an annual basis these differences were only occasionally reflected at higher trophic levels. The differences in fish biomass, however, might have been a consequence of higher structural diversity in GV provided by submersed macrophytes rather than its more eutrophic character. We conclude that the trophic characteristics and food web structure of Großer Vätersee and Kleiner Vätersee are similar enough to be suitable as manipulation and reference lakes in food web experiments.

Bacterioplankton Abundance and Activity in a Small Hypertrophic Stratified Lake

“…Similar to other lakes (Weinbauer & Ho¨fle, 1998;Kasprzak et al, 2000), TNB reached the highest values (15-20 · 10 6 cells ml )1 ) in the physically most homogenous hypolimnion. Abundance of bacteria in deep layers increased from 1990s to 2000s because of more rapid oxygen depletion in deep layers, caused most probably because of spring meromixis in warmer springs (No˜ges & Kangro, 2005).…”

Dietary niche partitioning in a piscivorous fish guild in response to stocking of an additional competitor – The role of diet specialisation

“…In case of invertebrates and piscivores the mean of two years 1998 in PP free; in PP) are given. Standing stocks of small roach, perch and rudd were estimated only in 1998 and 2002. has no in-or outflow and the catchment is mostly covered by forest (see Kasprzak et al 2000 for further details). Most of the lake's shore and the adjacent littoral zones are covered by reed (Phragmites australis) and Chara spp.…”

Chlorophyll a concentration across a trophic gradient of lakes: An estimator of phytoplankton biomass?

“…Table 1). For more information about the five study lakes see Casper (1985), Kasprzak et al (2000), Kasprzak et al (2003), Koschel and Adams (2003) and Koschel et al (2006).…”