Population dynamics of planktonic rotifers in Lake Loosdrecht, the Netherlands, in relation to their potential food and predators

Abstract

1. This study uses descriptive data to examine the shift in dominance in the rotifer community in summer from Keratella cochlearis to Anuraeopsis fissa in a shallow eutrophic lake. Population density and egg ratio were estimated from May to September for these small loricate rotifers, as well as the soft‐bodied Filinia longiseta and Polyarthra spp., to compare rates of population increase, birth and death. 2. Keratella cochlearis was succeeded by A. fissa in late May, perhaps as a result of the shorter egg development times of the latter at temperatures > 15 °C, and species‐specific responses to food and predation. Population variables suggest that the decline of K. cochlearis was the result of a food shortage which caused a decrease in reproduction and increased mortality. 3. High population densities of A. fissa and Polyarthra spp. were associated with low egg ratios, birth rates and rates of increase within a species, suggesting intraspecific competition. The egg ratios of the two soft‐bodied rotifers were strongly intercorrelated in the study period, although their diets supposedly differ. The egg ratios of A. fissa showed positively correlated fluctuations with the abundance of diatoms. 4. Short periods of higher rates of increase of A. fissa conferred advantage to this rotifer and manifested in its dominance. The mean birth rates of A. fissa and F. longiseta were twice as high as for K. cochlearis. Furthermore, death rates of loricate and soft‐bodied rotifers were similar and high, which suggests that food shortage similarly increased death rates, or that predation may be sometimes substantial for soft‐bodied and loricate species, or both. 5. Predation was probably not an important factor in steering the seasonal succession in the lake. A difference in abilities of the studied rotifers to exploit resources seems more important. Perhaps temperature is also a factor, but the specifics remain unclear and await more experimental work.

Using the hidden isotopic heterogeneity in phyto‐ and zooplankton to unmask disparity in trophic carbon transfer

“…and cyclopoid copepods, and an abundance of rotifers, predominantly Keratella, Anuraeopsis, Filinia, and Polyarthra spp. (Gulati 1990;Ooms-Wilms et al 1999). The annual means of crustacean densities may vary more than twofold in the lake, between approximately 400 and 940 individuals (ind.)…”

Daily and vertical dynamics of rotifers under the impact of diatom blooms in the Three Gorges Reservoir, China

“…Additionally, all the dominant rotifer species in the Xiangxi Bay were herbivorous grazers (Kirk, 2002;Zhou et al, 2007). For instance, S. tremula and P. vulgaris were macrofilter feeders which can feed on both small and large algae (Gołdyn et al, 1997;Ooms-Wilms et al, 1999;Š poljar et al, 2005;Grzegorz et al, 2006). B. calyciflorus can feed on a wide size range of phytoplankton but shows a clear preference for Cyclotella sp.…”

Factors Affecting Egg-ratio in Planktonic Rotifers

“…There are few estimates of the loss of eggs in natural waters, but laboratory studies reveal that loose eggs may constitute up to 10% of the total production (Sarma, 1987). Under field conditions, this percentage could be much higher (Ooms-Wilms et al, 1999). Dumont et al (1995), who cultured Anuraeopsis fissa using a wide range of algal (Scenedesmus obliquus) densities (0.5 · 10 6 to 8 · 10 6 cells ml )1 ), found not only that ER decreased with increasing densities of A. fissa, but also frequency of egg detachment increased as food level increased.…”

“…However, as resources become limiting, population growth reaches a stationary phase and parthenogenetic egg production declines (Fig. 1), which finally results in an inverse relation between population density and ER (Ooms-Wilms et al, 1999). Even if food is added at regular intervals (e.g., 24 h), as is common in laboratory studies , it is possible that the test animals face short periods of low food availability between food additions, particularly when population densities are high.…”