Temperature impact on the midsummer decline of Daphnia galeata: an analysis of long‐term data from the biomanipulated Bautzen Reservoir (Germany)

Abstract

1. The influence of water temperature on occurrence and duration of a midsummer decline (MSD) of Daphnia galeata was studied in the biomanipulated Bautzen Reservoir in Germany. The proportion of piscivores in the fish community of the reservoir has been enhanced experimentally since 1981. As a consequence, Daphnia galeata has dominated the zooplankton. Over 18 years of study (1981–1998), a long‐lasting MSD (longer than 30 days) occurred in 7 years, whereas a short MSD (shorter than 30 days) was observed in 6 years. During the remaining 5 years, an MSD was not observed. 2. Two hypotheses were examined to explain the observed patterns. First, we postulated that high water temperature during winter and early spring (January–April) leads to an MSD after an early and high spring peak of daphnids. On the other hand, low temperature during winter and early spring should not cause an MSD owing to a slower increase of the population, resulting in a later peak of daphnids. Second, we hypothesized that the mean water temperature during early summer (May and June) influences the occurrence of an MSD (by controlling young‐of‐the‐year (YOY) fish predation on daphnids). 3. The water temperature during winter and early spring explains 83%, and the early summer water temperature 55%, of interannual variation in the occurrence of an MSD. 4. The interannual variation in duration of an MSD was neither explained by temperature during winter and early spring nor by early summer temperature alone, but in 14 of the 18 years (78%) by a combination of both. 5. We conclude that water temperature during winter and early spring had a strong impact on Daphnia mortality by influencing height and timing of the spring peak which, in turn, influenced the extent of overexploitation of their food resources. By contrast, the water temperature during early summer probably influenced the mortality of daphnids caused by predation of YOY fish. The relative timing of both sources of mortality, which depends on the temperature regime during the first 6 months of the year, is the key process in controlling the occurrence and duration of an MSD. A long‐lasting MSD, therefore, is likely in Bautzen Reservoir only if temperatures are high during winter and early spring, as well as during early summer. 6. As a consequence of climate warming, recent climate records reveal warming during winter, spring and early summer in middle Europe, rather than an increase in mean annual temperatures. If our findings and conclusions are related to this regional and temporal pattern of climate warming, an increasing frequency of years with a long‐lasting MSD and, consequently, a decreasing efficiency of biomanipulation can be predicted.

Temperature is the key factor explaining interannual variability of Daphnia development in spring: a modelling study

“…There are several studies investigating long-term field data showing that climate variability has a strong impact on Daphnia phenology (e.g. Gerten and Adrian 2000;Benndorf et al 2001;Straile 2000Straile , 2002Anneville et al 2002), but there is no evidence that climate variability also affected Daphnia peak abundances in these studies. Hence, the results from long-term field data combined with the predictions from our model suggest that the inter-annual variability in Daphnia phenology observed in situ is most likely a consequence of variability in temperature rather than in phytoplankton abundance.…”

“…However, zooplankton growth also depends strongly on temperature (Hall 1964;Rinke and Petzoldt 2003) which, besides food availability, increases strongly during spring development. In fact, more recent analyses of long-term data suggest that the spring development of, for example, Daphnia may be governed primarily by temperature and not by food availability (Adrian and Deneke 1996;Benndorf et al 2001;Straile 2000;Straile and Adrian 2000).…”

“…Besides temperature development and food availability, Daphnia spring dynamics may also be influenced by other factors, for example, the timing of the Daphnia spring increase was strongly related to its winter abundance in Lake Washington, USA (Romare et al 2005), whereas in Bautzen reservoir, Germany, variability in Daphnia mortality due to fish predation was suggested to influence Daphnia spring dynamics (Benndorf et al 2001). Hence, interannual variability of Daphnia spring dynamics may be the result of several biotic and abiotic factors acting in concert.…”

Environmental Impacts—Lake Ecosystems

“…Temperature-driven changes in the timing of food availability and of predation by young-of-the-year fish during critical time windows in spring/early summer determined the mid-summer decline in daphnids (Benndorf et al 2001). More specifically, water temperatures in narrow time windows either before (2.2 weeks) or after the typical clear-water phase (3.2 weeks) affected the start-up populations of summer crustacean zooplankton and explained some of their contrasting success during three hot summers characterised by more or less the same average summer water temperature (Huber et al 2010).…”

Effect of suspended solids on interaction between filter-feeding fishAristichthys nobilisand zooplankton in a shallow lake using a mesocosm experiment

“…In the present study, the large-bodied cladoceran D. galeata was documented at the beginning of the experiment, but the low abundance of D. galeata at the end of the experiments appeared in all treatments, even in no-fish treatment. The low abundance of D. galeata may be attributable to high temperature (Huang & Hu 1984;Benndorf et al 2001). Compared with large-bodied zooplankton such as Daphnia spp., some small cladocerans, including copepods and rotifers, are more tolerant to SR (Kirk & Gilbert 1990;Levine et al 2005;Jiang et al 2010).…”