Warming induces shifts in microzooplankton phenology and reduces time-lags between phytoplankton and protozoan production

Abstract

Indoor mesocosm experiments were conducted to test for potential climate change effects on the spring succession of Baltic Sea plankton. Two different temperature (D0°C and D6°C) and three light scenarios (62, 57 and 49 % of the natural surface light intensity on sunny days), mimicking increasing cloudiness as predicted for warmer winters in the Baltic Sea region, were simulated. By combining experimental and modeling approaches, we were able to test for a potential dietary mismatch between phytoplankton and zooplankton. Two general predatorprey models, one representing the community as a tri-trophic food chain and one as a 5-guild food web were applied to test for the consequences of different temperature sensitivities of heterotrophic components of the plankton. During the experiments, we observed reduced time-lags between the peaks of phytoplankton and protozoan biomass in response to warming. Microzooplankton peak biomass was reached by 2.5 day°C -1 earlier and occurred almost synchronously with biomass peaks of phytoplankton in the warm mesocosms (D6°C). The peak magnitudes of microzooplankton biomass remained unaffected by temperature, and growth rates of microzooplankton were higher at D6°C (l D0°C = 0.12 day -1 and l D6°C = 0.25 day -1 ). Furthermore, warming induced a shift in microzooplankton phenology leading to a faster species turnover and a shorter window of microzooplankton occurrence. Moderate differences in the light levels had no significant effect on the time-lags between autotrophic and heterotrophic biomass and on the timing, biomass maxima and growth rate of microzooplankton biomass. Both models predicted reduced time-lags between the biomass peaks of phytoplankton and its predators (both microzooplankton and copepods) with warming. The reduction of time-lags increased with increasing Q 10 values of copepods and protozoans in the tritrophic food chain. Indirect trophic effects modified this pattern in the 5-guild food web. Our study shows that instead of a mismatch, warming might lead to a stronger match between protist grazers and their prey altering in turn the transfer of matter and energy toward higher trophic levels.

Low CO2 Sensitivity of Microzooplankton Communities in the Gullmar Fjord, Skagerrak: Evidence from a Long-Term Mesocosm Study

“…In contrast to phytoplankton, which is in large parts light-dependent due to photosynthesis, MZP shows a temperature-dependence due to the biochemical processes of its metabolism [63]. Therefore, a relationship between an increase in temperature and an increase in production has been observed [64–66]. At the beginning of this experiment, sea surface temperatures were ~1°C and during the 1 st phytoplankton bloom phase ~5°C (Fig 1).…”

The response of temperate aquatic ecosystems to global warming: novel insights from a multidisciplinary project

“…For two-link food chains, it is easy to predict an increasing disadvantage for the prey, if the predator profits more strongly from warming than the prey. Predictions become already less straightforward for tritrophic interactions with an intermediate consumer, which competes with the predator for prey but is also consumed by the predator (e.g., phytoplankton-heterotrophic protists-crustacean zooplankton, Aberle et al 2012) and will be still more difficult for complete food webs. Responses might be highly context-dependent, and it remains a challenge for future research to identify when and under which circumstances, trophic and non-trophic interactions act as shock absorbers or amplifiers of climate impacts.…”

Life history trade-offs, the intensity of competition, and coexistence in novel and evolving communities under climate change

“…However, it is still largely unknown how rates and modes of phenotypic change and adaptation will vary between interacting species, and how these evolutionary responses will affect biotic interactions, communities and ecosystems. Much work in this area has focused on the potential for mismatches between species across trophic levels [7,8]. Potentially equally or more important to future community diversity are effects of warming on changes in the outcomes of competitive interactions, but these have received much less attention to date.…”