Temperature fluctuations in a warmer environment: impacts on microbial plankton

Abstract

Warming can cause changes in the structure and functioning of microbial food webs. Experimental studies quantifying such impacts on microbial plankton have tended to consider constant temperature conditions. However, Jensen’s inequality (or the fallacy of the average) recognizes that organism performance under constant conditions is seldom equal to the mean performance under variable conditions, highlighting the need to consider in situ fluctuations over a range of time scales. Here we review some of the available evidence on how warming effects on the abundance, diversity, and metabolism of microbial plankton are altered when temperature fluctuations are considered. We found that fluctuating temperatures may accentuate warming-mediated reductions in phytoplankton evenness and gross photosynthesis while synergistically increasing phytoplankton growth. Also, fluctuating temperatures have been shown to reduce the positive warming effect on cyanobacterial biomass production and recruitment and to reverse a warming effect on cellular nutrient quotas. Other reports have shown that fluctuations in temperature did not alter plankton responses to constant warming. These investigations have mostly focused on a few phytoplankton species (i.e. diatoms and haptophytes) in temperate and marine ecosystems and considered short-term and transient responses. It remains unknown whether the same responses apply to other species and ecosystems and if evolutionary change in thermally varying environments could alter the magnitude and direction of the responses to warming observed over short-term scales. Thus, future research efforts should address the role of fluctuations in environmental drivers. We stress the need to study responses over different biological organization and trophic levels, nutritional modes, temporal scales, and ecosystem types.

Net effect of environmental fluctuations in multiple global-change drivers across the tree of life

“…After this reanalysis, we obtained a total of 218 and 629 studies from SCOPUS and WoS, respectively (i.e., screening phase). In addition, we screened the references (i.e., 543 references in total) of selected review articles addressing the effects of fluctuations on organisms ( 11 , 12 , 69 – 71 ), obtaining a total of 41 potentially eligible articles. In a second selection step, we reviewed the titles, abstracts, and full text and supplementary information (when available) of all entries recovered, obtaining a total of 36 (for WoS) and 50 (for SCOPUS) eligible studies together with the 41 mentioned above ( SI Appendix , Fig.…”

Unravelling the factors of evolutionary repeatability: insights and perspectives on predictability in evolutionary biology

“…In order to make accurate predictions about evolutionary outcomes, it is essential to consider the role that the environment plays in evolution (MacColl, 2011;Skinner, 2015;Baym et al, 2016). Changes in ecological factors can either inhibit or facilitate the evolvability of a population (Grant et al, 2017;Cabrerizo and Marañoń, 2021). These changes can affect various factors of evolutionary dynamics including population size, the strength and direction of selection and the amount and distribution of genetic variation (Allendorf et al, 2014;Chen et al, 2018;Raynes et al, 2018).…”

Heatwave responses of Arctic phytoplankton communities are driven by combined impacts of warming and cooling

“…Maximum growth rates are expected to generally increase with temperature (16,17), while warming beyond the optimum usually induces stress and decreases rates again (18). These temperature dependencies are typically derived from the responses of long-term acclimated laboratory strains, and it has been shown that they do not necessarily predict shortterm responses under fluctuating temperature dynamics (19,20). Depending on the optimum ranges of an organism and time frames of exposure, variable temperature conditions can have negative impacts on phytoplankton productivity (21,22), e.g., because acclimation and selection act into different directions in warm and cool phases.…”