Temperature Fluctuation Attenuates the Effects of Warming in Estuarine Microbial Plankton Communities

Abstract

Sea surface warming has the potential to alter the diversity, trophic organization and productivity of marine communities. However, it is unknown if temperature fluctuations that ecosystems naturally experience can alter the predicted impacts of warming. We address this uncertainty by exposing a natural marine plankton community to warming conditions (+3°C) under a constant vs. fluctuating (±3°C) temperature regime using an experimental mesocosm approach. We evaluated changes in stoichiometry, biomass, nutrient uptake, taxonomic composition, species richness and diversity, photosynthetic performance, and community metabolic balance. Overall, warming had a stronger impact than fluctuating temperature on all biological organization levels considered. As the ecological succession progressed toward post-bloom, the effects of warming on phytoplankton biomass, species richness, and net community productivity intensified, likely due to a stimulated microzooplankton grazing, and the community metabolic balance shifted toward a CO2 source. However, fluctuating temperatures reduced the negative effects of warming on photosynthetic performance and net community productivity by 40%. Our results demonstrate that temperature fluctuations may temper the negative effect of warming on marine net productivity. These findings highlight the need to consider short-term thermal fluctuations in experimental and modeling approaches because the use of constant warming conditions could lead to an overestimation of the real magnitude of climate change impacts on marine ecosystems.

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

“…For instance, we found a positive antagonistic effect of warming under thermally varying conditions on Chromista morphology and physiology. Recent results have shown that thermal fluctuations promote transient “benign” conditions for organisms during cooling periods ( 40 ) and allow rapid phenotypic changes in metabolic traits and elemental composition ( 20 ) that accelerate the adaptation to warming stress. In addition, it is likely that studies testing the effect of global-change drivers under a constant regime tend to consider shorter experimental periods than those in which environmental fluctuations are also evaluated, thus overestimating the frequency of the interactive responses detected.…”

Assessing warming impacts on marine fishes by integrating physiology‐guided distribution projections, life‐history changes and food web dynamics

“…Fourth, we did not consider warming‐induced changes in plankton size spectra, taxonomic composition and spatial distribution in this study. Although empirical data are relatively scarce outside of laboratory mesocosms and local studies (Benedetti et al, 2019; Cabrerizo et al, 2021; He et al, 2020; Murphy et al, 2020; Pulina et al, 2020), incorporating these information would yield more accurate model predictions whenever they are available. There are two specific directions for further implementations.…”

Environmental variability in aquatic ecosystems: Avenues for future multifactorial experiments

“…In addition, global changes caused by anthropogenic activities such as continuous press disturbances may impact differently on organisms that experience naturally variable or more constant environments. It has been proposed that warming effects on organisms' performance can be exacerbated by thermal fluctuations in comparison to warming effects under constant conditions (Wang et al 2019;Cabrerizo et al 2021;Gonz alez-Olalla et al 2022). However, water pH fluctuations under ocean acidification scenarios show less conclusive results, where negative, neutral, or positive effects on performance have been detected for corals and coralline algae when exposed to fluctuations under low pH (Cornwall et al 2013(Cornwall et al , 2018Rivest et al 2017).…”