Temperature fluctuation attenuates the effects of warming in estuarine microbial plankton communities Jabalera Cabrerizo, Marco Marañón, Emilio Fernández-González, Cristina Alonso-Núñez, Adrián Larsson, Henrik Aranguren-Gassis, María Coastal ecosystems Diversity Interacting effects This study was supported by a Transnational Access granted to MJC through AQUACOSM project, by European Union’s Horizon 2020 Research and Innovation Programme through project “Tropical and South Atlantic climate-based marine ecosystem predictions for sustainable management” (TRIATLAS, grant agreement no. 731065), and by Ministerio de Ciencia, Innovación y Universidades (MICINN) through project “Responses of marine phytoplankton to environmental variability across levels of biological organization” (POLARIS, grant number PGC2018-094553-B-I00) to EM. MJC was supported by Juan de la Cierva-Formación (FJCI2017-32318) and Incorporación (ICJ2019-040850-I) postdoctoral contracts from MICINN, MA-G by a postdoctoral contract from Xunta de Galicia (Tipo B) and by the Retención de Talento program from Universidade de Vigo, and CF-G by a predoctoral contract from Xunta de Galicia (ED481-2017/342). 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 (C3◦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. 2026-01-14T10:37:11Z 2026-01-14T10:37:11Z 2021-04-09 journal article Cabrerizo MJ, Marañón E, Fernández-González C, Alonso-Núñez A, Larsson H and Aranguren-Gassis M (2021) Temperature Fluctuation Attenuates the Effects of Warming in Estuarine Microbial Plankton Communities. Front. Mar. Sci. 8:656282. doi: 10.3389/fmars.2021.656282 https://hdl.handle.net/10481/109670 10.3389/fmars.2021.656282 eng http://creativecommons.org/licenses/by-nc/4.0/ open access Atribución-NoComercial 4.0 Internacional Frontiers in Marine Science