Abstract
Marine heatwaves are increasing worldwide, with several negative impacts on biological communities and ecosystems. This 24-day study tested heatwaves' effect with distinct duration and recovery periods on benthic estuarine communities' diversity and contribution to ecosystem functioning experimentally. The communities were obtained from a temperate estuary, usually subjected to high daily thermal amplitudes. Our goal was to understand the communities' response to the thermal change, including the community descriptors and behavioural changes expected during heat extremes. We measured community composition and structural changes and the bioturbation process and nutrient release as ecosystem functioning measurements. Overall, our findings highlight the potential tolerance of studied estuarine species to the temperature ranges tested in the study, as community composition and structure were similar, independently of the warming effect. We detected a slight trend for bioturbation and nutrient release increase in the communities under warming, yet these responses were not consistent with the heatwaves exposure duration. Overall, we conclude on the complexity of estuarine communities’ contribution to functioning under warming, and the importance of scalable experiments with benthic organisms' responses to climate variability, accommodating longer time scales and replication. Such an approach would set more efficient expectations towards climate change mitigation or adaptation in temperate estuarine ecosystems.
Highlights
All over the world, marine heatwaves are increasing in intensity, duration, and frequency at a dramatic rate[1,2,3]
Impacts of marine heatwaves combined with other anthropogenic impacts place several regions of the world at risk of species distribution shifts and decline in biodiversity and its sustained ecosystem s ervices[3]
Behavioural changes are expected[25,26], which for benthic fauna, changes in bioturbation may be of particular concern, influencing biogeochemical cycles, o xygenation[27,28,29] and preventing sediment e rosion[30] on the one hand, while contributing to destabilising the sediment structure if unbalanced, on the other hand[27,30,31,32]
Summary
Marine heatwaves are increasing in intensity, duration, and frequency at a dramatic rate[1,2,3]. Manipulative experiments provide a valuable tool because they allow exploring how species-environment interactions change under environmental stress and directly measure the change in ecosystem processes and f unctions[33,34] Such an approach would contribute to a broader understanding of the implications of climate change in marine communities. We still lack a better understanding of what happens after the heat occurrence (i.e., recovery period) and what may be driving species resistance or resilience to the warm from an ecological perspective These studies acquire particular relevance as heatwaves frequency, intensity, and duration will increase in the future[1,3]. This study aims to understand the impact of heatwaves, with different duration and recovery periods, on the biodiversity patterns and ecosystem functioning of estuarine communities, on the bioturbation process and nutrient release. We want to know the effect of the heatwave on benthic communities and whether the heatwave duration and temperature drop to previous levels can influence the community responses in general
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