In the current context of global warming, aquatic systems are experiencing an increase in both the frequency and intensity of extreme climatic events. As such, aquatic heatwaves, discrete periods of extreme warm water temperatures, are emerging as one of the most pervasive threats to both marine and freshwater biodiversity. From lakes to oceans, through estuaries, rivers, and seas worldwide, heatwaves are re-shaping aquatic life across all levels of ecological organization, compromising their resilience and their provision of ecosystem services to human societies. These extreme events are predicted to increase in the coming decades, even if emission reduction policies are effectively applied. Consequently, improving our understanding of the responses of ecological systems at different levels (from individuals to communities) to aquatic heatwaves is essential to anticipate irreversible changes to their structure, functioning and services. This session will therefore welcome contributions that explore the immediate and/or long-term impacts of aquatic heatwaves across disciplines (e.g., oceanography, limnology, population and community ecology, behavioral and functional ecology), levels of organization (e.g., individuals, populations, communities and ecosystems) and taxonomic groups (e.g., fish, plants, macroalgae, invertebrates, plankton). The session will also welcome studies taking place at different spatial and temporal scales, such as contributions related to the exploration of the past, current and future aquatic heatwave trends. Contributions using novel approaches (e.g., to better predict the occurrence of heatwaves) or exploring conservation, adaptation and/or management strategies will also be encouraged. Overall, the session aims to provide an interdisciplinary and cross-taxonomic view of one of the most pressing topics in aquatic sciences. The session will render a general overview of the vulnerability of aquatic systems to current and future heatwave conditions, with the opportunity to promote discussions about the future research challenges.
Lead Organizer: Daniel Gómez-Gras, Universitat de Barcelona/Hawaii Institute of Marine Biology (University of Hawaii at Manoa) (dgomezgr@hawaii.edu)
Co-organizers:
Daniel Gómez-Gras, Universitat de Barcelona/Hawaii Institute of Marine Biology (University of Hawaii at Manoa) (dgomezgr@hawaii.edu)
Pol Capdevila, Universitat de Barcelona (pcapdevila.pc@gmail.com)
Cristina Linares, Universitat de Barcelona (cristinalinares@ub.edu)
Núria Marbà, Mediterranean Institute for Advanced Studies (IMEDEA/CSIC) (nmarba@imedea.uib-csic.es)
Presentations
08:30 AM
The impacts of marine heatwaves on coastal biodiversity and the provision of ecosystem services (7121)
Tutorial/Invited: Invited
Primary Presenter: Dan Smale, Marine Biological Association (dansma@mba.ac.uk)
Climatic extremes are becoming increasingly common against a background trend of global warming. In the oceans, the frequency and duration of marine heatwaves (MHWs)—periods of anomalously warm water—have increased significantly over the past century, with wide-ranging impacts on ecosystems and coastal societies. Our understanding of MHW patterns, drivers and impacts has expanded rapidly in recent years, with MHWs emerging as pervasive drivers of ecosystem change. We quantified trends and physical attributes of MHWs heatwaves globally, and examined their biological impacts from individuals to ecosystems. The physical attributes of prominent recent MHWs varied considerably, but all had deleterious impacts across a range of biological processes and taxa, including critical foundation species (e.g. corals, seagrasses and kelps). Certain regions may be particularly vulnerable to MHW intensification, due to the co-existence of high levels of biodiversity or concurrent human impacts. An examination of how MHWs influence ecosystem service provision revealed significant socioeconomic impacts, and also highlighted opportunities and examples of successful management interventions. MHWs are now recognised as forceful agents of disturbance with the potential to restructure entire ecosystems and disrupt the provision of ecosystem services. Improved forecasting combined with a wider range of adaptation measures will facilitate management decisions and help guide conservation efforts, which will be integral for future-proofing marine biodiversity and ecosystems in a warmer world. Climatic extremes are becoming increasingly common against a background trend of global warming. In the oceans, the frequency and duration of marine heatwaves (MHWs)—periods of anomalously warm water—have increased significantly over the past century, with wide-ranging impacts on ecosystems and coastal societies. Our understanding of MHW patterns, drivers and impacts has expanded rapidly in recent years, with MHWs emerging as pervasive drivers of ecosystem change. We quantified trends and physical attributes of MHWs heatwaves globally, and examined their biological impacts from individuals to ecosystems. The physical attributes of prominent recent MHWs varied considerably, but all had deleterious impacts across a range of biological processes and taxa, including critical foundation species (e.g. corals, seagrasses and kelps). Certain regions may be particularly vulnerable to MHW intensification, due to the co-existence of high levels of biodiversity or concurrent human impacts. An examination of how MHWs influence ecosystem service provision revealed significant socioeconomic impacts, and also highlighted opportunities and examples of successful management interventions. MHWs are now recognised as forceful agents of disturbance with the potential to restructure entire ecosystems and disrupt the provision of ecosystem services. Improved forecasting combined with a wider range of adaptation measures will facilitate management decisions and help guide conservation efforts, which will be integral for future-proofing marine biodiversity and ecosystems in a warmer world.
08:45 AM
Lake heatwaves under climate change (7449)
Tutorial/Invited: Invited
Primary Presenter: R. Iestyn Woolway, Bangor University (iestyn.woolway@bangor.ac.uk)
Lake surface water temperature can increase considerably in response to climate change, leading to unprecedented shifts in lake thermal habitat and consequently in lake ecosystem functioning. The implications of lake warming are particularly severe when temperatures rise to extreme levels. Such conditions occur, by definition, during lake heatwaves - periods of extreme hot lake surface water temperatures. Here I use satellite observations and numerical models to investigate changes in lake heatwaves worldwide under historic and future climate change. I show global warming can result in a global increase in the frequency, intensity, and duration of lake heatwaves, an increase in their spatial extent, and increase the minimum horizontal distance that must be travelled away from a heatwave to track historic surface temperatures. Furthermore, evidence suggests that the occurrence probabilities of lake heatwaves have increased substantially due to human-influence. Observed and projected changes in these heatwave attributes could have a dramatic influence on lake ecosystems, resulting in numerous negative impacts on the many benefits that lakes provide to society, including the provision of safe water for drinking and irrigation, recreational use, and economic benefits such as fisheries and tourism.
09:00 AM
Marine heatwaves push kelp forests into alternative states near their equatorward range limit (6200)
Primary Presenter: Nur Arafeh Dalmau, University of California, Los Angeles and Stanford University (n.arafehdalmau@uq.net.au)
Marine heatwaves are driving ecosystem change and altering the distribution of foundation species globally. However, our understanding of the recovery of marine ecosystems from these events is limited. Here we use twenty years of satellite time series and scuba surveys to evaluate the state and recovery of giant kelp forests to the 2014-2016 unprecedented marine heatwaves in Baja California, Mexico, across 800km of latitude. For the post-marine heatwave period (2017-2022), we found an 85% recovery in the south and a 45% recovery of giant kelp forests in the north of Baja California, when compared to the pre-heatwave period (2004-2013). Since 2015, we found 100 kilometers of range contraction in the south (loss of ~ 99.9%), and in the north, 100 kilometers with 99% loss since 2021. Despite the range contraction, the rest of giant kelp in the south recovered better than in the north, with some places exceeding pre-heatwave coverage. Scuba surveys in 2022 revealed that competition with Eisenia arborea (palm kelp) drives giant kelp range contraction in the south. In contrast, sea urchin barrens and trophic cascades explain the loss in the north. In this highly human-populated region, the densities of sea urchin predators were very low (sheepheads and lobsters), and both giant and palm kelp were absent. Our results indicate that the recovery of foundational species may be localized and driven by various factors (e.g., human activities, species competition, environment), suggesting that alternative management strategies are needed, depending on the local status of ecosystems.
09:15 AM
PERSISTENT SHIFTS IN BENTHIC COMMUNITY STRUCTURE IN CALIFORNIA KELP FORESTS FOLLOWING A MARINE HEATWAVE (6723)
Primary Presenter: Kristen Michaud, University of California Santa Barbara (kmmichaud@ucsb.edu)
Ocean warming has both direct and indirect physiological and ecological consequences for marine organisms. Sessile animals and macroalgae may be particularly vulnerable to anomalous warming given constraints in resource acquisition and reproduction imposed by sessility. In temperate reef ecosystems, sessile suspension feeding invertebrates are a critical trophic link between the plankton and the benthos, and along with macroalgae, provide food for an array of mobile species. Using 14 years of seasonal benthic community data across five coastal reefs, we evaluated how communities of sessile invertebrates and understory macroalgae in southern California kelp forests responded to the “Blob” marine heat wave, a period of anomalously high temperatures and low phytoplankton production. We show that this event had prolonged consequences for kelp forest ecosystems including reductions in sessile invertebrate cover and species richness. Changes to community structure of invertebrates and macroalgae, including species invasions, have persisted six years post-Blob, suggesting that a climate-driven shift in California kelp forests is underway.
09:30 AM
Local thermal variation modulates resilience to warming in a marine foundation species: evidence from seagrass seedlings (7079)
Primary Presenter: Fiona Tomas Nash, IMEDEA (fionamedes@gmail.com)
Disturbances associated with climate change may push organisms beyond their resilience limits, and strong ecological consequences are expected when foundation species are affected. When predicting species’ responses to warming, species are typically considered as physiologically homogeneous. Yet, responses to extreme events may vary according to differences in phenotypic plasticity and local adaptation across the range of a species. Using a common-garden mesocosm experiment, we compared the resilience (i.e., response to and recovery from) to two warming events of different intensity on seagrass seedlings germinated from seeds collected at eight regions across the species’ distribution range. We show a positive relationship between resilience to warming and local thermal variability, suggesting seagrass evolutionary adaptation to local thermal conditions. Our results highlight the critical importance of incorporating intra-specific variability when making predictions and when developing conservation and restoration strategies about species vulnerability to climate change. Furthermore, strong negative lag-effects on seedlings performance were observed after the warming phase had already stopped, highlighting the importance of following species’ responses after a disturbance has finished, particularly because most experimental studies have only examined immediate, short-term, responses to stressors. Given the long-term common-garden approach used, we expect that differences in seedling responses will be mainly the result of genetic changes leading to local adaptation.
09:45 AM
SEAGRASS AND CARBON STOCK RESILIENCE TO A MARINE HEATWAVE (6196)
Primary Presenter: Karen McGlathery, University of Virginia (kjm4k@virginia.edu)
In temperate lagoons on the U.S. East Coast in Virginia, climate forcing has resulted in both rising water temperatures and an increase in the frequency of marine heatwaves. These lagoons host one of the largest seagrass restorations known, with over 40 km2 of seagrass meadows restored over the last two decades. Long-term monitoring captured a marine heatwave in 2015 that caused massive seagrass die-off in some regions, resulting in a loss of stored sediment carbon. Continued research has shown that the seagrass meadows were resilient, recovering to pre-disturbance densities within 2-4 years but that carbon stocks lagged behind. A large-scale replicated seagrass removal experiment designed to mimic seagrass loss due to a heatwave has provided a more detailed time series on seagrass recovery and changes in sediment accumulation and carbon stocks. This presentation synthesizes our results and provides guidelines for future restoration efforts to minimize vulnerability of seagrass populations and optimize conditions for carbon stock permanence.
SS064A Resilience of Aquatic Ecological Systems to Heatwaves
Description
Time: 8:30 AM
Date: 6/6/2023
Room: Sala Ibiza A