Successive extreme climatic events lead to immediate, large‐scale, and diverse responses from fish in the Arctic

Abstract

The warming trend of the Arctic is punctuated by several record-breaking warm years with very low sea ice concentrations. The nature and reversibility of marine ecosystem responses to these multiple extreme climatic events (ECEs) are poorly understood. Here, we investigate the ecological signatures of three successive bottom temperature maxima concomitant with surface ECEs between 2004 and 2017 in the Barents Sea across spatial and organizational scales. We observed community-level redistributions of fish concurrent with ECEs at the scale of the whole Barents Sea. Three groups, characterized by different sets of traits describing their capacity to cope with short-term perturbations, reacted with different timing and intensity to each ECE. Arctic species co-occurred more frequently with large predators and incoming boreal taxa during ECEs, potentially affecting food web structures and functional diversity, accelerating the impacts of long-term climate change. On the species level, responses were highly diversified, with different ECEs impacting different species, and species responses (expansion, geographical shift) varying from one ECE to another, despite the environmental perturbations being similar. Past ECEs impacts, with potential legacy effects, lagged responses, thresholds, and interactions with the underlying warming pressure, could constantly set up new initial conditions that drive the unique ecological signature of each ECE. These results highlight the complexity of ecological reactions to multiple ECEs and give prominence to several sources of process uncertainty in the predictions of climate change impact and risk for ecosystem management. Long-term monitoring and studies to characterize the vertical extent of each ECE are necessary to statistically link demersal species and environmental spatial-temporal patterns. In the future, regular monitoring will be crucial to detect early signals of change and understand the determinism of ECEs, but we need to adapt our models and management to better integrate risk and stochasticity from the complex impacts of global change.

Spatio‐temporal turnover and drivers of bentho‐demersal community and food web structure in a high‐latitude marine ecosystem

“…Note that in 2014 no ecological metrics data is available for the two western clusters (red and purple) and that in 2012 the sampling for megabenthos was irregular in the two eastern clusters (green and blue) due to the use of a different gear. The years 2012 and 2016 are highlighted by a vertical dashed line as these years were characterized by extreme environmental conditions in the Barents Sea, with very warm sea bottom temperature and very low ice‐cover, as identified in (Husson et al, 2022; Mohamed et al, 2022)…”

“…Some peaks, or dips, in the ecological metrics were noticeable, but not exclusively, in 2012 and 2016. During 2011–2012 and 2016, the Barents Sea experiences extreme climatic events with marine heatwaves and very low ice‐cover (Husson et al, 2022; Mohamed et al, 2022). Several fish populations in the Barents Sea reacted to these extreme years by changing their spatial distribution (Husson et al, 2022).…”

“…During 2011–2012 and 2016, the Barents Sea experiences extreme climatic events with marine heatwaves and very low ice‐cover (Husson et al, 2022; Mohamed et al, 2022). Several fish populations in the Barents Sea reacted to these extreme years by changing their spatial distribution (Husson et al, 2022). These extreme climatic events might have also impacted the recruitment and survival of early stages of fish and invertebrates.…”

Climate change and extreme events are changing the biology of Polar Regions

“…Extreme climate events are on the rise in polar regions, including marine and terrestrial heatwaves (Robinson et al, 2020) and drought and fires (Bokhorst et al, 2022). The long‐term biological effects of these extreme climatic events on polar biodiversity are being recognized (Bokhorst et al, 2022; Husson et al, 2022; Weydmann et al, 2018) and the implications for conservation of these ecosystems starting to be discussed (Bergstrom et al, 2021; Bokhorst et al, 2022; Chown et al, 2022). Future impacts of climate change are complex and challenging to quantify especially given lags in ecological expression of change (Constable et al, 2022).…”

Temperature change effects on marine fish range shifts: a meta-analysis of ecological and methodological predictors

“…While some methodological details need to be tailored to be suitable for specific taxa, ecosystems and geographical conditions, large heterogeneity in other variables potentially affecting accuracy such as population sampling effort, temporal resolution and statistical approaches remain. For example, redistribution inferences may be affected by sampling methods including choice of proxy for distribution measurement (Brown et al, 2011;Wernberg et al, 2012), including the 'center of distribution' (COD) which constitutes the mean latitude of the spatial extent (e.g., Li et al, 2019;Hsieh et al, 2009;Husson et al, 2022), or a population's most extreme boundaries of longitude, latitude or depth, inferred, for example, by presence-absence data (e.g., Fredston-Hermann et al, 2020). How these distribution indices are obtained also affects the predictions that are produced (Brown et al, 2016): popular data sources include abundance data from survey trawls by long term fisheries or research programs (Perry et al, 2005;Yemane et al, 2014), tagging-recapture data (Hammerschlag et al, 2022;Neat and Righton, 2007), historical records (Kumagai et al, 2018), or genetic-molecular methods (Knutsen et al, 2013;Spies et al, 2020).…”