Abstract
Extreme events are rare, stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms. Studies over time provide exceptional opportunities to detect the effects of extreme climatic events and to measure their impacts by quantifying rates of change at population and community levels. In this study, we show how an extreme storm event affected the dynamics of benthic coralligenous outcrops in the NW Mediterranean Sea using data acquired before (2006–2008) and after the impact (2009–2010) at four different sites. Storms of comparable severity have been documented to occur occasionally within periods of 50 years in the Mediterranean Sea. We assessed the effects derived from the storm comparing changes in benthic community composition at sites exposed to and sheltered from this extreme event. The sites analyzed showed different damage from severe to negligible. The most exposed and impacted site experienced a major shift immediately after the storm, represented by changes in the species richness and beta diversity of benthic species. This site also showed higher compositional variability immediately after the storm and over the following year. The loss of cover of benthic species resulted between 22% and 58%. The damage across these species (e.g. calcareous algae, sponges, anthozoans, bryozoans, tunicates) was uneven, and those with fragile forms were the most impacted, showing cover losses up to 50 to 100%. Interestingly, small patches survived after the storm and began to grow slightly during the following year. In contrast, sheltered sites showed no significant changes in all the studied parameters, indicating no variations due to the storm. This study provides new insights into the responses to large and rare extreme events of Mediterranean communities with low dynamics and long-lived species, which are among the most threatened by the effects of global change.
Highlights
Extreme events are rare, stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms [1], [2], [3]
When ecosystems are forced beyond a threshold, regime shifts occur and the system enters into alternate stable states with a structure and function that are fundamentally different from the previous regime [10], [11]
This lack of knowledge may partially be explained by the rarity and stochastic nature of extreme storms in the Mediterranean Sea, combined with the scarcity of baseline data and long-term studies, making it difficult to study the effects of these events
Summary
Stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms [1], [2], [3]. Under the conditions of ongoing climate change, observations and global change models predict increases in the frequency and intensity of extreme weather and climatic events, including heat waves, droughts, and intense tropical and mid-latitude storms [2], [16] Extreme storms, such as hurricanes and severe storms in the tropics and mid-latitude storms in temperate areas abruptly alter ecological processes and structure and severely affect marine littoral communities [17], [18], [19], [6]. [20], [21], [22], [23], [24]), there is little knowledge about how extreme storms affect rocky benthic communities in temperate regions such as the Mediterranean Sea. In comparison with our understanding regarding the effects of hurricanes and tropical storms affecting coral reefs Analyzing the impacts of these events may provide new insights into processes that shape the structure of benthic communities in this region
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