Marine systems have been severely affected in recent years by mass mortality events related to positive thermal anomalies. Although the immediate effects of warming-related mortality in species’ demography are well known, the mid- to long-term effects at the community level are much less documented.

This study shows how an extreme warming event in the Western Mediterranean (Cabrera National Park, Spain) caused the replacement of a structurally complex habitat, dominated by long-lived species, by a simplified habitat with lower diversity and richness, dominated by turf-forming species.

Additionally, the authors performed a manipulation experiment with the red gorgonian Paramuricea clavata, which results showed that its presence mitigated the effects of warming by maintaining the original assemblage dominated by macroinvertebrates and delaying the proliferation and spread of the invasive alga Caulerpa cylindracea.

The authors highlight the evidence of the synergic and additive effects of global and local stressors that are affecting ecosystems around the world. It is underlined that being the Mediterranean Sea one of the regions most affected by warming and extreme climatic events, the results of this study are of especial relevance as they show a degradation of an entire Mediterranean assemblage to levels never reported before.

Verdura et al. (2019) Biodiversity loss in a Mediterranean ecosystem due to an extreme warming event unveils the role of an engineering gorgonian species. Scientific Reports 9:5911.