Climate change transforms the functional identity of Mediterranean coralligenous assemblages

Abstract

Quantifying changes in functional community structure driven by disturbance is critical to anticipate potential shifts in ecosystem functioning. However, how marine heatwaves (MHWs) affect the functional structure of temperate coral‐dominated communities is poorly understood. Here, we used five long‐term (> 10 years) records of Mediterranean coralligenous assemblages in a multi‐taxa, trait‐based analysis to investigate MHW‐driven changes in functional structure. We show that, despite stability in functional richness (i.e. the range of species functional traits), MHW‐impacted assemblages experienced long‐term directional changes in functional identity (i.e. their dominant trait values). Declining traits included large sizes, long lifespans, arborescent morphologies, filter‐feeding strategies or calcified skeletons. These traits, which were mostly supported by few sensitive and irreplaceable species from a single functional group (habitat‐forming octocorals), disproportionally influence certain ecosystem functions (e.g. 3D‐habitat provision). Hence, MHWs are leading to assemblages that are deficient in key functional traits, with likely consequences for the ecosystem functioning.

Extensive Marine Heatwaves at the Sea Surface in the Northwestern Pacific Ocean in Summer 2021

“…Moreover, it has been projected that these historical trends in MHW properties will continue over the coming decades under global warming caused by anthropogenic climate change [10]. Furthermore, MHWs have devastatingly affected marine ecosystems in the past, and they are expected to do so in the future, through abrupt changes in biological habitat, mortality, reproduction, community structure, and so on [10][11][12][13][14][15].…”

Demo-Genetic Approach for the Conservation and Restoration of a Habitat-Forming Octocoral: The Case of Red Coral, Corallium rubrum, in the Réserve Naturelle de Scandola

“…Changes in heterozygosity values are difficult to detect (Riquet et al, 2017), and a delay in the detection of genetic erosion is expected in long-lived species with overlapping generations such as red coral (e.g., Hailer et al, 2006). However, this apparent stability in the pattern of genetic structure and diversity remains surprising considering the dramatic demographic decline reported in red coral in this area (Gómez-Gras et al, 2021). While deserving cautious interpretation, this result highlights the need to consider complementary metrics such as effective population sizes to characterize temporal trend in genetic diversity.…”

“…Located in a cave, PLU can be isolated from neighboring populations due to hydrodynamic factors (e.g., Costantini et al, 2018). PLU is also impacted by a dramatic demographic decline with more than 90% of biomass lost during the last 15 years due to warming-induced MMEs (Gómez-Gras et al, 2021). This decline can potentially increase the effect of genetic drift in this particular population.…”

“…Populations of long-lived and habitat-forming macrobenthic species such as sponges, octocorals, or bryozoans were dramatically impacted by MMEs, with up to 80% of impacted individuals in some locations (Cerrano et al, 2000;Garrabou et al, 2001Garrabou et al, , 2009Garrabou et al, , 2019. The reported high incidence and mortality rates in these key species may induce cascading effects at the ecosystem level, questioning the future of coralligenous communities (Gómez-Gras et al, 2021).…”

Editorial: Biogenic Reefs at Risk: Facing Globally Widespread Local Threats and Their Interaction With Climate Change

“…Indeed, both tropical and temperate biogenic reefs are increasingly threatened by multiple stressors resulting in the decline of reef communities worldwide (e.g., Harborne et al, 2017;Ellis et al, 2019;Maher et al, 2019;Bevilacqua et al, 2021). Natural and anthropogenic stressors include decline in water quality, overexploitation of resources, habitat destruction, and global climate change among others, which have all been linked in tropical and temperate areas with the occurrence of mass coral bleaching and a variety of diseases and mass mortality events (e.g., Carpenter et al, 2008;Garrabou et al, 2009;Ban et al, 2014;Burge et al, 2014;Thompson et al, 2014;Ponti et al, 2016;Gómez-Gras et al, 2021).…”