Vulnerability of Mediterranean Sea Species to Climate Variation at Local and Regional Scales

[eng] The impact of climate change is of increasing concern at a global scale due to the need to develop climate-adaptive management of natural resources. Therefore, understanding ecosystem dynamics is essential to effectively address and predict the vulnerability of the communities inhabiting the marine ecosystems. This includes improving our capability to separate natural from anthropogenic variability, but also to differentiate local from regional environmental effects to correctly design adaptation measures. Previous studies have proven the effectiveness of analyzing physical factors at the large, regional, and local scale to better understand population dynamics and provide information on their sensitivity to climate and oceanographic variations and marine production regimes, showing the link between the biological cycle of the species and how it could be affected by abiotic oceanographic factors. However, it is still a challenge the identification of the relative influence of this drivers on the temporal variation of the spatial distributions, and particularly to disentangle influence on the dynamics and the static components. This is of paramount importance in the Mediterranean Sea since the environment and biological communities display high spatial heterogeneity. In this study, we analyze the vulnerability to different components of the climate variation by contrasting the response of the spatial distribution and regional abundances of mentioned demersal species to regional and local climate along the coast of the Iberian Peninsula in the Western Mediterranean Sea. To do that, the present work focus on the sensitivity of three contrasting species, M. merluccius, I. coindetii, and L. depurator in the Western Mediterranean Sea (GSA6) to climate variation on a regional, sub-regional, and local scale, using the observations in abundance and distribution of the MEDITS bottom trawl survey performed every year during late spring-early summer covering a time lapse of 23 years from 1994 to 2017. Climate variables include large scale climatic indices such as the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the Western Mediterranean Oscillation, and a Regional Hydroclimatic Index. At small (i.e. sub-regional) scale, environmental variables and indices representing the local climate conditions were sea surface temperature, primary production, the runoff of the Ebro river and the local climatic index. Employing a multivariate reduction technique, we first extrapolated the two large scale explanatory factors that determine the different modes recurrent in the spatial distribution of the selected species. Afterwards, we investigated the influence of environmental variables across different spatial scales for each species via matrix correlations and spatial correlations. The three species responded to different drivers and provide evidence of spatially decoupled and cross-scaled effects, while the influence of chlorophyll a being a recurrent driver in all of them. The first and second empirical ordination factors were significantly correlated with some of the environmental variables considered, validating this technique for investigating long term variability and sensitivity to climate in the spatial distribution of marine species