When resilience is not enough: 2022 extreme marine heatwave threatens climatic refugia for a habitat-forming Mediterranean octocoral

Climate change is impacting ecosystems worldwide, and the Mediterranean Sea is no exception. Extreme climatic events, such as marine heat waves (MHWs), are increasing in frequency, extent, and intensity during the last decades, which has been associated with an increase in mass mortality events for multiple species. Coralligenous assemblages, where the octocoral Paramuricea clavata lives, are strongly affected by MHWs. The Medes Islands Marine Reserve (NW Mediterranean) was considered a climate refugia for P. clavata, as their populations were showing some resilience to these changing conditions. In this study, we assessed the impacts of the MHWs that occurred between 2016 and 2022 in seven shallow populations of the octocoral P. clavata from a Mediterranean Marine Protected Area. The years that the mortality rates increased significantly were associated with the ones with strong MHWs, 2022 being the one with higher mortalities. In 2022, with 50 MHW days, the proportion of total affecte..., , , # When resilience is not enough: 2022 extreme marine heatwave threatens climatic refugia for a habitat-forming Mediterranean octocoral

[https://doi.org/10.5061/dryad.tmpg4f569](https://doi.org/10.5061/dryad.tmpg4f569)

## Description of the data and file structure

The data set contains 3 documents:

1\) \"QuadratsMedesTot.csv\" is the collected data of each gorgonian, each year in each location. Any cells without information count as NA values. The variables are:

Data: date in which the data was collected.

Any: year of the sampling.

Observador: name of the observer.

Proteccio: protection degree of the location.

Parc: name of the natural parc where the data was collected.

Lloc: name of the site/location.

Fondaria: depth.

Quadrat: number of the quadrat.

Talla: size of the colony (cm).

Necrosi: proportion (%) of early mortality/necrosis of the tissue of each colony.

Epibiosi: proportion (%) of late mortality/epibiosis of the tissue of each colony.

Observacions: any other additi...