Canopy-forming macroalgae can adapt to marine heatwaves

Description

This data set is the result of a laboratory experiment carried out as a part of research activities supported by the European Community within the EASME – EMFF (Sustainable Blue Economy) Project AFRIMED (http://afrimed-project.eu/, grant agreement N. 789059), To test the effect of MHWs on recruits of G. barbata, a two fixed factorial design with asymmetrical controls was used. A control condition not exposed to MHWs was compared against two orthogonal factors: i) MHWs duration, fixed factor with two levels: short MHW and long MHW; ii) MHWs timing, fixed factor with two levels: an early (summer) MHW and a late (summer) MHW. Every treatment was replicated in three separate tanks with three stones each, apart from the control condition where an additional tank with two stones was used. At the beginning of the experiment, the number of individuals (i.e., replicates) per treatment ranged between 35 and 46 (Fig. 1). The experiment lasted from the 14th of July to the 12th of September 2021. After two acclimation days in which all tanks were at 25 °C, temperature for the control condition was set following the seasonal average trend registered at La Strea lagoon from 1982 to 2021, ranging between 25,5 and 26,5 °C. Accordingly, temperatures simulating MHWs were set increasing by 2 °C the average values based on the detection of historical MHWs events. Thus, they ranged between 27,5 and 28,5° C respectively for the early and late MHWs. The duration of the MHWs was set to 13 and 26 days respectively for the short and the long treatment, reproducing MHWs events that actually occurred in the summer season. Mean intensity (°C) and cumulative duration (days) of MHWs events were calculated using the R package ‘heatwaveR’. Daily data of Sea Surface Temperature (SST) from 1982 to 2021 were retrieved from the geoportal Copernicus (https://cds.climate.copernicus.eu/cdsapp#!/dataset/satellite-sea-surface-temperature?tab=overview). The Copernicus dataset provides global SST data in the raster format (NetCDF) based on multiple sensors with a spatial resolution of 0.05° x 0.05° and no spatial gaps. From each raster file, we extracted daily SSTs for the pixel corresponding to the lagoon of Porto Cesareo using the Open Source software QGIS (QGIS Development Team, 2022) QGIS Geographic Information System. O3.Open Source Geospatial Foundation; https://www.qgis.org/it/site/). Recruits length, PSII maximal photochemical efficiency (Fv/Fm), photosynthetic pigments content (total chlorophylls and total carotenoids), concentrations of antioxidant compounds (polyphenols, flavonoids and tannins) and total antioxidant activity (DPPH) were the response variables measured during the experiment. The present dataset is composed by the measured response variable.

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