This product provides the Community Temperature Index (CTI) of macroalgae intertidal communities from NW Spain. The CTI has been calculated for 18 sites along a longitudinal thermal gradient in NW Spain, two intertidal levels (Low and Mid) and two different years (2011 and 2017). Results are stored in a csv file with the coordinates of each site ("decimalLongitude" and "decimalLatitude" columns), their codes ("Site" and "Intertidal_level" columns), the sampling year ("Year" column) and the mean CTI ("CTI column").
Ocean warming is expected to drive quick shifts in marine species distributions modifying coastal communities. Previous research has shown how the southern Bay of Biscay is particularly affected and the canopy-forming subtidal and intertidal macroalgal assemblages are expected to be replaced by turf-forming Mediterranean-like communities with warmer affinities by the end of the century. The effect of temperature on macroalgal communities could be assessed using thermal metrics that can target temperature effects alone. An example is the Community Temperature Index (CTI) which is an abundance-weighted mean of the species’ optimal temperature. It has been previously used to understand the thermal preferences of different organisms such us birds, fish or invertebrates.