Responses of intertidal seaweeds to warming: A 38-year time series shows differences of sizes

The increase of sea temperature is a key driver affecting marine organisms. The ongoing decline of cold temperate macroalgae, e.g. kelp or fucoids, is pervasive. Edge populations of fucoids in subtropical latitudes are particularly sensitive to environmental changes. We here studied long-term variability (38-year period, 1978-2016) of morphological characters of three fucoid species using herbarium records from the subtropical archipelago of the Canaries (NE Atlantic Ocean). The study species were Gongolaria abies-marina, Cystoseira compressa and Cystoseira humilis that have been recently reported population decline. Rising temperatures had effects on the morphology of these species, probably due to an excess of thermal tolerance and this may be related to the algae size, ocean warming has been contrasted as a significant effect on the growth and distribution of the studied populations, and the tolerance temperature has key implications in the adaptive capacity of the studied species.

Automated summary

Rising sea temperatures have an impact on the morphological characteristics of marine algae species, especially edge populations of fucoids in subtropical latitudes. Excess thermal tolerance may lead to morphological variations in these species, and ocean warming has significant effects on their growth and distribution.