Global warming and ultraviolet radiation (UVR) affect marine organisms worldwide. However, we still lack knowledge about the consequences of these environmental changes to range-restricted macroalgae species, such as Gelidium canariense, a habitat-forming endemic of the Canary Islands. The aim of this study is to provide useful data for analyzing the conservation status of this endemic species. To do this, (1) we compared distributional data from 1987 with the data collected in 2008 and 2019 along the northern coast of Tenerife; (2) we assessed the variation in macroalgae assemblages dominated by G. canariense over the last decade on this same cost; and (3) we explored the correlation of these results with the actual trends of sea surface temperature (SST), air temperature at 2 m above the sea surface (T2m), UVR, and downward solar radiation (DSR). The results showed significant changes in the distribution of G. canariense in the last 30 years at Tenerife. More than 90% of its populations have declined. The endemic macroalgae have been replaced by the globally distributed species Pterocladiella capillacea at nearly all the sites studied. The cover of G. canariense and Gelidium arbuscula decreased significantly with increasing SST and T2m. Additionally, G. canariense is negatively related to the rise in UVR. These results highlight the vulnerability of both species of Gelidium to global warming and UVR, but especially of G. canariense. The drastic decline of this species reveals the need to upgrade its conservation status and implement protection measures to reduce the damage that predicted global change scenario may have to their relict populations.
Abstractis a canopy-forming endemic macroalga from the Canary Islands. Vegetative and reproductive characteristics of all phases in its life cycle are examined. Key macromorphological features are its blackish color and the corymbose-to-subfastigiate branching pattern that differentiates
Gelidium canarienseandGelidium arbusculumcoexist in the upper sublittoral zone in the Canary Islands and are the only Gelidiales registered as vulnerable species. Spore germination and the formation of rhizoids are vital steps for the successful growth of new plants. We investigated the initial germination stages of tetraspores and the growth of the primary rhizoid in these two vulnerable species. Both Gelidiales exhibitedGelidium-type germination. However, liberated tetraspores ofG. canarienseandG. arbusculumgerminated earlier than those of other species of the Gelidiales. The growth curves of primary rhizoids were similar in both species.
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