Fast climatic changes place an endemic Canary Island macroalga at extinction risk

Abstract

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 The endemic macroalgae have been replaced by the globally distributed species Pterocladiella capillacea at nearly all the sites studied.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.

A New Species from the Canary Islands Increases the Diversity of the Red Algal Genus Pterocladiella in the Northeastern Atlantic

“…In recent years, as a result of environmental and human factors, numerous studies are showing a drastic decline in some species of Canarian marine algae that are at risk of extinction [ 58 , 59 , 60 , 61 ]. Simultaneously, undescribed algal species continue to be discovered [ 62 , 63 , 64 ], proof that current knowledge of the marine diversity of the Canary Islands is still incomplete, and that it is possible that part of the diversity is being lost when it has not yet been properly identified and catalogued.…”

Thermal vulnerability of the Levantine endemic and endangered habitat-forming macroalga, Gongolaria rayssiae: implications for reef carbon

“…If the same happens to G. rayssiae, due to its limited distribution, this might become globally extinct, and this could have repercussion on many other associated species. To the best of our knowledge, no endemic macroalga has gone through a global extinction yet, but a similar rare example for an endemic habitat-forming macroalgae in sharp decline (90% in the last 30 years) that may face global extinction due to ocean warming is Gelidium canariense in the Canary Islands (Alfonso et al, 2021). Additionally, the limited narrow geographical distribution of G. rayssiae in the Levantine basin does not allow for comparisons among warm-, central-and cool-edge populations (Bennett et al, 2022a;Bennett et al, 2022b), so that adaptive management strategy including targeted translocations cannot be applied.…”

“…Global climate change is a major threat to marine biodiversity (Hillebrand et al, 2012). Ocean warming triggers the redistribution of species and is of especially high risk to ecologically important endemic species with restricted distributions and relatively narrow thermal tolerance ranges (Pimm et al, 2014;Da Silva et al, 2019;Alfonso et al, 2021). Species with small distribution ranges face three possible future scenarios: (1) shifting their distribution to an optimal or sustainable thermal habitat, (2) adapting to the temperature change, or (3) undergoing decline and possibly extinction (Sunday et al, 2015).…”

“…Macroalgae distribution, in particular, is strongly constrained by temperature (Breeman, 1990;Ji and Gao, 2021). However, there is a lack of knowledge on the impacts of ocean warming on narrow range endemic macroalgae and the consequences of their decline on the associated communities (Alfonso et al, 2021).…”

Genetic Diversity and Phylogeography of a Turf-Forming Cosmopolitan Marine Alga, Gelidium crinale (Gelidiales, Rhodo-Phyta)

“…Coastal ecosystems face manifold problems stemming from climate change, and large canopy-forming species have gradually been replaced by small turf-forming species or introduced aliens [ 2 , 3 ]. Although turf-forming species often contribute less to the structure and function of coastal ecosystems, in the case of the absence of canopy species, they may take over an important function as habitat formers [ 4 , 5 ]. Our knowledge has yet to figure out the genetic diversity and geographical distribution of turf-forming species with a global distribution.…”