Herbarium macroalgae specimens reveal a rapid reduction of thallus size and reproductive effort related with climate change.

Understanding and forecasting the effects of climate changes on vulnerable species are leading concerns for ecologists and conservation biologists. Herbaria are invaluable for use in long-term data series, and one of the few available methods for quantifying biodiversity changes over large periods of time. Gelidium canariense is an endemic and habitat-forming macroalga of the Canary Islands that coexists with two other habitat-forming Gelidiales: G. arbuscula and Pterocladiella capillacea. This study assesses long-term changes in thallus size and reproductive effort of all specimens deposited in the Herbarium of Universidad de La Laguna of these three Gelidiales species. Also assessed were the effects of seawater temperature and increased incident light on net primary production (NPP), and the effects of extreme desiccation conditions on the relative water content and NPP of the three Gelidiales species. The length of the thallus of the endemic species G. canariense was halved during the past 40 years. The shortening of the thallus coincided with a significant decrease in the number of reproductive structures in both Gelidium species. These morphological changes coincide with a significant increase of the sea surface temperature, air temperature above sea surface and ultraviolet radiation in the studied area. The experiments have revealed the deleterious effects of extreme desiccation and extreme irradiance on all three species. Hence, these results suggest that air temperature and irradiance are related with these morphological changes over time in the habitat-forming Gelidium species and that are most likely compromising the survival of their populations which are already declining.

A new CO2 vent for the study of ocean acidification in the Atlantic.

Natural CO2 vents are considered the gold standard of ocean acidification (OA) studies. In coastal areas these rare vents have only been investigated at the Mediterranean temperate rocky reefs and at Indo-Pacific coral reefs, although there should be more at other volcanic shores around the world. Substantial scientific efforts on investigating OA effects have been mostly performed by laboratory experiments. However, there is a debate on how acute this kind of approach truly represents the responses to OA scenarios, since it generally involves short-term, rapid perturbation and single variable and species experiments. Due to these limitations, world areas with natural CO2 vents are essential to understand long-term marine ecosystem responses to rising human derived atmospheric CO2 concentrations. Here, we presented a new vent found in the subtropical North East Atlantic reefs (28°N, La Palma Island) that shows moderate CO2 emission (900ppm), reducing pH values to an annual average of 7.86±0.16.