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The project is proposed with the aim of promoting the restoration of populations of three threatened macroalgae on the seabed of the Canary Islands, which constitute habitats where high biodiversity develops and offer important ecosystem services. According to the University of La Laguna, in recent decades, these species have been seriously affected by various alterations in the marine environment that have caused their decline or disappearance in many localities. These species are included as vulnerable in state legislation and the extinction of their populations, according to the entity, would lead to the disappearance of the biodiversity they harbor, causing a cascade effect on the natural resources of the area (fishing, shellfishing, etc.).

The general objective of the project has been to promote the restoration and conservation of some populations of three macroalgae that structure threatened Canarian marine ecosystems.

The specific objectives were as follows:

• Raise awareness of the species and conservation status of resilient populations.
• Transplantation of adult individuals of Gelidium arbuscula and canariensis from locations with high densities to others with lower density.
• Transplantation of adult individuals of Cystoseira abies-marina from four localities with high genetic diversity to two localities with lower genetic diversity.

To know the effect of different environmental variables on the first stages of development of the species under study (critical phases).

• Restoration and monitoring of populations of Gelidium arbusculum and Canarian.
• Restoration and monitoring of Cystoseira abies-marina populations.
• Improvement of knowledge about the effect of environmental variables and pollutants in the early stages of development of the species under study.
• Dissemination and communication activities of the project.

The RESTAURALG project has contributed to scientific knowledge on the life cycle and the adaptation and recovery of the populations of three coastal macroalgae in the Canary Islands that are currently seriously threatened by the effects of climate change.

These macroalgae Gelidium arbusculum, G. canariense and Cystoseira abies-marina are key habitats where high marine biodiversity develops and offer important ecosystem services. Environmental and anthropogenic changes have caused their decline or disappearance in native localities, where they are currently vulnerable or extinct, causing a cascade effect on the natural resources of the area (e.g. fishing, shellfishing, etc.).

For the development of the initiative, various methods of transplantation with adult individuals have been evaluated. In addition, laboratory experiments have been carried out to obtain seedlings on natural rocky substrates, which were placed back at the potential distribution level of these species.

Good results were obtained with transplants of adult individuals and obtaining numerous seedlings in the laboratory in the case of the species G. abies-marina, but they were not very viable in the remaining two species.

The effects of different environmental factors (temperature, irradiance, UVB radiation and pollutants) on the release, fixation and growth of the first stages of development of these macroalgae (zygotes in the case of Cystoseira abies-marina and tetraspores in Gelidium arbusculum and G. canariense) have also been evaluated.

These stages, according to the entity, are very sensitive to habitat alterations that may be preventing the recruitment and subsequent maintenance of populations. All three species showed the best diaspore release and growth results at 21 °C. However, the optimal irradiance for diaspores differs depending on the species. In addition, UVB radiation showed the best results in the release and growth of tetraspores of Gelidium canariense at low intensity, and the data regarding pollutants (phosphates) determined that they favor the growth and number of seedlings in Pterocladiella capillacea, a species that is replacing Gelidium arbusculum and G. canariense in their natural populations.

In conclusion, the results indicate that the increase in temperature, irradiance, UVB radiation and pollutants negatively affect the early phases of the life cycle of these macroalgae.