Marine reserves are fundamental tools for the conservation of worldwide marine biodiversity. According to a new study published in the journal PLOS ONE, the analysis of both genetic and demographic structures of some habitat-forming species, for example the red gorgonian, is a key factor to improve marine reserve conservation management plans.

The new study, which provides some conclusions that can be applied to gorgonian populations in the Mediterranean Sea and other marine regions, is signed by a scientific team composed by Cristina Linares and Rosana Arizmendi Mejía, lecturers in the Department of Ecology of the University of Barcelona (UB); Joaquim Garrabou (Institute of Marine Sciences, ICM-CSIC), Enric Ballesteros and Emma Cebrián (Centre for Advanced Studies of Blanes, CEAB-CSIC), David Díaz (Spanish Oceanographic Institute, IEO), and Agostinho Antunes and Jean-Baptiste Ledoux (Interdisciplinary Centre of Marine and Environmental Research, CIMAR/CIIMAR).

A gorgonian forest on the seabed

The red gorgonian (Paramuricea clavata) is a sessile marine habitat-forming organism of the Mediterranean coralligenous assemblages. Like other habitat-forming species, its 3D structure contributes to marine ecosystem landscape.

UB researcher Cristina Linares explains that "this species are like trees in terrestrial ecosystems. Particularly, the red gorgonian is a very important species for benthic ecosystems from an ecological point of view as it provides a great part of its 3D structure, biomass and complexity to the marine habitat, what means a great biodiversity. It also gives an extraordinary hereditary value."

"As it is a long-lived species with a very slow population dynamics, it is very sensitive to environmental changes, natural or human-caused," points out the expert. Therefore, the red gorgonian is a good indicator of perturbation changes in magnitude and intensity which affect communities.

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A good indicator for environmental management

To date, most management plans and studies on marine reserves have been focused on fish populations, which are organisms with a quick response to protection. According to authors, it is necessary to include habitat-forming species in design and management protocols because the conservation of these species and the habitats where they live is crucial to ensure the preservation of a good part of protected areas' biodiversity.

In the study, authors prove that combining genetic and demographic factors allows determining the conservation status of populations and the role they play in maintaining population connectivity (which ones act as donors and which ones are the receivers). Authors emphasize that this aspect must be considered in order to establish the different protection levels that a future marine reserve including the islets located on the west coast of Ibiza should have.

Endangered gorgonian populations

Nowadays, the climate change and the impact of human activity (scuba diving, fishing, etc.) are the main threats against red gorgonian populations. On the Catalan coast, for example, evidence shows that populations have not suffered in a significant way the impact of climate change but they have suffered so much the effects of human activity. Moreover, there are other factors that also affect the species, for example the presence of invasive algae.

The research team continues studying these structural species in different Mediterranean reserves like the Cabrera Archipielago National Park; Cap de Creus Natural Park, Montgrí, Medes Islands and Baix Ter Natural Park; Columbretes Islands Marine Reserve; Scandola Nature Reserve (Corsica), and the Port-Cros National Park (France). Experts want to study the synergetic effect of perturbations affecting Paramuricea clavata.

"It is necessary to consider -- alerts Linares -- that impacts do not take place in an isolated way, but in many cases they occur together, resulting in severer impacts." Moreover, scientists analyse the mechanisms that favour species' high resistance to climate change and other perturbations. The final aim is to understand what kind of conservation and management actions are the most effective to improve species conservation.

The study is part of the project SMART (Resilience of long-lived marine structural species in a changing world: towards a sustainable coastal management and restoration), funded by the Spanish Ministry of Economy and Competitiveness.