3D Photogrammetry Modeling Highlights Efficient Reserve Effect Apparition After 5 Years and Stillness After 40 for Red Coral (Corallium rubrum) Conservation in French MPAs

Imaging the marine environment is more and more useful to understand relationships between species, as well as natural processes. Developing photogrammetry allowed the use of 3D measuring to study populations dynamics of sessile organisms at various scales: from colony to population. This study focuses on red coral (Corallium rubrum), as known as precious coral. Metrics measured at a colony scale (e.g., maximum height, diameter and number of branches) allowed population understanding and a comparison between an old (Cerbère-Banyuls reserve) vs. a new (Calanques National Park) MPA. Our results suggested a 5-year time step allows the appearance of a significant difference between populations inside vs. outside the Calanques National Park no-take zones. Red coral colonies were taller and had more branches inside no-take zones. A significant difference was still observable for the populations inside the Cerbère-Banyuls reserve after 40 years of protection, reflecting the sustainability and effectiveness of precautionary measures set by the reserve. The impacts at the local level (mechanical destruction) and those presumed to occur via global change (climatic variations) underline the need to develop strategies both to follow the evolutions of red coral populations but also to understand their resilience. Photogrammetry induced modeling is a time and cost effective as well as non-invasive method which could be used to understand population dynamics at a seascape scale on coralligenous reefs.

First record of Eualus drachi Noël, 1978 (Decapoda: Caridea) in the Adriatic Sea

Three specimens of decapod shrimp Eualus drachi Noël, 1978, were found in the red coral rem-nant collected for commercial purposes near the island Sveti Andrija, Croatia. It is the first record of this species in the Adriatic Sea. The decapod biodiversity of deeper coralligenous habitats, such as the red coral colonies, is poorly investigated in contrast to coastal areas and soft bottoms of traditional trawling grounds. This paper highlights the usefulness of examining the remnants of a commercial coral extraction originating from previously less investigated marine habitats in order to improve the knowledge on the biodiversity of such habitats.

Demo-Genetic Approach for the Conservation and Restoration of a Habitat-Forming Octocoral: The Case of Red Coral, Corallium rubrum, in the Réserve Naturelle de Scandola

Marine protected areas (MPAs) are one of the most efficient conservation tools to buffer marine biodiversity loss induced by human activities. Beside effective enforcement, an accurate understanding of the eco-evolutionary processes underlying the patterns of biodiversity is needed to reap the benefits of management policies. In this context, integrating population genetics with demographic data, the demo-genetic approach, is particularly relevant to shift from a “species-based pattern” toward an “eco-evolutionary-based processes” conservation. Here, targeting a key species in the Mediterranean coralligenous, the red coral, Corallium rubrum, in an emblematic Mediterranean MPA, the “Réserve Naturelle de Scandola” (France), we applied demo-genetic approaches at two contrasted spatial scales, among populations and within one population, to (i) infer the demographic connectivity among populations in the metapopulation network and (ii) shed new light on the genetic connectivity and on the demographic transitions underlying the dynamics of a near-pristine population. Integrating different spatial and temporal scales, we demonstrated (i) an apparent temporal stability in the pattern of genetic diversity and structure in the MPA in spite of a dramatic demographic decline and (ii) contrasted levels of genetic isolation but substantial demographic connectivity among populations. Focusing on the near-pristine population, we complemented the characterization of red coral demographic connectivity suggesting (iii) temporal variability and (iv) the occurrence of collective dispersal. In addition, we demonstrated (v) contrasted patterns of spatial genetic structure (SGS), depending on the considered stage-class (adults vs. juveniles), in the near-pristine population. This last result points out that the overall SGS resulted from a restricted dispersal of locally produced juveniles (SGS among adults and juveniles) combined to mortality during early life stages (decrease of SGS from juveniles to adults). Demonstrating the occurrence of two management units and the importance of two populations (CAVB and ALE) for the network of connectivity, we made recommendations for the management of the Réserve Naturelle de Scandola. Besides, we contributed to the implementation of scientifically driven restoration protocols in red coral by providing estimates for the size, density, and distances among patches of transplanted colonies.

First report of chimerism in the Mediterranean red coral (Corallium rubrum)

The phenomenon of chimerism in the Mediterranean red coral (Corallium rubrum) is reported and quantified in semi-natural conditions. 1688 larvae were maintained in closed circuit in presence of a suitable settlement surface (marble tiles). Post settlement survival and chimera formation were monitored for 1 year. According to our observation, when polyps settle at close contact, a high frequency of chimerism is observed (32%). After 1 year, only 33% of chimeric individuals survived but they are 40% bigger than not chimeric ones, suggesting that chimerism could confer a competitive advantage linked to increased growth rate.

The sub-fossil red coral of Sciacca (Sicily Channel, Mediterranean Sea): colony size and age estimates

The Mediterranean red coral, Corallium rubrum (L.), has been a valuable economic resource for more than 2000 years. The Sicily Channel and surrounding areas are one of the most famous red coral fishing grounds of the whole region, hosting the deepest ever found living colonies and large sub-fossil red coral deposits; the so-called Sciacca banks are a unique location in the whole Mediterranean Sea. In this paper, a morphometric description of this sub-fossil population is presented for the first time from studies of colonies in the collection of several coral factories from Torre del Greco (Naples), with radiocarbon age estimations and growth rate evaluations. From the results of this study, after several thousand years Sciacca red coral colonies maintained the organic matrix structure with evident annual discontinuities, allowing estimations of the annual growth rate (about 0.3 mm/year) and the average population age (about 33.5 years). These resulting data are similar to the values determined for deep-dwelling living red coral populations. The radiocarbon dating evidenced a range of ages, from 8300 to 40 years before 1950 CE, mostly falling between 2700 and 3900 YBP, suggesting that colonies accumulated over a wide span of time. In view of the tectonically active nature of the area, several catastrophic events affected these ancient populations, maintaining them in a persistent state of early-stage, structurally similar to the those in current over-exploited areas.