Population structure and conservation status of the red gorgonian Paramuricea clavata (Risso, 1826) in the Eastern Adriatic Sea

Abstract

Gorgonians are important structuring species of the Mediterranean hard‐bottom communities that are threatened by disturbances such as increasing seawater temperature, mucilaginous events and destructive fishing, among others. In this study we assessed for the first time the population structure and conservation status of one of the most common gorgonians in the Eastern Adriatic Sea, the red gorgonian Paramuricea clavata. During late spring 2009, nine populations dwelling between 30 and 50 m depth were examined by SCUBA diving along 200 km of the Croatian coastline. The density ranged between 7 and 20 colonies·m−2. The mean and maximum colony heights were 31.2 ± 22.7 cm (±SD) and 138 cm, respectively. Two main patterns of P. clavata size frequency distributions were observed: the first one with a higher proportion of juveniles (~30%) observed mostly in the northernmost populations, and the second one with a higher proportion of larger colonies (>25% of colonies >40 cm in height). Regarding the disturbance impact level, the proportion of healthy colonies (with <10% of injured surface) was high in almost all of the studied populations (>60%) and the mean extent of injury (i.e. denuded axis or epibiosis) was 9.7 ± 4% (±SD), indicating low impacts. Contrasting population size structures with high recruitment in mature populations provides new insights into the demographic structure of the Mediterranean gorgonian forests dwelling in their upper bathymetric range (<50 m depth). Furthermore, these size structures and the low impact levels suggest a current favorable conservation status of the studied populations in the Eastern Adriatic Sea and provide a baseline for their monitoring in the future.

Regional and local environmental conditions do not shape the response to warming of a marine habitat-forming species

“…This hypothesis is strengthened by the fact that Mediterranean gorgonians, in general, and P. clavata , in particular, shift their distribution to greater depths in warmer areas 40, 41 . Specifically, Linares et al .…”

Postglacial range expansion shaped the spatial genetic structure in a marine habitat‐forming species: Implications for conservation plans in the Eastern Adriatic Sea

“…In spite of these studies, the evolutionary history of P. clavata remains poorly understood. In addition, a recent characterization of the demographic structure of P. clavata in the Eastern Adriatic revealed well‐structured and mature populations composed of both small and large‐size colonies, highlighting their conservation value (Kipson et al., ).…”

“…Based on a hierarchical sampling (13 populations from four areas and including populations surveyed by Kipson et al. ()) conducted along the Croatian coast, we: (a) characterized the spatial patterns of neutral genetic structure; (b) reconstructed the populations’ demographic history; and (c) inferred the contemporary underlying processes with emphasis on connectivity. Integrating the obtained results, we discuss their implications for the conservation of this species and associated coralligenous biodiversity.…”

Overlooked habitat of a vulnerable gorgonian revealed in the Mediterranean and Eastern Atlantic by ecological niche modelling

“…Major threats include mechanical disturbances (e.g., fishing with bottom tending gear, recreational SCUBA diving and anchoring), pollution and increasing seawater temperatures, which have caused mass mortality events throughout the northwestern Mediterranean567. The species is essentially found in the western Mediterranean Sea, but also in the eastern basin in the Adriatic and Aegean Seas, where it presumably occurs deeper8 (V. Gerovasileiou and M. Sini pers. comm.…”

“…19) whereas only limited data exists for a wide area of this species’ distribution (eastern and southern Mediterranean and Atlantic89). The significant lack of continuous information over vast areas has caused effective marine spatial planning measures to be spatially disarticulated and reach limited outcomes20.…”