Towards a local mass mortality of the Mediterranean orange coral Astroides calycularis (Pallas, 1766) in the Pelagie Islands Marine Protected Area (Italy)

Abstract

In late summer 2020, a widespread mortality event severely affected colonies of the Mediterranean endemic orange coral Astroides calycularis in the Pelagie Islands (Strait of Sicily, southern Mediterranean Sea). The degree of the mortality impact at seven study sites of the archipelago (five within the Pelagie Islands Marine Protected Area) was quantified by estimating the proportion of affected colonies in populations of A. calycularis. Five of the seven surveyed sites revealed a low degree of impact, but Punta Ruperta and Cala Creta (both on the island of Lampedusa) showed a medium impact with values of 32.3% and 30.5% of affected colonies respectively. The 2020 mortality event coincided with a longer lasting and warmer anomalous summer period, with sea surface water reaching the highest temperatures recorded in the last decade across the archipelago. Given the alarming climatic predictions for the near future, new mortality events could occur, causing potentially new local extinctions in the Mediterranean Sea. In this context, the role of marine protected area management becomes crucial to detect mortality events of vulnerable species.

Response of two temperate scleractinian corals to projected ocean warming and marine heatwaves

“…In the Warming treatment, however, three colonies of C. caespitosa showed partial necrosis and loss of six polyps while four colonies of A. calycularis had lost up to 14 polyps. Necrosis observed in situ for both species exposed to MHWs up to 29°C [ 21 , 24 ] has been more important than described in this study, with a recurrent increase in mass mortalities these past few years [ 5 ]. The projected warming of +3.2°C for the end of the century tested in this study had the strongest impact, with severe bleaching of C. caespitosa and higher necrosis of A. calycularis leading only to a partial recovery after four months.…”

“…In the laboratory, A. calycularis showed a decrease in calcification by 25% and an increase in the porosity of the skeleton when exposed to an increase of 3°C compared with the natural annual temperature cycle measured at the sampling site [ 23 ]. Mortality events of A. calycularis during late summer have been reported during the last years on the coast of Ischia and Pelagie Islands [ 5 , 24 ] with the warm summer of 2020 causing a widespread mortality event.…”

Early life stages of a Mediterranean coral are vulnerable to ocean warming and acidification

“…The warm temperature used for the experiment, 26 • C, is the mean temperature during the summer months in Ischia (July and August, Teixido et al, 2020). The colonies of A. calycularis have been suffering mass mortalities in Ischia and north of Sicily in summer when temperatures reach 28 • C (Gambi et al, 2018;Bisanti et al, 2022).…”

The swim-survey archive of the Mediterranean rocky coasts: Potentials and future perspectives

“…(De Sabata et al, 2015), very rare in the Mediterranean. Bisanti et al (2022) published a paper regarding al local mass mortality of the Mediterranean orange coral Astroides Calycularis in the Pelagie Islands Marine Protected Area (Italy). The degree of the mortality impact at seven study sites of the archipelago (five within the Pelagie Islands Marine Protected Area) was quantified by estimating the proportion of affected colonies in populations of A. calycularis.…”