Effects of thermal stress on early developmental stages of a gorgonian coral

Abstract

10 pages, 6 figures ; Ongoing sea temperature increase threatens reefs worldwide. In this study we experimentally examined for the first time the response of the early life stages of a long-lived structural gorgonian, the Mediterranean species Paramuricea clavata (Risso 1826), to the highest summer temperature recorded so far in the study area (25°C; the Medes Islands, Northwestern Mediterranean). This temperature also simulates the end-of-century predicted warming (+3°C) over the temperature maxima recorded during the species' reproductive period. The results showed a severe negative impact of constant thermal stress on the viability of P. clavata embryos and larvae, resulting in reduced survivorship, completely abnormal embryonic development and impaired metamorphosis. The deteriorating effect was rapid for embryos (after 7 h), whereas the impact on larvae became evident after 10 d of stress. Larval modifications started 7 d earlier under elevated temperature conditions, but the appearance of spherical, aberrant shapes prevented an assessment of whether metamorphosis was initiated but abnormal, or deterred altogether. The apparent higher sensitivity of embryos suggests that thermal stress during embryonic development may be the most critical factor for the viability of P. clavata larvae. In the context of an ongoing warming trend, the reduced viability of early life stages would jeopardize the persistence of P. clavata, which relies on successful recruitment for replenishment of its populations. Further research into the effects of thermal stress on the reproduction of structural invertebrate species and the viability of their early life stages will improve our understanding of the long-term consequences of environmental global change in marine benthic communities ; We thank J. M. Fortuño for assistance with scanning electronic microscopy, the Medes Islands MPA Staff for their continuous support, and O. Ross and M. Buklijas Caleta for help in image editing. We further thank the 3 anonymous reviewers for their constructive comments. S.K. acknowledges Research Fellowship 2009-11 from the Spanish Agency for International Development Cooperation (AECID). This study was funded by the Spanish Ministry of Science and Innovation (Biorock project ref. CTM2009−08045), Juan de la Cierva and Ramon y Cajal contracts to C.L. and Beatriu de Pinós contract to N.T. This is a contribution from the Medrecover research group, funded by the Generalitat de Catalunya (Catalan government) ; Peer reviewed