RESUMO
Rising temperature can adversely affect specific functions of corals. Coral gametes and planulae of Acropora pulchra were evaluated to determine their temperature resistances, and the potential of developmental thermal acclimation was examined on gametes. Results highlight that fertilization success displays a relatively high thermal resistance at ET50 (median effective temperature) 31.5⯱â¯0.5⯰C after 4â¯h and 30â¯min. Additionally, probability of larval survival is halved at LT50 (median lethal temperature) 28.4⯱â¯0.42⯰C after 14 days. The pre-exposure of oocytes to 30⯰C and 32⯰C for 1â¯h increases the cell development pace during fertilization at ambient temperature. Pre-exposure of gametes, separately at 32⯰C for 1â¯h, increases fertilization success rate by 63% at 32°C, conversely, pre-exposure to 30⯰C induces more variable results. These results evidenced the occurrence of developmental thermal acclimation as a result of thermal pre-exposure of oocytes.
Assuntos
Aclimatação , Antozoários/fisiologia , Recifes de Corais , Animais , Células Germinativas , Larva/fisiologia , TemperaturaRESUMO
The life cycle of coral is affected by natural and anthropogenic perturbations occurring in the marine environment. In the context of global changes, it is likely that rainfall events will be more intense and that coastal reefs will be exposed to sudden drops in salinity. Therefore, a better understanding of how corals-especially during the pelagic life stages-are able to deal with declines in salinity is crucial. To fill this knowledge gap, this work investigated how gametes and larva stages of two species of Acropora (Acropora cytherea and Acropora pulchra) from French Polynesia cope with drops in salinity. An analysis of collected results highlights that both Acropora coral gametes displayed the same resistance to salinity changes, with 4h30-ES50 (effective salinity that decrease by 50% the fertilization success after 4h30 exposure) of 26.6 ± 0.1 and 27.5 ± 0.3 for A. cytherea and A. pulchra, respectively. This study also revealed that coral gametes were more sensitive to decreases in salinity than larvae, for which significant changes are only observed at 26 for A. cytherea after 14 d of exposure. Although rising seawater temperatures and ocean acidification are often perceived as the main threat for the survival of coral reefs, our work indicates that 70% of the gametes could be killed during a single night of spawning by a rainfall event that decreases salinity to 26. This suggests that changes in the frequency and intensity of rainfall events associated with climate changes should be taken seriously in efforts to both preserve coral gametes and ensure the persistence and renewal of coral populations.
Assuntos
Antozoários/fisiologia , Fertilização/fisiologia , Salinidade , Estresse Fisiológico , Animais , Células Germinativas/fisiologia , Larva/fisiologia , Polinésia , ChuvaRESUMO
Pollution by heavy metals remains today an important threat to the health of humans and ecosystems, but there is still a paucity of data on the response of early life stages of key organisms. In this context, the present work assessed the fertilization success rate of two Acropora species (A. cytherea and A. pulchra) from the French Polynesia reefs exposed to six increasing copper concentrations in seawater. The two species showed a relatively high tolerance to copper (4h30-EC50 was 69.4 ± 4.8 µg L(-1) and 75.4 ± 6.4 µg L(-1) for A. cytherea and A. pulchra, respectively). As Cu concentration increases, an increasing proportion of deformed embryos was recorded (67.6% and 58.5% for A. cytherea and A. pulchra, respectively, at 220 µg Cu L(-1)). These results demonstrated thus, that high levels of copper could negatively impair the normal fertilization process of coral gametes and therefore alter the renewal of coral populations. Since the two Acropora species investigated in this study displayed a high resistance to copper, these results should be considered in the context of multiple stressors associated with climate change, where rising temperature or ocean acidification may significantly exacerbate copper toxicity.