Photosynthetic responses of corals Mussismilia harttii (Verrill, 1867) from turbid waters to changes in temperature and presence/absence of light

Respostas de corais a estresses de mudanças de temperatura são específicas e dependem também da localidade. Como a luz é um componente importante dos estresses induzidos pela temperatura, testamos experimentalmente as respostas de Mussismilia hartii, coral originário de águas turvas, a mudanças de temperatura, na presença e ausência de luz. Parâmetros de fluorescência da clorofila foram medidos com Diving-PAM. Os experimentos foram mantidos a temperaturas distintas. Os pólipos permaneceram no escuro ou foram continuamente expostos a 300 µmol photons m-2.s-1 de irradiância. Nenhum branqueamento visível foi observado entre as temperaturas de 26,5 a 35,0 ºC, mas a maioria dos pólipos expostos a temperaturas elevadas mostraram sinais de necrose do tecido. Houve uma redução de Fv/Fm em resposta ao aumento da temperatura, que foi exacerbada na presença de luz, indicando um efeito sinergético desses fatores. Sugerimos que o fotodano sofrido pelos endossimbiontes de M. harttii, desencadeados nas temperaturas de 33,0 e 35,0 ºC, resultou de uma diminuição do processo de reparação, assim como o efeito da luz sobre o PSII. A recuperação de pólipos mantidos a 31,0 ºC indicou que essa temperatura parece ser limítrofe (dependendo do tempo de exposição); temperaturas acima de 31,0 ºC levaram a danos irreversíveis ou morte de M. harttii.Responses of corals to climate change stresses are species and locality specific. As light is an important component of temperature-induced stresses, we experimentally tested the responses of a turbid water coral, Mussismilia harttii, to changes in temperature in the presence and absence of light. Chlorophyll fluorescence parameters were measured using a diving-PAM. Experiments were carried out at distinct temperatures. Polyps were kept in the dark or were continuously exposed to 300 µmol photons m-2.s-1 irradiance. No visible bleaching of coral samples was seen in temperatures between 26.5 and 35.0 ºC, but most polyps at higher temperatures showed signs of tissue necrosis. There was a reduction of Fv/Fm as temperature increased, with a further drop in the presence of light, indicating a synergistic effect of these factors. We suggest that the photodamage to M. harttii endosymbionts triggered by temperatures of 33.0 ºC and 35.0 ºC results from a decline of the repair process, as well as the effect of light on the PSII. Recovery data for polyps kept in 31.0 ºC showed that this temperature (depending on time of exposure) seems to be borderline; temperatures higher than 31.0 ºC lead to long-term damage or death of M. harttii

Photosynthetic responses of corals Mussismilia harttii (Verrill, 1867) from turbid waters to changes in temperature and presence/absence of light

Abstract Responses of corals to climate change stresses are species and locality specific. As light is an important component of temperature-induced stresses, we experimentally tested the responses of a turbid water coral, Mussismilia harttii, to changes in temperature in the presence and absence of light. Chlorophyll fluorescence parameters were measured using a diving-PAM. Experiments were carried out at distinct temperatures. Polyps were kept in the dark or were continuously exposed to 300 µmol photons m-2.s-1 irradiance. No visible bleaching of coral samples was seen in temperatures between 26.5 and 35.0 ºC, but most polyps at higher temperatures showed signs of tissue necrosis. There was a reduction of Fv/Fm as temperature increased, with a further drop in the presence of light, indicating a synergistic effect of these factors. We suggest that the photodamage to M. harttii endosymbionts triggered by temperatures of 33.0 ºC and 35.0 ºC results from a decline of the repair process, as well as the effect of light on the PSII. Recovery data for polyps kept in 31.0 ºC showed that this temperature (depending on time of exposure) seems to be borderline; temperatures higher than 31.0 ºC lead to long-term damage or death of M. harttii

Impact of oil spills on coral reefs can be reduced by bioremediation using probiotic microbiota

Several anthropogenic factors, including contamination by oil spills, constitute a threat to coral reef health. Current methodologies to remediate polluted marine environments are based on the use of chemical dispersants; however, these can be toxic to the coral holobiont. In this study, a probiotic bacterial consortium was produced from the coral Mussismilia harttii and was trained to degrade water-soluble oil fractions (WSFs). Additionally, we assessed the effect of WSFs on the health of M. harttii in tanks and evaluated the bacterial consortium as a bioremediation agent. The consortium was responsible for the highly efficient degradation of petroleum hydrocarbons, and it minimised the effects of WSFs on coral health, as indicated by raised photosynthetic efficiencies. Moreover, the impact of WSFs on the coral microbiome was diminished by the introduced bacterial consortium. Following introduction, the bacterial consortium thus had a dual function, i.e promoting oil WSF degradation and improving coral health with its probiotic features