The physiological response of reef corals to diel fluctuations in seawater temperature

Abstract

An opportunity to explore the effects of fluctuating temperatures on tropical scleractinian corals arose when diurnal warming (as large as 4.7°C) was detected over the rich coral communities found within the back reef of Moorea, French Polynesia. In April and May 2007, experiments were completed to determine the effects of fluctuating temperature on Pocillopora meandrina and Porites rus, and consecutive trials were used to expose them for 13 days to 26°C, 28°C (ambient conditions), 30°C, or a fluctuating treatment ranging from 26 to 30°C over 24 h. The multivariate response was assessed using maximum dark-adapted quantum yield of PSII (F V /F M ), Symbiodinium density, chlorophyll-a content, and calcification. In trial 1, multivariate physiology of both species was significantly affected by treatments, with the fluctuating temperature resulting in a 17-45% decline in Symbiodinium density (relative to the ambient) matching that occurring at a constant 30°C; F V /F M , chlorophyll-a content, and calcification, did not differ between the fluctuating and the steady treatments. In contrast, in trial 2 that utilized corals collected two weeks after those used in trial 1, the corals were unaffected by the treatments, likely due to an environment × trial interaction caused by seasonal declines in Symbiodinium density. Together, these results demonstrate that short transgressions to ecologically relevant high and low temperatures can elicit a potentially detrimental response equivalent to that occurring upon exposure to a constant high temperature. The dissimilar responses among dependent variables and consecutive trials underscore the importance of temporal replication and multivariate approaches in coral ecophysiology. It is likely that recent history has a stronger effect on the response of corals to treatments than is currently recognized.

Resilience of coral calcification to extreme temperature variations in the Kimberley region, northwest Australia

“…For example, prior studies have found that massive Porites living in high-temperature environments with annual sea surface temperatures greater than 29°C calcify at rates that are comparable to or faster than those living in more average tropical waters of *25°C (Smith et al 2007;Lough and Cantin 2014). In other cases, there may be no clear optimal temperature for a given reef habitat (e.g., Putnam and Edmunds 2011).…”

“…Numerous studies have already examined the community structure (Craig et al 2001;Riegl et al 2001), physiology (Smith et al 2007;Putnam and Edmunds 2011), and/or genomics (Oliver and Palumbi 2009;Barshis et al 2013) of corals living in various high-temperature environments. In the present study, we measured seasonal changes in the calcification rates of three coral species: the branching Acropora aspera, the flabello-meandroid Trachyphyllia geoffroyi, and the massive Dipsastraea favus, in both subtidal and intertidal environments over a 17-month period (April 2011 through September 2012; Fig.…”

Effects of pCO2 on the interaction between an excavating sponge, Cliona varians, and a hermatypic coral, Porites furcata

“…1) may be related to the biotic history of the corals. Putnam andedmunds (2011) andDufault et al (2012) demonstrated that corals from sites that experienced large daily fluctuations in temperature or pCO 2 were often unaffected by elevated levels of these parameters in experimental conditions. The P. furcata fragments used in this experiment were collected from a reef tract on Isla Pastores that, like most reefs inside the archipelago of Bocas del Toro, Panama, lies directly adjacent to a large mangrove habitat (<10 m distance).…”

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

“…Due to logistic constraints, all polyps were collected in a single day and kept under these conditions for 5-12 days for acclimation (PHILIPP;FABRICIUS, 2003;SAXBAY et al, 2003;WINTERS et al, 2009;KUGURO et al, 2010;PUTNAM;EDMUNDS, 2011) prior to the experiments. They were monitored visually once a day and the F v /F m verified prior to the start of the experiment in order to demonstrate the health of the samples.…”