Photoacclimation of Stylophora pistillata to light extremes: metabolism and calcification

Abstract

The hermatypic coral Stylophora pistillata has a wide bathymetric distribution (0 to 70 m). Within this range, light intensity decreases exponentially. Deep-water colonies are generally planar in morphology, with the upper part being dark and the bottom-facing part pale. Shallow-water colonies are generally subspherical and ivory in coloration. We studied the effects of photoacclimation on photosynthesis, respiration, and calcification in S. pistillata colonies along its bathymetric range over a reef profile (5 to 65 m) in Eilat, Gulf of Aqaba, Red Sea, during winter and summer, using a submersible respirometer. Respiration rate, light-saturated rate of photosynthesis (P max ), compensation light intensity (E c ), and light intensity of incipient saturation (E k ), all decreased with depth. In contrast, the efficiency of photosynthesis (α) increased with depth. All colonies displayed 'lightenhanced calcification' during daytime and decreasing calcification rates with depth. These results indicate an adjustment in harvesting and utilization of light by the algal symbionts to the light environment. At all light intensities except the lowest ones, there was a consistent ratio of calcification to photosynthesis, in agreement with the concept of light-enhanced calcification. In the deepest, lowlight corals, there was no evidence for support of calcification by photosynthesis, and we assume that these colonies subsist mainly by preying on zooplankton.

Variation in photosynthesis and respiration in ­geographically distinct populations of two reef‑building coral species

“…Coles & Jokiel 1977), the effect of spatial differences in irradiance are not. However, Mass et al (2007) found that rates of photosynthesis and dark respiration decreased with increasing depth (and decreasing irradiance) over a 70 m depth gradient. A study by Cooper et al (2011) confirmed this pattern but also found that a depth-related shift in Symbiodinium type in the coral Seriatopora hystrix over similar depths correlated with a non-linear response in the photosynthesis: respiration ratio.…”

“…While the interaction between Symbiodinium type and patterns of photosynthesis and respiration activity has been investigated over local-scale depth gradients (Mass et al 2007), our understanding of such patterns of variation at larger spatial scales is currently limited. However, a recent study by Hennige et al (2010) of the photosynthesis and respiration activity of corals across an environmental gradient of temperature, light and turbidity confirmed that metabolic rates were governed by acclimatisation to the local environment coupled with adaptation, which was manifested through a shift in Symbiodinium clade for one of their study species.…”

Nutritional status and metabolism of the coral Stylophora subseriata along a eutrophication gradient in Spermonde Archipelago (Indonesia)

“…In low light and nutrient-replete conditions, photoacclimation increases the photosynthetic efficiency in corals (Dustan 1982;Mass et al 2007;Hoogenboom et al 2009) by increasing the areal pigment (e.g., chl a) and light harvesting protein concentrations (Dubinsky et al 1990;Titlyanov et al 2001). The efficiency of the photosystem is proportional to the light absorbed by the photosystem II in the chloroplasts.…”

Modelling coral calcification accounting for the impacts of coral bleaching and ocean acidification

“…the amount of solar radiation incident to the Earth's surface (kW m −2 day −1 ; see equation in the Appendix). Photosynthesis-irradiance (P − I ) curves for corals have been extensively studied, and how their parameters change with local light environment has been well established (Anthony and Hoegh-Guldberg, 2003a;Chalker et al, 1983;Dubinsky et al, 1984;Mass et al, 2007;Porter et al, 1984). These studies show that there is a strong decrease in the saturation intensity as ambient light levels decrease, which corresponds to an increase in the efficiency of photosynthesis.…”

“…Nevertheless, there is evidence that this assumption holds when considering the community average of a coral living in typical reef conditions. For example, Mass et al (2007) reported constant rates of photosynthesis and calcification at 5 and 10 m depths despite a 50 % reduction in ambient light levels, and Hennige et al (2008) demonstrated that Porites lutea from two sites and multiple depths regulates how much light is absorbed in order to maintain a constant load on its photosystem.…”