We sought to determine whether the Indo-Pacific reef-building coral Seriatopora hystrix performs in a similar manner in the laboratory as it does in situ by measuring Symbiodinium density, chlorophyll a (chl-a) concentration, and the maximum quantum yield of photosystem II ( ) at the time of field sampling (in situ), as well as after three weeks of acclimation and one week of experimentation (ex situ). Symbiodinium density was similar between corals of the two study sites, Houbihu (an upwelling reef) and Houwan (a nonupwelling reef), and also remained at similar levels ex situ as in situ. On the other hand, both areal and cell-specific chl-a concentrations approximately doubled ex situ relative to in situ, an increase that may be due to having employed a light regime that differed from that experienced by these corals on the reefs of southern Taiwan from which they were collected. As this change in Symbiodinium chl-a content was documented in corals of both sites, the experiment itself was not biased by this difference. Furthermore, increased by only 1% ex situ relative to in situ, indicating that the corals maintained a similar level of photosynthetic performance as displayed in situ even after one month in captivity. 1. Introduction Molecular biology promises to yield insight into the subcellular mechanisms underlying the stable mutualism between reef-building scleractinians and dinoflagellates of the genus Symbiodinium [1, 2], as well as their macromolecular responses to changes in their environment [3–5]. The latter topic is of particular interest given that global climate change (GCC)-driven temperature and pCO2 increases have been hypothesized to lead to more frequent coral bleaching events in the years to come [6]. Alongside other anthropogenic pressures, such GCC-derived threats have generated an urgent need to shift the monitoring of coral reef health from a retroactive process to a proactive one [7]. Assessment of reef health is currently conducted by visual surveys in which the number of dying or dead corals is quantified (e.g., [8]). However, such late-stage manifestations of health decline likely occurred well after the initial insult. An analysis of the expression or activity of subcellular biomarkers, such as stress genes and proteins, may allow for the determination of which corals are at risk from anthropogenic impacts on a proactive timescale. Such a monitoring approach could potentially allow for scientists and managers to work together to mitigate local-scale insults to reef stability, such as water pollution [9], prior to extensive
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