Investigating the Effects of High Light Versus Low Light in Two Different Types of Symbiodinium within the Reef-Building Coral, Acropora Millepora
Date
2015-05
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Publisher
University of Delaware
Abstract
Coral reefs are invaluable ecosystems upon which a massive number of coastal
organisms rely, including human communities. The reefs themselves are composed
primarily of colonial organisms, and the vast majority of their energetic budget is
provided by glucose-rich photosynthate derived from their endosymbiotic
dinoflagellates (genus Symbiodinium). Here, two different types of Symbiodinium
were investigated, Symbiodinium C1 and D3, within the same species of Indo-Pacific
coral, Acropora millepora, which was acclimated to either high- (1000 μmol quanta
m-2 s-1) or low-light (100 μmol quanta m-2 s-1) conditions. Samples were analyzed by
means of traditional coral metrics, biochemical composition, and targeted gene
expression in order to gauge differences in photoacclimation mechanisms between the
two symbiont types, as well as to better understand each alga’s respective role in
holobiont health and photobiology. The coral harboring the D3 symbiont had higher
levels of protein and carbohydrate, as well as increased expression for genes that
encode an intracellular carbonic anhydrase, GAPDH, and glutamine synthetase, all of
which were higher under the high-light treatment. In contrast, extracellular carbonic
anhydrase expression was greater in the coral hosting the C1 symbiont, under highlight-
acclimation. Average chlorophyll a concentration was greater in Symbiodinium
C1 than D3, and the photosynthetic and respiratory data suggest that the coral hosting
Symbiodinium D3 may have a higher respiratory demand. These findings, in
conjunction with previous studies, provide a continued groundwork for understanding
both symbiont diversity and the role that members of Symbiodinium play in the health
of their host.
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Keywords
Marine Science