Giant clams (Tridacninae subfamily) are prominent members of Indo-Pacific corals reefs,
including the Red Sea, where they play multiple roles and are of distinct ecological significance
for these communities. Tridacninae stand out among other bivalves as one of the few molluscan
groups that live in a symbiosis with dinoflagellate Symbiodiniaceae. This relationship is
comparable to the symbiosis of corals and their associated algae, where the symbionts provide
a substantial amount of the respiratory carbon demand of the host through their photosynthetic
activity. Their photosymbiosis restricts the distribution of the Tridacninae holobiont (i.e. giant
clam host, symbiotic algae and associated bacteria) to the sunlit, shallow waters of the euphotic
zone, where organisms receive sufficient incident light to maintain their high rates of primary
production and calcification. However, giant clams in these shallow reefs are simultaneously
exposed to potentially high and damaging levels of solar (UV) radiation.
This thesis includes research on the Red Sea Tridacna spp. holobiont from an ecosystem to
microscale level. It assess the abundance and distribution of Red Sea giant clams, including
their associated symbiotic microalgae and bacterial microbiome. Further, it describes the strong
light-dependency of calcification and primary production of Red Sea Tridacna maxima clams
and reports on the effective photo-protective mechanisms that have been evolved by these
clams to thrive in shallow reefs, despite levels of high solar irradiance. Tridacninae developed
effective behavioral mechanisms for photo-protection, by which the clam is able to flexibly
adjust its shell gaping behavior to incident light levels within a narrow time frame. On a
microscale, Tridacninae use advanced photonic structures (iridocytes) within their tissues to
mitigate the potential negative effects of high solar UV radiation, and to promote the
photosynthesis of their symbiotic algae.
Understanding the role of the Tridacna spp. holobiont for Red Sea coral reefs, its contributions
to overall productivity, and its abundances in the region may serve as a baseline for further
studies on this charismatic invertebrate. It may also contribute to the conservation efforts from
local to regional scales, and eventually aid the protection of Tridacninae in the Red Sea and
elsewhere.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/666999 |
| Date | 01 1900 |
| Creators | Rossbach, Susann |
| Contributors | Duarte, Carlos M., Biological and Environmental Sciences and Engineering (BESE) Division, Voolstra, Christian R., Daffonchio, Daniele, Benzoni, Francesca, Todd, Peter A. |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
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