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Demographics, conservation, and optical properties of giant clams (Subfamily: Tridacninae) in Palau
Dissertation   Open access

Demographics, conservation, and optical properties of giant clams (Subfamily: Tridacninae) in Palau

Lincoln Rehm
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2023
DOI:
https://doi.org/10.17918/00001713
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Abstract

Wildlife conservation
Giant clams are known for their unique obligatory symbiosis with the dinoflagellate Family Symbiodiniaceae. Giant clams have enhanced this photosynthesis by developing iridocyte cells to scatter light towards the algae, or zooxanthellae, and by arranging the zooxanthellae in algal pillars. However, giant clams continue to be impacted by both poachers, because of their brightly colored mantle, and changes in their environment. This dissertation focuses on three important areas of giant clam ecology. Here I examine the population demographics of giant clams across the Palauan archipelago, where we found a new record for T. noae. I quantified giant clam mantle hues into three bins: yellow, blue, and green and found that mantle hue varies across a clam's ontogeny. I tested whether there is a relationship between reef habitat and mantle hue. I also compared the absorption of light in clams to a similar system, coral reefs. Finally, I tested whether natural variations in nutrients or light levels can impact the clam's mantle hue and then used a novel approach to characterize the algal pillars within the mantle tissues across the same abiotic variables. The findings of this work suggest that conservation methods in Palau have promoted populations of giant clams and these same clams are among the most photoefficient organisms on the reef. This work developed new methods for large-scale sampling of giant clam hue and algal pillars while also generating new hypotheses for future work on giant clam ecology.

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