Investigation into the functional role of chromoproteins in the physiology and ecology of the Hawaiian stony coral Montipora flabellata in Kāne‘ohe Bay, O‘ahu

Richards Dona, Angela

Investigation into the functional role of chromoproteins in the physiology and ecology of the Hawaiian stony coral Montipora flabellata in Kāne‘ohe Bay, O‘ahu

Files

RichardsDona_hawii_0085A_10461.pdf (26.47 MB)

Date

2019

Authors

Richards Dona, Angela

Advisor

Hunter, Cynthia L.

Department

Marine Biology

Abstract

The distinctly purple, stony coral Montipora flabellata Studer is endemic to Hawai‘i and stands out in bright contrast among the muted brown tones of most other coral species on the reef. Its unique coloration is due to the presence of non-fluorescent pigment protein complexes called chromoproteins (CPs). CPs absorb light energy in the yellow region of the photosynthetically active radiation (PAR) spectrum, which is potentially harmful to the mechanism of electron replacement in photosynthesis. These pigments, however, are separate and distinct from the brown photosynthetic pigments in the symbiotic dinoflagellates (zooxanthellae). Colonies appear uniformly brownish purple suggesting a homogeneous surface distribution of CPs that are as well-distributed as the symbionts. Pigment location across the colony surface provides some insight into the potential functions these pigments serve, i.e., growth enhancement, photoprotection, or an immune response, but this topic has not been explored in Hawaiian coral species. Several common corals in Hawai‘i have been extensively researched, but no studies have looked specifically at CP or fluorescent pigment (FP) function, and very little research has been conducted on M. flabellata for any purpose. The principal goal of the present investigation was to determine whether CPs in M. flabellata serve a photoprotective function. Since photoprotection entails blocking light energy before it reaches the symbionts, the CPs would necessarily be located between the coral tissue/seawater interface and the zooxanthellae, i.e., in the coral epidermis. I employed the use of histological staining techniques, light microscopy, and confocal laser scanning microscopy to locate CPs and FPs in coral epithelia. The investigation expanded to include basic information on anatomy, photosynthetic efficiency, and habitat requirements for M. flabellata when a lack of fundamental information on the species was exposed. This research fills some of the gaps in our knowledge of this species and by comparison several other common species in Kāne‘ohe Bay. Entire reef surveys from 22 patch reefs provide updated information on the distribution of M. flabellata in the lagoon region of the Bay. Analysis of M. flabellata histoslides provide evidence of CPs in the epidermis and a highly reduced number or lack of mucocytes. This trade-off suggests CPs are more important than production of mucus in M. flabellata and is consistent with a photoprotective function. Whole coral reflectance measurements provide details of coral host and symbiont pigment absorbance in hospite, while they also highlight the challenges of working with an intact, biological system. Photosynthetic parameters; Fv/Fm, ETRmax, ΔNPQ, and Ek, were characterized from rapid light curves (RLCs) using pulse amplitude-modulated (PAM) fluorometry and provided valuable information that improves our understanding of the photo-physiological functioning of the species and its relationship to the light environment. Best practices for PAM fluorometry use are discussed in detail since this powerful tool was extensively utilized during the investigation and important lessons were learned.

Keywords

Biology, Physiology, Histology, chromoproteins, coral histology, coral photophysiology, Montipora flabellata, PAM fluorometry

URI

http://hdl.handle.net/10125/66236

Extent

191 pages

Rights

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Collections

Ph.D. - Marine Biology

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