Theses and Dissertations

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Defense Date

1990

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Ocean Science

Department

Oceanographic Center

First Advisor

G. S. Kleppel

Second Advisor

Richard Dodge

Third Advisor

R. Snyder

Fourth Advisor

A. Szmant

Abstract

The purpose of this study was to assess whether phagotrophy may be proportionally more important to coral nutrition with decreasing light intensity. An animal carotenoid pigment, possibly astaxanthin, isolated from Montastrea annularis was used as an indicator of phagotrophy. This carotenoid was measured in corals collected over a depth transect in the field and in corals exposed to varying amounts of food and light in laboratory experiments.

In the field, multiple cores of the same and different coral heads were collected at each of four depths, 4.6, 7.6, 18.3 and 22.9 m. In the laboratory, cores from the same coral head were maintained at three light intensities (0.024, 24 and 90 μE m-2s-l) with three feeding schedules at each intensity (no Artemia, 2-3 Artemia/ml, and 8-10 Artemia/ml).

The pigments from the corals' symbiotic algae, zooxanthellae, and from the coral polyp were acetoneextracted and quantitatively isolated by reverse-phase, high performance liquid chromatography (HPLC). Parametric statistics were used to determine whether carotenoid concentrations in corals varied significantly with depth along the transect in the field, or with light intensity or particulate food concentration in the laboratory.

In the field, mean concentrations of the animal carotenoid increased significantly between 7.6 and 18.3 m over a depth range from 4.6 to 22.9 m. A significant increase in animal carotenoid concentration was also found when 4.6 and 7.6 m data were pooled and compared with pooled data from 18.3 and 22.9 m. This suggests the possibility of two populations.

In the laboratory, animal carotenoid concentrations increased significantly with decreasing irradiance. However, at each individual light intensity the absolute concentrations of animal carotenoid were similar no matter what the feeding regime. Between the light intensities of 24 and 0.024 μE m-2s-l animal carotenoid content increased in corals fed 8-10 Artemia/ml and in un-fed corals. That no difference was found between light intensities in corals fed 2-3 Artemia/ml may be because of the high variability observed in animal carotenoid content for this group.

The animal carotenoid content from combined field and laboratory data varied proportionally with the natural logarithm of light. It appeared that below approximately 200-400 μE m-2s-l (10% and 20% PAR) the rate of change in carotenoid content increased with respect to light.

The animal carotenoid:peridinin ratio may reflect the relative importance of phagotrophy to coral nutrition. The ratio increased with depth with one exception.

In conclusion, the carotenoid isolated from the coral polyp increased with decreasing irradiance. This increase may result from a carotenoid-rich diet. Such an increase may reflect an increase in phagotrophy.

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