Goals of this investigation were: 1) Differentiate between the effects of
turbidity and sedimentation on corals. 2) Differentiate the effects of carbonate
and terrigenous sediments on coral growth and metabolism. 3) Develop a
predictive model relating increased sediment loading to the photosynthetic rate,
growth and survival of corals. 4) Evaluate the validity of the widely cited "10 mg
cut-off point" and determine the levels of turbidity and sedimentation that are
tolerated by corals. Earlier studies suggest that coral reefs decline when sediment loading levels exceed a sediment trapping rate of 10 mg cm-2 d-1 or a
turbidity of 10 mg I-1.
An integrated experimental design linked field and laboratory experiments.
In the field, corals were transplanted to sites with varying levels of sedimentation.
Turbidity, as linked to reduced light availability, had a significant affect on coral
growth and metabolism in laboratory experiments but not coral growth or survival
in field experiments. Turbidity in the field was highly variable and influenced
greatly by wind velocity and rainfall.
Terrigenous (or land-derived) sediments influenced light extinction more
than carbonate (reef-derived) sediments. In laboratory experiments turbidity was
more important than sediment trapping rate in affecting the photosynthetic ability
and growth rates of corals.
The predictive model stated that the lower the light level (as caused by
increased turbidity) the lower the photosynthetic production of corals. The model
was supported by results of laboratory experiments where conditions were precisely controlled and monitored. Under field conditions, the predictive model
did not hold due to extreme natural variability in sediment loading and variation in
a wide range of other environmental factors encountered at the experimental
sites.
Corals tolerated turbidity exceeding 120 mg I-1 and sediment trapping
rates in excess of 11 mg cm2 d-1. Sediment loading is correlated with other
environmental factors such as nutrient loading and reduced salinity. Composition
of sediment varies widely between different locations. The "10 mg cutoff may
prove to be useful in setting limits to vigorous coral reef development, although
individual corals or coral assemblages may be able to survive and grow at levels
exceeding this value. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. Includes bibliographical references (leaves 235-264).
| Identifer | oai:union.ndltd.org:UHAWAII/oai:scholarspace.manoa.hawaii.edu:10125/15323 |
| Date | 01 May 2001 |
| Creators | Te, Franklyn Tan |
| Publisher | University of Hawai'i, Honolulu |
| Source Sets | University of Hawaii at Manoa Libraries |
| Language | en-US |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 281 pages |
| Rights | All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner. |
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