Analysis of the pattern of zonation of reef corals off
the Kona coast of Hawaii revealed the existence of four
clearly defined zones. This pattern was confirmed at three
sites where corals were counted using a series of 45 meter
long transects running parallel to shore from depths of 3 to
40 meters. Clustering analysis dendrographs, spatial changes
in illumination and rates of water movement, as well as
growth and survival of coral transplants also confirmed the
zonation pattern.
Each of the four zones is characterized by a dominant
coral species, substratum type, depth, and range of physical
conditions. Each zone also appears to be in a different stage
of community succession due to the frequency of large scale
environmental disturbances from winter storm waves.
The shallowest zone begins at the base of the shoreline
cliff, ranges in depth from 2.5 to 8 meters, and has a bottom
cover consisting mainly of irregularly shaped basaltic boulders;
Pocillopora meandrina dominates coral cover in this zone.
This species appears to be the first to colonize new substrata
and persists in large numbers only in the near-shore boulder
zone where mechanical stress from wave action is great enough
to restrict the growth forms of more competitive species.
Due to this high wave stress, the P. meandrina bolder zone
appears to be in an early successional stage with low coral
cover and dominance and relatively hiqh species diversity.
Moving into deeper water the Porites lobata reef
building zone ranges in depth from 6 to 14 meters and is
characterized by a gently sloping solid basalt and limestone
bottom. Porites lobata dominates coral cover by growing in
massive lobed and encrusting colonies. While succession
seems to be in an advanced stage, monopolization of available
space does not appear to be complete enough to exclude a
variety of less competitive species, resulting in relatively
high species diversities.
The third zone occurs on the reef slope and ranges in
depth from 14 to 30 meters. Solid substrata is scarce and
succession may be a late stage due to domination of bottom
cover by thickets of Porites compressa. Most of the other
species that persist in this zone avoid competitive interactions
by growing above the level of P. compressa. Storm
wave stress is most devastating to corals in this zone, and
breakage of living colonies seems to increase diversity by
reducing P. compressa dominance. Transport of living coral
fragments appears to extend zonal boundaries and create new
colonies. Extensive "rubble channels" occur in this zone,
and these channels may get progressively larger due to
churning of rubble fragments with each successive storm.
The Porites lobata rubble zone occurs below the deep border of the
P. compressa thickets and extends to approximately
50 meters, the depth at which coraIs cease to appear.
Substrata consists mostly of fine sand and a variety of small
encrusting corals are found growing on scattered rubble
fragments. Specialized species with narrow physiological
tolerances limited to this zone also increase species diversity.
While maximum size of corals may be reduced in this
zone due to low light intensity, lack of solid substrata
probably determines the lower depth limit of coral occurance.
Sand and rubble that is carried downslope during storms
cause this zone to be physically unstable and succession
appears to be constantly interrupted at early stages. This
is in contrast to other deep reef areas, such as off Maui
and the Red Sea, where substrata is solid to the depth limit
of coral growth. These communities appear to be highly
stable and diverse, and in late or climax stages.
The depauperate nature of Hawaiian coral fauna is
probably due to fairly rigorous environmental conditions in
combination with difficulties in larval transport from coral
evolutionary centers in the western Pacific. However, reef
areas off Kona are relatively rich for Hawaii due to complete
protection from tradewind generated seas, partial protection
from long period north swells, and the steep nearshore slopes
that extend below wavebase. / Typescript. Bibliography: leaves 173-181.
| Identifer | oai:union.ndltd.org:UHAWAII/oai:scholarspace.manoa.hawaii.edu:10125/18141 |
| Date | 05 1900 |
| Creators | Dollar, Stephen J. |
| Publisher | University of Hawaii, Honolulu |
| Source Sets | University of Hawaii at Manoa Libraries |
| Language | en-US |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 195 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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