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Regeneration functions and microbial ecology of coral reefs

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Item Summary

Title: Regeneration functions and microbial ecology of coral reefs
Authors: DiSalvo, Louis H.
Issue Date: May 1905
Publisher: University of North Carolina, Chapel Hill
Citation: DiSalvo, Louis H. Regeneration functions and microbial ecology of coral reefs. Chapel Hill, NC: University of North Carolina, 1969.
Abstract: Rapid rates of production and consumption on coral reefs have been
indirectly measured by several investigators who suggested the existence
of rapid regeneration rates in these ecosystems. During 15 months in
1967-68 I attempted to characterize mechanisms and rates of regenerative
functioning in coral reefs at Kaneohe Bay, Oahu, Hawaii and Eniwetok
Atoll. Marshall Islands. Emphasis was placed on the study of bacteria
and other microorganisms based on their typically important regenerative
roles in other ecosystems.
Complex internal spaces in reef formations and non-living porous
coral skeletons appeared to be major sites of regenerative processing.
Dead coral heads were obtained from several reef stations and returned to
the laboratory for study of internally contained regenerative sediments.
Sediments were characterized by chemical and biological assays, and
results were compared between local stations as well as between the
two major study regions. Additional measurements were made on selected
fragments of reef regenerative mass (dead coral).
Eniwetok Atoll regenerative sediments contained less than 1% acid-soluble
residues, while similarly collected sediments from Kaneohe Bay
contained about 24% insoluble (terrigenous) residues. Station averages
for total sediment organic matter by ashing ranged from 6 to 12%, and
Kjeldhal nitrogen values ranged from 0.2 to 0.7%. Significant amounts
of soluble phosphorus and amino nitrogen were released from the dead head spaces during sediment recovery.
Regenerative sediments and adjacent skeletal substrates were
heavily populated by bacteria, diatoms, protozoa and meiofauna. Bacterial plate counts gave average values of 10 8 - 10 9 colonies per gram sediment.
Significant numbers of bacteria were chitin or agar digesting types.
Visual counts of diatoms gave values as high as 10 6 cells per gram dry
sediment, and were directly proportional to chlorophyll "a" content of
the sediments.
Bottle respirometry showed consumption of 0.06 to 0.50 mg 02 per g
dry sediment per hour. Characteristic mean values obtained for each
station appeared to be directly related to the wave and current energy
at each station. Antibiotics significantly reduced sediment respiration.
Respirometry of algal-encrusted dead coral fragments showed rapid
rates of production (P) and consumption (R). Antibiotic treatment of
these fragments interfered with their Rand P in a coupled manner.
Respirometry of entire dead heads showed that sediment respiration
accounted for about 10% of the total respiration in each head.
Bacteria were actively removed from water circulated over living
and dead coral heads in a laboratory reef simulation. Some infaunal
animals apparently digested bacteria that were removed from the water.
Observations on infauna of the regenerative system indicated an
active role in sediment production and processing, and in maintenance
of internal spaces. The infauna apparently acted in symbiosis with the
microorganisms to promote rapid organic breakdown processes. Total
organic matter, Kjeldahl nitrogen, terrigenous derivatives, and pheophytin
showed highest mean levels in sediments from Kaneohe Bay nearshore
heads, whereas bacterial counts, diatom counts, and sediment metabolism were highest in sediments from offshore heads. These comparative
differences were indications of stressed regenerative function
in nearshore reefs, possibly due to land-derived inputs.
Parameters measured for outer Kaneohe Bay were strikingly
similar to various measurements at Eniwetok, suggesting that regenerative function was similar in geographically separated reefs.
Some simplified energy diagrams for simulation suggest how
animals and microorganisms are coupled to perform effective mineral recycling and structural renewal of reefs.
Pages/Duration: 351 pages
Appears in Collections:Kaneohe Bay Research

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