Journal Article

Dissolution of Dead Corals by Euendolithic Microorganisms Across the Northern Great Barrier Reef (Australia)

Aline, Tribollet

2008

Overview

Spatial and temporal variabilities in species composition, abundance, distribution, and bioeroding activity of euendolithic microorganisms were investigated in experimental blocks of the massive coral Porites along an inshore-offshore transect across the northern Great Barrier Reef (Australia) over a 3-year period. Inshore reefs showed turbid and eutrophic waters, whereas the offshore reefs were characterized by oligotrophic waters. The euendolithic microorganisms and their ecological characteristics were studied using techniques of microscopy, petrographic sections, and image analysis. Results showed that euendolithic communities found in blocks of coral were mature. These communities were dominated by the chlorophyte Ostreobium quekettii, the cyanobacterium Plectonema terebrans, and fungi. O. quekettii was found to be the principal agent of microbioerosion, responsible for 70-90% of carbonate removal. In the offshore reefs, this oligophotic chlorophyte showed extensive systems of filaments that penetrated deep inside coral skeletons (up to 4.1 mm) eroding as much as 1 kg CaCO₃ eroded m⁻² year⁻¹. The percentage of colonization by euendolithic filaments at the surface of blocks did not vary significantly among sites, while their depths of penetration, especially that of O. quekettii (0.6-4.1 mm), increased significantly and gradually with the distance from the shore. Rates of microbioerosion (0.1-1.4 kg m⁻² after 1 year and 0.2-1.3 kg m⁻² after 3 years of exposure) showed a pattern similar to the one found for the depth of penetration of O. quekettii filaments. Accordingly, oligotrophic reefs had the highest rates of microbioerosion of up to 1.3 kg m⁻² year⁻¹, whereas the development of euendolithic communities in inshore reefs appeared to be limited by turbidity, high sedimentation rates, and low grazing pressure (rates <0.5 kg m⁻² after 3 years). Those results suggest that boring microorganisms, including O. quekettii, have a significant impact on the overall calcium carbonate budget of coral reef ecosystems, which varies according to environmental conditions.

• Publisher: New York : Springer-Verlag,Springer Science + Business Media, Inc,Springer-Verlag,Springer,Springer Nature B.V
• Subject: Animals / Anthozoa / Anthozoa - chemistry / Anthozoa - microbiology / Australia / Barrier reefs / Biodegradation, Environmental / Biodiversity / Biological and medical sciences / Biomedical and Life Sciences / Calcium / Calcium carbonate / Calcium Carbonate - chemistry / Calcium carbonates / Carbonates / chemistry / Chlorophyta / Chlorophyta - metabolism / Community composition / community development / Coral reef ecosystems / Coral reefs / Corals / Cyanobacteria / Ecology / Ecosystem / ecosystems / Environmental conditions / environmental factors / Environmental Monitoring / Eutrophic environments / Eutrophic waters / Eutrophication / Filaments / Fundamental and applied biological sciences. Psychology / Fungi / Fungi - metabolism / Geoecology/Natural Processes / Geographical distribution / Great Barrier Reef / Image analysis / Image processing / interspecific variation / Islands / Life Sciences / metabolism / Microbial Ecology / Microbiology / Microorganisms / Microscopy / Nature Conservation / Offshore / Oligotrophic waters / Original Article / Ostreobium / Ostreobium quekettii / Penetration depth / Plectonema / Plectonema - metabolism / Population Dynamics / Reefs / Seawater / Seawater - microbiology / Sedimentation rates / Skeleton / Snapper / Species composition / species diversity / Surface areas / temporal variation / Turbidity / Water Microbiology / Water Quality/Water Pollution