Phosphorus pathways in atolls: interstitial nutrient pool, cyanobacterial accumulation and Carbonate-Fluoro-Apatite (CFA) precipitation
| Autor: | Francis Rougerie, J. Trichet, Caroline Jehl |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Mineralogy
UPWELLING BACTERIE Oceanography Sink (geography) Apatite chemistry.chemical_compound Nutrient Geochemistry and Petrology CARBONATE Organic matter ROCHE PHOSPHATEE ACCUMULATION chemistry.chemical_classification GEOLOGIE MARINE geography geography.geographical_feature_category Brackish water MATIERE ORGANIQUE fungi PHOSPHORE Geology NUTRIMENT Phosphate CYCLE GEOCHIMIQUE chemistry GEOCHIMIE PRECIPITATION Environmental chemistry visual_art Humin visual_art.visual_art_medium Carbonate ATOLL |
| Zdroj: | Marine Geology. 139:201-217 |
| ISSN: | 0025-3227 |
| DOI: | 10.1016/s0025-3227(96)00111-9 |
| Popis: | Significant dissolved phosphate concentrations were measured in reef interstitial waters and in small brackish ponds (free water and underlying interstitial water) occupying the emerged rim of the Tuamotu atolls, French Polynesia. These ponds are the sites of accumulation of organic matter of pure microbial origin, in the form of thick stromatolitic cyanobacterial mats called kupara by Tuamotu natives. The profiles of dissolved phosphate interstitial waters seem to show a positive trend with depth. Within kopara, the phosphorus pathway after biological uptake is studied by measuring the C and P concentrations in raw material and in humic substances (humin, fulvic and humic acids) in order to examine the liberation of P from organic matter. For comparison, the same analysis is led on the residual organic matter of phosphate samples from Mataiva deposit (Tuamotu). The results show a relative enrichment in phosphorus with age of kopara, and a similar distribution of humic substances in kopara and phosphate samples. Other work on hydrocarbons from kopara and phosphate samples demonstrates the strong relationship of these materials. If such evolution of organic matter can be observed in kopara ponds, it should be possible to generalize to closed atoll-lagoons which function as mega kopara ponds and where phosphorus-rich layers are present (e.g., the Niau atoll). The different steps leading to atoll phosphogenesis, viewed as phosphorus sink in cyanobacterial mats to final massive CFA accumulation, could then be rationally explained. The interstitial nutrient pool can be a necessary and sufficient factor to provide phosphorus for the kopara growth and accumulation. O Elsevier Science B.V. All rights reserved Keyvords: Interstitial nutrients; Cyanobacterial mats; Apatite precipitation |
| Databáze: | OpenAIRE |
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