To compare atoll lagoon POM concentrations, we used data collected from sixteen atolls during various expeditions (TATU expedition in November 1985, TYPATOLL expeditions in November 1995 and March 1996), from  16 surveys performed in Takapoto between 1991 and 1992 and from 15 surveys performed in Tikehau between 1982 and 1987. To remove the sampling time effect and decrease the seasonal variability, we only used data obtained from sampling performed in the morning and during the months of March and November.

Four atoll lagoons (Rangiroa, Reka-Reka, Taiaro and Tikehau) presented a higher POC content (» 200 mg m^-3) and one (Tekokota) a POC concentration close to oceanic level (» 50 mg m^-3). Other atolls presented intermediate POC concentrations. The high POC concentration observed in the Reka-Reka lagoon can be explained by the resuspension of benthic microphytes and detritus due to the shallowness of the lagoon (1.5 m). 

Indeed, Dandonneau & Eldin (1987) considered that the position of the transition between the waters deriving from the Peruvian and equatorial upwellings, and the oligotrophic waters of the central Pacific varies between 5 and 17°S. These authors used sea-surface chlorophyll sampling carried out by merchant ships on the Tahiti-Panama track. Between December 1979 and September 1985, the Tuamotu atolls were observed to be reached by upwelling-derived waters on 14% of the 118 transects. They considered that the influence of rich waters on Tuamotu might help to explain the anomalous abundance of life on these atolls.

 Occasional incoming of rich water inside northern atoll lagoons may produce an increase in the lagoon primary production and therefore an increase in the POC standing stock. The average Takapoto lagoon POC concentration is largely below the regression fit. Takapoto, located in the north of the Tuamotu Archipelago, has no deep passage linking the lagoon and the ocean and a large residence time (4.3 yr). Therefore, the effects of oceanic waters derived from the upwellings would be lower in this lagoon than in open atoll lagoons. In addition, the presence of numerous cultivated pearl oysters and other filter feeding organisms in Takapoto lagoons could be responsible for the relative low POC content. 

Reference

Dandonneau Y, Eldin G (1987) Southwestward extent of chlorophyll-enriched waters from the Peruvian and Equatorial upwellings between Tahiti and Panama. Mar Ecol Prog Ser 38: 283-294

This page was taken in part from:

Charpy L., Dufour P., Garcia N. (1997) Particulate organic matter in sixteen Tuamotu atoll lagoons (French Polynesia). Mar Ecol Prog Ser 151 : 55-65