Database on the atolls

• Biogeochemichal database on the water column 

Persons wishing to consult this database are requested to kindly contact either of the two site editors, Loïc Charpy and Philippe Dufour, Loïc Charpy et Philippe Dufour.

 

Data were collected on 12 atolls in the framework of the CYEL and TYPATOLL projects and presented in 2 files:

·        the file entitled bdcesh.htm corresponds to the wet season (November)

·        the file entitled bdcess.htm corresponds to the dry season (March)

 

Codes used: INT: integrated sampling covering 10 m at a time with an integration belljar NO23 : NO2 + NO3 Z Int PI : integration depth as far as the primary production is concerned Prod I : Primary Production Zpk: Zooplankton

• Morphometric database on 49 Tuamotu atolls scanned with the SPOT imaging procedure

Persons wishing to consult this database are requested to kindly contact the author, Serge Andréfouet.

 

This file, entitled atolltot.htm, contains information about a number of parameters.

 

Codes used: Rimi : Percentage of the atoll ring corresponding to the Rimi  type. Ouvi : Percentage of the atoll ring corresponding to the Ouvi type. Perimeter: perimeter of the atoll at the level of the reef ridge. Area: total surface are of the atoll. Lagoon Area: surface area of the lagoon. Protection: an index giving an estimate of the level of protection from the predominant southerly sea swell.  An atoll can be protected either by another atoll, or if it is located in the very north of the archipelago. We have adopted a semi-quantitative scale of protection ranging between 0 (highly protected) and 1 (highly exposed). Mean latitude and longitude: means of the digitised coordinates around the perimeter of the atoll. The atoll perimeters were digitised by Lydie Sichoix. Shape: The shape of the atolls was expressed using Miller's Circularity Ratio: Shape=Area/(2pPerimeter2) An atoll with a circular shape will obtain an index of approximately 1. This index tends towards 0 with atolls having oblong or complex shapes. Stoddard (1965) has pointed out that this index is not very suitable for use with crenellated objects. We calculated the fractal value of the coasts of several atolls using the counting box method. The maximum value was obtained with Marokau, an atoll with a rather complex shape, which rated only 1.1. This shows that the atolls in general have a fairly smooth perimeter. FactAllong: an index ranging between 0 and 4,  which gives an indication as to whether the position of an atoll is east-to-west (1), north-east-to-south-west (2), north-to-south (3), north-west-to-south-east (4), or corresponds to no particular direction (0). SomLinMax: sum of the linear apertures, including the immersed and inter-tidal parts. SomLinMin: sum of the linear apertures including only the immersed parts. SomLinMax%: ratio between the SomLinMax and the Perimeter SomLinMin%: ratio between the SomLinMin and the Perimeter Log(Lmax): value of the base 10 (common) logarithm of SomLinMax% Log(Area): value of the base 10 (common) logarithm of the Area Log(LagArea): value of the base 10 (common) logarithm of the Lagoon Area Dufour aperture index: an index of aperture proposed by Philippe Dufour, which has been used up to now in the Typatoll studies. This is a weighted index based on both the SomLinMax% and the SomLinMin%. Log(DufourApInd): value of the base 10 (common) logarithm of the Dufour Aperture Index.