*****************************************************************
Mon  5 May 2003 11:14:54 -0400: Journal for accession number: 0001009
Created on:                    Mon  5 May 2003 11:14:54 -0400
By:                            Carla Forgy, SSMC3 4306, 713-3295 x184


Source:  Chlorophyll, nutrients and other profile data downloaded at on 06/04/03 by Hernan Garcia from 
http://www.lodyc.jussieu.fr/gepco/gepco.html, data downloaded from ftp site from:

Yves Dandonneau
Laboratoire d'Océanographie Dynamique et de Climatologie
Tower 15, 2nd floor
Université Pierre et Marie Curie
4 place Jussieu
75252 Paris cedex 05
France

Abstract:
A set of phytoplankton pigment measurements collected on eight quarterly transects from France to New Caledonia is analyzed 
in order to identify the main assemblages of phytoplankton and to relate their occurrence to oceanic conditions. Pigment 
concentrations are first divided by the sum [monovinyl chlorophyll a plus divinyl chlorophyll a] to remove the effect of 
biomass, and second are normalized to give an equal weight to all pigments. The resulting 17 pigments × 799 observations 
matrix is then classified into 10 clusters using neural methodology. Eight out of these 10 clusters have a well marked 
regional or seasonal character, thus evidencing adapted responses of the phytoplankton communities. The main gradient 
opposes two clusters with high fucoxanthin and chlorophyll c1+2 in the North Atlantic in January, April and July, to three 
clusters in the South Pacific Subtropical Gyre with high divinyl chlorophyll a, zeaxanthin and phycoerythrin. One of the 
clusters in the South Pacific Subtropical Gyre has relatively high zeaxanthin and phycoerythrin contents and dominates in 
November and February (austral summer), while another with relatively high divinyl chlorophylls a and b dominates in May and
August (austral winter). The third one in the South Pacific is characterized by high carotene concentration and its 
occurrence peaks in February and May. In the equatorial current system, one cluster, rich in chlorophylls b and c1+2, is 
strictly located in a narrow zone centred at the equator, while another with relatively high violaxanthin concentration is 
restricted to the high nutrient – low chlorophyll waters in only the southern part of the South Equatorial Current. One 
cluster with relatively high prasinoxanthin content has a spatial distribution spanning the entire South Equatorial Current.
Two clusters have a ubiquitous distribution: one in the equatorial Pacific, the Carribbean Sea and the North Atlantic during
summer has pigment concentrations close to the average of the entire dataset, and the other in the South Pacific Subtropical
Gyre, the Carribbean Sea and the North Atlantic during autumn clearly has an oligotrophic character. Many of the differences
between clusters are caused by diagnostic pigments of nano- or picoflagellates. While the space and time characteristics of 
the clusters are well marked and might correspond to differences in physical and chemical forcing, knowledge of the 
ecological requirements of these flagellates is generally lacking to explain how the variability of the environment triggers
these clusters.

Data methods in /about directory "methods.pdf"

More information about this dataset can be found in the directory /about


GEP&CO = Geochemistry Phytoplankton and Color of the Ocean