Light limitation and distribution of chlorophyll pigments in a highly turbid estuary: The Gironde (SW France)

X. Irigoien*, J. Castel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

178 Scopus citations


Chlorophyll pigment and suspended particulate matter (SPM) concentrations were measured in two well-differentiated areas in the Gironde Estuary. The maximum turbidity zone (MTZ) was characterized by very high turbidities, low Chl a/SPM ratios and associated low variability of this ratio, and by a highly significant relationship between chlorophyll pigments (chlorophyll a and phaeopigments) and SPM. Seaward of the MTZ, where SPM concentration is lower, the relationship between Chl a and SPM disappeared during phytoplanktonic blooms, the values of Chl a/SPM ratio were higher and there was a high variability of this ratio. Data obtained from stations positioned along the salinity gradient indicate that the spatial distribution of Chl a/SPM ratio in the Gironde is explained by the relation between the mixing depth (Zm) and euphotic depth (Zeu). The estimate of the Zm/Zeu ratio suggests that there is virtually no possibility for phytoplankton primary production in the MTZ but cannot explain the presence of Chl a in very highly turbid areas (> 1 g l-1). An important percentage of the chlorophyll in the MTZ probably originates from re-suspended microphytobenthos. Photosynthetic activity is reduced as a consequence of light limitation due to high turbidities. This enables the ecosystem to contain a great input of nutrients without eutrophication.

Original languageEnglish (US)
Pages (from-to)507-517
Number of pages11
JournalEstuarine, Coastal and Shelf Science
Issue number4
StatePublished - Apr 1997
Externally publishedYes


  • Gironde Estuary
  • chlorophyll
  • euphotic zone
  • light limitation
  • mixing depth
  • turbidity maximum

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science


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