Distribution of phytoplankton biomass and abundance in the Arabian Gulf and the Sea of Oman

A study of the chlorophyll-a concentrations together with biodiversity of phytoplankton community based on basin-wide survey during regional cruise in February-March 2006 evaluated the spatial distribution in the Arabian/Persian Gulf (hereafter the Gulf) and the Sea of Oman (SO) during the productive early spring season.

Chlorophyll-a and pheophytin concentrations in water samples were measured using in vitro method with fluorescence detection. Almost four hundred species of phytoplankton were enumerated and identified in the same samples using microscopy. The relationships between the concentrations of satellite remotely sensed chlorophyll (SeaWiFS and MODIS spectroradiometers) and laboratory in-vitro measured chlorophyll-a were found to be generally in good agreement. However, the chlorophyll concentrations assessed as in-vivo fluorescence measured by submersible fluorometer were considerably lower.

The average concentration of in vitro measured surface chlorophyll-a in the studied area was 2.5±2.16 mg/m³, with the maximum 9.45 mg/m³ in the northwestern part of the SO. Several zones demonstrated low chlorophyll (< 1 mg/m³), with the highest concentrations (> 4 mg/m³) observed in the central part of the Gulf, in the Strait of Hormuz, and in the SO. The chlorophyll concentration in the northwestern nearshore Gulf waters affected by Shatt Al-Arab River reached 3.58 mg/m³. High phytoplankton abundance was associated with diatom-dominated phytoplankton blooms in the central and northwestern part of the Gulf, in the Strait of Hormuz and in the SO.

The main outcome of this study was that this is the first data set of in-vitro chlorophyll concentrations, phytoplankton abundance and diversity obtained from the entire region of the Gulf and the SO, which can be used for remote sensing measurements validation.