The influence of dissolved petroleum hydrocarbon residues on natural phytoplankton biomass

Abstract

The effect of dissolved petroleum hydrocarbons in the environment on phytoplankton biomass measured as chlorophyll a was studied near the oil tanker route in the southern Bay of Bengal. In the transect from 5 degrees N, 77 degrees E to 5 degrees N, 87 degrees E the concentrations of dissolved petroleum hydrocarbons were negatively correlated with phytoplankton biomass, whereas in the 0 degrees N, 87 limit of E to 1 degree N, 79 degrees E transect they were positively correlated with phytoplankton biomass. The mean petroleum hydrocarbon concentrations in the two transects were 12.12 plus or minus 4.67 mu g litre-1 and 11.23 plus or minus 4.5 mu g litre-1, respectively. It is surmised that the effect of dissolved petroleum hydrocarbons on phytoplankton biomass varies depending on the nature rather than the quantity of petroleum hydrocarbons present. Culture studies with unialgal Nitzschia sp. in seawater collected from selected stations in the study area as well as in artificial seawater spiked with the water soluble petroleum hydrocarbon fraction of light Arabian Crude support this