Kuwait Bay being shallow and eutrophic can sustain rich phytoplankton growth. The Bay ecosystem is severely stressed mostly due to urbanization, shipping, and dual-purpose desalination power plants. Hydrographical conditions (1995/96) in the surface waters show averages ranging from: temperature 14.20 - 30.23 deg. C, 34.80-40.70 psu, oxygen 2.06-6.21 ml/l, and nutrients (ug-at/l) 0-3.21, NH3-N, 0.06-9.03 NO3-N, 0.01-1.15 PO4-P, 9.45-36.26 SiO3-Si. Phytoplankton biomass ranged between 1.81-18.91 ug Chl a/l with 3 ug Chl a/l during August to October. However, during September and October 1999, although the hydrographical conditions were seasonal, thirty tonnes of surface feeding wild mullets and 150 tonnes of caged sea bream died. Out side the cages there were broken patches (10 m x 3 m) of discoloration caused by the benign diatoms Chaetoceros curvisetus, Nitzschia longissima, and the ciliate Mesodinium rubrum. Some of the patches had 3 to 15 million cells/l of the dinoflagellate Gymnodinium sp., suspected toxigenic, and yielded chlorophyll a concentrations from 10 to 265 ug Chl a/l. Confirmatory data on the identity of the suspect toxigenic organisms, nature of the toxin, bioassay, total quantity of toxin delivered, not available, but are crucial before implicating the ephemeral algal patches as causative agents of fish kills. Of interest is a mauve colored patch of unknown origin 500m wide, 1m thick and 5km long with no abnormal levels of phytoplankton. Gills of cultured sea bream yielded levels (ug g-1) of As (20-24), Fe (274-987), Ni (7-13.5), Cu (18-31) and Zn (45-252) much higher than the corresponding 4, 36, 1.6, 1.9, and 15 in the gills of wild sea bream. The Se:Ni, Fe:As, Fe:Ni, Zn:Pb ratios in the gills were higher than those in wild fish. The plausible compounding role of these metallic elements causing mass mortality of fish is discussed.