Effects of crude oil treated seawater on the metabolism of phytoplankton and seaweeds

Abstract

Prudhoe Bay crude oil was applied to natural populations of phytoplankton from Port Valdez, Alaska to examine its effect on photosynthesis. Studies were made at various times between July 1971 and June 1972., at oil concentrations ranging from about 0.001 - 10 ppm, and under various conditions of temperature, light and exposure time. Varying degrees of photosynthetic inhibition and stimulation were observed, apparently resulting from a complex interaction of physical, chemical and biological factors and the amount of oil present. Inhibition of photosynthesis occurred at oil concentrations of 0.06 ppm or greater during June, with stimulation observed at about 0.003 ppm. Light levels above 0.2 ly/min, 25% of full natural light intensity in April, caused a reduction in photosynthesis at about 0.03 ppm. Variations in temperature affected the degree of oil toxicity to phytoplankton. At 1 - 2 ppm photosynthesis decreased with increasing temperature (5 - 20 C) in March while in April photosynthesis was optimum between 10 - 15 C. The species composition was significantly altered by a 48-hour exposure to oil, showing an increase in Phaeocysti pouchetii and a decrease in Thalassiosira nordenskioldii. The photosynthetic response of 8 species of seaweeds were tested at different oil concentrations. Both inhibition and stimulation of photosynthesis were observed. The green algae Cladophora stirrrpsonii, Enteromorpha intestinalis and Ulva fenestvata appeared to be most adversely affected by oil.