Studies on phytoplankton () and zooplankton () of Galveston Bay, Texas, indicate decreased species diversity in the area near the Houston Ship Channel, which is heavily burdened with petrochemical as well as other toxic wastes. The effects of lowered salinity and other toxicants compound the picture, however, and the field evidence that chronic oil pollution affects planktonic communities is not complete. However, the experiments of Gordon and Prouse () indicate that photosynthesis in chronically polluted coastal waters may be affected.

Swimming animals may vacate an unfavorable area and thus avoid harm. Hence, fish may be absent or less diverse around refinery outfalls or bleedwater discharges (). This may effectively stop fishery productivity in certain areas, or at least reduce it ().

Among the shallow water ecosystems of the Texas coast those receiving oily wastes are characterized by lowered species diversity, large diurnal fluctuations in dissolved oxygen concentration, and sometimes near-anaerobic reducing conditions at the bottom (). Community metabolism—the combined amount and relationship of photosynthesis and respiration of the whole community—fluctuates wildly. Under some conditions, both photosynthesis and respiration are depressed by highly toxic materials; under others, metabolism is stimulated due to the decomposition of waste products and release of nutrients.

The effects of oil inputs from such land-based sources as domestic and industrial wastes and urban runoff have received even less attention. Farrington and Quinn () traced the cause of high concentrations of petroleum hydrocarbons in sediments and clams in Narragansett Bay, Rhode Island, to domestic sewage effluents. Clams from contaminated sediments there showed signs of physiological stress and abnormal growth (). Based on the analysis of sewage discharges in Southern California, Storrs () has estimated the total U.S. input of petroleum into the marine environment via sewage as 200,000 metric tons per year, an amount roughly equal to the worldwide loss from tanker accidents.