San Francisco Bay is much cleaner than it used to be, although part of the reason for that is it is so turbid that excess phytoplankton production does not happen in spite of high nutrient concentrations. Oil spills and leakage Catastrophic oil spills like Exxon Valdez make a big news splash, and there is a lot of attention to the cleanup process. They can produce a huge amount of damage, especially in intertidal zones, marshes, and other areas where the oil tends to collect. The Exxon Valdez spill probably had a substantial effect on local salmon fisheries. Subsequent inspections of the beaches cleaned up and those left alone revealed more lasting damage at the cleaned beaches.
Different compounds behave differently and have different effects.
For example, metals tend to be taken up by plants and passed up the food chain, but they also tend to bind with sediments and stay around a long time. Slow seeps and leakage may not be as newsworthy but puts much more oil in the ocean than the big spills. These sources are much harder to track and police, and politically more difficult to solve. Any beach or shoreline, particularly in heavily-used areas, is covered with a litter of plastic trash. Although much of this rubbish is merely unsightly, it can also cause harm to marine life.