Sea-floor minerals, fisheries, coastal pollution, global warming, and hydrothermal processes are among the many subjects in oceanography which may be studied from a chemical point of view. Marine chemistry, however cannot be learned independently of other processes. The chemistry, biology, geology, and physics of the sea are interrelated. One of the many examples of the interdisciplinary nature of ocean science are the red tides that occur with increasing frequency in coastal waters, threatening shellfish and human health.
Red tides are dense blooms of certain toxin-producing algae.
Some scientists argue that the blooms are triggered by changes in water chemistry, specifically, in the relative amounts of nitrogen, phosphorous and silicon present in seawater. Once the chemical stage for the bloom is set, the sediment bottom can play an important supporting role. The cysts may be thought of as the 'seeds' that are the starting material for the bloom. The geographic extent and duration of a red tide are also moderated by circulation patterns in the affected area. Finally the chemistry of the water within the red tide is itself altered by the algae as the bloom progresses.