The physical and chemical properties of Earth's oceans influence what types of organisms can live in certain areas of the ocean. Plant and animal communities have adapted to live in certain temperature and salinity conditions, with a lot or a little sunlight available to them, and in harsh intertidal conditions.

Pollution and changing sea levels greatly affect ecosystems, as well as human populations that live along the coast. Toxic chemicals and oil spills have caused a decline in the health and reproductive functions of organisms. Pollution has also led to the contamination of entire food webs, genetic mutations, and harms sensitive systems of the body such as the respiratory and digestive systems.