Ocean water is very salty. The amount of salinity in the ocean affects the buoyancy of an object. Scientists group types of ocean life by their marine environments. The three environments are plankton , nekton , and benthos . The food cycle in the sea begins with the plankton .
Plankton consists of two categories of organisms, phytoplankton and zooplankton .
Phytoplankton use sunlight, carbon dioxide, and nutrients to produce their own food. Phytoplankton are called producers . The zooplankton eat the phytoplankton. These plankton in turn become food for fish and other marine animals. These organisms are called consumers .