Free-swimming, large and active life forms such as fish, corals and other attached organisms, burrowing animals, parasites, and microscopic animals are all of interest to the marine zoologist. Animals are found in a stunning variety of physical conditions everywhere in the sea, from above the high tide mark to the abyssal depths. Zoologists study animals at all depths, but given the enormous difficulty and expense of studying abyssal life, have concentrated their efforts close to the sea surface and the coast. Zoologists may study the biochemistry or physiology of animals in the laboratory or, with the advent of automatic data loggers and transmitters carried by the animals, in their natural habitat. Other zoologists study animal behaviour, genetics or ecology.
Ecologists study the numbers of and interactions between organisms at several levels.
They may concentrate on the dynamics of populations of particular species or communities of interacting species. An understanding of community dynamics and how species interact is vital in fisheries and in the management of marine ecosystems. Some marine ecologists investigate the movement of energy and molecules through ecosystems. They may work from major cities or from remote field stations in studying animals on coral reefs, rocky shores, sandy beaches, mudflats, and in mangrove forests or in seagrass beds. They also work in the laboratory sorting and processing samples, which usually requires identifying, counting and measuring animals, and analysing and interpreting data with the aid of a computer.