The study of the organisms- from microscopic ones to the huge whales, that dwell in the ocean and other brackish water bodies (estuaries, wetlands), is known as Marine Biology. It covers all aspects of their life also – existence, physiology, genetics, behavior patterns and ecosystem, and relation with their environment.  

Because of its multidisciplinary nature, marine biology includes the study of chemistry, molecular biology and applied mathematics. Other essential elements of study are – astronomy, geology, meteorology, zoology, bio-geography, botany, anthropology, economics and marine law. And thus the specialization options are also quite a few. Here are some of the most significant of the branches of marine biology mentioned.

Aquaculture

Aquaculture is the art of breeding fish and other marine life in controlled environment. It is then used for study or research, and consumption. Technological discoveries and new techniques have made this field quite popular and economic. Harvesting and acculturation is a part of it. 

Molecular Biology

Molecular biology principles are being applied to different kinds of water bodies and environments, coastal ponds, deep sea, and to different organisms like microscopic bacteria, plants, marine animal etc. it is also used to identify the presence of organisms at a place. This is particularly useful if the organism is microscopic. It aids in finding the diseases that affect organisms, and the effect of pollutants on them. 

Ecology of Fishery

This is the study of the population dynamics, habitat, living and reproduction behavior and patterns, food habits etc of the organisms. 

Fishery Management

It is to research the impact of overfishing and habitat destruction of marine life, the effect of pollution and toxin on them, and inventing of ways to increase the population of organisms, especially where they are in scarcity. 

Ichthyology

This branch of marine biology deals with the study of all kinds of fishes found in all kinds of water bodies, both salt and freshwater species. It includes studying all about fishes – evolution, life cycle, habitat, ecology, reproduction, classification, morphology, and diversity. It is at times clubbed with the aquaculture. 

Marine Mammology

This is the study of the marine mammals, like dolphins and whales, sharks and pinnipeds (walrus, seals, sea lion). This is like Ichthyology, and thus studies all aspects of mammal life of the sea. 

Marine ethology

This field of study researches ways to protect the endangered marine species (by nature or man). 

Environmental marine biology

It is the study of the health of the ocean. The quality of marine environment affects the health of marine life. Pollutants and sediment are threats to the health of marine life in the coastal places. It is also the study of sea beds and pollutants there, effects of erosion and chemical dispositions, the impact of shipping, oil drilling and other sea activities.

Study of Protists

Protists are one celled marine organisms (protozoa and micro-algae). They are essential to maintain an ecological balance under the ocean. They serve as food for many species of marine organisms. So to study them and save them from extinction is important as their disappearance will affect the food cycle.

Deep-sea ecology 

Study of organisms that dwell in the deeper precincts of the ocean – the ocean floors and where the depth of the ocean is too great. These places are usually very dark. It is to study how these organisms survive there, their eating, living and reproductive habits, and the study of biological characteristics and the processes. 

Toxicology

This branch tries to determine the harmful effects of various toxins and chemicals on marine life that are present in the water bodies due to natural or man made causes and activities. This is one of the very essential areas of study as it affects fatally all marine life and environment. The discovering of symptoms of poisoning, and its treatment are part of this branch.