Marine microbiology is the study of marine life forms that cannot be seen with the naked eye, including viruses, bacteria, fungi, protozoa and microscopic algae. Representatives of each group have been found in almost every marine habitat examined, from tropical coral reefs to the Antarctic and the greatest depths of the ocean. Microbes occur in the water column and sediments, on the surfaces of marine plants, animals and inanimate objects, in the intestinal tracts of fishes and invertebrates and even within the tissues of other living things. There is a staggering diversity of forms and modes of life among marine microbes. Some require light for growth, many require the saline nature of sea water, while others can survive without oxygen.
Because of their small size, the importance of microbes to life in the oceans is often not appreciated. Knowledge of their activities assumes a new importance when one considers that each millilitre of sea water may be the home for millions of individuals, and each gram of sediment may support thousands of millions of microbes. Microbes play a crucial role in ocean food webs, which support the diversity of life in the sea. Scientists therefore study the microscopic plants that fix carbon dioxide, the bacteria which grow on the myriad of organic, inorganic, dissolved and particulate chemicals in the sea, and the protozoa which feed on them. In this way knowledge is gained about how each life form contributes to all levels of the food web.
Other microbiologists investigate the unique ways in which microbes change chemicals from one form to another, and the importance of this to the health of the oceans. For example, particular kinds of microbes carry out some steps in the cycling of nitrogen from a dissolved gas in the sea to proteins in plants, animals and microbes, to inorganic forms and finally back to a gas. Maintenance of this cycle is essential for life in the oceans.
Many aspects of marine microbiological research have the potential to provide practical information and to form the basis of new biotechnological developments. Microbiologists studying diseases of marine organisms are providing disease diagnosis and control strategies to those attempting to grow marine animals such as prawns, molluscs and fish. New chemicals with potential industrial applications, such as friction-reducing lubricants on the surfaces of some fish, have been found to be produced by marine microbes. Major efforts are also being put into the search for new pharmaceuticals from marine microbes, such as antibiotics and anti-cancer agents.
The incredible diversity of microbes, their wide distribution in marine habitats, metabolic capabilities and intimate involvement in processes occurring in the oceans ensures lifetimes of discovery for scientists. Research into the activities of microbes involves opportunities for collaboration with scientists from disparate disciplines such as botany, geology, zoology, chemistry and marine biology. Field work and laboratory analysis using traditional microbiological methods as well as sophisticated techniques such as DNA technology are all tools of trade for the marine microbiologist. Marine microbiologists require tertiary qualifications and are employed by universities, a variety of state and federal departments and instrumentalities, and by private industry.
Photos: (Top) A scientist collects water in a mangrove forest for microbiological analysis. (Bottom) Processing marine bacteria in the laboratory.