Marine botany involves the study of a broad range of organisms including flowering plants, algae and fungi. With the exception of fungi, these organisms are all photosynthetic and are therefore restricted to the well-lit upper ocean and inshore regions. Life in the oceans is almost entirely dependent on these photosynthetic organisms, which are known as primary producers.
Different kinds of primary producers occur in different marine habitats. In the open ocean the producer organisms are minute, often single-celled, algae called phytoplankton, while larger attached seaweeds, seagrasses, saltmarsh plants and mangroves usually dominate the shallower waters of coastal and estuarine regions.
Some research focuses on the organisms themselves. Examples include investigations of the evolutionary relationships and classification of marine algae and plants using techniques such as molecular biology and ultrastructural research, studies of basic physiological processes such as salt tolerance and photosynthesis, and cataloguing the biodiversity of the unique Australian marine flora.
The ecological relationships of marine plants are studied to understand fundamental processes such as succession and competition, the formation of population 'outbreaks' or blooms, ecosystem productivity, the transfer of energy to higher levels in food webs, and the role of algae in nutrient cycling. Plants play particular roles in specific environments, for example seagrasses and mangroves help to stabilise shorelines, and calcareous algae are major contributors in the formation of coral reefs. Interactions between organisms such as competition, consumer interactions, symbioses, and the production of chemicals that influence the behaviour of grazers or settling larvae also attract considerable attention. At the global level there is great interest in the influence of phytoplankton on world climate and their use as indicators of climatic change.
The role of algae and other marine plants is vital to studies of conservation, human impact, environmental change, and management of the marine environment. This is especially the case in relation to the effects of excessive nutrients, algal blooms, and the effects of red tides on human health. Marine plants also serve as indicators of environmental degradation.
Another important focus in marine botany is the use of marine plant communities as a source of food and shelter for commercial fish and prawns. This interest extends to the culture of microalgae as an essential source of animal food in mariculture. Algae are also mass cultured for human consumption, food additives (colouring and gelling compounds), fodder, pharmaceuticals, and other fine chemicals.
Marine botanists are employed in research or management in universities, departments of agriculture and fisheries, museums, maritime services, water boards, sewerage and drainage boards, the CSIRO, institutes of marine science, and environmental agencies. There are also growing private industries in the areas of environmental consultancy services, mariculture and marine chemistry.
Photo: Diver conducting research in seagrass beds in Western Australia.