Trichodesmium

File:Trichodesmium erythraeum.jpg

File:Nitrogen fixation reaction.jpg

Trichodesmium

Trichodesmium is a genus of filamentous cyanobacteria that is found in nutrient-poor tropical and subtropical ocean waters. It is known for its ability to fix atmospheric nitrogen, which plays a crucial role in the marine nitrogen cycle. This genus is often referred to as "sea sawdust" due to its appearance when it forms large blooms on the ocean surface.

Taxonomy and Classification

Trichodesmium belongs to the phylum Cyanobacteria, class Cyanophyceae, order Oscillatoriales, and family Oscillatoriaceae. The genus was first described by Ehrenberg in 1830.

Morphology

Trichodesmium species are characterized by their filamentous structure, forming colonies that can be free-floating or aggregated into larger mats. The filaments, known as trichomes, are composed of a series of cells arranged in a linear fashion. These trichomes can be several millimeters in length and are often bundled together in a gelatinous matrix.

Physiology and Metabolism

Trichodesmium is a diazotroph, meaning it can fix atmospheric nitrogen (N₂) into ammonia (NH₃), a form of nitrogen that can be utilized by other organisms. This process is facilitated by the enzyme nitrogenase, which is sensitive to oxygen. Trichodesmium has developed a unique strategy to protect nitrogenase from oxygen: it spatially separates photosynthesis and nitrogen fixation within its cells.

Ecological Role

Trichodesmium plays a vital role in the marine nitrogen cycle, particularly in oligotrophic (nutrient-poor) regions of the ocean. By fixing nitrogen, it provides an essential nutrient that supports the growth of other marine organisms, including phytoplankton and zooplankton. This process contributes significantly to the productivity of tropical and subtropical ocean ecosystems.

Distribution

Trichodesmium is predominantly found in tropical and subtropical oceans, including the Atlantic, Pacific, and Indian Oceans. It thrives in warm, nutrient-poor waters and is often associated with regions of upwelling, where nutrient-rich deep waters are brought to the surface.

Blooms and Environmental Impact

Trichodesmium can form extensive blooms that are visible from space. These blooms can have significant ecological impacts, including altering local nutrient dynamics and affecting the composition of marine communities. While Trichodesmium blooms are a natural phenomenon, they can be influenced by anthropogenic factors such as climate change and nutrient pollution.

Research and Importance

Research on Trichodesmium is important for understanding global biogeochemical cycles, particularly the nitrogen cycle. Studies focus on its physiology, genetic diversity, and ecological interactions. Understanding Trichodesmium's role in the ocean can help predict the impacts of environmental changes on marine ecosystems.

Also see

• Cyanobacteria
• Nitrogen fixation
• Marine ecosystems
• Phytoplankton
• Biogeochemical cycle