Trichodesmium

Trichodesmium

[[File:

Trichodesmium filaments

|frameless|alt=]]

Trichodesmium is a genus of filamentous cyanobacteria that is found in nutrient-poor tropical and subtropical ocean waters. It is notable for its ability to fix atmospheric nitrogen, a process that is crucial for the marine nitrogen cycle.

Description

Trichodesmium is a colonial cyanobacterium that forms long filaments, which can aggregate into larger colonies. These colonies are often visible to the naked eye and can form extensive blooms on the ocean surface. The filaments are composed of trichomes, which are chains of cells surrounded by a mucilaginous sheath.

Trichodesmium bloom in the Southwest Pacific

Ecology

Trichodesmium plays a significant role in the marine ecosystem as a primary producer and a nitrogen fixer. It is one of the few marine organisms capable of fixing atmospheric nitrogen into a form that can be used by other organisms. This process is particularly important in oligotrophic (nutrient-poor) waters where nitrogen is a limiting nutrient.

Trichodesmium blooms can cover large areas of the ocean and are often associated with the discoloration of the water, sometimes referred to as "sea sawdust" due to their appearance. These blooms can have both positive and negative impacts on the marine environment. While they contribute to the nitrogen budget of the ocean, they can also lead to hypoxic conditions when they decay.

Morphology

Trichodesmium colonies can be classified into several morphological types, including "puffs" and "tufts". Puffs are spherical aggregates of filaments, while tufts are more elongated and brush-like.

Trichodesmium colonies sorted into morphological classes

Nitrogen Fixation

The ability of Trichodesmium to fix nitrogen is facilitated by specialized cells called heterocysts, which provide an anaerobic environment necessary for the nitrogenase enzyme to function. This process is energy-intensive and requires a significant amount of sunlight, which is why Trichodesmium is typically found in well-lit surface waters.

Distribution

Trichodesmium is widely distributed in tropical and subtropical oceans, particularly in the Atlantic, Pacific, and Indian Oceans. It thrives in warm, oligotrophic waters where it can outcompete other phytoplankton due to its nitrogen-fixing capabilities.

Research and Importance

Research on Trichodesmium has increased due to its role in global biogeochemical cycles and its potential response to climate change. Understanding how Trichodesmium populations respond to changes in temperature, CO2 levels, and nutrient availability is crucial for predicting future oceanic nitrogen cycles.

Also see

• Cyanobacteria
• Nitrogen fixation
• Marine phytoplankton
• Oceanic nutrient cycles