Cyanobacteria

Definition

Cyanobacteria, also known as blue-green algae, are photosynthetic microorganisms found in a variety of environments, including freshwater, marine ecosystems, and even terrestrial habitats. They are crucial for nitrogen fixation, converting atmospheric nitrogen into forms usable by living organisms, thereby playing a key role in nutrient cycling and ecosystem productivity.

5 Must Know Facts For Your Next Test

1. Cyanobacteria are among the earliest organisms on Earth, with a history dating back over 3 billion years, significantly contributing to the oxygenation of the atmosphere.
2. These microorganisms are unique in their ability to fix nitrogen due to specialized cells called heterocysts, which provide an anaerobic environment for the nitrogenase enzyme to function.
3. Cyanobacteria can form harmful algal blooms in nutrient-rich waters, leading to issues such as oxygen depletion and the production of toxins that affect aquatic life and human health.
4. They play a vital role in aquatic ecosystems as primary producers, supporting food webs by providing energy and nutrients to higher trophic levels.
5. Some species of cyanobacteria have symbiotic relationships with plants, such as in the case of certain ferns and cycads, enhancing their growth through nitrogen supply.

Review Questions

• How do cyanobacteria contribute to nitrogen fixation in aquatic ecosystems?
  • Cyanobacteria play a significant role in nitrogen fixation by converting atmospheric nitrogen into ammonia through the action of specialized cells called heterocysts. This process allows them to thrive in nutrient-poor environments and supports the growth of surrounding plant life by providing essential nitrogen compounds. Their ability to fix nitrogen not only enhances local productivity but also helps maintain ecosystem balance by enriching the nutrient content of water bodies.
• What are the ecological impacts of harmful algal blooms caused by cyanobacteria?
  • Harmful algal blooms caused by cyanobacteria can lead to serious ecological consequences, including hypoxia or oxygen depletion in water bodies as the blooms die off and decompose. This can result in fish kills and loss of biodiversity. Additionally, some cyanobacterial species produce toxins that can harm aquatic organisms and pose risks to human health through contaminated drinking water or recreational waters. These impacts highlight the importance of monitoring nutrient levels to prevent bloom formation.
• Evaluate the importance of cyanobacteria in historical and modern contexts regarding Earth's atmosphere and current environmental challenges.
  • Historically, cyanobacteria played a crucial role in shaping Earth's atmosphere by producing oxygen during photosynthesis, paving the way for aerobic life forms. In modern contexts, they remain vital for ecosystem functioning but also pose challenges due to their potential for causing harmful algal blooms in response to nutrient pollution. This duality emphasizes the need for sustainable management practices to harness their benefits while mitigating risks associated with excessive nutrient inputs from agricultural runoff and urban waste.

Related terms

Nitrogen Fixation: The process by which certain bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃) or related compounds, making nitrogen available to plants.

Photosynthesis: The process by which green plants, algae, and cyanobacteria convert light energy into chemical energy, using carbon dioxide and water to produce glucose and oxygen.

Phytoplankton: Microscopic plants found in aquatic environments that perform photosynthesis; cyanobacteria are a significant component of phytoplankton communities.