Cyanobacteria

Definition

Cyanobacteria, often referred to as blue-green algae, are a group of photosynthetic bacteria that play a crucial role in aquatic ecosystems and global nitrogen cycling. They are unique in their ability to fix atmospheric nitrogen into forms that can be used by plants and other organisms, making them vital for nutrient cycling in both freshwater and marine environments. Cyanobacteria also contribute to primary productivity through photosynthesis, influencing the overall health and balance of ecosystems.

5 Must Know Facts For Your Next Test

1. Cyanobacteria are one of the oldest known life forms on Earth, with fossils dating back over 3 billion years.
2. These organisms can thrive in a wide range of environments, including freshwater lakes, oceans, and even extreme habitats like hot springs.
3. Cyanobacteria can form harmful algal blooms (HABs), which can produce toxins affecting water quality and aquatic life.
4. They play a significant role in the nitrogen cycle by converting atmospheric nitrogen into bioavailable forms through their nitrogen-fixing capabilities.
5. Some species of cyanobacteria have specialized cells called heterocysts that provide an anaerobic environment for nitrogen fixation to occur.

Review Questions

• How do cyanobacteria contribute to the nitrogen cycle and why is this important for ecosystems?
  • Cyanobacteria contribute to the nitrogen cycle through their ability to fix atmospheric nitrogen into ammonia, a form that is usable by plants. This process is essential for maintaining soil fertility and supporting plant growth. By enriching the nitrogen content of aquatic environments, cyanobacteria help sustain diverse ecosystems and support the food web.
• Discuss the impacts of eutrophication on cyanobacterial populations and the potential consequences for aquatic ecosystems.
  • Eutrophication leads to an overabundance of nutrients in water bodies, which can trigger rapid growth of cyanobacteria. This excessive growth can result in harmful algal blooms that deplete oxygen levels when they die off, harming aquatic life and disrupting ecosystems. The toxins produced by some cyanobacterial species during blooms can also pose risks to human health and local economies reliant on clean water.
• Evaluate the role of cyanobacteria in ancient Earth's atmosphere and how they influenced the evolution of life on the planet.
  • Cyanobacteria played a pivotal role in shaping Earth's ancient atmosphere through their photosynthetic activity, producing oxygen as a byproduct. This 'Great Oxygenation Event' around 2.4 billion years ago transformed the planet's atmosphere, making it hospitable for aerobic organisms and leading to the evolution of complex life forms. Their contribution to oxygen production was fundamental in establishing the conditions necessary for life as we know it today.

Related terms

Nitrogen fixation: The process by which certain microorganisms convert atmospheric nitrogen (N₂) into ammonia (NH₃), making it accessible for biological use.

Eutrophication: A process where water bodies become overly enriched with nutrients, often leading to excessive growth of algae, including cyanobacteria, and subsequent depletion of oxygen.

Photosynthesis: The process by which green plants, algae, and some bacteria convert light energy into chemical energy, producing oxygen and organic compounds from carbon dioxide and water.