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The Miracle of Photosynthesis: How Blue-Green Algae Changed Earth's Atmosphere
Cyanobacteria, which get their name from the ancient Greek word meaning "blue", the source of their color, are autotrophic Gram-negative bacteria that obtain bioenergy through photosynthesis. Blue-green algae are one of the most diverse groups of organisms in Earth's history. Its fossils have been found to be at least more than 2.1 billion years old. These tiny creatures were the first to release oxygen, and through the photosynthesis of blue-green algae, Earth's original atmosphere underwent major changes.
"Blue-green algae are not just the building blocks of life on Earth, their photosynthetic process changes entire ecosystems."
Photosynthesis in blue-green algae occurs by absorbing the red and blue wavelengths of sunlight, a process that splits water molecules to produce hydrogen ions and oxygen. These hydrogen ions react with carbon dioxide to form complex organic compounds such as carbohydrates, with oxygen being released as a by-product. This repeated process continued for billions of years, eventually transforming the earth's oxygen-free atmosphere into an oxygen-containing terrestrial environment, resulting in a phenomenon known as the "Great Oxygenation Event."
In order to adapt to an oxygen-containing environment, early single-celled organisms underwent the evolution process of endosymbiosis, which eventually led to the emergence of eukaryotes. The photosynthesis of blue-green algae utilizes various pigments, including chlorophyll, carotenoids and phycocyanins, to convert light energy into chemical energy. Unlike other heterotrophs, blue-green algae have an inner membrane structure. Their thylakoids are where photosynthesis takes place.
“Oxygen released by ancient blue-green algae quietly drove the evolution of complex life on Earth.”
Blue-green algae are widespread around the world and play an important role in biogeochemical cycles. Their ecological status is not limited to waters, but also extends to deserts, rocks, and microbial beds in extreme environments. The presence of these microorganisms, and their photosynthetic efficiency, are known to account for a small fraction of the primary productivity of Earth's oceans, especially in areas with regular oxygen supply and abundant light. Blue-green algae such as Prochlorococcus may even be the smallest photosynthetic organisms on Earth today, but they make an astonishing contribution to the maintenance of atmospheric oxygen.
Currently, blue-green algae not only plays a role as a producer in the ecosystem, but may also pose a threat to human health. Toxic substances in blue-green algae, called cyanobacterial toxins, can cause adverse health effects in aquatic life and humans. This situation is becoming increasingly serious, leading to increasingly prominent problems such as the closure of water bodies and algae contamination of drinking water.
"The growth of blue-green algae is a double-edged sword that may promote ecological balance, but may also threaten the survival of organisms."
From a historical perspective, the presence and prosperity of blue-green algae not only changed the composition of Earth's atmosphere but also influenced the evolution of early life forms. The growth of these microorganisms is closely related to the living environment, and factors such as climate change and man-made eutrophication may affect their ecological roles. With global warming and changes in the water environment, the blooming of blue-green algae is likely to intensify. Can we find a way to balance the growth of blue-green algae with the development of a healthy ecosystem?
