sinilevien

Sinilevät, or cyanobacteria, are a group of photosynthetic prokaryotes that occur as single cells, filaments, or colonies. They are among the oldest organisms on Earth and can form diverse shapes and life cycles. They perform oxygenic photosynthesis and some species can fix atmospheric nitrogen. In aquatic ecosystems they contribute to primary production and nutrient cycling. Their pigments, including chlorophyll a and phycobiliproteins, give them blue-green to olive colors; the term blue-green algae is common in public usage, but sinilevät are not true algae.

Sinilevät inhabit freshwater, brackish, and marine environments and often proliferate when nutrients such as phosphorus and nitrogen are elevated and the water is warm, calm, and well-lit. Dense blooms can discolor water, reduce clarity, and create surface scums. Some sinilevät produce cyanotoxins, including microcystins, cylindrospermopsins, anatoxins, and saxitoxins, which can affect the liver or nervous system in humans and animals. Toxins may contaminate drinking water and complicate recreational use.

Ecology and life cycles: many species form resting cells called akinetes that survive adverse conditions; others fix nitrogen in specialized cells called heterocysts. Monitoring programs use microscopy, pigment analysis, and molecular methods to detect and quantify blooms and toxins. Management focuses on reducing nutrient inputs, improving water exchange, and treating water to remove toxins when necessary.

Taxonomy and terminology: sinilevät were historically grouped with algae, but current classification places them in Bacteria. The term blue-green algae remains common in public discourse, contributing to confusion with eukaryotic algae.