Microcystis densa is a colonial cyanobacterium found in freshwater environments worldwide. It forms spherical or irregular colonies composed of ovoid or spherical cells ranging from 2 to 8 micrometers in diameter. Each cell has a thin cell wall and contains pigments like chlorophyll-a, phycocyanin, and phycoerythrin. The species is known for its ability to regulate buoyancy with gas vesicles and reproduces through both asexual division and formation of akinetes for sexual reproduction. Microcystis densa thrives in nutrient-rich waters and can produce toxins called microcystins, posing risks to aquatic life and human health in eutrophic conditions.