Chrysophyta

Chrysophyta, commonly known as golden algae or chrysophytes, are a diverse group of mostly unicellular aquatic protists belonging to the stramenopile lineage. They are found in freshwater and marine environments, from rivers and ponds to coastal seas, and can form blooms under favorable nutrient conditions. Most chrysophytes are photosynthetic, containing chlorophylls and carotenoids that give them a golden-brown color; some members are mixotrophic, capable of ingesting bacteria or other small particles.

Morphology varies widely. Many are flagellate, with two flagella of unequal length; the longer flagellum typically bears mastigonemes, a type of hair-like projection. The cell surface may be covered by ornate silica scales or organic plates, sometimes forming a siliceous lorica. Most reproduce asexually by simple mitotic division, while sexual reproduction is known in some groups.

Ecology: Chrysophytes are important components of phytoplankton in freshwater and coastal ecosystems, contributing to primary production and carbon cycling. They are generally adapted to well-lit, nutrient-variable waters, and some can form seasonal blooms. In many environments they help link microbial food webs with higher trophic levels.

Taxonomy: Chrysophyta is a traditional, albeit somewhat broad, grouping that historically covered golden algae and related silica-scaled chrysophytes. In modern systematics, chrysophytes are placed within the heterokont group Stramenopiles, and the rank and circumscription of Chrysophyta vary with taxonomy updates.