Diatoms

Diatoms are unicellular, photosynthetic algae with unique silica cell walls and are major components of aquatic phytoplankton, contributing significantly to global oxygen production.​

Structure and Classification

Diatoms possess a rigid, glass-like cell wall called a frustule made of silicon dioxide, which has intricate and distinct geometrical patterns.​

They are generally classified into two main groups:

Centric diatoms: Radially symmetrical and typically found in marine environments.​

Pennate diatoms: Bilaterally symmetrical, usually found in freshwater habitats, and capable of slow gliding movement by secreting mucilage.​

Cellular size ranges from about 5 μm to 0.5 mm, making them among the larger unicellular microorganisms.​

Habitat and Ecological Role

Diatoms are distributed globally in marine and freshwater environments, often forming large blooms in cold or nutrient-rich waters.​

They serve as primary producers, forming the base of aquatic food chains and providing sustenance for zooplankton and fish larvae.​

Diatoms account for 20–25% of global oxygen production through photosynthesis, thus playing a major role in atmospheric and aquatic oxygen dynamics.​

Reproduction and Life Cycle

Diatoms primarily reproduce asexually by binary fission, which leads to a gradual decrease in cell size due to the unique bipartite frustule structure.​

To restore their maximum size, diatoms undergo sexual reproduction and produce auxospores—a specialized structure that enlarges before forming a new frustule.​

Some diatoms form resting spores or auxospores to withstand unfavorable environmental conditions and resume growth when conditions improve.​

Unique Features

Their pigment composition (chlorophyll a & c, carotenoids like fucoxanthin) gives diatoms a characteristic golden-brown color.​

Food reserves are primarily stored as chrysolaminarin and oil, instead of starch.​

Diatoms lack flagella except in the male gametes of centric types.​

Diatoms are crucial in environmental monitoring, paleontology, and biotechnology due to their abundance, ecological roles, and uniquely patterned silica shells.​