Types of phytoplankton - Diatoms

-Possess a hard external inorganic frustule silicate. -Generally unicellular, fast growing and some form aggregates. -Dominate the Spring bloom. -"Pill-box" description. -Asexual reproduction, but sexual reproduction makes auxospore: larger cell, produce a frustule and have normal size and shape. -Pennate diatoms: elongate and usually benthic. -Centric diatoms: valves are arranged radially or concentrically around a point-common in the plankton. Mechanisms which retard sinking & allow diatoms to remain in lit surface waters