English: Three selection forces operating on phytoplankton in the pelagic
Predation is generally largest on small-sized phytoplankton. Sedimentation is usually highest for large cells, colonies, and aggregates that have no buoyancy control, and small cells that have rather high specific mass (diatoms). Competition is mostly strongest on larger cells and colonies that have a less favorable surface-to-volume ratio, and thus lower growth rates. Consequently, small-celled, fast-growing cells suffer most from predation (1) but have in general low sinking loss, and because of favorable surface-to-volume ratio generally experiences less competition. Diatoms can only prevail in a mixed water column (4). Large, sometimes armored cells or colonies have lower growth rates, experience higher sinking rates, but are protected against grazing (2). Some of the slow-growing colonies or filaments possess the capacity of buoyancy control. The gray arrows indicate potential phenotypic plasticity