Phytoplankton

Description: Phytoplankton are planktonic plants - they use sunlight for energy and use the currents to move around their ocean world. They are also the base of the food web, feeding zooplankton which feed small fish which feed larger fish and so on. Phytoplankton blooms depend on a number of factors: sunlight, nutrients, carbon dioxide, temperature, salinity, and more. When there is an abundance of sunlight and nutrients for these plankton to grow (as these are often the limiting factors), they can form large blooms that may even produce toxic compounds. These are called harmful algal blooms and can be harmful to fish, shellfish, mammals, birds and even humans. Even after these massive blooms die, the bacteria that then break down the phytoplankton take up so much oxygen it can deplete the waters oxygen supply, killing other species in the area.

Habitat: Because of their reliance on sunlight, most phytoplankton live near the surface of the water to maximize exposure. Blooms also need nutrients which are most available near runoff from land or places with upwelling. This means places like rivers especially with nearby farmlands and even wind-swept areas near deserts with nutrient-rich sands. Upwelling is where deep, cold, nutrient-rich water is brought up to the surface and this also mostly happens near coastlines.

Tide Pool Tidbits:

• Phytoplankton blooms can be hundreds of square kilometers wide and are easily visible from space!

• Individual phytoplankton tend to only live for a matter of days but the entire bloom may last for multiple weeks.

• While trees and land plants get most of the credit, phytoplankton actually generate about half of the planet’s oxygen.

References: NOAA, NASA Earth Observatory, Woods Hole Oceanographic Institution