phytoplankton (redirected from Phytoplankton bloom)

phytoplankton

Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. In fresh water, large numbers of green algae often colour lakes and ponds, and cyanobacteria may affect the taste of drinking water. Oceanic phytoplankton is the primary food source, directly or indirectly, of all sea organisms. Composed of groups with silica-containing skeletons, such as diatoms and dinoflagellates, phytoplankton varies seasonally in amount, increasing in spring and fall with favourable light, temperature, and minerals.

---

phytoplankton [¦fīd·ə′plaŋk·tən]

(ecology)

Planktonic plant life.

---

Phytoplankton

Mostly autotrophic microscopic algae which inhabit the illuminated surface waters of the sea, estuaries, lakes, and ponds. Many are motile. Some perform diel (diurnal) vertical migrations, others do not. Some nonmotile forms regulate their buoyancy. However, their locomotor abilities are limited, and they are largely transported by horizontal and vertical water motions.

A great variety of algae make up the phytoplankton. Diatoms (class Bacillariophyceae) are often conspicuous members of marine, estuarine, and fresh-water plankton. Dinoflagellates (class Dinophyceae) occur in both marine and fresh-water environments and are important primary producers in marine and estuarine environments. Coccolithophorids (class Haptophyceae) are also marine primary producers of some importance. They do not occur in fresh water.

Even though marine and fresh-water phytoplankton communities contain a number of algal classes in common, phytoplankton samples from these two environments will appear quite different. These habitats support different genera and species and groups of higher rank in these classes. Furthermore, fresh-water plankton contains algae belonging to additional algal classes either absent or rarely common in open ocean environments. These include the green algae (class Chlorophyceae), the euglenoid flagellates (class Euglenophyceae), and members of the Prasinophyceae.

The phytoplankton in aquatic environments which have not been too drastically affected by human activity exhibit rather regular and predictable seasonal cycles. Coastal upwelling and divergences, zones where deeper water rises to the surface, are examples of naturally occurring phenomena which enrich the mixed layer with needed nutrients and greatly increase phytoplankton production. In the ocean these are the sites of the world's most productive fisheries.