phase speed
230
phase speed ~wave characteristics.
pheromones organic substances released by the exocrine glands of some organisms to the environment, in order to influence the behavior of other members of the same species. Pheromones thus represent a means of communication and transferring information by smell or taste. They evoke specific
behavior, developmental or reproductive responses in the recipient, which
may be of great significance for the survival of the species.
phoresis ~symbiosis.
Phoronida phylum of the Lophophorata (~Iophophore). Marine free-living
worm-like animals, that live in a chitinous tube. Their main characteristic is
the lophophore, a row of tentacles around the mouth in the form of a horseshoe. The gut is U-shaped, and the anus is close to the mouth. Hermaphroditic
or of separate sex. The eggs hatch into pelagic larvae. The animals are buried
into the hard substrate, sit in soft sediment or live in association with
Ceriantharia. They are filter feeders and are found until depths of 400 m.
phosphorescence physical phenomenon denoting the re-emittance of light
absorbed by certain materials for several seconds, or even several minutes,
after the excitation radiation has stopped. There is no essential difference
between phosphorescence and fluorescence, except that the former persists
after the excitation has ceased, whereas in the latter the light is re-emitted
within 10- 7 s. The light produced by some marine organisms (bioluminescence)
is the result of chemiluminescent reactions (in which a substrate is oxidized)
and should not be confused with phosphorescence.
phosphorites marine deposits consisting largely of minerals dominated by the
occurrence of the element phosphorus.
phosphorus cycle phosphorus (P) occurs in seawater in living organisms (LOP)
or as dissolved inorganic P (DIP), dissolved organic P (DOP) and particulate P (POP). In surface waters LOP is usually highest and DIP low, due to
uptake during primary production. This uptake shows a strong seasonal cycle
with a maximum during algal blooms (in spring in temperate areas).
Zooplankton grazing on phytoplankton regenerates substantial amounts of P
fixed by algae. Further release occurs during exudation, autolysis and bacterial
breakdown (mineralization). Renewed uptake by phytoplankton closes the
cycle. Mineralization occurs in the water column as well as in the sediment.
The presence of a thermocline may block the sedimentary P source from the
surface waters, but vertical mixing in coastal waters and upwelling will bring
this P within reach of the phytoplankton in the euphotic zone. Locally seabirds
bring appreciable amounts of P to land, where their feces (guano) in breed-
230
phase speed ~wave characteristics.
pheromones organic substances released by the exocrine glands of some organisms to the environment, in order to influence the behavior of other members of the same species. Pheromones thus represent a means of communication and transferring information by smell or taste. They evoke specific
behavior, developmental or reproductive responses in the recipient, which
may be of great significance for the survival of the species.
phoresis ~symbiosis.
Phoronida phylum of the Lophophorata (~Iophophore). Marine free-living
worm-like animals, that live in a chitinous tube. Their main characteristic is
the lophophore, a row of tentacles around the mouth in the form of a horseshoe. The gut is U-shaped, and the anus is close to the mouth. Hermaphroditic
or of separate sex. The eggs hatch into pelagic larvae. The animals are buried
into the hard substrate, sit in soft sediment or live in association with
Ceriantharia. They are filter feeders and are found until depths of 400 m.
phosphorescence physical phenomenon denoting the re-emittance of light
absorbed by certain materials for several seconds, or even several minutes,
after the excitation radiation has stopped. There is no essential difference
between phosphorescence and fluorescence, except that the former persists
after the excitation has ceased, whereas in the latter the light is re-emitted
within 10- 7 s. The light produced by some marine organisms (bioluminescence)
is the result of chemiluminescent reactions (in which a substrate is oxidized)
and should not be confused with phosphorescence.
phosphorites marine deposits consisting largely of minerals dominated by the
occurrence of the element phosphorus.
phosphorus cycle phosphorus (P) occurs in seawater in living organisms (LOP)
or as dissolved inorganic P (DIP), dissolved organic P (DOP) and particulate P (POP). In surface waters LOP is usually highest and DIP low, due to
uptake during primary production. This uptake shows a strong seasonal cycle
with a maximum during algal blooms (in spring in temperate areas).
Zooplankton grazing on phytoplankton regenerates substantial amounts of P
fixed by algae. Further release occurs during exudation, autolysis and bacterial
breakdown (mineralization). Renewed uptake by phytoplankton closes the
cycle. Mineralization occurs in the water column as well as in the sediment.
The presence of a thermocline may block the sedimentary P source from the
surface waters, but vertical mixing in coastal waters and upwelling will bring
this P within reach of the phytoplankton in the euphotic zone. Locally seabirds
bring appreciable amounts of P to land, where their feces (guano) in breed-