143
group velocity
grazing in the marine environment, the ingestion of phytoplankton or sedentary
algae by marine animals. These grazers filter the water [Porifera (sponges),
Crustacea, Mollusca, Thaliacea (salps)] or rasp the substrate [Echinoidea (sea
urchins), Gastropoda (snails)]. The amount of grazing is experimentally measured by the decline of food in the ambient medium (chlorophyll, or number of
algal cells via particle counters) or by the increase in the animal of 14C from labeled
food, or of degraded chlorophyll in the gut content). Overgrazing (ingestion larger
than the digestion can cope with) may occur when food (phytoplankton) is
very abundant, resulting in fecal pellets rich in undigested algal cells.
Great Barrier Reef -treef.
Great Barrier Reef Expedition (1928-1929) using Low Isles 45 miles North of
Cairns as a base this British-Museum (Natural History) expedition studied
marine biology of the Reef. The hydrography and plankton of the water column was studied using the Luana and several other small ships by i.a. ES.
Russell, S.M. Marshall and A.P. Orr. T.A. and A. Stephenson, S.M. Manton and
E.A. Fraser conducted detailed ecological surveys of the reef. Physiology of
corals (feeding, digestion, excretion, respiration and the role of symbiontic
zooxanthellae) was studied by C.M. Yonge. This expedition greatly increased
the knowledge of coral reefs.
green algae -tChlorophyta.
greenhouse effect the elevation of the temperature of the earth and its atmosphere due to the presence in the atmosphere of so-called greenhouse gasses
(C0 2 , CH 4 , N 2 0, CFCs like the Freons, 03) which diminish the reradiation of
heat into space. The expected rise in global temperature, due to increased
concentration of these gases, ranges from 1.5 to 4.5 °C within the next 100
years and may be one of the major long-term environmental problems. In
the marine environment this is expected to cause a rise in sea level of 0.5 to
several meters, due to the expansion of seawater at higher temperature,
melting of snow and ice on land, and possibly, but not yet likely, breakingoff of quantities of Antarctic ice, which will melt at lower latitudes. The difficulty of measuring this temperature increase, due to the large interannual
variations (-tclimatic variation), makes the greenhouse effect difficult to prove,
hence the uncertainty in the prediction of its size and effects. Changes of the
temperature of seawater will also greatly affect areal distribution of marine
organisms.
gross primary production -tproduction.
group velocity the velocity at which wave energy is propagating. For short waves the
group velocity is half the phase velocity (-twave characteristics), for long waves it
group velocity
grazing in the marine environment, the ingestion of phytoplankton or sedentary
algae by marine animals. These grazers filter the water [Porifera (sponges),
Crustacea, Mollusca, Thaliacea (salps)] or rasp the substrate [Echinoidea (sea
urchins), Gastropoda (snails)]. The amount of grazing is experimentally measured by the decline of food in the ambient medium (chlorophyll, or number of
algal cells via particle counters) or by the increase in the animal of 14C from labeled
food, or of degraded chlorophyll in the gut content). Overgrazing (ingestion larger
than the digestion can cope with) may occur when food (phytoplankton) is
very abundant, resulting in fecal pellets rich in undigested algal cells.
Great Barrier Reef -treef.
Great Barrier Reef Expedition (1928-1929) using Low Isles 45 miles North of
Cairns as a base this British-Museum (Natural History) expedition studied
marine biology of the Reef. The hydrography and plankton of the water column was studied using the Luana and several other small ships by i.a. ES.
Russell, S.M. Marshall and A.P. Orr. T.A. and A. Stephenson, S.M. Manton and
E.A. Fraser conducted detailed ecological surveys of the reef. Physiology of
corals (feeding, digestion, excretion, respiration and the role of symbiontic
zooxanthellae) was studied by C.M. Yonge. This expedition greatly increased
the knowledge of coral reefs.
green algae -tChlorophyta.
greenhouse effect the elevation of the temperature of the earth and its atmosphere due to the presence in the atmosphere of so-called greenhouse gasses
(C0 2 , CH 4 , N 2 0, CFCs like the Freons, 03) which diminish the reradiation of
heat into space. The expected rise in global temperature, due to increased
concentration of these gases, ranges from 1.5 to 4.5 °C within the next 100
years and may be one of the major long-term environmental problems. In
the marine environment this is expected to cause a rise in sea level of 0.5 to
several meters, due to the expansion of seawater at higher temperature,
melting of snow and ice on land, and possibly, but not yet likely, breakingoff of quantities of Antarctic ice, which will melt at lower latitudes. The difficulty of measuring this temperature increase, due to the large interannual
variations (-tclimatic variation), makes the greenhouse effect difficult to prove,
hence the uncertainty in the prediction of its size and effects. Changes of the
temperature of seawater will also greatly affect areal distribution of marine
organisms.
gross primary production -tproduction.
group velocity the velocity at which wave energy is propagating. For short waves the
group velocity is half the phase velocity (-twave characteristics), for long waves it