327
tropical area/zone
tritium (T) cosmogenic radioisotope of hydrogen with mass = 3, as opposed to mass
1 for normal hydrogen and mass 2 for stable isotope deuterium. Additional
input to ocean surface largely through bomb testing in the early 1960s, as
3H 2 0. Radioactive decay leads to formation of 3He. The ensuing shift in
3He/4He isotopic ratio in seawater serves as time clock for the age of the water
mass.
Triton Expedition (1882) under John Murray and T.H. Tizard charted the submarine Faroe Islands - Iceland - Greenland Ridge (Wyville Thomson Ridge)
and did extensive sounding, temperature measurements, tow-netting and
trawling.
trochophore (syn. trochosphere) free-swimming larval stage of, e.g., Polychaeta,
Bryozoa, Brachiopoda, and Mollusca.
trochosphere -Hrochophore.
trophic level level in a food chain at which an organism takes its food. When primary producers are allotted trophic levell, those eating plants (herbivores)
stand one step higher in the food chain, at trophic level 2; proceeding stepwise, carnivores eating herbivores stand at level 3, top carnivores at 4, etc.
Because at every trophic step in the food chain the food is only partially
converted into edible new biomass, the organisms feeding at successive
trophic levels in a system together build a food pyramid with a large mass
of plant food eaten at the basis, and little meat eaten at the top by the highest carnivore level. In reality, most organisms take their food from more
than one trophic level, so that the concept is only a rough approximation;
thus trophic levels become average trophic levels for a defined group of animals. For instance, all North Sea fish together stand at an average trophic
level of 3.7. Trophic structure of a given ecosystem shows the stepwise conversion of an amount of plant material produced at the basis, in the different
trophic levels. The trophic structure can give only a simplified view of a system, but it can be highly informative in comparing different systems. ~food
chain.
trophic structure ~trophic level.
tropical area/zone basically the part of the world between the tropics (Cancer
and Capricorn), which lie at the latitudes 23° 27' north and south. In the
marine environment, due to the prevailing ocean currents, the tropical areas
show a more irregular distribution, related to high temperatures of the surface water and the occurrence of tropical organisms such as reef-building
corals and mangroves. ~biogeography.
tropical area/zone
tritium (T) cosmogenic radioisotope of hydrogen with mass = 3, as opposed to mass
1 for normal hydrogen and mass 2 for stable isotope deuterium. Additional
input to ocean surface largely through bomb testing in the early 1960s, as
3H 2 0. Radioactive decay leads to formation of 3He. The ensuing shift in
3He/4He isotopic ratio in seawater serves as time clock for the age of the water
mass.
Triton Expedition (1882) under John Murray and T.H. Tizard charted the submarine Faroe Islands - Iceland - Greenland Ridge (Wyville Thomson Ridge)
and did extensive sounding, temperature measurements, tow-netting and
trawling.
trochophore (syn. trochosphere) free-swimming larval stage of, e.g., Polychaeta,
Bryozoa, Brachiopoda, and Mollusca.
trochosphere -Hrochophore.
trophic level level in a food chain at which an organism takes its food. When primary producers are allotted trophic levell, those eating plants (herbivores)
stand one step higher in the food chain, at trophic level 2; proceeding stepwise, carnivores eating herbivores stand at level 3, top carnivores at 4, etc.
Because at every trophic step in the food chain the food is only partially
converted into edible new biomass, the organisms feeding at successive
trophic levels in a system together build a food pyramid with a large mass
of plant food eaten at the basis, and little meat eaten at the top by the highest carnivore level. In reality, most organisms take their food from more
than one trophic level, so that the concept is only a rough approximation;
thus trophic levels become average trophic levels for a defined group of animals. For instance, all North Sea fish together stand at an average trophic
level of 3.7. Trophic structure of a given ecosystem shows the stepwise conversion of an amount of plant material produced at the basis, in the different
trophic levels. The trophic structure can give only a simplified view of a system, but it can be highly informative in comparing different systems. ~food
chain.
trophic structure ~trophic level.
tropical area/zone basically the part of the world between the tropics (Cancer
and Capricorn), which lie at the latitudes 23° 27' north and south. In the
marine environment, due to the prevailing ocean currents, the tropical areas
show a more irregular distribution, related to high temperatures of the surface water and the occurrence of tropical organisms such as reef-building
corals and mangroves. ~biogeography.