red tide
262
teins, pigments, etc. Not only in the plankton itself, but also in the deep water
column of the oceans do these nutritional elements, subsequent to phytoplankton degradation, occur in the dissolved state in this ratio. The name of
this characteristic ratio is associated with the American oceanographer A.D.
Redfield, who contributed significantly to the understanding of the occurrence of a permanent relationship between concentrations of different
nutrients.
red tide a red or reddish brown discoloring of surface waters, most frequent in
coastal regions, caused by concentrations (blooms) of plankton, particularly
Dinoflagellata. Sometimes mass mortality occurs due to poisonous substances
produced by the algae, or to low oxygen concentrations due to high amounts
of oxygen used for decomposition of the algae at the end of the bloom.
redox potential the energy required by all forms of life is ultimately derived from
the process of electron transfer. Hydrogen atom pairs (equivalent to
2H++2e-) are removed from certain intermediates of carbohydrates, fat, and
protein degradation, and fed into the electron transport chain, donating
their electrons to carrier components of the chain while the associated H+
ions enter the aqueous environment. The electron transport chain comprises redox couples whose redox potential displays a small difference from its
neighbors; consequently, the transfer of electrons is associated with the
release of free energy. The free energy change (G) of the reaction involving
electron transfer from a donor couple to an acceptor couple is given by the
equation !'J.G = -nF!'J.E, where n is the number of electrons transferred, F is
the Faraday constant (equal to 96486 coulombs) and !'J.E the difference in
electrode potential between the two redox couples.
reduced gravity -tbuoyancy.
reducing conditions environments where in the absence of oxygen (bio-)chemical processes occur with other electron-acceptors such as nitrate (denitrification), iron oxide and manganese oxide, sulfate (sulfate reduction).
Reducing conditions are in general exceptional in the water column (only in
stagnant basins like the Black Sea, Cariaco Trench, etc.), but are common in
the sediment, where below the restricted penetration depth of oxygen
reducing conditions prevail.
reef elevated structures on the seabed usually built by calcareous organisms. In
the past Porifera (sponges) and Bryozoa were important; the most important
modern reef-building organisms are stony corals (Madreporaria). Although
reef-like structures occur in deep water, e.g., in the northeastern Atlantic,
most reefs occur in shallow tropical marine environments and these are
characterized by high rates of carbonate accumulation. Coral reefs grow in
262
teins, pigments, etc. Not only in the plankton itself, but also in the deep water
column of the oceans do these nutritional elements, subsequent to phytoplankton degradation, occur in the dissolved state in this ratio. The name of
this characteristic ratio is associated with the American oceanographer A.D.
Redfield, who contributed significantly to the understanding of the occurrence of a permanent relationship between concentrations of different
nutrients.
red tide a red or reddish brown discoloring of surface waters, most frequent in
coastal regions, caused by concentrations (blooms) of plankton, particularly
Dinoflagellata. Sometimes mass mortality occurs due to poisonous substances
produced by the algae, or to low oxygen concentrations due to high amounts
of oxygen used for decomposition of the algae at the end of the bloom.
redox potential the energy required by all forms of life is ultimately derived from
the process of electron transfer. Hydrogen atom pairs (equivalent to
2H++2e-) are removed from certain intermediates of carbohydrates, fat, and
protein degradation, and fed into the electron transport chain, donating
their electrons to carrier components of the chain while the associated H+
ions enter the aqueous environment. The electron transport chain comprises redox couples whose redox potential displays a small difference from its
neighbors; consequently, the transfer of electrons is associated with the
release of free energy. The free energy change (G) of the reaction involving
electron transfer from a donor couple to an acceptor couple is given by the
equation !'J.G = -nF!'J.E, where n is the number of electrons transferred, F is
the Faraday constant (equal to 96486 coulombs) and !'J.E the difference in
electrode potential between the two redox couples.
reduced gravity -tbuoyancy.
reducing conditions environments where in the absence of oxygen (bio-)chemical processes occur with other electron-acceptors such as nitrate (denitrification), iron oxide and manganese oxide, sulfate (sulfate reduction).
Reducing conditions are in general exceptional in the water column (only in
stagnant basins like the Black Sea, Cariaco Trench, etc.), but are common in
the sediment, where below the restricted penetration depth of oxygen
reducing conditions prevail.
reef elevated structures on the seabed usually built by calcareous organisms. In
the past Porifera (sponges) and Bryozoa were important; the most important
modern reef-building organisms are stony corals (Madreporaria). Although
reef-like structures occur in deep water, e.g., in the northeastern Atlantic,
most reefs occur in shallow tropical marine environments and these are
characterized by high rates of carbonate accumulation. Coral reefs grow in