5
aggregation
Aegean Sea Expedition (1840-1841) a dredging expedition with the Beacon under
the Scottish biologist Edward Forbes, who defined a number of depth zones
in the vertical distribution of marine organisms. Numbers of organisms
diminished with depth and no animals were dredged below 300 fathoms,
leading to the conclusion that no life was possible in the deep ocean, it was
azoic. Forbes did not know that in 1818, Sir John Ross had accidentally collected an ophiuroid (--?Ophiuroidea) from a depth of 800 fathoms at 73°37' N.
Later in 1850 and 1864 M. Sars and his son G.O. Sars published on living
deep sea animals including a stalked crinoid (--?Crinoidea) Rhizocrinus
lofotensis, a "living fossil" with its nearest relatives in the Cretaceous,
dredged in Norwegian waters below 300 fathoms. Another proof of deep sea
life was made by Fleeming Jenkin (1860) when a telegraph cable between
Sardinia and North Africa was raised for repair from 1200 fathoms to which
a solitary coral Caryophyllia was attached. The deep sea was not azoic and
expeditions were planned to survey deep sea life.
aeolian sediment --?eolian sediment.
aerobic in presence of free oxygen, opposite to anaerobic. E.g., aerobic organisms
require oxygen for their metabolic processes; they may be facultative or
obligate aerobic; aerobic processes can only be carried out in the presence
of oxygen; aerobic zone is the oxygen-containing zone in the sea bottom,
--?benthic system.
age determination (of organisms) determination of the age of organisms is a
requirement, for instance, in studies of production and population dynamics. Length may give an indication, but hard parts may show (daily) growthlines and (annual) winter rings, which allow more precise age determinations. Such growth lines occur in otoliths and scales of fish, in molluskan
shells, in teeth of whales, etc. --?absolute age.
age distribution the relative frequency of individuals of different age classes
within a population, --?population parameters.
age-length key (ALK) matrix of the percentage age composition within each
length class based on stratified sampling for age by length classes of fish.
When applied to length distributions of catches, the age composition of
these are derived. ALKs are often extended to include information on sexes
and maturity (SMALKs).
aggregation process resulting in uniting single particles into larger units
(aggregates, flocs). In the sea this occurs primarily by organic matter that
glues mineral particles together. Colloid particles are also flocculated by
electrolytes dissolved in the water (salt flocculation). Suspended particles
aggregation
Aegean Sea Expedition (1840-1841) a dredging expedition with the Beacon under
the Scottish biologist Edward Forbes, who defined a number of depth zones
in the vertical distribution of marine organisms. Numbers of organisms
diminished with depth and no animals were dredged below 300 fathoms,
leading to the conclusion that no life was possible in the deep ocean, it was
azoic. Forbes did not know that in 1818, Sir John Ross had accidentally collected an ophiuroid (--?Ophiuroidea) from a depth of 800 fathoms at 73°37' N.
Later in 1850 and 1864 M. Sars and his son G.O. Sars published on living
deep sea animals including a stalked crinoid (--?Crinoidea) Rhizocrinus
lofotensis, a "living fossil" with its nearest relatives in the Cretaceous,
dredged in Norwegian waters below 300 fathoms. Another proof of deep sea
life was made by Fleeming Jenkin (1860) when a telegraph cable between
Sardinia and North Africa was raised for repair from 1200 fathoms to which
a solitary coral Caryophyllia was attached. The deep sea was not azoic and
expeditions were planned to survey deep sea life.
aeolian sediment --?eolian sediment.
aerobic in presence of free oxygen, opposite to anaerobic. E.g., aerobic organisms
require oxygen for their metabolic processes; they may be facultative or
obligate aerobic; aerobic processes can only be carried out in the presence
of oxygen; aerobic zone is the oxygen-containing zone in the sea bottom,
--?benthic system.
age determination (of organisms) determination of the age of organisms is a
requirement, for instance, in studies of production and population dynamics. Length may give an indication, but hard parts may show (daily) growthlines and (annual) winter rings, which allow more precise age determinations. Such growth lines occur in otoliths and scales of fish, in molluskan
shells, in teeth of whales, etc. --?absolute age.
age distribution the relative frequency of individuals of different age classes
within a population, --?population parameters.
age-length key (ALK) matrix of the percentage age composition within each
length class based on stratified sampling for age by length classes of fish.
When applied to length distributions of catches, the age composition of
these are derived. ALKs are often extended to include information on sexes
and maturity (SMALKs).
aggregation process resulting in uniting single particles into larger units
(aggregates, flocs). In the sea this occurs primarily by organic matter that
glues mineral particles together. Colloid particles are also flocculated by
electrolytes dissolved in the water (salt flocculation). Suspended particles