430
Hjalmar THIEL
this type of influence is known for deep-sea biota, but
there is no reason to believe that fish and invertebrates
there would not be affected at sufficiently high
concentrations. Whereas infertility and other sexual
deviations were discovered earlier in coastal regions,
female gastropods in the open North Sea were found to
be affected by tributyltin used in anti-fouling paints on
ship hulls (Ten Hallers-Tjabbes et al., 1994). Takahashi
et al. (1997) discovered this same contaminant to
a depth of 980 m in Suruga Bay (Japan) in fish,
crustaceans, cephalopods, gastropods and echinoderms.
Although these observations were made close to shore,
the data demonstrate the penetration of organotin
compounds into offshore and deep-water food chains.
Flux to great depth and reactive contaminants
As noted above, predominantly inert substances such
as the chlorofluorocarbons will enter the deep ocean,
and be transported around in it, with the thermohaline
circulation system. Consequently, although chlorofluorocarbons, like the radionuclides resulting from nuclear
tests, occur throughout the earth’s atmosphere, their
main entry into the deeper parts of the ocean takes
place through the formation of bottom water by downwelling of dense water masses, which occurs in rather
limited regions around Antarctica and in the Greenland
and Labrador Seas (e.g., Rudels and Quadfasel, 1991;
Schlosser et al., 1995b). The bottom waters of enclosed
deep basins like the Mediterranean and the Red Seas
are also formed in fairly restricted areas and also
carry contaminants into the deeper layers. Lipiatou
et al. (1997) calculated mass budgets and dynamics
for polycyclic aromatic hydrocarbons which enter the
Mediterranean from atmospheric fallout and riverine
input. Some of this material and other contaminants
settle to the seafloor within the Mediterranean, but
some find their way into the Atlantic with the
Mediterranean outflow over the sill 300 m deep in the
Strait of Gibraltar, to form a well-marked water mass
slowly spreading throughout the North-east Atlantic at
a depth between 600 and 1000 m.
A more direct and widespread route into the deep
sea, particularly for those substances which enter the
metabolism of living organisms or are scavenged by
particulate matter, is through the sinking of particles,
which may occur at all latitudes. This route into the
deep ocean by the sinking of particulate matter has
been recognized for more than hundred years, but
it is only within the last twenty years or so that it
has been realized that mass particulate transport to
great depth can occur in a matter of weeks (Billett
et al., 1983; Rice et al., 1986; Thiel et al., 1988/89;
Smith et al., 1996; De Wilde et al., 1998). Although
this transport mechanism probably exists throughout
the world oceans, its extent varies markedly in space
and time, being largely dependent upon the level of
primary production and season. For example, aggregate
formation and rapid sinking of organic matter, with any
associated contaminants, occurs in the North Atlantic
predominantly after the spring phytoplankton bloom,
and this phytodetritus arrives at the seafloor after about
six weeks. In tropical regions, where both the seasonal
influence and the standing stocks are lower, aggregation
and sinking are much less important, and it may be
expected that contaminant transport to great depth by
this means is smaller and less episodic.
Speculation on this rather direct route for deep-sea
contamination finds support in the demonstration of
various substances accumulating on particles and concentrating in deep-sea organisms. Flegal and Patterson
(1983), Duce et al. (1991) and Mason et al. (1994)
described vertical profiles in the water column for the
concentrations of various metals; heavy metals were
found in deep-sea shrimps and fish, for instance, by
Kobayashi et al. (1979), Thiel et al. (1986), Karbe
(1987), Steimle et al. (1990), Mason and Fitzgerald
(1993) and Monteiro et al. (1996). However, not all
high concentration values are due to anthropogenic
inputs to the ocean; they may be due to age and
food-chain relationships (Windom et al., 1987; Vas
et al., 1993; Cronin et al., 1998). Data from the
Red Sea (Thiel et al., 1986; Karbe, 1987) clearly
indicate increasing concentrations in organisms above
the Atlantis-II-Deep, a region subject to hydrothermal
influence. Various organic contaminants in deep-sea
fish were reported by Kr¨ amer et al. (1984) and Steimle
et al. (1990).
Further transport mechanisms exist in the sedimentary environment. Reactive substances of riverine or
atmospheric origin may be adsorbed to particulate
matter and transported far into the open ocean, for
instance by the large visible plumes shed into the
Atlantic Ocean by the rivers Amazon and Congo.
Sediment may accumulate in shallow waters on the
outer shelf, the shelf edge or the upper continental
slope. Sediment masses, predominantly below the shelf
edge, may become unstable and mass flows may be
triggered, transporting sediment and contaminants in
slumps, slides or turbidity currents to great depths.
Hjalmar THIEL
this type of influence is known for deep-sea biota, but
there is no reason to believe that fish and invertebrates
there would not be affected at sufficiently high
concentrations. Whereas infertility and other sexual
deviations were discovered earlier in coastal regions,
female gastropods in the open North Sea were found to
be affected by tributyltin used in anti-fouling paints on
ship hulls (Ten Hallers-Tjabbes et al., 1994). Takahashi
et al. (1997) discovered this same contaminant to
a depth of 980 m in Suruga Bay (Japan) in fish,
crustaceans, cephalopods, gastropods and echinoderms.
Although these observations were made close to shore,
the data demonstrate the penetration of organotin
compounds into offshore and deep-water food chains.
Flux to great depth and reactive contaminants
As noted above, predominantly inert substances such
as the chlorofluorocarbons will enter the deep ocean,
and be transported around in it, with the thermohaline
circulation system. Consequently, although chlorofluorocarbons, like the radionuclides resulting from nuclear
tests, occur throughout the earth’s atmosphere, their
main entry into the deeper parts of the ocean takes
place through the formation of bottom water by downwelling of dense water masses, which occurs in rather
limited regions around Antarctica and in the Greenland
and Labrador Seas (e.g., Rudels and Quadfasel, 1991;
Schlosser et al., 1995b). The bottom waters of enclosed
deep basins like the Mediterranean and the Red Seas
are also formed in fairly restricted areas and also
carry contaminants into the deeper layers. Lipiatou
et al. (1997) calculated mass budgets and dynamics
for polycyclic aromatic hydrocarbons which enter the
Mediterranean from atmospheric fallout and riverine
input. Some of this material and other contaminants
settle to the seafloor within the Mediterranean, but
some find their way into the Atlantic with the
Mediterranean outflow over the sill 300 m deep in the
Strait of Gibraltar, to form a well-marked water mass
slowly spreading throughout the North-east Atlantic at
a depth between 600 and 1000 m.
A more direct and widespread route into the deep
sea, particularly for those substances which enter the
metabolism of living organisms or are scavenged by
particulate matter, is through the sinking of particles,
which may occur at all latitudes. This route into the
deep ocean by the sinking of particulate matter has
been recognized for more than hundred years, but
it is only within the last twenty years or so that it
has been realized that mass particulate transport to
great depth can occur in a matter of weeks (Billett
et al., 1983; Rice et al., 1986; Thiel et al., 1988/89;
Smith et al., 1996; De Wilde et al., 1998). Although
this transport mechanism probably exists throughout
the world oceans, its extent varies markedly in space
and time, being largely dependent upon the level of
primary production and season. For example, aggregate
formation and rapid sinking of organic matter, with any
associated contaminants, occurs in the North Atlantic
predominantly after the spring phytoplankton bloom,
and this phytodetritus arrives at the seafloor after about
six weeks. In tropical regions, where both the seasonal
influence and the standing stocks are lower, aggregation
and sinking are much less important, and it may be
expected that contaminant transport to great depth by
this means is smaller and less episodic.
Speculation on this rather direct route for deep-sea
contamination finds support in the demonstration of
various substances accumulating on particles and concentrating in deep-sea organisms. Flegal and Patterson
(1983), Duce et al. (1991) and Mason et al. (1994)
described vertical profiles in the water column for the
concentrations of various metals; heavy metals were
found in deep-sea shrimps and fish, for instance, by
Kobayashi et al. (1979), Thiel et al. (1986), Karbe
(1987), Steimle et al. (1990), Mason and Fitzgerald
(1993) and Monteiro et al. (1996). However, not all
high concentration values are due to anthropogenic
inputs to the ocean; they may be due to age and
food-chain relationships (Windom et al., 1987; Vas
et al., 1993; Cronin et al., 1998). Data from the
Red Sea (Thiel et al., 1986; Karbe, 1987) clearly
indicate increasing concentrations in organisms above
the Atlantis-II-Deep, a region subject to hydrothermal
influence. Various organic contaminants in deep-sea
fish were reported by Kr¨ amer et al. (1984) and Steimle
et al. (1990).
Further transport mechanisms exist in the sedimentary environment. Reactive substances of riverine or
atmospheric origin may be adsorbed to particulate
matter and transported far into the open ocean, for
instance by the large visible plumes shed into the
Atlantic Ocean by the rivers Amazon and Congo.
Sediment may accumulate in shallow waters on the
outer shelf, the shelf edge or the upper continental
slope. Sediment masses, predominantly below the shelf
edge, may become unstable and mass flows may be
triggered, transporting sediment and contaminants in
slumps, slides or turbidity currents to great depths.