7.2 Accumulation 6
Some heavy metals and other trace elements, radioactive elements and chlorinated
hydrocarbons are accumulated so intensely by organisms that considerable concen·
trations result in the tissues of the organisms from the extremest dissolutions in sea·
water. Such accumulations have previously been noted and been considered a curiosity. It was learned that tunicates accumulate vanadium, and later that a number of
trace elements are essential for biochemical processes, especially for the synthesis of
vitamins and enzymes. Among these are copper, zinc, cobalt, and manganese. It is
evident that organisms needing these substances must be equipped to accumulate
them from the strongest dissolutions.
During earlier stages of marine pollution research, it became clear that an accumulation of such elements and organic compounds results, too, which according to current knowledge, have no positive metabolic function; on the contrary, they can manifest harmful effects. Now, following important nrst-stage results, research is beginning
to explain the different mechanisms of uptake which are evidently different from
substance to substance, to localize the point of storage, and to understand the mechanisms of elimination. Here too, it will not be possible to make sure judgments for a
number of years. To date, interest has centered only on those substances which seem
to be of direct importance to those fish that man uses as a source of nutrition.
In the smallest concentration it occurs in seawater, DDT is difficult to analyze quantitatively. In experiments, however, radioactively marked DDT can be used because
even the smallest doses of radioactivity can easily be measured and the traces of radioactively marked DDT can be tracked. If only 0.01 p.g/l of DDT is present in aquarium
water, marine worms (Lanice) absorb enough DDT to attain a more than 200-fold
wet weight concentration. Higher concentrations are attained if the experiments run
longer (Ernst 1972), until nnally an eqUilibrium concentration between concentration in the seawater and concentration in the tissues may be reached. There is a wide
range of concentration factors as the result of many experiments using many different organisms and experimental conditions (Table 27).
Methodological errors from past experiments may be responsible for the divergence
of existing data. But certain regular features are also implied, and it is possible that
there is a direct connection between the solubility of a hydrocarbon substance and
the concentration factor (Fig. 64). It is also known that accumulation is stronger in
tissues that are rich in fat than in those that contain little fat.
The accumulation of chlorinated hydrocarbons takes place not only from the surrounding seawater, but through food as well. Under experimental conditions, soles
can be fed pieces of meat that have been prepared with DDT. If a fish has been fed
17 p.g of DDT in a 4-week period, a DDT content of 0.5-0.8 p.g shows up in its muscles, while its brain and liver show a higher concentration. During the experiment,
these fish stored up approximately 60% of the total amount of DDT fed to them
(Fig. 65). Likewise, 58%-93% of the PCB's fed to them through food was found in
the body tissue of the polychaete Nereis virens after a 3-week period of digestion
(Goerke and Ernst 1977).
6 In this text the term accumulation includes bioconcentration (from concentration in seawater)
and biomagnification (from concentration in food)
126
Some heavy metals and other trace elements, radioactive elements and chlorinated
hydrocarbons are accumulated so intensely by organisms that considerable concen·
trations result in the tissues of the organisms from the extremest dissolutions in sea·
water. Such accumulations have previously been noted and been considered a curiosity. It was learned that tunicates accumulate vanadium, and later that a number of
trace elements are essential for biochemical processes, especially for the synthesis of
vitamins and enzymes. Among these are copper, zinc, cobalt, and manganese. It is
evident that organisms needing these substances must be equipped to accumulate
them from the strongest dissolutions.
During earlier stages of marine pollution research, it became clear that an accumulation of such elements and organic compounds results, too, which according to current knowledge, have no positive metabolic function; on the contrary, they can manifest harmful effects. Now, following important nrst-stage results, research is beginning
to explain the different mechanisms of uptake which are evidently different from
substance to substance, to localize the point of storage, and to understand the mechanisms of elimination. Here too, it will not be possible to make sure judgments for a
number of years. To date, interest has centered only on those substances which seem
to be of direct importance to those fish that man uses as a source of nutrition.
In the smallest concentration it occurs in seawater, DDT is difficult to analyze quantitatively. In experiments, however, radioactively marked DDT can be used because
even the smallest doses of radioactivity can easily be measured and the traces of radioactively marked DDT can be tracked. If only 0.01 p.g/l of DDT is present in aquarium
water, marine worms (Lanice) absorb enough DDT to attain a more than 200-fold
wet weight concentration. Higher concentrations are attained if the experiments run
longer (Ernst 1972), until nnally an eqUilibrium concentration between concentration in the seawater and concentration in the tissues may be reached. There is a wide
range of concentration factors as the result of many experiments using many different organisms and experimental conditions (Table 27).
Methodological errors from past experiments may be responsible for the divergence
of existing data. But certain regular features are also implied, and it is possible that
there is a direct connection between the solubility of a hydrocarbon substance and
the concentration factor (Fig. 64). It is also known that accumulation is stronger in
tissues that are rich in fat than in those that contain little fat.
The accumulation of chlorinated hydrocarbons takes place not only from the surrounding seawater, but through food as well. Under experimental conditions, soles
can be fed pieces of meat that have been prepared with DDT. If a fish has been fed
17 p.g of DDT in a 4-week period, a DDT content of 0.5-0.8 p.g shows up in its muscles, while its brain and liver show a higher concentration. During the experiment,
these fish stored up approximately 60% of the total amount of DDT fed to them
(Fig. 65). Likewise, 58%-93% of the PCB's fed to them through food was found in
the body tissue of the polychaete Nereis virens after a 3-week period of digestion
(Goerke and Ernst 1977).
6 In this text the term accumulation includes bioconcentration (from concentration in seawater)
and biomagnification (from concentration in food)
126