or weeks before they are ready to metamorphize. Tidal currents in the German Bight
transport larvae of benthic animals continuously, so that it is certain that they are
not able to settle down where their parents lived. A community of benthic animals is
therefore dependent on larvae from elsewhere ready to metamorphize when they
pass over the area. For many species that are distributed over an expansive area, one
can assume that their larvae are present everywhere in the plankton in the corresponding season and that they are able to settle anywhere that offers them the possibility to live. However, with species that are distributed in patches, the larvae are
transported in clouds by the water, and it is a matter of chance whether such a cloud
will settle in a certain area or not. Sometimes the corresponding species is missing
right next to it, even though the conditions for life might be favorable. Marine biologists then try in vain to deduce what reasons there may be for the various animal
settlements he encounters in his research.
One must be familiar with these complicated alternating relationships if one has to
diagnose possible pollution effects as a cause for changes in the stocks of organisms.
This is easy in the case of very strong effects (Fig. 4), but in the case of subtle effects,
only research conducted over a long period of time can lead to significant results.
This limitation of field results holds true for macrobenthos (now 11 years of evidence)
and for fish diseases (to be confirmed by future research) as methods to monitor
pollution effects northwest of Helgoland.
If it should be true that daily amounts of 1800 t of waste acid have no effect on the
organisms of a marine area, then this finding is of great importance, because it contradicts laboratory results. Experiments in which waste acid was added to various
marine organisms showed an adverse effect of industrial effluents from the titanium
plant, even at dilutions of 1 part to 50,000. Obviously however, such concentrations
occur only in the immediate area of the propeller wash. A dilution of the waste fluid
of I to 1000 is immediately accomplished by the ship's propeller. In the mixing process, this figure is reduced to 1 to 20,000 in 2 h. The acid effect of the waste does
not penetrate to the sea bottom at 28 m depth where a pH indicator was installed.
In the surface water of the area the reduction of the pH is less than 0.1 (Weichart
1975b).
If waste acid gets into seawater, a portion of the natural alkalinity of the seawater is
required for neutralization, and the amount of sulfate in the seawater is increased.
We do not know much at present about the influence of reduced alkalinity or increased
sulfate content on marine aminals. Ferreous sulfate is hydrolyzed in seawater. While
absorbing oxygen, iron 2+ oxidizes to iron 3+ and forms flakes of ferreous hydroxide
(Table 1). There is ample oxygen available north of Helgoland in surface water so that
there is no danger of a shortage. However, the iron concentration in the seawater has
measurably risen. Values were analyzed that correspond roughly to those found to be
produced by nature close to the coast and in estuarine areas (Fig. 36). Apparently a
balanced situation is thereby attained, and just as much iron is transported to the north
by currents as is introduced by effluents (Weichart 1975a). The concentration of chromium in the fine fraction of the sediment is about twice as high in the surrounding of
the disposal area in Helgoland Bight, compared with the regions farther away.
The news about possible correlations between skin tumors of a flat-fish, the dab, and
the wastes of the titanium dioxide plant have again intensified the discussion whether
62
transport larvae of benthic animals continuously, so that it is certain that they are
not able to settle down where their parents lived. A community of benthic animals is
therefore dependent on larvae from elsewhere ready to metamorphize when they
pass over the area. For many species that are distributed over an expansive area, one
can assume that their larvae are present everywhere in the plankton in the corresponding season and that they are able to settle anywhere that offers them the possibility to live. However, with species that are distributed in patches, the larvae are
transported in clouds by the water, and it is a matter of chance whether such a cloud
will settle in a certain area or not. Sometimes the corresponding species is missing
right next to it, even though the conditions for life might be favorable. Marine biologists then try in vain to deduce what reasons there may be for the various animal
settlements he encounters in his research.
One must be familiar with these complicated alternating relationships if one has to
diagnose possible pollution effects as a cause for changes in the stocks of organisms.
This is easy in the case of very strong effects (Fig. 4), but in the case of subtle effects,
only research conducted over a long period of time can lead to significant results.
This limitation of field results holds true for macrobenthos (now 11 years of evidence)
and for fish diseases (to be confirmed by future research) as methods to monitor
pollution effects northwest of Helgoland.
If it should be true that daily amounts of 1800 t of waste acid have no effect on the
organisms of a marine area, then this finding is of great importance, because it contradicts laboratory results. Experiments in which waste acid was added to various
marine organisms showed an adverse effect of industrial effluents from the titanium
plant, even at dilutions of 1 part to 50,000. Obviously however, such concentrations
occur only in the immediate area of the propeller wash. A dilution of the waste fluid
of I to 1000 is immediately accomplished by the ship's propeller. In the mixing process, this figure is reduced to 1 to 20,000 in 2 h. The acid effect of the waste does
not penetrate to the sea bottom at 28 m depth where a pH indicator was installed.
In the surface water of the area the reduction of the pH is less than 0.1 (Weichart
1975b).
If waste acid gets into seawater, a portion of the natural alkalinity of the seawater is
required for neutralization, and the amount of sulfate in the seawater is increased.
We do not know much at present about the influence of reduced alkalinity or increased
sulfate content on marine aminals. Ferreous sulfate is hydrolyzed in seawater. While
absorbing oxygen, iron 2+ oxidizes to iron 3+ and forms flakes of ferreous hydroxide
(Table 1). There is ample oxygen available north of Helgoland in surface water so that
there is no danger of a shortage. However, the iron concentration in the seawater has
measurably risen. Values were analyzed that correspond roughly to those found to be
produced by nature close to the coast and in estuarine areas (Fig. 36). Apparently a
balanced situation is thereby attained, and just as much iron is transported to the north
by currents as is introduced by effluents (Weichart 1975a). The concentration of chromium in the fine fraction of the sediment is about twice as high in the surrounding of
the disposal area in Helgoland Bight, compared with the regions farther away.
The news about possible correlations between skin tumors of a flat-fish, the dab, and
the wastes of the titanium dioxide plant have again intensified the discussion whether
62