7 General Problems of Harmful Substances in the Sea
7.1 Toxicity
Many environmental chemicals have a toxic effect on marine organisms. They reduce
the number of survivors, influence metabolism, photosynthesis or breeding efficiency,
and alter behavioral patterns. To date, too little has been known about sublethal toxic
effects and long-term effects. It is also uncertain to what degree laboratory tests apply
to effects in natural environments. The toxic effect of a heavy metal, for example, may
be quite different, depending on the composition in which that element occurs.
In the presence of chelating or complexing substances, the toxicity of heavy metals
is often less than when metal ions have a direct effect. Metalorgano complexes are
not absorbed by organisms from seawater to the same degree, and since natural seawater contains different amounts of complexing substances, different samples of
seawater may result in different toxicity reactions, after the addition of the same
amounts of heavy metals. However, detergents may facilitate the entry of heavy metals
and other poisonous substances into organisms and increase the toxic effect.
Certain metalorgano compounds are much more poisonous than the metal is in ion
form. These are applied in plant insecticides and fungicides (Fig. 60). Under microbial
influence in marine environments, lead salts are changed into methyllead which in
experiments has a much more poisonous effect on diatoms than lead nitrate (Wong
et a1. 1975). Methylmercury is not only produced via bacteria from metallic mercury,
but also from various anorganic mercury compounds. Certain bacteria can also make
metallic mercury from methylmercury (Spangler et a1. 1973). Under anaerobic culture conditions, some bacteria are not harmed by mercury because the mercury
introduced is changed directly into nontoxic mercury sulfide (Gillespie and Scott
1971; Vo~an and van der Hoek 1972).
No wonder, then, that natural bacteria populations in experiments react unpredictably
to increased amounts of heavy metals. Within a few days, a selection takes place.
Sensitive species, which can only take 0.1 mg/kg of cadmium in the agar nutrition
substratum, die off at higher toxic concentrations. In 2-3 days, however, species that
tolerate cadmium increase and even thrive on concentrations of 5 mg/kg of cadmium
(Thormann 1975). In corresponding experiments, lead-resisting bacteria can survive
200 mg/kg of lead in the nutrient substratum.
Under natural conditions, not just one, but a whole variety of harmful substances has
an effect on organisms. But to date, little is known about whether the toxic effect of
various harmful substances increases or reduces the effect of a certain poison or
whether a synergistic, hyperproportionally harmful effect might also occur. The
small number of findings are contradictory.
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7.1 Toxicity
Many environmental chemicals have a toxic effect on marine organisms. They reduce
the number of survivors, influence metabolism, photosynthesis or breeding efficiency,
and alter behavioral patterns. To date, too little has been known about sublethal toxic
effects and long-term effects. It is also uncertain to what degree laboratory tests apply
to effects in natural environments. The toxic effect of a heavy metal, for example, may
be quite different, depending on the composition in which that element occurs.
In the presence of chelating or complexing substances, the toxicity of heavy metals
is often less than when metal ions have a direct effect. Metalorgano complexes are
not absorbed by organisms from seawater to the same degree, and since natural seawater contains different amounts of complexing substances, different samples of
seawater may result in different toxicity reactions, after the addition of the same
amounts of heavy metals. However, detergents may facilitate the entry of heavy metals
and other poisonous substances into organisms and increase the toxic effect.
Certain metalorgano compounds are much more poisonous than the metal is in ion
form. These are applied in plant insecticides and fungicides (Fig. 60). Under microbial
influence in marine environments, lead salts are changed into methyllead which in
experiments has a much more poisonous effect on diatoms than lead nitrate (Wong
et a1. 1975). Methylmercury is not only produced via bacteria from metallic mercury,
but also from various anorganic mercury compounds. Certain bacteria can also make
metallic mercury from methylmercury (Spangler et a1. 1973). Under anaerobic culture conditions, some bacteria are not harmed by mercury because the mercury
introduced is changed directly into nontoxic mercury sulfide (Gillespie and Scott
1971; Vo~an and van der Hoek 1972).
No wonder, then, that natural bacteria populations in experiments react unpredictably
to increased amounts of heavy metals. Within a few days, a selection takes place.
Sensitive species, which can only take 0.1 mg/kg of cadmium in the agar nutrition
substratum, die off at higher toxic concentrations. In 2-3 days, however, species that
tolerate cadmium increase and even thrive on concentrations of 5 mg/kg of cadmium
(Thormann 1975). In corresponding experiments, lead-resisting bacteria can survive
200 mg/kg of lead in the nutrient substratum.
Under natural conditions, not just one, but a whole variety of harmful substances has
an effect on organisms. But to date, little is known about whether the toxic effect of
various harmful substances increases or reduces the effect of a certain poison or
whether a synergistic, hyperproportionally harmful effect might also occur. The
small number of findings are contradictory.
120