Effects of sulfuric water pollutants on fertilization,embryonic development and larvae of the herring,Clupea harengus

Using herring (Clupea harengus) eggs and larvae from Baltic spring spawners, the biological effects of sulfuric pollutants (largely FeSO₄ and H₂SO₄) which are scheduled to be released daily into the North Sea in large quantities, have been tested. Dilutions (1:8000, 1:16000, 1:24000 and 1:32000) of the sulfuric pollutants were used as test media. Throughout all experiments water temperature was maintained at 8.0°±0.2°C, salinity near 16.5; eggs were artificially fertilized 1 or 6 to 7 h after catching the parent individuals and, attached to glass plates, incubated in 1 l aerated containers. In all test media brownish precipitates, which resulted from diluting the sulfuric pollutants with 50% sea water, tend to adhere to the egg surfaces, thereby possibly interfering with gaseous and other exchanges between egg and surrounding medium. Under conditions of maximum test medium effectiveness, percentages of successful fertilization and of egg survival are considerably reduced; diameter of fertilized eggs remains smaller; embryonic growth rate is retarded while the heart frequency tends to increase (indicating physiological stress); duration of incubation is shortened: percentage of successful hatching decreases and structural abnormalities of freshly hatched larvae increases. Dilutions down to 1:24000 and 1:32000 have rather limited effects. Exposure of 1 to 3 day old, healthy herring larvae to the 4 test media leads to failure of performing prey catching manoeuvres in 1:32000 and 1:24000, to impaired locomotory performances in 1:16000, and practically to paralysis, shrinkage, permanently bent bodies and death within a few days in 1:8000. Although the present study needs deepening through further and more detailed experiments, it can be said that the pollutants under consideration represent a danger to herring eggs and larvae at least up to a dilution of 1:32000.