Wirkungen von „Rotschlamm“ auf Embryonen und Larven des HeringsClupea harengus

Abstract

Bauxite, a hydrated alumina, has very great technological importance as raw material for aluminium production. In the process of dry decomposition, it is sintered at red heat with soda ash and quicklime. On subsequent treatment with water, the aluminium goes into solution, while the iron remains undissolved as ferric hydroxide (red mud). Using herring eggs and larvae from Baltic spring spawners, the biological effects of red mud (which is intended to be released into the North Sea in large quantities) have been tested (at 14.0°±0.2° C and salinity near 15 ‰). Eggs were artificially fertilized and incubated in 1 l aerated containers. The addition of red mud considerably reduced percentages of survival to about 40 to 50% (controls: 90 %), when the eggs were exposed to various concentrations of suspended red-mud particles (1, 2, 5 and 10 ml/l). The red-mud particles adhered to the eggshells, forming an almost regular layer, thereby possibly interfering with gaseous and other exchanges between eggs and surrounding medium. In addition, the effects of sedimentation of red-mud suspensions of various initial concentrations on herring eggs, spread out in one layer, were studied. In concentrations of 1.25, 2.50, 6.25 and 12.50 ml red-mud per litre sea water, percentage mortality to hatching increased to about 78, 88, 95 and 100% (controls 13%). Speed of development was retarded and number of embryonic malformations increased with increasing concentrations; also the total length of hatched larvae decreased significantly more than in the controls. Many larvae took up red-mud particles, which blocked food intake.

Zusammenfassung

1. In 2 Versuchsreihen wurde der Einfluß verschiedener Rotschlamm-Suspensionen auf die Embryonalentwicklung des Herings geprüft.

2. In allen benutzten Rotschlammkonzentrationen traten im Vergleich zu den Kontrollen hohe Sterblichkeits- und Mißbildungsraten auf.

3. Mit steigender Konzentration der Rotschlamm-Suspension schlüpften kleinere Larven mit größerem Dotter und zunehmendem prozentualen Anteil an Verkrümmungen in der Kopfregion.

4. Blieben die geschlüpften Larven der Rotschlammsuspension ausgesetzt, so stieg der Anteil der Larven mit verstopften Mäulern in Abhängigkeit von der Konzentration und Einwirkungszeit an.