Pollution in the harbour of Ostend (Belgium): biological and hydrographical consequences

1. Ostend, situated in the middle of the Belgian coast, is a typical seaside resort with a population of 60,000 in the winter and up to 200,000 in summer. All sewage (to the major part raw dornestic sewage, to a lesser extent sewage of industrial origin) flows into its harbour, causing a daily in flow of ca. one part of sewage per 100 parts of harbour water. This heavy pollution load causes significant physico-chemical and biological consequences. 2. The number of "estuarine" bacteria has increased enormously due to the great daily input of organic matter. The number of coliform bacteria is high; it decreases towards the seaward entrance of the harbour. 3. The beach in the small vicinity of the harbour is polluted. 4. The harbour water contains low amounts of dissolved oxygen; its transparency is reduced resulting in poor or in non-existent phyto-plankton production. 5. The number of zooplankton species decreases from the outer- to the inner parts of the harbour. 6. The benthos consists of black, completely anoxic mud, which strongly smells of sulfides; its content of organic matter is much higher than that of sediments in the open sea. 7. Rich development of a typical " Aufwuchs" biocoenosis which thrives on the richness in organic matter of the water . 8. Pollution of the harbour must be reduced or halted if even more serious danger is to be prevented