A serious environmental hazard is building up on the bed of the North Sea in the form of steadily increasing petroleum sludge deposits. The presence of this accumulating layer of oil residue deep beneath the often-turbulent waters of the North Sea is being cited as a possible factor in the death of an estimated 200,000 sea birds off the coast of Norway and Sweden.
Ocean scientists called in to suggest explanations for the Scandinavian disaster say the petroleum deposits during stormy weather can be whipped up the surface of the sea.
The scientists say the expanding offshore oil industry in northern waters make it inevitable that the buildup of sludge will continue unless far-reaching new regulations are introduced to combat it.
The dimensions of the sea-bird tragedy in Scandinavian waters began to become clear at the weekend as tens of thousands of petrels and other birds came drifting in on the tide. Some were already dead, others had to be put out of their misery because their feathers were hopelessly polluted.
Estimates suggest that 200,000 sea birds will be lost when a final count is made.
At first the cause of the disaster was a total mystery. Antipollution officials thought an oil tanker discharging its tanks in open water may have been the culprit. Another theory was that there had been an unreported spill from an offshore oil rig.
Scientists, however, are coming around to the view that such incidents are contributing to a much greater lurking danger as a petroleum, from whatever source, sinks to the seabed.
Even when an oil slick is identified and chemicals are used to disperse it, a residue of petroleum sinks beneath the ocean surface. When oil slicks disperse of their own accord, the heavier petroleum components fall to the seabed, where they begin to buildup up.
It only needs sustained gales and violent deep sea water currents for the sludge to begin rising to the surface.
One worrying aspect of the sea bird disaster is that many of the birds being washed up in Scandinavia bore leg rings fitted in Britain. This points to the likelihood of the original cause being in British North Sea waters.
For so many birds to have been affected in one incident would require a massive oil spill from a rig or tanker, scientists say.
They point out that a little-known pollution hazard in the North Sea is created by tanker skippers who encounter an oil slick and, instead of reporting it, discharge their own waste into the midst of it in the hope that they will not be discovered.
Such behavior increases the risk that large quantities of sludge will disappear in particular places and begin building up on the seabed where it will destroy life.