Sea-bed Oxygenation Can Solve Eutrophication

We have been hearing about this problem world wide as a result of excessive nutrient run off overwhelming the sea bed and making it a dead zone.  Here the Norwegians have come up with the idea of simply pumping oxygenated water to the bottom and it works.

While they are at it, they may as well allow the bottom water to rise through a second tube to provide driving energy.   Self sustaining system is always way more popular.

It is early days but this needs to be played with.  A static buoy may be able draw rich deep water to the surface to encourage biology while taking oxy water down to energerised the seabed.  A real win – win exchange.

Sea-bed oxygenation can solve eutrophication

May 30, 2011

http://environmentalresearchweb.org/cws/article/news/46110

Researchers at the University of Gothenburg in Sweden have demonstrated that pumping oxygen-rich surface water down to the sea floor is an effective method of dealing with eutrophication.

The researchers, led by Anders Stigebrandt, conducted pilot studies in two fjords in Sweden. A large wind-driven pump is now to be tested in open water in the Baltic.

The team found that oxygenation of the sea bed creates the necessary conditions for the establishment of new ecosystems that enable nature to deal with eutrophication.

"Today everyone is focused on reducing nutrient inputs to the sea to reduce eutrophication in the Baltic, but by helping nature to deal with the phosphorus that is discharged we can create a turbo effect in the battle against eutrophication," says Stigebrandt. "If oxygen-free bottoms in the Baltic are oxygenated, it can be anticipated that every square kilometre of bottom surface will be able to bind 3 tonnes of phosphorus in a short time, which is a purely geochemical effect. If the bottoms are then kept oxygenated for a prolonged period, fauna becomes established on and in the bottoms.

This leads to the bottom sediments being oxygenated down to a depth of several centimetres, and the new ecosystem probably contributes to the possibility of further phosphorus being bound to the sediment."

The research project Baltic Deepwater Oxygenation, directed by Stigebrandt, is testing the hypothesis that prolonged oxygenation of the Baltic deep-water results in long-term and increasing binding of phosphorus in bottom sediment. An important question to be answered is how the oxygenated deep-water areas can bind phosphorus in the longer term. The answers are being sought through pilot studies in Byfjorden on the west coast and Kanholmsfjärden on the east coast, as well as in laboratory experiments. The project includes examining how the oxygenated bottoms are colonised and how this affects phosphorus uptake.

Stigebrandt is now planning a trial involving large-scale wind-driven pumping in the open water of the Baltic, in cooperation with Inocean AB, which is designing the pump on the basis of established technology from the off-shore industry. The pump will be contained in a 60 metre high and 100 metre deep tubular buoy that is anchored in an open location, in a deep basin yet to be decided off the east coast of Sweden. As a result of the buoy being given a small cross-sectional area at the water surface, the pump becomes non-sensitive to wave motions.

"The pump is to have capacity to pump 30 cubic metres of water per second, which is 15 times more than the pump in the Byfjord experiment," says Stigebrandt. "If this works, using a five times larger pump in a buoy around 120 metres deep should not pose major problems. This is the size we anticipate pumps needing to have in a future large-scale system for oxygenation of the Baltic deep water."