Oxygenation of the Bornholm Basin would promote cod reproduction and feeding

A recently published paper in the scientific journal Ocean Science shows that oxygenation of the Bornholm Basin by pumping down well oxygenated water from 30 m depth into the stagnant deepwater would have a number of positive effects, see the Abstract below. The paper, written by Anders Stigebrandt, Rutger Rosenberg, Love Råman Vinnå and Malin Ödalen, can be found under the tab Downloads (scroll down to “Other publications”). Interested may also want to download the original manuscript of the paper together with reviews and external comments to the manuscript and the authors comments to these, all published together in Ocean Science Discussions.

We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping well oxygenated so-called winter water to the greatest depth, where it is forced to mix with the resident water, the rate of deepwater density reduction increases as well as the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m3 s-1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (cod reproduction volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O2 > 2 mL L-1), should every year be greater than 54 km3, which is an immense improvement, since it has been much less in certain years. Anoxic bottoms should no longer occur in the basin, and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.

Sweden now positive to start testing large scale oxygenation of the Baltic Sea

Positive news for oxygenation solutions for the Baltic Sea have been published in Swedish newspaper Sydsvenskan. The original text can be found here (in Swedish):
Sydsvenskan – Ingenjörskonst motar algsörja.

English translation:
The Swedish Ministry of the Environment proposes that Helcom should consider methods in the open sea to decrease eutrophication and stop vast cyanobacteria blooms. It is about trying to speed up the recovery of the Baltic says Senior administrative officer Mr Anders Alm who will present the suggestion at the forthcoming Helcom meeting.

The outlet of phosphorus from sewage treatment plants, industries and agriculture has decreased strongly the last twenty years. In spite of this the number and strength of algal blooms increase. Anders Alm says that it might take fifty or one hundred years for the Baltic to recover if efforts are limited to decrease land sources. The countries around the Baltic do it well in building sewage treatment plants and decreasing the leakage from agriculture but in spite of this the situation has not improved.

The bottoms contain huge amounts of phosphorus that is released under anoxic conditions. According to Professor Anders Stigebrandt is the phosphorus supply from bottoms about three times greater than the supply from water rivers and other sources on land. According to Stigebrandt and his research group is the solution to pump oxygen rich water down into the deepwater to bind the phosphorus. The method has been tested in smaller scale in the By Fjord at Uddevalla and he sees only positive effects. In large scale the method should also be of benefit for cod.

Anders Alm has a small bundle of suggestions to Helsinki that he hopes that Helcom’s experts can evaluate. One method is the Stigebrandt oxygenation pump. Another method aims at chemically bind phosphorus to the bottom sediment. A third method is to dredge the uppermost nutrient rich layer of the bottom sediment. The method sucks the sediment layer without spreading sediment particles Anders Alm says. He don’t consider it obvious that Helcom will welcome thoughts of using engineering methods to decrease algal blooms and bottom death.

Those who want to make scaremongering of this call it geoengineering and says that we manipulate natural systems. But we manipulate in many other ways, for instance through large scale fisheries and our farming landscapes, senior administrative officer Mr Anders Alm says.

Results of ByFjord oxygenation experiment

A paper regarding the recently ended oxygenation experiment in the ByFjord on the Swedish west coast and major geochemical, toxocological and ecological results has just been published in the scientific journal AMBIO. First author of the paper is BOX-WIN project leader Anders Stigebrandt.

The paper can be downloaded from our Downloads-page and is found under the topic “Other publications”.


In a 2.5-year-long environmental engineering experiment in the By Fjord, surface water was pumped into the deepwater where the frequency of deepwater renewals increased by a factor of 10. During the experiment, the deepwater became long-term oxic, and nitrate became the dominating dissolved inorganic nitrogen component. The amount of phosphate in the water column decreased by a factor of 5 due to the increase in flushing and reduction in the leakage of phosphate from the sediments when the sediment surface became oxidized. Oxygenation of the sediments did not increase the leakage of toxic metals and organic pollutants. The bacterial community was the first to show changes after the oxygenation, with aerobic bacteria also thriving in the deepwater. The earlier azoic deepwater bottom sediments were colonized by animals. No structural difference between the phytoplankton communities in the By Fjord and the adjacent Havsten Fjord, with oxygenated deepwater, could be detected during the experiment.

New phosphorus paradigm for the Baltic Sea

A paper with BOX-WIN project leader Anders Stigebrandt as first author and staff member Malin Ödalen as one of the co-authors regarding the phosphorus dynamics in the Baltic proper and the Bornholm Basin has just been published in the journal AMBIO.

The paper can be downloaded from our Downloads-page and is found under the topic “Other publications”.


The external phosphorus (P) loading has been halved, but the P content in the water column and the area of anoxic bottoms in Baltic proper has increased during the last 30 years. This can be explained by a temporary internal source of dissolved inorganic phosphorus (DIP) that is turned on when the water above the bottom sediment becomes anoxic. A load-response model, explaining the evolution from 1980 to 2005, suggests that the average specific DIP flux from anoxic bottoms in the Baltic proper is about 2.3 g P m-2 year-1. This is commensurable with fluxes estimated in situ from anoxic bottoms in the open Baltic proper and from hydrographic data in the deep part of Bornholm Basin. Oxygenation of anoxic bottoms, natural or manmade, may quickly turn off the internal P source from anoxic bottoms. This new P-paradigm should have far-reaching implications for abatement of eutrophication in the Baltic proper.

New BOX-WIN report published

A new report with results of the BOX-WIN project has now been published;

Technical Report no. 9
Application procedure requirements for concession to anchor and use a floating offshore wind turbine with pumping package in the Bornholm Basin – based on national legislation and the Espoo (EIA) Convention”

An application for concession will be required if a Demonstrator is to be tested in the Bornholm Basin. This report focuses on the guidelines for formulation of an application for concession, following Danish procedure and with regard to the Espoo Convention.

All BOX-WIN Technical Reports are available for download at our Downloads page.

BOX-WIN Technical Report no. 8 published

The latest report with results of the BOX-WIN project has just been published;

Technical Report no. 8
“Plan and Cost Estimate for a Demonstrator – a floating wind turbine unit equipped with pumps for oxygenation of the deepwater, and associated patents and immaterial rights”

In this report, the estimated costs for the realization of a Demonstrator are presented together with an expected time schedule. Costs for alternative configurations and larger systems of pumps are also estimated.

This Technical Report can now be downloaded from our Downloads page.

More BOX-WIN results published

Two new reports with results of the BOX-WIN project have now been published. These Technical Reports can now be downloaded from our Downloads page.

Technical Report no. 6
“Long-time behaviour of mustard gas dumped in the Bornholm Basin”

Technical Report no. 7
“Survey of Swedish suppliers to a floating wind turbine unit equipped with pumps for oxygenation of the deepwater”

The results presented in these reports are important for the environmental assessment and the construction of a Demonstrator in the Bornholm Basin.

New BOX-WIN reports published

The latest results of the BOX-WIN project have now been published. The results are presented in two Technical Reports which can be downloaded from our Downloads page.

Technical Report no. 4
“Assessing feasible mooring technologies for a Demonstrator in the Bornholm Basin as restricted to the modes of operation and limitations for the Demonstrator”

Technical Report no. 5
“Assessing important technical risks from use of a floating wind turbine unit equipped with pumps for oxygenation of the deepwater”

These reports concern mooring of a Demonstrator and technical risks which need to be considered in the construction of the Demonstrator.

BOX-WIN results published

The first results of the BOX-WIN project have now been published and are available for download here. These first results are presented in three separate reports:

Technical Report no. 1
Hydrographical conditions in the Bornholm Basin of importance for oxygenation of the deepwater by pumping down oxygen saturated water from above the halocline”

Technical Report no. 2
”Factors of potential importance for the location of wind-driven water pumps in the Bornholm Basin” 

Technical Report no. 3
Improving oxygen conditions in the deeper parts of Bornholm Sea by pumped injection of winter water” 

BOX-WIN in Sea Technology magazine

BOX-WIN project leader Anders Stigebrandt has written ”Evaluating Geoengineering as a method to Revive Baltic Sea Dead Zones” in the December 2012 Soapbox column in Sea Technology magazine.

In this feature he describes the general ideas of oxygenation of the Baltic Sea anoxic bottoms by pumping down oxygen saturated winter water from above the halocline to the deepwater. He also assesses the possibilities and requirements of the work within the BOX-WIN project.

The feature can be downloaded from our Downloads-page and is found under the topic ”Other publications”.