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.