On the response of the Baltic proper to changes of the total phosphorus supply.

Using a time-dependent phosphorus (P) budget model for the Baltic proper, describing sources and sinks at the external borders of the water column, one may compute the e-folding time T of the adjustment of the winter surface water P concentration c to abruptly changed total P supply. The restoration time TR = 3T is introduced as a practical measure of the time it takes to achieve 95% of the change of c towards the final, equilibrium, state c . The P budget model, including an internal source emanating from deep anoxic bottoms, also shows that c is proportional to the total P supply to the water column.

Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden.

Oxygen-depleted bodies of water are becoming increasingly common in marine ecosystems. Solutions to reverse this trend are needed and under development, for example, by the Baltic deep-water OXygenation (BOX) project. In the framework of this project, the Swedish Byfjord was chosen for a pilot study, investigating the effects of an engineered oxygenation on long-term anoxic bottom waters.

An experiment with forced oxygenation of the deepwater of the anoxic By Fjord, western Sweden.

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.

A new phosphorus paradigm for the Baltic proper.

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.

Improving oxygen conditions in the deeper parts of bornholm sea by pumped injection of winter water.

Vertical diffusivity and oxygen consumption in the basin water, the water below the sill level at about 59 m depth, have been estimated by applying budget methods to monitoring data from hydrographical stations BY4 and BY5 for periods without water renewal. From the vertical diffusivity, the mean rate of work against the buoyancy forces below 65 m depth is estimated to about 0.10 mW m(-2).

Improvement of Baltic proper water quality using large-scale ecological engineering.

Eutrophication of the Baltic proper has led to impaired water quality, demonstrated by, e.g., extensive blooming of cyanobacteria during the premium summer holiday season and severe oxygen deficit in the deepwater.