Aquascope Facts
Different coastal areas vary in sensitivity to over-fertilization depending on the amount of nutrients that are supplied and how large and quickly the water exchange is. This implies that the problems caused by over-fertilization can be combated in different ways depending on the environment. In certain areas, for example around Tjörn on the Swedish west coast, water exchange is low, while the delivery of nutrients is high. In such areas, local measures would be more suitable and effective by reducing the nitrogen delivery. In other areas, such as around Gotland in the Baltic, the majority of the nitrogen delivery comes from other coastal areas. Here the problem is not as acute, but such a large scale problem needs to tackled on a national and international plane.

Nitrogen or phosphorus?

Blue-green bacteria in a bay
Blue-green bacteria can exploit nitrogen gas from the air and is therefore restricted in its growth by the lack of phosphorus. Shown above, we see how large quantities of the bacteria Nodularia spumigena have driven into a small bay.
The question is, should measures be taken against nitrogen or phosphorus, or maybe both ? The answer is not easy. It has been seen that the growth of plant plankton is inhibited by the lack of nitrogen. An exception is the blooming of the blue-green bacterias, which are inhibited by the lack of phosphorus. Even the blooming of algae in the Gulf of Bothnia is inhibited by the lack of phosphorus.
    It is difficult to decision to make as to whether it is best to decrease the discharge of phosphorous or nitrogen. Probably it is best to lower the discharge of nitrogen along the Swedish coastline, to enable a decrease in the growth of plant plankton and the finely threaded algae.

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A splendid outing ?
Problems and expectations
”It was better before"
Seawater and soluble salts
The sea moves
Coastal waters are close to us
What is eutrofication?
Sources of over-fertilization
How the open masses of water are effected
How shallow bays are effected
What can we do?
Alga harvest

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Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson