Aquascope Facts
Unfortunately the situation is not so simple, as different types of plankton bloom in different areas along the coastline. For example in the Stockholm archipelago it has been seen that a decrease in the growth of the blue-green bacterias coincided with a decrease in phosphorus discharge, but at the same time there was a surplus of nitrogen in the water, probably because people concentrated on reducing the phosphorus discharge. Today, nitrogen discharges reach further out into the archipelago and has caused an increase in the production of plant plankton.
    An increase in the amount of blue-green bacteria also increases the amount of fixed nitrogen. A conclusion is that in the Stockholm area, measures should be taken to decrease the discharge of phosphorus, thus reducing the extent of the blue-green bacteria blooming and to reduce the absorption of nitrogen.
    It is even possible to reason that if, on a large scale, the discharge of phosphorus should decrease to such a degree that it would became the limiting factor for the growth of plant plankton and the finely threaded algae, independent of the nitrogen content of the water. To decrease the discharge of phosphorus is considered to be simplest technically, but also the cheapest if compared to nitrogen. The discharge of phosphorus originates mainly from sewage and sewage plants are able to improve the reduction of phosphorus by a process of chemical precipitation.

Measures within agriculture

As we discussed earlier, the spreading of liquid manure as a rest product from animal farming also contributes to the problem of over-fertilization. To reduce the seepage of nitrogen, this type of fertilization should occur at the beginning of the season when plants begin to grow and are able to consume the nitrogen before seepage occurs. If liquid manure is layed on bare arable mark, it is important that it is ploughed down as soon as possible.
    It is even possible to ferment liquid manure to produce methane, and use it as an energy source locally. Problems with liquid manure can also be reduced if the demand for products from the kind of animal keeping that produce it, can also be reduced.
    An exaggerated use of chemical fertilizers also causes seepage of nitrogen and phosporus from arable land. It is of vital importance that the amounts of chemical fertilizers being used should be adjusted to what the crops can absorb from the environment, but it can be difficult to sow sufficient quantities, so there is a tendency to sow a surplus to be on the safe side.
    With modern agriculture, it is common to specilize in one crop type so the land usually lies fallow during the winter, which results in the lack of plants to absorb the remaining nitrogen in the soil.
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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