 |
|
Why are shallow bays effected by over-fertilization
To be able to explain why 68% of the bays
along the coast of Bohuslän became choked-up, several factors need
to be taken into consideration. As we have disussed earlier, different human
activities result in a large nitrogen
load. Because of this increased supply of nutritive elements, the short
lived algae has through competition ousted other algae and we have a new
ecosystem where new specie establish themselves, which in turn can result
in that certain bottom-living organisms are eradicated. With this course
of events, we get fewer bottom-living organisms that can utilize the increased
supplies of nutrients and this can have an accelerating effect: increased
supplies of nutritive elements and fewer organisms that consume them.
Man can also cause problems by stopping or redirecting water
currents. As the years have passed we have built roads between different
islands in the archipelagoes, for example embankments that are often built
and choke the natural flow and hinder the exchange of water. Stagnant water
usually results in that no new oxygen is supplied to the system. Today we
have learned that by placing large piping in the embankments in a certain
way, embankments can be built without choking the flow of water.
Even when building other constructions, such as piers and
carparks, a large exchange of water can still occur, but careful planning
is needed and measures taken so that the flow of water is not changed in
an unfavourable manner.
That the occurrance of finely threaded algae is higher in northern
Bohuslän compared to the southern areas can also be due to a naturally
lower water exchange. Archipelagoes also have a great many islands and narrow
passages that also reduce the flow of water.
 |
Page
19 of 28 |
 |
|
