Last ned - Direktoratet for naturforvaltning

Klimaendringer, havforsuring og langtransportert forurensning
Ocean acidification
Carbon dioxide concentrations both in the atmosphere and in the oceans have risen due to
anthropogenic greenhouse gas emissions. As a result, the average pH of ocean surface water is now
about 0.1 pH units lower than the pre-industrial level. It is estimated that pH may drop by almost 0.4
units in Norway’s sea areas in the period up to 2100, although no modelling studies have been
carried out in the Norwegian part of the North Sea and Skagerrak. Monitoring of acidification in the
North Sea has recently been started, and the results so far show large diurnal and seasonal variations
caused by biological activity.
Five pressures and impacts have been defined for ocean acidification. Changes in pH and the carbon
system are expected to have the greatest effects on ecosystem components. These changes may
result in lower saturation levels of calcium minerals that organisms such as diatoms, crustaceans,
molluscs and corals use to build calcium shells and skeletons. Food supplies for other organisms
could be affected as a result, with repercussions along food chains. Lower pH in itself may also have
direct effects on certain ecosystem components.
There is also concern about whether ocean acidification may result in changes in the nutrient and
organic material content of seawater, for example by affecting the nitrogen cycle. It could also result
in changes in the bioavailability of micronutrients. The future effects of these two factors are
assessed as moderate and minor respectively, but the knowledge base is very inadequate.
Ocean acidification could also result in changes in the transport, mobilisation and metabolism of
hazardous substances. The very limited knowledge we have at present makes it impossible to draw
any conclusions about the effects on the ecosystem components that have been assessed.
The final factor considered was a decrease in low-frequency ocean sound absorption. The assessment
concluded that this will have no effect in the management plan area.
It is expected that ocean acidification will have major cumulative effects in the management plan
area in the future.
Long-range pollution
The cumulative effects of long-range pollution have been assessed both for the current situation and
for the two scenarios for 2030, with most emphasis on the current situation.
Four different pressures and impacts have been defined under the theme of long-range pollution.
Long-range transport of hazardous substances (excluding radioactivity) is the factor that is assessed
to have the greatest effect in the management plan area today. Pollution levels are generally low in
the North Sea and Skagerrak, but higher than in the Norwegian and Barents Seas. The content of
hazardous substances in sediments is low, but somewhat higher near the coast. Levels in biota are
also low, but show wider geographical variation and variation between species, sampling media and
pollutants. However, since many of the pollutants in question are bioaccumulative, they may be
present at relatively high levels in species at the top of food chains. It is of particular concern that
levels of dioxins and dioxin-like PCBs in the liver of a large proportion of the gadids sampled in the
open sea exceeded the maximum levels permitted in foodstuffs. Moreover, levels of mercury in cod
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