The increase in particles in the seawater is a result of mild winters, which have created conditions for increased transport of water-borne particles from the Continent to the coast of southern Norway, and on-shore interventions that have produced greater run-offs also from Norwegian rivers.

A summary of twelve years of monitoring
Commissioned by the Norwegian Pollution Control Authority (SFT) and drawn up by the Norwegian Insitute for Water Research (Norsk institutt for vannforskning – NIVA) and the Norwegian Institute of Marine Research (Havforskningsinstituttet), the report compiles the results from twelve years of monitoring the water quality along Norways’s southern coastline.

Sugar kelp: More particles in the sea means less seaweed and kelp. Taken by the Buøya monitoring station near Arendal, the picture on the left is from 1992, that on the right from the same area in 2002. Photos: Frithjof Moy, NIVA

Changes in biological diversity
Increased quantities of particles cause the light to fade more quickly in the deep, and with, kelp and other algae depending on light to grow, this means that they are now unable to flourish at the depths they were previously known to inhabit. Mud deposits also reduce germination and growth.

The problem of mud deposits is most serious for algae and creatures that live in the deep, although life in littoral zone is not necessarily visibly affected. Less seaweed and kelp produces poorer growth conditions for fish and other creatures.

Sugar kelp disappearing
The particles increase the deposits of mud on the sea bottom, and this badly affects sugar kelp, which dies and is replaced by other species, or the bottom is left without any vegetation at al. The increased concentration of particles is probably a contributory factor for these changes in biological diversity. The pictures above, taken at the Buøya monitoring station near Arendal, show that the sugar kelp has disappeared.

Climate affecting water quality
Since the monitoring started in 1990, we have enjoyed mostly mild winters with heavy precipitation. This has caused an increase in the long-distance transport of water-borne particles to the Norwegian coast from the Continent. What’s more, these mild winters have in certain years also produced floods in Norwegian rivers, giving particles runoffs to the sea.

Run-offs from land an important source
Long-distance transport is of far greater significance than the particles generated locally, and are dominant in the autumn and winter. In the spring and summer, local Norwegian input of nitrogen are important for the production of phytoplankton and thus also the particle quantity in coastal waters. 

In addition to the climatic effects, human interventions in areas of precipitation (drainage along watercourses, removal of wetland areas, deforestation and removal of other vegetation that holds back water and particles), both on the Continent and in Norway, have led to an increase in the run-off of particles into the sea from rivers.

Read more:

• Long-term monitoring of the quality of the environment in Norway’s coastal areas: Annual report for 2002 (PDF file of 1982 kB)

For enquiries, please contact:

• SFT: Kari Holden, Head of Section for Environmental Data
  tel. +47 22 57 35 18, e-mail: kari.holden@sft.no      
• SFT: Karen Fjøsne, Adviser, Section for Environmental Data
  tel. +47 22 57 34 68, e-mail: karen.fjosne@sft.no      
• NIVA: Frithjof Moy, Research Scientist
  tel. +47 37 29 50 71, mobile: +47 957 71 328, e-mail: frithjof.moy@niva.no