#5769 Shallow grassy area, Mariager Fjord, Denmark

Environment

Environment

Affected by human activity

Affected by human activity

Agriculture

Agriculture

Advanced

Surrounding area

Mariager Fjord is a beautiful inlet, but as it is with most other parts of Denmark it’s not wild. Much of the area surrounding the fjord is cultivated by agriculture or human settlement. In some areas of the Fjord, there are farm animals grassing close to the shore.

A lot of the fjord is dominated by forest, and some of the forests are even relatively old. Most of it is dominated by human activity though. The most wild area is perhaps Bramslev Bakker (Bramslev Hills). This area is dominated by old forests, heather, and some “wild” living cows.

Underwater landscape

The underwater landscape of Mariager Fjord is relatively varying. If one disregards areas dominated by stones, the bottom of the fjord is very silty and plain. The bottom is mostly sand, covered with a thick layer of silt, which is swirled around in the water by the slightest disturbance. Some areas, close to the shore, are dominated by stones. These areas an inhabited by other types of fish than the silty areas.

Close to the shoreline the underwater landscape is dominated by large open areas, with only sand and silt. This is broken only by small islands of plants – mostly Ruppia maritima. In these plant groups of juvenile Gasterosteus aculeatus lives. The open sandy areas are only inhabited by Pomatoschistus microps.

The level of salinity declines as the closer we get to the shoreline. In this habitat the salinity is relatively low.

Threats to ecology

The biggest threat to Mariager Fjord is by far the recurring oxygen depletion. This is a major problem for the inlet. The problem occurs when the summers become too hot, and without either wind or rain to circulate oxygen into the water. When this happens much of the aquatic life of the fjord dies. Big amounts of fish can be seen drifting around with the belly’s in the fender. This latest major depletion was in 1997.

The depletion of oxygen is a natural phenomenon, but it is reinforced by agricultural emissions of nitrogen into the water.

Furthermore, the fjord is also used for industrial shipping, which is also a problem for aquatic life.

Human activity and settlement close to the fjord is a problem as well.

Riparian zone

Trees near the aquatic habitat

Few -

Bibliography

• → Geografisk Institut, University of Copenhagen - Iltsvind i Mariager Fjord - Hvorfor kom det i 1997? (Oxygen depletation in Mariager Fjord - why did it occur in 1997?) by Professor Christian Christiansen
  

Sitography