In shallow water, divers collect samples of flora, fauna and seabed materials in the Fehmarnbelt. (photo: NATURFOCUS / Christian B. Hvidt)

The sea floor shelves down from both Fehmarn and Lolland to the deepest parts where the water is 25-30 metres deep. At some points on the slope, there are typical giant sandbanks. Changed current and wave conditions and the extraction and moving around of sea bed material can affect the appearance of the coastline and sea floor and can lead to the loss of habitat for animals and plants.

Mapping of the seabed
Diving below the surface of the water reveals a landscape of hills and valleys very reminiscent of the

scene on land. There are, however, no forests of trees or grassy meadows here, but forests of seaweed on the stones of the sea floor and meadows of sea grasses growing on the sea floor itself. Among the plants, there is a wealth of animal life.

There is also plentiful plant and animal life in and on the broad expanses of what looks like barren sea floor. So one requirement for a good environmental evaluation is detailed knowledge of the landscape of the sea floor, and the location of sand, mud and stones. To obtain this information, Femern A/S performed a range of surveys in summer of 2009, scanning the seabed with advanced instruments, retrieving samples and taking them to a laboratory for analysis.

Giant sandbanks
The giant sandbanks in the Fehmarnbelt and the surrounding seas were only discovered a few years ago, and it is still not known how large these areas are or how dynamic the sandbanks are. They may move around, as sand dunes are known to do on land. As they are very large – up to 3 metres high and with wavelengths of 12-100 metres – it is possible that their presence affects the water dynamics around them. Femern A/S expects that the environmental survey will give us answers to these questions.