Algae are a fundamental, essential part of the ecosystem. Therefore, special attention is also being paid to the algae in connection with the environmental studies being carried out prior to the construction of the Fehmarnbelt Fixed Link.

"Algae are one of the first links in the food chain and therefore one of the most fundamental elements in life. They are eaten by zooplankton, which are, in turn, eaten by fish, which ultimately end up on our refrigerated display counters and our dining tables," says biologist Louise Schlüter, DHI.

Efficient chemistry
Many different species of algae need to be charted to assess the conditions of the algae during and after the construction of the fixed link. Different algae species are distinguished from each other by the pigments found in them. A microscope is traditionally used for this task. However, it is a fairly big task to analyse, count and measure algae under a microscope. A new method has now been introduced as part of the environmental studies.

"For the first time in Denmark we are using a method called HPLC for our studies. It is a chemical method that sorts the algae by pigments. Essentially, you could say that we are using a machine to look into the microscope for us. It is much cheaper and more efficient because the machine automatically analyses approximately 35 samples a day," explains Louise Schlüter.

Data from 12 stations
"When excavations are carried out for a bridge or tunnel across the Fehmarnbelt, a number of nutrients will be released from the sea bed. This may increase the volume of algae in the Fehmarnbelt. It is also possible that the project will change the water flows, which may also be of importance to the algae. Of course, this is all speculation, but these are the factors that we are studying carefully in advance."

"We have collected data from 12 stations in deep water and 10 stations near the Danish and German coasts in the Fehmarnbelt. The data collected is being compared using the HPLC method. We are also using the microscope method at three stations. All in all, this ensures that the environmental studies are both thorough and adequate," says Louise Schlüter.