Algae against eutrophication
Short description
Since the late 1980s, the amount of filamentous algae in shallow bays has increased sharply in northern Bohuslän. One cause is eutrophication, caused by nutrient run-off from land. Silted-up and overgrown sea bays are now a major problem.
The aim of this experiment is to investigate whether algae can absorb nutrients from the bottom sediment and thereby help purify the water.
Algae against eutrophication
Shallow enclosed bays are environments where filamentous algae thrive. Limited water exchange and high temperatures cause nutrients from the surrounding land to remain trapped in the bays, promoting algal growth. Since the 1980s, overgrown and silted-up bays have become an increasing problem, with dense mats of algae covering the water surface and negatively affecting other marine life.
At the same time, several algal species are now cultivated commercially. Because algae absorb nutrients from the water, they could potentially be used as “catch crops” in bays with high nutrient levels. The nutrients could then be removed from the bays when the algae are harvested and taken away.
Sediment from three bays
In this project, nutrient-rich bottom sediment has been collected from three enclosed bays and placed in tubes. During the summer, water is circulated through the sediment and through containers holding different amounts of algae of two different species. Nutrient levels in both the water and the sediment are measured regularly, and once the experiment is completed, the nutrient content of the algae is also analysed, together with levels of phosphorus, nitrogen and heavy metals. The results are then evaluated and theoretical estimates are produced for how much algae would need to be cultivated in order to reduce nutrient concentrations in the water.
The idea is that commercially cultivated algae could be used to lower nutrient levels in the bottom sediments of enclosed bays, thereby improving water quality and creating better habitats for other species.
