One of today´s water problems, in addition to plastic and oil spills, is the spread of harmful plants. Minor overgrowths is part of the natural development of shallow lakes, but due to human activities, change is many times quicker than in the natural state.
Due to human activities, water systems become eutrophic, which leads to their deterioration, proliferation of abundant algae deposit, changes in ecological community and the loss of oxygen in the bottoms. In an eutrophic water system, shores and shallows will overgrow, which makes it more difficult to use them for recreation. The spread of invasive species may also take up living space from native species.
Removal of Eurasian watermilfoil in Kokkola, Finland
Eurasian watermilfoil is not invasive species in Finland, but anyway harmful for swimming, fishing and boating. When the plant has arised to the surface, boating is impossible, so it must be removed step by step. Clewat was working in Kokkola on summers 2019 and 2020 with removal of Eurasian watermilfoil. Plants were removed with our vessel and at the same time the cutting head was developed to be even more functional.
Infrastructure manager of Kokkola city, Visa Wennström was closely involved in the work. “Many other plants are mowed usually, but removal of Eurasian watermilfoil is difficult. It has to be removed with its roots, because new plants are growing from floating parts of the plant and roots.” Wennström is happy with the collaboration: “Plants, which had been cut, were mostly removed, so that they were not left in the water to add nutrients and produce new plants.”
Harmful plants are widespread
Wennström tells that Eurasian watermilfoil has become as a real problem in the 2010s. In addition to it, also other harmful plants are spreading, as Hornwort, which occupies entire lakes and Canadian waterweed. While the climate is changing, the submerged plants may spread even more. Abundant plants are changing the aquatic ecosystem. Dead Eurasian watermilfoils sink to the bottom and release nutrients to the water systems. Some algaes, as Sargassum, may harm the biodiversity of the coast, fishing and tourism. It prevents nesting of the turtles and captures the dolphins and fishes.
Eutrophication and rising temperatures are the ideal combination for harmful plants to entry to new areas. New harmful species may conquer even large water areas only in few years, killing the biodiversity and also often the viability and the usability of the area. Even poisonous algaes and plants are conquering the water systems quickly, as is happening in Turkey now. There has tradiotinally been no effective control for these more challenging plants, but Clewat´s new tehcnology has changed it.
Harvested biomass can also be utilized. “The removed Eurasian watermilfoils were taken in Kokkola to the garden vast reception site, where the waste is composted and processed into soil, which is used in the city´s landscaping”, Wennström is telling. ” In the removal of water plants it is important to pay attention also to the monitoring methods, so that the effect of removal can be measured. This year we will photograph with drone this area in Kokkola and refer it to the areas, where removal has not been done.”
Significant work for the environment
So the growth of Eurasian watermilfoil is still followed in Kokkola, but the infrastructure manager gives already positive feedback. “The cooperation was great. Clewat has some enthusiastic employees there and also expertise.” Wennström tells that together with the personnel of Clewat also the logistics of removed plants was discussed, how it could be done without any interruption.
“Vessels are suitable for removal of many plants and litter. I think Clewat has good views for future – you are making significant work for the environment”, says Wennstöm in the end.
Clewat thanks for the feedback and continues the work for clean water systems!
Katja Vaulio