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Recreational boat owners´ increased knowledge improves sea environment


sailingboats in a doc in the archipelago

Having your own boat makes it easier to reach fine bathing spots and beaches that are not located on the mainland. However, such recreational boating can also affect our coasts and seas. A new doctoral thesis highlights how recreational boat owners can use the sea more sustainably.

Studies in the new thesis show there is a connection between the number of bottom-anchoring boats and the number of anchor traces on soft bottoms. Furthermore, as anchoring takes place where there are important and sensitive species (e.g. eelgrass), there can be consequences for ecosystems and environments.

“The anchors we traditionally use dig into the sediments. Thus, they can destroy eelgrass roots and tear up the plants. In the long term, this can result in reduced eelgrass distribution. In its turn, this can have consequences for, amongst other species, cod. Cod use eelgrass as nursery areas,” explains thesis author Jenny Egardt, the University of Gothenburg.

Found higher than permitted concentrations of boat bottom paints

The thesis also shows that the concentration of the long banned tributyltin (TBT, a biocide used in antifouling paint) is above the limit value in the studied sediments.

underwater photo of eelgrass and two anchors“This is noteworthy. The use of TBT on recreational boats has been banned in Sweden since 1989,” comments Jenny.

Notwithstanding the negative impact from recreational boats, she is positive and believes that boat owners’ increased knowledge can lead to changed behaviour and a more sustainable use of natural amenities.

“After all, if you’re unaware of the impact you’re having through, for example, anchoring or use of boat paints, it is difficult to know that you should be acting differently. Through information and increased knowledge, we can continue the recreational use of our coastal areas while reducing our impact and ensuring we maintain our wonderful environment,” says Jenny.

Using the sea sustainably

She suggests that recreational boat owners should avoid bottom anchoring, especially in areas where eelgrass is natural habour with three sailingboatsvisible on the bed. Instead, they should reduce negative impact by anchoring alongside islands.

“We should also review whether bottom paint is necessary, or if we could use other methods. Hull covers and brush washing are examples. To reduce fuel emissions, we could also switch to alkylated petrol,” states Jenny.

Jenny EgardtListen to the podcast in which Jenny Egardt takes part:

Jenny Egardt, the Department of Biological and Environmental Sciences, the University of Gothenburg: telephone +46 (0)31 786 2935; mobile +46 (0)704 79 04 39; email

Thesis title: Impacts of Recreational Boating in Coastal Seascapes and Implications for Management.
Link to the thesis:
Supervisors: Per Nilsson, Ingela Dahlöf.

Bottom-anchored boats at Ursholmarna, Kosterhavet (photographer, Jenny Egardt).

Litter from the outdoor life can also be found in the shallows – here a disposable barbecue (photographer, Jenny Egardt).

Bottom anchoring occurs in the national park’s eelgrass – this can damage important habitats (photographer, Jenny Egardt).

Jenny Egardt (photographer, Albin Dahlin).