A detailed survey of marinas and rocky shores in south Devon and Cornwall have identified a link between populations of invasive seaweeds. Under certain conditions it seems that marinas facilitate the spread of the invasive kelp Wakame into natural rocky coastlines.

Wakame, or Undaria pinnatifida, is a non-native kelp that has been present in the UK since 1994. It is predominantly found in marinas or harbours, growing on man-made structures such as floating pontoons. Using a mixture of pontoon surveys, snorkelling and video techniques, Wakame was found at all marinas surveyed, but in only around half of the natural coastal sites.

Wakame was more likely to be found growing on natural coastlines when the site was close to a marina with a high abundance of the invader. Locations with larger areas of pontoons were also more likely to contain natural reef sites with higher amounts of Wakame. Where Wakame was found on natural coastlines, it was found in smaller amounts when the rock was more densely covered in native kelps, or was exposed to larger waves, suggesting that these factors may limit its spread.

Overall, this study shows that in many locations Wakame is still restricted to marina environments; but suggests that managing populations of Wakame in marinas and maintaining good environmental status for native kelps in natural rocky coastlines, could restrict the further spread of this invasive species around the UK.

“Environmental and ecological factors influencing the spillover of the non-native kelp, Undaria pinnatifida, from marinas into natural rocky reef communities”

Read the article in the journal Biological Invasions at https://link.springer.com/article/10.1007/s10530-017-1610-2

Find out more about the Benthic ecosytems and environmental change research group

Nov 2, 2017 By guba