Artificial marine structures facilitate the spread of a non-indigenous green alga, Codium fragile ssp. tomentosoides, in the north Adriatic Sea
Article first published online: 31 OCT 2005
Journal of Applied Ecology
Volume 42, Issue 6, pages 1063–1072, December 2005
How to Cite
BULLERI, F. and AIROLDI, L. (2005), Artificial marine structures facilitate the spread of a non-indigenous green alga, Codium fragile ssp. tomentosoides, in the north Adriatic Sea. Journal of Applied Ecology, 42: 1063–1072. doi: 10.1111/j.1365-2664.2005.01096.x
- Issue published online: 23 NOV 2005
- Article first published online: 31 OCT 2005
- Received 25 March 2005; final copy received 20 July 2005 Editor: Phil Hulme
- biological invasions;
- Codium fragile ssp. tomentosoides;
- hard coastal defence structures;
- wave exposure
- 1Artificial structures have become ubiquitous features of coastal landscapes. Although they provide novel habitats for the colonization of marine organisms, their role in facilitating biological invasions has been largely unexplored.
- 2We investigated the distribution and dynamics of the introduced green alga, Codium fragile ssp. tomentosoides, at a variety of spatial scales on breakwaters in the north Adriatic Sea, and analysed experimentally the mechanisms underlying its establishment. We assessed the provision of sheltered habitats by breakwaters, the role of disturbance (e.g. from recreational harvesting and storms) acting at different times of the year, and the interactions between Codium and the dominant native space-occupier, the mussel Mytilus galloprovincialis.
- 3Codium fragile ssp. tomentosoides has established viable populations on artificial structures along the shores investigated. The density, cover and size (length, branching and weight) of annual erect thalli of Codium was enhanced in sheltered conditions, resulting in the monopolization of landward low-shore habitats of breakwaters.
- 4On the landward sides of breakwaters, disturbance enhanced recruitment of Codium. The time when bare space was provided within mussels beds was crucial. Removal of mussels in April or January did not affect the recruitment of Codium, whereas harvest in August, shortly before Codium gamete release, doubled its success. On the seaward sides of breakwaters, the effects of disturbance were more complex because mussels both inhibited recruitment of Codium and provided shelter from wave action to adult thalli.
- 5Synthesis and applications. Artificial structures can provide suitable habitats for non-indigenous marine species and function as corridors for their expansion. Physical (wave exposure) and biotic (resident assemblages) features of artificial habitats can be important determinants of their susceptibility to biological invasions. Alternative options in the design of artificial structures and effective management of native assemblages could minimize their role in biological invasions. In particular, increased water motion and retention of space by mussels in spring–summer would be effective in reducing the ability of C. fragile ssp. tomentosoides to persist on the breakwaters investigated in this study.