Effect of vessel voyage speed on survival of biofouling organisms: implications for translocation of non-indigenous marine species

Abstract

This study experimentally determined the effect of different vessel voyage speeds (5, 10 and 18 knots = 2.6, 5.1 and 9.3 ms-1, respectively) and morphological characteristics including growth form (solitary or colonial), profile (erect or encrusting) and structure (soft, hard or flexible) on the survival of a range of common biofouling organisms. A custom built hydrodynamic keel attached to the bottom of a 6 m aluminium powerboat was used to subject pre-fouled settlement plates for this purpose. Vessel speeds of 5 and 10 knots had little effect on the species richness of biofouling assemblages tested, however richness decreased by 50% following 18 knots treatments. Species percentage cover decreased with increasing speed across all speed treatments and this decrease was most pronounced at 10 and 18 knots, with cover reduced by 24 and 85% respectively. Survival was greatest for organisms with colonial, encrusting, hard and/or flexible morphological characteristics, and this effect increased with increasing speed. This study suggests that there is predictive power in forecasting future introductions if we can understand the extent to which such traits explain the world-wide distributions of non-indigenous species. Future introductions are a certainty and can only provide an increasing source of new information on which to test the validity of these predications.