Effect of ballast water treatments and source port in the microplankton survival: consequences for colonization and propagule pressure

PAOLUCCI, ESTEBAN; LEILA RON; HERNANDEZ, MARCO; HUGH MACISAAC

Buenos Aires

Conferencia; Marine and Freshwater Invasive Species: Ecology, Impact and Management; 2016

CONICET & Aquatic Ecosystem Health and Management Society

Species richness and abundance (colonization and propagule pressure respectively) are commonly used to characterize invasion risk on ballast water mediated introductions. Even when an introduction event is characterized by low number of individuals per species but a large number of species, a high invasion risk scenario can be expected, mostly due to the high likelihood for establishment of multiple species. Despite that, new D2-IMO´s standards only consider total abundance of two size-based groups, and three bacterial indicators without consideration for the richness or source community. Based on fixed samples collected during a study of ballast water treatments we assessed changes in colonization and propagule pressure (CP and PP, respectively) of one of the D2-IMO´s indicators (> 10µm and < 50µm; microplankton) after ballast water exchange (BWE), chlorination, or the combinations of both (hybrid treatment). In addition we examined whether variation on CP or PP was related to the ballast water´s source. The log transformed ratios between final and initial CP and PP values were analyzed using one-way ANOVA. Probably due to the environment conditions inside of the tanks and treatment effects, a strong reduction of PP were observed in all the experimental trials and taxonomic groups; however, even when these samples included nonviable organisms, the hybrid treatment was the only one that met the D2-IMO´s standard. The reduction in CP was lower for control tanks, 24 of the 25 taxonomic groups at the end of the experiment. For BWE, chlorine, and the hybrid treatments, CP was reduced to 18, 20, and 16 groups, respectively. In the case of the hybrid treatment, final composition was dominated mostly by dinoflagellates and diatoms. In addition, the impact of the different treatments on CP and PP was always lower when the vessel was ballasted in a brackish port.