Transportation of bloom forming species in ballast water by commercial vessels at Yangshan deep water port

摘要

The introduction of bloom forming species through discharge of ships' ballast water is recognized as a global challenge to marine ecosystem. Harmful algal bloom species in ballast water is of special concern. This study examines the abundance and diversity of bloom forming species in ballast water from 44 samples collected in 2015–2016 from 40 commercial ships arriving at Yangshan deep water port, the world's largest intelligent container terminal. In total 21 bloom forming species were identified in these samples uptake from 10 different sea areas, belonging to Ochrophyta (13 species) and Myzozoa (8 species). Among these species, Dinophysis caudata, Prorocentrum lima, Prorocentrum cordatum and Prorocentrum micans could produce toxins. In the examined samples, the average abundance of organisms in size class ≥10–50 μm ranged from 183 ± 33 to 8055 ± 5648 cells L?1, among which the average abundance of bloom forming species ranged from 25 ± 35 to 2200 ± 2400 cells L?1. Although the average number of bloom forming species identified from the samples during the survey were in compliance with discharge standard according to the Regulation D-2 of the IMO BWM Convention, in some of the samples, these species accounted for 70%–97% of the total number of organisms in size class ≥10–50 μm. The results from this study also reveals that the abundance of bloom forming species is higher in water samples ballasted from coastal water than the ones from open sea. This study aims to collect data on harmful bloom forming species persisting in ballast water transported by commercial vessels arriving at Yangshan deep water port, with emphasis on identifying major species of the harmful marine micro-algae. It is quite essential to select a reliable detection method for detailed species analysis. It can provide biological mapping of harmful marine microalgae in the examined eco-system for better decision-making on biological invasion management.