Invasion risk to Yangtze River Estuary posed by resting eggs in ballast sediments from transoceanic ships

Biological invasions and loss of biodiversity are serious problems of increasing globalization. The hypothesis that resting eggs in ballast sediments from transoceanic ships provide an invasion of nonindigenous species was tested by directly comparing egg communities between ballast and natural sediment. The richness, abundance and taxonomic composition of resting eggs were quantified for sediments collected from transoceanic ships arriving at Shanghai Port and natural seafloor of the Yangtze River Estuary. Twelve species were identified in ballast sediments with an average abundance of 19.0 ind. kg⁻¹, while eleven species were identified in natural sediments with an average abundance of 55.3 ind. kg⁻¹. Seven of twelve ballast species were potential invaders compared with natural sediments. The invertebrate communities of resting eggs in ballast sediments differed from those in natural sediments, based on non-metric multidimensional scaling and analysis of similarity. Hatching experiments on resting eggs from ballast sediments showed that there were 1.4 ind. kg⁻¹ copepod nauplii hatched within the first 24 h, suggesting the invasive risk would be present during the first day of de-ballasting. These results indicate that sediments within ballast tanks posed a potential risk for estuarine communities.