Association of bacteria with marine invertebrates: implications for ballast water management

Abstract

Bacteria associated with plankton are of importance in marine bioinvasions and the implementation of ship’s ballast water treatment technologies. In this study, epibiotic and endobiotic bacteria associated with zooplankton, including barnacle nauplii, veliger larvae, and adults of the copepod Oithona sp., were characterized and quantified. Barnacle nauplius and veliger larva harbored ~4.4 × 10⁵ cells ind⁻¹ whereas Oithona sp. had 8.8 × 10⁵ cells ind^-1. Computation of bacterial contribution based on biovolume indicated that despite being the smallest zooplankton tested, veliger larvae harbored the highest number of bacteria, while barnacle nauplii, the largest of the zooplankton, tested in terms of volume contributed the least. Pulverization of zooplankton led to an increase in bacterial numbers; for example, Vibrio cholerae, which was initially 3.5 × 10³, increased to 5.4 × 10⁵ CFU g^-1; Escherichia coli increased from 5.0 × 10² to 1.3 × 10⁴ CFU g^-1; and Streptococcus faecalis increased from 2.1 × 10² to 2.5 × 10⁵ CFU g^-1, respectively. Pulverized zooplankton was aged in the dark to assess the contribution of bacteria from decaying debris. Aging of pulverized zooplankton led to emergence of Chromobacterium violaceum, which is an opportunistic pathogen in animals and humans.