Potential transfer of aquatic organisms via ballast water with a particular focus on harmful and non-indigenous species: A survey from Adriatic ports

Ballast water discharges may cause negative impacts to aquatic ecosystems, human health and economic activities by the introduction of potentially harmful species. Fifty untreated ballast water tanks, ten in each port,were sampled in four Adriatic Italian ports and one Slovenian port. Salinity, temperature and fluorescence weremeasured on board. Faecal indicator bacteria (FIB), phyto- and zooplankton were qualitatively and quantitatively determined to identify the species assemblage arriving in ballast water. FIB exceeded the conventionstandard limits in 12% of the sampled tanks. Vibrio cholerae was not detected. The number of viable organisms inthe size groups (minimum dimension) < 50 and ≥10 μm and ≥50 μm resulted above the abundances requiredfrom the Ballast Water Management Convention in 55 and 86% of the samples, respectively. This is not surprising as unmanaged ballast waters were sampled. Some potentially toxic and non-indigenous species wereobserved in both phyto- and zooplankton assemblages.