TRANSOCEANIC BALLASTED AND NO-BALLAST-ON-BOARD VESSELS AS VECTORS OF NONINDIGENOUS FORAMINIFERAL INTRODUCTIONS
Transoceanic vessels, including tankers and bulk carriers, take on water to maintain their stability during transit. Most often, ballast water is obtained in shallow ports and sediment is incidentally pumped into holding tanks as well. Entrained in this sediment is a wide array of aquatic organisms, including benthic foraminifers, which may be discharged into distant ports when the vessels are subsequently deballasted. At least five NIS foraminiferal species have been reported worldwide, all in active shipping ports, and all are suspected of having been introduced by transoceanic vessels. In this study, we investigated the presence of foraminifers in ballast sediment samples obtained from three locations in the United States.
Most of the vessels arriving in Prince William Sound, Alaska are tankers which originated in western U.S. ports, although a few arrive from overseas. The sediment from twelve of these ballasted vessels was sampled, nine of which contained foraminifers, including Ammonia beccarii, Rosalina globularis, Trochammina charlottensis, T. inflata, Miliammina fusca, Jadammina macrescens, Bulimina denudata, Elphidium, Globobulimina, Lagena,and Haplophragmoides. The NIS Trochammina hadaiwas also present in six samples, often in great abundance. Most of these species were also present in sediment obtained from a ballasted vessel from San Francisco Bay, and about 40% of the individuals were recovered alive.
Vessels which have deballasted are referred to as NOBOB (No-Ballast-On-Board). Although most ballast water and sediment has been removed, residual amounts often remain behind. Sediment from eight of these vessels was sampled from the Great Lakes and numerous living individuals of Ammonia, Elphidium,and Textulariawere recovered. Clearly, both ballasted and NOBOB vessels are a potential source of nonindigenous foraminiferal introductions.