Mid-Ocean Ballast Water Exchange: Approach & Methods for Verification

摘要

Ballast water management of ships entering the United States is a key component in stopping invasions of non-indigenous aquatic species. Ballast water exchange (BWE) is currently the most common method of ballast water management and it is likely to remain an approved management technique for the foreseeable future. The United States Coast Guard's present salinity-based BWE verification procedure is ineffective when ships' tanks are ballasted in high salinity ports. In an attempt to improve this procedure, a suite of parameters was sought to better discriminate between open ocean and coastal waters. Analyses indicated that salinity, colored dissolved organic matter (CDOM), certain trace metals, and radium isotopes provided good discrimination power. Univariate and multi variate analyses conducted on the separate and combined data sets indicated that radium was the best single discriminator and that salinity coupled with six trace metals (barium, manganese, phosphorus, molybdenum, uranium, and vanadium) was the most successful suite for discriminating open ocean from coastal water. CDOM combined with salinity proved to be a successful discriminator. Water clarity and phytoplankton salinity tolerance proved unsuitable. Sampling and analysis procedures are included in the report.