Characteristics of global port phytoplankton and implications for current ballast water regulations

摘要

The International Maritime Organization and U.S. Coast Guard have implemented regulations to reduce introductions of non-indigenous species via ballast water (BW). For phytoplankton, regulations limit discharges to 10 live/viable cells mL(-1) (size: 10-50 mu m), ignoring other size fractions. Additionally, challenge conditions of 100 (shipboard) and 1000 (land-based) cells mL(-1) are required in BW management system certification testing. How these requirements correspond to natural phytoplankton populations is poorly resolved. We analyzed phytoplankton samples from 31 major ports to evaluate: a) how natural communities compare to challenge requirements and b) abundances of unregulated size fractions (i.e., 10 and = 50 mu m). None of the ports met land-based challenge conditions, and only 32% met requirements for shipboard testing. Approximately 71% of organisms = 50 mu m were centric diatoms, also unregulated by current protocols. This study demonstrates that current regulations do not consider natural phytoplankton populations, limiting control efforts for potentially harmful non-indigenous species.