In response to US Coast Guard regulations, a variety of ballast water management approaches have been developed to decrease the likelihood that ballast water discharged by ships will introduce non-indigenous species (NIS) to the unique marine bioregions of United States and elsewhere. The most obvious strategy is for ships to not release their ballast water (and the organisms it contains) to ports and coastal waters, when possible. Ships arriving to US ports may also use water sourced from a US Public Water System in ballast water tanks, which should be free of any organisms. Until recently, for those ships that must release ballast at port but which are not carrying US public water in their tanks, the most widespread ballast water management approach has been open-ocean exchange, whereby ships exchange coastal ballast water with open-ocean water to reduce the number of coastal biota introduced to next port of call. Open-ocean exchange requires pumping coast water out of a tank and refilling with oceanic water (empty/refill exchange), or via the flow-through exchange where several tank volumes of oceanic water are pumped continually into a ballast water tank to displace the coastal water and biota into the open ocean. Open-ocean ballast water exchange creates a habitat mismatch whereby oceanic organisms rather than coastal organisms are released in next port of call.
While these methods of ballast water management reduce the risk of introducing a non-indigenous species, they do fully not eliminate risk. However, ballast water treatment systems are now being developed and used to treat ballast water in the US and elsewhere, typically onboard ships. These technologies allow the ballast water to be treated upon entering and/or before exiting the ballast water tank to reduce the number of viable organisms that are ultimately released to the environment. Ballast water treatment operations may be carried out at port or while underway, thereby eliminating the need for ballast water water exchanges while further reducing risk of NIS introductions. In 2012, the US Coast Guard adopted a a set of discharge standards as specified in 33 CFR § 151.2030(d) that specifies the concentrations and types of marine biota that can be legally discharged per volume of ballast water. As such, onboard ballast water technologies are a rapidly growing industry and have been increasingly adopted for ballast water management of water discharged into US waters.
This section presents and quantifies discharged ballast water volumes reported to the NBIC, including whether the water was managed prior to discharge into US territorial waters. ALL options to actively manage BW discharge are those specified in 33 CFR 151.2025:
- Ballast Water Exchange
- Ballast Water Treatment
- Use water from a US Public Water System
- Discharge to a facility or ship for treatment
Because federal and state regulatory requirements may differ to some extent depending on where ships are operating and on the origin of their ballast water, it is important to evaluate overseas and coastwise discharge independently when analyzing all types of ballast water management simultaneously.
Note: All data available in graphs and tables extend through the last complete month and are refreshed monthly. Because ballast water management reports may be amended, corrected or changed during quality control processes, particularly within the 20 days from arrival date for the last complete month, this may result in updates that will register when the data are next refreshed. All data are subject to change and use of any of the NBIC data implies agreement with the NBIC Data Use Agreement policy. Cite our data.
Temporal Patterns of BW Management