Environmental concerns
Diagram showing the water pollution of the seas from untreated ballast water discharges
Main article: Ballast water discharge and the environment
Ballast water taken into a tank from one body of water and discharged in another body of water can introduce invasive species of aquatic life. The taking in of water from ballast tanks has been responsible for the introduction of species that cause environmental and economic damage. For example, zebra mussels in the Great Lakes of Canada and the United States.
Non native macroinvertebrates can find their way into a ballast tank. This can cause problems ecologically and economically. Macro-invertebrates are transported by transoceanic and coastal vessels arriving in ports all over the world. Researchers from Switzerland sampled 67 ballast tanks from 62 different vessels operating along geographic pathways and tested for mid ocean exchange or voyage length that had a high chance of macro-invertebrate relocating to a different part of the world. An assessment was done between the relationship of macro-invertebrate presence, and the amount of sediment in ballast tanks. The Switzerland researchers had discovered a presence of a highly invasive European green crab, mud crab, common periwinkle, soft shell clam, and blue mussel in the ballast tanks of the sampled ships. Although the densities of macro-invertebrate were low, invasion of none native macro-invertebrates can be worrisome during their mating season. The worst thing that can happen is if a female macro-invertebrate is carrying millions of eggs per animal.
Migration of living animals and settling particle-attached organisms can lead to an uneven distributions of biota at different locations of the world. When small organisms find their way into a ballast tank, the foreign organism or animal can upset the balance of the local habitat. When a local habitat is changed, it can interfere with the natural habitat and potentially damage the existing animal life. Vessel workers check the ballast tank for living organisms ≥50 μm in discrete segments of the drain, it also represents the level of sedimentary of different rock or soil in the tank. Throughout the sample collection, concentrations of organisms and marine life varied in result in the drain segments, patterns also varied in level of stratification in other trials. To have the best sampling strategy for stratified tanks, is to collect various time-integrated samples spaced evenly throughout each discharge.
All Trans-Oceanic vessels that enter the Great Lakes are required to manage ballast water and ballast tank residuals with ballast water to clear out and exchange for tank flushing. Even though management and procedures reduce the density and richness of biota effectively in ballast waters and thus reducing the risk of transporting organisms from other parts of the world to none native areas. Although most ships do ballast water management not all are able to clear the tanks. In an emergency when residual organisms are not able to be cleaned, vessel workers use sodium chloride brine to treat the ballast tanks. Vessels arriving in the Great Lakes, and North Sea ports, were exposed to high concentrations of sodium chloride until the mortality rate of 100% is reached. Results show that an exposure of 115% of brine is extremely effective treatment resulting in a 99.9 mortality rate of living organisms in ballast tanks regardless of the type of organism. There was a median of 0%. About 0.00-5.33 of organisms are expect to survive treatment of the sodium chloride.
One of the most common problems among vessel construction and maintenance is the corrosion that takes place in the double hull space ballast tanks have in merchant vessels.[6] Bio-degradation takes place in ballast tank coatings in marine environments. To avoid biodegradation, paint has been a new idea to stop the corrosion of ballast tank. Ballast tanks can carry more than ballast water, most of the time ballast tanks are filled with other bacteria or organisms. Some of these bacteria can that can be picked up from other parts of the world can cause the ballast tank to get damaged. Bacteria from different regions plus the natural bacteria can cause ballast tanks to break down. The natural bacteria community has an interaction of the natural bio-films with the coating, an aspect which is not covered in standard procedures. Researchers have shown that biological activity indeed significantly affects the coating properties. Micro-cracks and small holes have been found in ballast tanks. Acidic bacteria created holes with 0.2-0.9 μm in length and 4–9 μm in width. The natural community caused cracks of 2-8 μm in depth and 1 μm in length. The EIS technique was used to examine the degradation. The bacterial affected coatings decreased in corrosion resistance. The natural community, has a clear loss in coating resistance over time. Also, coating corrosion resistance declines after 40 days of exposure to the natural community, resulting in blisters in the ballast tank. Bacteria might be linked to certain bio-film patterns affecting various types of coating attacks.