Editing Ship (section)

===Ballast water===
{{Main|Ballast water discharge and the environment}}
[[File:Ship pumping ballast water.jpg|thumb|upright|A cargo ship pumps ballast water over the side]]
When a large vessel such as a [[container ship]] or an oil tanker unloads cargo, seawater is pumped into other compartments in the hull to help stabilize and balance the ship. During loading, this ballast water is pumped out from these compartments.<ref>{{cite news|url=https://www.bbc.co.uk/news/science-environment-22397076|title=Scientists map global routes of ship-borne invasive species|newspaper=BBC News|access-date=4 May 2015|date=2013-05-05|last1=McGrath|first1=Matt}}</ref>

One of the problems with ballast water transfer is the transport of harmful organisms. Meinesz<ref name="Meinesz" /> believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless [[plankton]]ic organism . ''[[Mnemiopsis leidyi]]'', a species of [[comb jelly]] that inhabits estuaries from the United States to the Valdés peninsula in [[Argentina]] along the [[Atlantic]] coast, has caused notable damage in the [[Black Sea]]. It was first introduced in 1982, and thought to have been transported to the Black Sea in a ship's ballast water. The population of the comb jelly shot up exponentially and, by 1988, it was wreaking havoc upon the local [[fishing]] industry. "The [[anchovy]] catch fell from {{convert|204000|t|ST LT|sigfig=3|lk=on}} in 1984 to {{convert|200|t|ST LT|sigfig=3}} in 1993; sprat from {{convert|24600|t|ST LT|sigfig=3}} in 1984 to {{convert|12000|t|ST LT|sigfig=3}} in 1993; [[horse mackerel (disambiguation)|horse mackerel]] from {{convert|4000|t|ST LT|sigfig=3}} in 1984 to zero in 1993."<ref name="Meinesz" /> Now that the comb jellies have exhausted the [[zooplankton]], including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the [[ecosystem]]. Recently the comb jellies have been discovered in the [[Caspian Sea]]. Invasive species can take over once occupied areas, facilitate the spread of new [[diseases]], introduce new [[Genetics|genetic]] material, alter landscapes and jeopardize the ability of native species to obtain food. "On land and in the sea, invasive species are responsible for about 137&nbsp;billion dollars in lost revenue and management costs in the U.S. each year."<ref name="Panetta" />

Ballast and [[bilge]] discharge from ships can also spread human [[pathogens]] and other harmful diseases and [[toxins]] potentially causing health issues for humans and marine life alike.<ref>National Research Council, Committee on the Ocean's Role in Human Health, Ocean Studies Board, Commission on Geosciences, Environment, and Resources. (1999). ''From monsoons to microbes: understanding the ocean's role in human health''. Washington, DC: National Academy Press</ref> Discharges into coastal waters, along with other sources of marine pollution, have the potential to be toxic to marine plants, animals, and [[microorganisms]], causing alterations such as changes in growth, disruption of [[hormone]] cycles, birth defects, suppression of the [[immune system]], and disorders resulting in [[cancer]], [[tumors]], and genetic abnormalities or even death.<ref name="Panetta" />