Editing Ctenophora (section)

=== Ecological impacts ===

[[File:Medusa010.jpg|thumb|right|''Beroe ovata'' at the surface on the Black Sea coast]]

Ctenophores may balance marine ecosystems by preventing an over-abundance of copepods from eating all the [[phytoplankton]] (planktonic plants),<ref name=ChandyGreene1995PredatoryImpact>{{cite journal |last1=Chandy |first1=Shonali T. |last2=Greene |first2=Charles H. |date=July 1995 |title=Estimating the predatory impact of gelatinous zooplankton |journal=[[Limnology and Oceanography]] |volume=40 |issue=5 |pages=947–955 |doi=10.4319/lo.1995.40.5.0947 |doi-access=free |bibcode=1995LimOc..40..947C}}</ref> which are the dominant marine producers of organic matter from non-organic ingredients.<ref>{{cite journal  |last1=Field |first1=Christopher B. |last2=Behrenfeld |first2=Michael J. |last3=Randerson |first3=James T. |last4=Falkowski |first4=Paul |date=10 July 1998 |title=Primary production of the biosphere: Integrating terrestrial and oceanic components |journal=[[Science (journal)|Science]] |volume=281 |issue=5374 |pages=237–240 |doi=10.1126/science.281.5374.237 |pmid=9657713 |bibcode=1998Sci...281..237F |url=http://www.escholarship.org/uc/item/9gm7074q}}</ref>

On the other hand, in the late 1980s the Western Atlantic ctenophore ''[[Mnemiopsis leidyi]]'' was accidentally [[introduced species|introduced]] into the [[Black Sea]] and [[Sea of Azov]] via the [[ballast tanks]] of ships, and has been blamed for causing sharp drops in fish catches by eating both fish larvae and small crustaceans that would otherwise feed the adult fish.<ref name="ChandyGreene1995PredatoryImpact"/> ''Mnemiopsis'' is well equipped to invade new territories (although this was not predicted until after it so successfully colonized the Black Sea), as it can breed very rapidly and tolerate a wide range of water temperatures and [[salinity|salinities]].<ref name=PurcellShiganova2001MnemiopsisNativeAndExotic>{{cite journal |last1=Purcell |first1=Jennifer E. |last2=Shiganova |first2=Tamara A. |last3=Decker |first3=Mary Beth |last4=Houde |first4=Edward D. |year=2001 |title=The ctenophore ''Mnemiopsis'' in native and exotic habitats: U.S. estuaries versus the Black Sea basin |journal=Hydrobiologia |volume=451 |issue=1–3 |pages=145–176 |doi=10.1023/A:1011826618539 |s2cid=23336715}}</ref> The impact was increased by chronic overfishing, and by [[eutrophication]] that gave the entire ecosystem a short-term boost, causing the ''Mnemiopsis'' population to increase even faster than normal<ref name=OguzFachSalihoglu2008InvasionDynamics>{{cite journal |last1=Oguz |first1=T. |last2=Fach |first2=B. |last3=Salihoglu |first3=B. |date=December 2008 |title=Invasion dynamics of the alien ctenophore ''Mnemiopsis leidyi'' and its impact on anchovy collapse in the Black Sea |journal=Journal of Plankton Research |volume=30 |issue=12 |pages=1385–1397 |doi=10.1093/plankt/fbn094 |doi-access=free}}</ref> – and above all by the absence of efficient predators on these introduced ctenophores.<ref name="PurcellShiganova2001MnemiopsisNativeAndExotic"/> ''Mnemiopsis'' populations in those areas were eventually brought under control by the accidental introduction of the ''Mnemiopsis''-eating North American ctenophore ''[[Beroe ovata]]'',<ref>{{cite book |last1=Bayha |first1=K.M. |last2=Harbison |first2=R. |last3=McDonald |first3=J.H. |last4=Gaffney |first4=P.M. |year=2004 |section=Preliminary investigation on the molecular systematics of the invasive ctenophore ''Beroe ovata'' |editor1-last=Dumont |editor1-first=H. |editor2-last=Shiganova |editor2-first=T.A. |editor3-last=Niermann |editor3-first=U. |title=Aquatic invasions in the Black, Caspian, and Mediterranean seas |volume=35 |pages=167–175 |series=NATO Science Series&nbsp;IV: Earth and Environmental Sciences |publisher=Springer Netherlands |isbn=978-1-4020-1866-4 |doi=10.1007/1-4020-2152-6_7}}</ref> and by a cooling of the local climate from 1991 to 1993,<ref name=OguzFachSalihoglu2008InvasionDynamics/> which significantly slowed the animal's metabolism.<ref name=PurcellShiganova2001MnemiopsisNativeAndExotic/> However the abundance of plankton in the area seems unlikely to be restored to pre-''Mnemiopsis'' levels.<ref>{{cite book |last=Kamburska |first=L. |year=2006 |section=Effects of ''Beroe'' c.f. ''ovata'' on gelatinous and other zooplankton along the Bulgarian Black Sea Coast |editor1-last=Dumont |editor1-first=H. |editor2-last=Shiganova |editor2-first=T.A. |editor3-last=Niermann |editor3-first=U. |title=Aquatic Invasions in the Black, Caspian, and Mediterranean Seas |volume=35 |pages=137–154 |series=NATO Science Series&nbsp;IV: Earth and Environmental Sciences |publisher=Springer Netherlands |isbn=978-1-4020-1866-4 |doi=10.1007/1-4020-2152-6_5}}</ref>

In the late 1990s ''Mnemiopsis'' appeared in the [[Caspian Sea]].<!---probably via the canals that connect the Caspian to the Black Sea --- There are no salt water channels connecting the Caspian and the Black seas ---> ''Beroe ovata'' arrived shortly after, and is expected to reduce but not eliminate the impact of ''Mnemiopsis'' there. ''Mnemiopsis'' also reached the eastern [[Mediterranean]] in the late 1990s and now appears to be thriving in the [[North Sea]] and [[Baltic Sea]].<ref name=MillsNotesFromExpert/>