Inligting

Kan jellievisse die Swartsee-ekosisteem verbeter?

Kan jellievisse die Swartsee-ekosisteem verbeter?



We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Volgens hierdie studie, wat deur baie gewilde wetenskaplike tydskrifte, jellievisse en ander genoem word, kan kleiner diere soveel bydra tot die vertikale oseaanroering soos strome doen.

Swart See chemie en biodiversiteit is hoogs gepaard met die gebrek aan vertikale strome, teenwoordig in oseane of groter see. Sommige van die gevolge is lae soutgehalte in die boonste lae - baie oseaan vissoorte kan nie die soutgehalte van die Swart See duld nie, en beperkte lewensruimte (onder 50 meter is daar geen suurstof nie)

Kan die jellievispopulasie (wat nou ontplof) die stratifikasie van die waterlae genoeg verander sodat die hoogs soutwater van onder af styg, en suurstof na die dieper lae gaan, wat 'n heeltemal nuwe ekosisteem hier moontlik maak?

Indien wel, wat is die uitkomste van sulke vooruitsigte? Behalwe die potensieel katastrofale vrystelling van waterstofsulfied in die bodem, kan dit 'n verbetering vir die biodiversiteit hier wees?


Om die PI uit die BBC -artikel aan te haal:

Maar, het dr Dabiri verduidelik, dit is onwaarskynlik dat die jellievisse die "primêre mengers van die see" sal wees. "Skaaldiere - soos copepods en kril - is waarskynlik die primêre biogene mengers, want daar is so baie van hulle," het hy verduidelik.

"Maar baie van die oop see is soos woestyn," het hy bygevoeg, "en die digtheid van hierdie diere sal waarskynlik nie voldoende wees (om vermenging te veroorsaak)."

My raaiskoot is dus nee, jellievisse is nie voldoende om die huidige struktuur van oseaanlae dramaties te verander nie. Diere in die algemeen, soos die koerant en sy verwysings suggereer, doen dra aansienlik by, gelykstaande aan getye en wind.


Jellievisse aan die toeneem in die wêreld se kus-ekosisteme

Jellievis neem toe in die meerderheid van die kus -ekosisteme ter wêreld, volgens die eerste wêreldwye studie van oorvloed jellievisse deur navorsers aan die Universiteit van British Columbia.

In 'n studie wat in hierdie maand se uitgawe van die tydskrif gepubliseer is Hidrobiologie, UBC-wetenskaplikes het data vir talle soorte jellievisse vir 45 van die wêreld se 66 Groot Mariene Ekosisteme ondersoek. Hulle het toenemende populasies van jellievisse gevind in 62 persent van die geanaliseerde streke, waaronder Oos -Asië, die Swart See, die Middellandse See, die noordooste van die Amerikaanse rak, Hawaii en Antarktika.

"Daar was anekdotiese bewyse dat die jellievis die afgelope dekades aan die toeneem was, maar daar was nog nie 'n wêreldwye studie wat al die bestaande data versamel het nie," sê Lucas Brotz, 'n PhD -student by die See Om Ons Projek by UBC en hoofskrywer van die studie.

"Ons studie bevestig hierdie waarnemings wetenskaplik na ontleding van beskikbare inligting van 1950 tot hede vir meer as 138 verskillende jelliebevolkings regoor die wêreld."

Jellievis belemmer baie menslike aktiwiteite - deur swemmers te steek, die inname van kragsentrales te verstop en om vis te belemmer. Sommige spesies jellievis is nou 'n voedselbron in sommige dele van die wêreld.

"Deur gepubliseerde wetenskaplike data te kombineer met ander ongepubliseerde data en waarnemings, kan ons hierdie studie werklik wêreldwyd maak - en die beste beskikbare wetenskaplike skatting bied van 'n verskynsel wat wyd bespreek is," sê Daniel Pauly, hoofnavorser van die See rondom ons Projek en mede-outeur van die studie. "Ons kan ook sien dat die plekke waar ons 'n toenemende aantal jellievisse sien, dikwels gebiede is wat swaar deur mense geraak word deur besoedeling, oorbevissing en warm water."

Pauly voeg by dat toenemende anekdotiese verslae oor die oorvloed van jellievisse moontlik die gevolg was van 'n uitbreiding van menslike aktiwiteite in mariene habitatte, en daarom bied die studie ook 'n konkrete basis vir toekomstige studies.

Die studie wys ook op afnames in die hoeveelheid jellievis in sewe persent van kusstreke, terwyl die res van die mariene ekosisteme geen duidelike neiging getoon het nie.


Animal Diversity Web

Beroe ovata bewoon natuurlik die Atlantiese Oseaan en die kuswaters naby die Verenigde State en Kanada, sowel as in die Golf van Mexiko en die Europese waters. Beroe ovata is ook gevind in die Oos-Chinese See sowel as die Indo-Wes Stille Oseaan. Hierdie ctenofore is bekendgestel aan die Alborán -see, die Swart See en die Kaspiese See in die Middellandse See om bevolkings van hul prooi Mnemiopsis leidyi te beheer. Hulle is tydelik as 'n indringerspesie beskou, maar bevolkings het sedertdien afgeneem. ("Ekosisteme waar Beroe ovata voorkom", 2010 Mills, 1996)

Habitat

Beroe ovata is 'n pelagiese mariene organisme wat vrylik in die waterkolom swem. Beroe ovata is gevind op dieptes wat wissel van net onder die oppervlak op 0,5 meter tot 1719 meter onder die oppervlak, wat beteken dat B. ovata in staat is om te oorleef in die epipelagiese sone, mesopelagiese sone en die boonste gebied van die badypelagiese sone. Benewens oseaniese habitatte, woon B. ovata in kuswater sowel as riviermondings, waaronder die Yorkrivier, die Mississippirivier en die Chesapeakebaai. Hierdie spesie oorleef in verskillende soutgehalte, wat wissel van 1,2% in die Kaspiese See tot 3,3-3,7% op die oppervlak van die Atlantiese Oseaan. Benewens sy vermoë om in verskillende vlakke van soutgehalte te oorleef, kan B. ovata gebiede van verskillende temperature bewoon, insluitend pool-, gematigde en tropiese streke. ("Beroe ovata Bruguière, 1789", 2011 "Ekosisteme waar Beroe ovata voorkom", 2010)

  • Habitatstreke
  • soutwater of mariene
  • Aquatiese biome
  • pelagies
  • riviere en strome
  • kus
  • Ander habitatkenmerke
  • riviermonding
  • tussengety of kuste
  • Reeks diepte 0,5 tot 1719 m 1,64 tot 5639,76 voet

Fisiese beskrywing

Beroe ovata het 'n pienk kleur en 'n ovaalvormige lyf. Die jong organismes het breër liggame aan beide die mondelinge en die aborale kant. Na ontwikkeling is die orale einde van die volwasse organisme wyer en die liggaam sak af na die aborale einde. Alhoewel dit afneem, eindig die liggaam nie op 'n punt nie. Die lengte is 10 en 120 millimeter met 'n gemiddelde massa van 0,85 milligram. Hierdie organisme gebruik ook cilia vir beweging en voeding. In die Swart See is kleiner eksemplare Beroe ovata langs die kus. Buite word matige tot groot organismes aangetref. Larwes is beroid, wat beteken dat hulle nie tentakels het om te voed nie. 'n Kenmerkende eienskap vir hierdie spesie is dat hul meridiaankanale anostomo's (verbindende kanale) tussen hulle het. (Finenko, et al., 2003 Shiganova, et al., 2001)

  • Ander fisiese kenmerke
  • ektotermies
  • heterotermies
  • radiale simmetrie
  • Seksuele dimorfisme
  • geslagte gelyk
  • Gemiddelde massa 0,85 g 0,03 onse
  • Bereiklengte 10 tot 120 mm 0,39 tot 4,72 in

Ontwikkeling

Daar is min spesifiek oor B. ovata-ontwikkeling bekend, maar die lewensiklusse van ctenofore is baie eenvoudig. Die ctenofore is hermafrodities, wat beteken dat hulle beide manlike en vroulike gonades insluit. Hulle stel beide eier- en spermselle vry. Die eiers bly vryswewend totdat larwes uitbroei. Ctenofore verander nie hul algemene liggaamstipes nie, maar vergroot slegs hul liggaamsgrootte. (Mills, 2001)

Reproduksie

Alhoewel daar baie min inligting spesifiek oor die spesie Beroe ovata is, is ctenofore in die algemeen hermafrodities, 'n enkele organisme met beide manlike en vroulike gonades. Elke organisme stel eiers en sperms in die water vry. Dit is nie bekend watter leidrade hierdie ctenofore veroorsaak om te paar nie, maar hulle sal voortdurend eiers en sperms vrystel onder gunstige temperature en voedingstoestande. (Finenko, et al., 2003 Mills, 2001)

Alhoewel daar baie min inligting spesifiek oor die spesie Beroe ovata is, is ctenofore in die algemeen hermafrodities, 'n enkele organisme met beide manlike en vroulike gonades. Elke organisme stel eiers en sperm in die water vry. Die ekstern bevrugte eiers bly vryswewend totdat die larwes uitbroei. Ctenofore is in staat om op baie vroeë ouderdomme voort te plant terwyl hulle klein van grootte is, wat vinnige generasietye moontlik maak. Solank voldoende voedselbronne teenwoordig is, ondergaan die ctenofore produksie van eier en sperms en word dit vir 'n paar weke vrygestel. (Finenko, et al., 2003 Mills, 2001)

  • Belangrike voortplantingsfunksies
  • die hele jaar deur teel
  • gelyktydige hermafrodiet
  • bevrugting
    • ekstern
    • Teelinterval Ctenophores kuit eiers en spermselle voortdurend vir 'n paar weke met voldoende voedselbronne.

    Beroe ovata stel sperm en eiers gelyktydig in die water vry. Die eiers word lukraak bevrug, dus is daar geen ouerbetrokkenheid by die bevrugting of ontwikkeling van die larwes en jong Beroe ovata nie. (Finenko, et al., 2003 Mills, 2001)

    Lewensduur/Lang lewe

    Daar is geen spesifieke inligting oor die spesie Beroe ovata nie, maar ander ctenofore het 'n seisoenale lewensduur. Een spesie ctenophore leef in die somer minder as 'n maand, terwyl dit in die winter drie maande duur. Studie oor die Beroe ovata kan seisoenaal afhanklike getalle vind, ook as gevolg van verskillende faktore. (Kasuya, et al., 2002)

    Gedrag

    Beroe ovata sal buig en strek terwyl hulle vinnig swem as 'n ontsnappingsreaksie begin word. As Beroe ovata herhaaldelik op dieselfde manier aan soortgelyke stimuli blootgestel word, kan dit van binne na buite draai. Terwyl hy kos soek, swem Beroe ovata in 'n spiraalpatroon en is ook bioluminescent. Tydens swem en jag gebruik Beroe ovata omkeerbare epiteelhechting om die mond toe te hou en 'n vaartbelynde vorm te bevorder. Dit word bewerkstellig sonder die hulp van 'n spier- of senuweestelsel en in plaas daarvan met opponerende gepaarde stroke kleef-epiteelselle. (Matsumoto en Harbison, 1991 Tamm en Tamm, 1991)

    Home Range

    Soos die meeste ctenofore, is Beroe ovata 'n pelagiese organisme, wat beteken dat dit vrylik deur die waterkolom swem. Soos dit in baie streke van die wêreld se oseane voorkom, is die gebied groot en waarskynlik verbygaande as gevolg van seestrome. ("Ekosisteme waar Beroe ovata voorkom", 2010)

    Kommunikasie en persepsie

    In die filum Ctenophora het B. ovata 'n netagtige senuweestelsel wat konsekwent deur die hele epidermis versprei word. Hierdie spesie het geen sentralisering van die senuweestelsel of sintuie soos gesien in ander filums nie. Alhoewel dit bioluminescent is, word dit waarskynlik nie vir kommunikasie gebruik nie. (Haddock and Case, 1999 Hay-Schmidt, 2000)

    Voedselgewoontes

    Beroe ovata voed hoofsaaklik op ander ctenofore, waaronder Bolinopsis infundibulum, Cestum veneris, Mnemiopsis leidyi en verskillende spesies Ocyropsis. Beroe ovata is 'n nie-visuele roofdier. Terwyl hy kos soek, swem B. ovata in 'n spiraalvormige patroon. Die teenwoordigheid van prooi veroorsaak chemokinetiese reaksies in B. ovata wat aanpassings in swemgedrag veroorsaak. Beroe ovata voel ook sy prooi deur met hom in aanraking te kom terwyl hy swem. Macrocilia word gebruik om weefsel effektief van prooi in 'n hanteerbare grootte te sny. Voedsel word ingeneem as gevolg van die negatiewe druk wat veroorsaak word wanneer die ctenofoor sy mond oopmaak. (Matsumoto en Harbison, 1991 Swanberg, 1974)

    • Primêre dieet
    • vleisetende
      • eet ander mariene ongewerweldes
      • Dierevoedsel
      • cnidarians
      • dierplankton
      • Voedselgedrag
      • filtervoeding

      Predasie

      Min inligting is beskikbaar oor die roofdiere van Beroe ovata spesifiek, maar dit is waarskynlik dat dit roofdiere met ander lede van sy filum sal deel. Ktenofore val tipies ten prooi aan 'n wye verskeidenheid organismes, insluitend haaie, seeskilpaaie, baie spesies ontbeende visse, seevoëls, asook ander ctenofore.

      Ekosisteem Rolle

      In die Swart See het die indringende Beroe ovata gehelp om die ekosisteem te red van 'n skadelike indringende spesie Mnemiopsis leidyi. Deur te voed op die mede-indringer ctenofoor, het Beroe ovata gehelp om 'n balans te skep tussen die organismes wat in die Swart See leef. Terwyl die meeste studies die belangrikheid van hierdie spesie in die Swart See bespreek, speel dit waarskynlik dieselfde belangrike rolle in die watermassas waar dit 'n inheemse spesie is. (Finenko, et al., 2003 Mutlu, 2009)

      Ekonomiese belangrikheid vir mense: positief

      Op plekke waar Beroe ovata natuurlik voorkom, is dit van min ekonomiese belang vir die mens. Toe dit egter in die laat 1980's aan die Swart See bekendgestel is as 'n metode van bevolkingsbeheer vir die indringerspesie Mnemiopsis leidyi, het B. ovata ekonomiese hulpbronne indirek beïnvloed. Deur daagliks tot 10% van die M. leidyi-bevolking te verbruik, het populasies van soöplankton, ichthyplankton en pelagiese visse wat deur M. leidyi geëet is, toegeneem. Een van die pelagiese visse wat toegeneem het met die beheer van M. leidyi was die ansjovisspesie, Engraulis encrasicolus, wat ekonomies belangrik is in die Swartsee-streek. (Kube, et al., 2007 Shiganova, et al., 2001)

      Ekonomiese Belang vir Mense: Negatief

      Beroe ovata hou geen bedreiging in vir fisiese skade aan mense nie, aangesien dit nie brandende tentakels het wat algemeen met ctenofore verband hou nie. Die invoering in die Swart See het egter die vermoë van hierdie spesie getoon om 'n ekosisteem heeltemal en vinnig te oorheers. Onbestuurde insettings kan moontlik pelagiese visse en ander waardevolle populasies beïnvloed. (Kube, et al., 2007 Shiganova, et al., 2001)

      Bewaringstatus

      • IUCN Rooilys nie geëvalueer nie
      • Amerikaanse federale lys Geen spesiale status nie
      • CITES Geen spesiale status nie
      • Lys van die staat Michigan Geen spesiale status nie

      Bydraers

      Collette Dougherty (skrywer), Radford Universiteit, Sarah Rimmer (outeur), Radford Universiteit, Gregory Zagursky (redakteur), Radford Universiteit, Renee Mulcrone (redakteur), Spesiale projekte.

      Woordelys

      die watermassa tussen Afrika, Europa, die suidelike oseaan (bo 60 grade suidelike breedtegraad) en die westelike halfrond. Dit is die tweede grootste oseaan ter wêreld naas die Stille Oseaan.

      watermassa tussen die suidelike oseaan (bo 60 grade suidbreedte), Australië, Asië en die westelike halfrond. Dit is die grootste oseaan ter wêreld en beslaan ongeveer 28% van die wêreld se oppervlak.

      'n dier wat hoofsaaklik vleis eet

      gebruik reuke of ander chemikalieë om te kommunikeer

      die nabygeleë waterhabitats naby 'n kus, of kuslyn.

      diere wat hitte wat uit die omgewing verkry word en gedragsaanpassings moet gebruik om liggaamstemperatuur te reguleer

      'n gebied waar 'n varswaterrivier die see ontmoet en getyinvloede lei tot skommelinge in soutgehalte.

      bevrugting vind plaas buite die vroulike liggaam

      vereniging van eier en spermatozoa

      'n voedingsmetode waar klein voedseldeeltjies deur verskillende meganismes uit die omliggende water gefiltreer word. Word hoofsaaklik deur ongewerwelde waterdiere gebruik, veral plankton, maar ook deur baleinwalvisse.

      met 'n liggaamstemperatuur wat wissel met die van die onmiddellike omgewing, sonder 'n meganisme of 'n swak ontwikkelde meganisme om die interne liggaamstemperatuur te reguleer.

      Diere met onbepaalde groei groei steeds gedurende hul lewens.

      die kusgebied wat hoofsaaklik deur die getye beïnvloed word, tussen die hoogste en laagste bereik van die gety. 'n Waterhabitat.

      verwys na dierspesies wat na en gevestigde bevolkings in streke buite hul natuurlike omvang vervoer is, gewoonlik deur menslike optrede.

      met die vermoë om van die een plek na die ander te beweeg.

      die gebied waarin die dier natuurlik voorkom, die streek waarin dit endemies is.

      dwaal gewoonlik van plek tot plek, gewoonlik binne 'n goed gedefinieerde reeks.

      ’n Waterbioom wat uit die oop oseaan bestaan, ver van land af, sluit nie seebodem (bentiese sone) in nie.

      die soort poligamie waarin 'n wyfie met verskeie mannetjies paar, wat elkeen ook met verskillende wyfies paar.

      'n vorm van liggaamssimmetrie waarin die dele van 'n dier konsentries rondom 'n sentrale orale/aborale as gerangskik is en meer as een denkbeeldige vlak deur hierdie as lei tot helftes wat spieëlbeelde van mekaar is. Voorbeelde is cnidarians (Phylum Cnidaria, jellievis, anemone en koraal).

      leef hoofsaaklik in oseane, seë of ander liggame soutwater.

      gebruik aanraking om te kommunikeer

      teling vind deur die jaar plaas

      dierlike bestanddeel van plankton, veral klein skaaldiere en vislarwes. (Vergelyk met fitoplankton.)

      Verwysings

      2011. "Beroe ovata Bruguière, 1789 "(aanlyn). Ensiklopedie van lewe. Besoek op 22 Junie 2011 om http://www.eol.org/pages/509867?text_id=9024923.

      Arashkevich, E. 2001. Reproduksie strategie van Beroe ovata (Ctenophora, Atentaculata, Beroida): 'n nuwe indringer in die Swart See. Okeanologiya, 41: 116.

      Bayha, K. 2006. Die molekulêre sistematiek en bevolkingsgenetika van vier kus -ctenofore en scyphozoa -jellievisse van die Amerikaanse Atlantiese Oseaan en die Golf van Mexiko. Proefskrif Abstracts International Deel B: Wetenskap en Ingenieurswese, 66: 3590.

      Finenko, G., Z. Romanova, G. Abolmasova, B. Anninsky, L. Svetlichny, E. Hubavera, L. Bat, A. Kidneys. 2003. Bevolkingsdinamika, inname, groei en reproduksietempo van die indringer Beroe ovata en die impak daarvan op planktongemeenskap in Sevastopolbaai, die Swart See. Journal of Plankton Research, 25 (5): 539-549. Besoek op 22 Junie 2011 om http://plankt.oxfordjournals.org/content/25/5/539.full.

      Haddock, S., J. Case. 1999. Bioluminescentiespektra van vlak en diepsee gelatienagtige dierplankton: ctenophores, medusae en sifonofore. Marine Biology, 133: 571-582.

      Hay-Schmidt, A. 2000. Die evolusie van die serotonergiese senuweestelsel. Proceedings of the Royal Society B: Biological Sciences, 267: 1071-1079.

      Kasuya, T., T. Ishimaru, M. Murano. 2002. Laboratoriumstudie van groei van die lobate-ctenofoor Bolinopsis mikado (Moser). Plankton Biol Ecol, 49: 81-87.

      Kideys, A., G. Finenko, B. Anninsky, T. Shiganova, A. Roohi. 2004. Fisiologiese eienskappe van die ctenofoor Beroe ovata in die water van die Kaspiese See. Mariene ekologie, 226: 111.

      Kube, S., L. Postel, C. Honnef, C. Augustin. 2007. Mnemiopsis leidyi in die Baltiese See – verspreiding en oorwintering tussen herfs 2006 en lente 2007. Aquatic Invasions , 2 (2): 137-145.

      Matsumoto, G., G. Harbison. 1991. In situ waarnemings van vreet-, voeding- en ontsnappingsgedrag in drie ordes oseaniese ctenofore: Lobata, Cestida en Beroida. Mariene biologie, 117 (2): 279-287. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/q9245n0282972844/.

      Miller, R., R. Williams. 1978. Energiebehoeftes en voedselvoorrade van ctenofore en jellievisse in die Patuxentriviermond. Chesapeake Science, 13 (4): 328-331. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/50571138j5341m76/.

      Mills, C. 1996. Medusae, sifonofore en ctenofore van die Alboránsee, suidwestelike Middellandse See. Scientia Marina, 60: 145-163.

      Mutlu, E. 2009. Onlangse verspreiding en grootte struktuur van gelatienagtige organismes in die suidelike Swart See en hul interaksies met visvangste. Marine Biology, 156 (5): 935-957. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/l2n6uw5652u2701w/.

      Nelson, T. 1925. Oor die voorkoms en voedselgewoontes van ctenofore in New Jersey binnelandse kuswaters. Die Biologiese Bulletin, 48 (2): 92-111. Besoek op 22 Junie 2011 om http://www.jstor.org/stable/1536706.

      Purcell, J., W. Graham, H. Dumont. 2001. Kwallen bloei: ekologiese en maatskaplike belangrikheid. Hydrobiologia, 451: 333.

      Shiganova, T., Y. Bulgakova, S. Volovik, Z. Mirzoyan, S. Dudkin. 2001. Die nuwe indringer Beroe ovata Mayer 1912 en die uitwerking daarvan op die ekosisteem in die noordoostelike Swart See. Hydrobiologia, 451 (1-3): 187-197. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/u417x62p70646858/.

      Swanberg, N. 1974. Die voedingsgedrag van Beroe ovata. Mariene biologie, 24 (1): 69-76. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/x348516010343p0t/.

      Tamm, S., S. Tamm. 1991. Omkeerbare epiteel hechting sluit die mond van Beroe, 'n vleisetende mariene jellie. Biologiese Bulletin, 181: 463-473.

      Tamm, S., S. Tamm. 1993. Verskeidenheid van makrociliêre grootte, tandpatrone en verspreiding in Beroe (Ctenophora). Zoomorphology , 113 (2): 78-89. Besoek op 22 Junie 2011 om http://www.springerlink.com/content/n4221u9437088041/.

      Vostokov, S., E. Arashkevich, A. Dritz, Y. Lukashev. 2001. Ekologiese en fisiologiese eienskappe van die ctenofoor Beroe ovata in die kuswater van die Swart See: oorvloed, biomassa, grootteverspreiding, gedrag, voeding en metabolisme. Russiese Akademie van Wetenskappe, 41: 105.


      Jellievisse floreer in die mensgemaakte ontwrigting van die oseane

      Jellievis broei teen 'n baie hoër tempo as voorheen, danksy veranderinge in hul omgewing deur menslike aktiwiteite

      Duisende van hulle teister ons strande tot die afgryse van vakansiegangers wat hul angel vrees, maar danksy die mens se ontwrigting van die oseane floreer jellievisse.

      Jellievisse was al langer op die aarde as ons - daar word vermoed dat hulle byna 600 miljoen jaar in die oseane rondgeloop het.

      Maar menslike aktiwiteite, van oorvissery tot plastiekafval en klimaatsverandering, het 'n omgewing geskep waarin hulle selfs meer tuis is.

      Die verspreiding van die jellievisse kan lei tot wat sommige waarnemers die "jellifikasie" van die oseane noem, wat ingrypende veranderinge in die gesig staar volgens 'n konsep-VN-verslag wat Woensdag uitgereik word.

      Fabien Lombard, 'n Franse mariene bioloog aan die Sorbonne-universiteit wat spesialiseer in die ekologie van plankton en jellievisse, sou nie so ver gaan nie.

      “Daar is meer jellievisse in sekere sones in die wêreld,” het hy aan AFP gesê: die Swart See, aan die Namibiese kus en die See van Japan.

      Dit is nie duidelik of hul teenwoordigheid in ander dele van die wêreld toegeneem het nie, want dit is moeilik om dit werklik te tel, hoewel 'n wêreldwye databasis in 2014 opgestel is om dit op te spoor.

      Jellievisse, wat onder die eerste bewoners van die planeet was, leef vandag in alle seë en oseane van die wêreld en op elke diepte.

      Die ongewerwelde diere het geen brein nie, is 95-98% water en dryf en swem saam met die seestrome.

      Dit is ongelooflik uiteenlopende wesens, wat in 'n groot verskeidenheid kleure en groottes voorkom.

      Jellievisse kan in al die seë en oseane van die wêreld gevind word

      'Absoluut ongelooflike hoeveelhede'

      Jellievis reproduseer selfs op verskillende maniere tydens hul lewensiklusse.

      Volwassenes kuit en laat 'n groot hoeveelheid eiers en sperms in die water vry. Die bevrugte eiers sak tot by die seediepte voordat 'n klein poliep uitbroei, wat dan self kan kloon.

      Wanneer groot getalle jellievisse saammassa staan ​​dit bekend as 'n "bloei". In die verlede sou dit met gereelde tussenposes gebeur, sê Anais Courtet, 'n bioloog by die Parys -akwarium - byvoorbeeld elke 12 jaar in die Middellandse See.

      'Vandag word hierdie siklus nie lank gerespekteer nie, en u sien dit elke jaar,' het sy bygevoeg.

      Vir Philippe Cury, 'n spesialis in mariene ekosisteme by die Frankryk se nasionale navorsingsinstituut vir ontwikkeling, is dit te danke aan mensgemaakte faktore soos oorbevissing, diepseevissery en die verhitting van die oseane.

      'Hierdie drie faktore veroorsaak uitbarstings van die jellievisbevolking,' het hy gesê. 'Dit gebeur altyd,' het hy bygevoeg, 'maar dit kom baie meer voor en ons sien soms ongelooflike hoeveelhede.'

      Oorbevissing het van hul natuurlike roofdiere uitgeskakel, soos tuna en seeskilpaaie wat dikwels per ongeluk in nette gevang word, maar ook die visse wat op plankton vreet.

      Aangesien hul roofdiere in getal verminder is, het die jellievis meer plankton om op hulself te voed en het hulle ongemerk gedy.

      Die blote grootte van sommige jellievisse kan 'n bedreiging vir vissermanne wees as hulle in hul nette vang

      Diepseevissery het hulle ook gehelp. Die treilers sleep reuse nette oor die seebodem en trek alles sonder onderskeid op: sponse, wurms en koraal.

      Dit laat 'n omgewing waarin die jelliepoliepe ongemerk kan voortplant, verduidelik Cury.

      En hulle het menslike voorwerpe ook deel van hul eie habitat gemaak, van boeie tot oliebore.

      'Hulle is mal oor plastiek,' het Lombard gesê. Plastiekafval van net 'n paar sentimeter kan vir hulle as 'n broeikolonie dien.

      En hoewel aardverwarming en die versuring van die oseane sommige spesies kon getref het, het dit jellievisse geen skade berokken nie, het Courtet gesê.

      Hulle vermeerdering het tot op die punt gekom dat hulle selfs nou inmeng met menslike aktiwiteite - en dit strek veel verder as om onverskrokke vakansiegangers te stuit.

      Dit is 'n probleem vir visvang, vir visboerdery en vir ontsoutingsaanlegte. Hulle kan selfs die verkoelingstelsels op kerninstallasies verstop.

      Byvoorbeeld, in 2007 het jellievisse die salm by 'n visplaas buite Noord-Ierland vernietig en die visse gesteek wat nie kon ontsnap nie.

      In Japan beëindig vissers soms visvanguitstappies as daar te veel jellievisse in die waters is, uit vrees dat die gewig van die diere hulle nette sal laat verloor of selfs omslaan.

      “Ons het ekosisteme nodig wat normaal funksioneer, met breë biodiversiteit,” het Cury gesê.

      Enige gedagte om self die jellievisse te vang—of om dit te eet of net van hulle ontslae te raak—is nie prakties nie, het hy bygevoeg. "Hulle plant baie vinnig voort."


      WNC Jellievisbioloog veldtogte vir oop see

      'N Plaaslike bioloog wat golwe gemaak het vir haar navorsing oor kwallen wat in varswater -ekosisteme voorkom, waaronder sommige hier in Wes -Noord -Carolina, is deel van 'n internasionale veldtog om die seelewe in 'n groot stuk soutwater te beskerm en beter te verstaan ​​- die meeste van ons sal nooit sien nie.

      UNC Asheville Assistent Professor in Biologie Rebecca Helm, PhD, spandeer baie van haar tyd om die piepklein varswater jellievis te vind en te bestudeer wat in die damme en mere in Wes-Noord-Carolina woon.

      "Hou jou oog uit vir min nikkelgrootte, halfhelder, effens gryserige jellievisse wat rondbeweeg," sê Helm. "Hulle lyk soos jellievisse. Hulle het daardie baie stereotipiese polsende beweging, en dit lyk asof hulle in sekere areas van 'n dam versamel. En dit is een van die dinge wat ons hoop om uit te vind, jy weet, hoekom gaan hulle na hierdie spesifieke gebiede? Beweeg hulle aktief na die gebiede, is die sirkulasie van die dam?

      beweeg hulle rond - ons wil uitvind.”

      Maar die afgelope tyd is dit die jellievisse en ander seelewe wat in groter watermassas woon, veral op 'n gebied wat 200 seemyl van die kus af is - die oop see genoem.

      'Een persent van die oop see is ten volle beskerm en bewaar. En hierdie gebied beslaan ongeveer die helfte van ons planeetoppervlak en meer as 90% van die leefbare habitat op aarde, ”sê Helm. 'En so beskik ons ​​oor hierdie ongelooflike rykdom aan biodiversiteit op die oop see waarop ons as mense op talle maniere staatmaak. En daar is geen meganisme vir die oorgrote meerderheid van die diere nie, insluitend jellievis, vir bewaring of beskerming. En daarom wil ons die verandering sien. ”

      Die Verenigde Nasies werk aan 'n ooreenkoms om bewaring en volhoubaarheid op die oop see aan te spreek, maar Helm sê dat hulle meer moet doen, insluitend die monitering van biodiversiteit. Saam met van die wêreld se voorste wetenskaplikes het sy daardie gedagtes neergepen in 'n brief aan die VN, wat in die Journal Science gepubliseer is.

      'Daar is soveel dinge wat ons oor die see geleer het, omdat ons gedink het dat dit nooit uitgeput sou wees nie. En toe besef ons dat dit kan wees. En toe ons besef dat ons visserye ineenstort, sien ons agteruitgang van die ekosisteem. Dit was dus eintlik 'n bewustheid dat die see nie 'n oneindige bron is nie. En noudat ons weet dat ons vorentoe kan beweeg met daardie ingesteldheid voor en in die middel en beter doen as wat ons voorheen gedoen het.”

      Die COVID -pandemie het die oop see van die VN -verdraggesprekke opgehou. Tyd wat hierdie jellie -navorser in Wes -Noord -Carolina en haar kollegas gebruik om die publiek op te voed en te werf om deel te neem aan hul veldtog om 'n stuk see te beskerm wat die meeste van ons nooit sal sien nie, maar waarop ons almal staatmaak.

      Ek is Helen Chickering BPR nuus.

      Besoek Wetenskap Tydskrif om die amptelike brief te lees wat Helm en haar kollegas geskryf het en 'n beroep op die Verenigde Nasies doen om die oop see te beskerm en meer te wete te kom oor hul veldtog om biodiversiteit in die oop see hier te beskerm. Besoek Helm's Jelly Lab by UNC-Asheville hier.


      Nasionale Wetenskapstigting - Waar ontdekkings begin

      Waarom word groot swerms jellievisse en ander gelatienagtige diere in baie van die wêreld se gewilde visvang- en vakansieplekke aangemeld?


      In die Golf van Mexiko se digste jellie-swerms is daar meer jellievisse as wat daar water is.


      16 Desember 2008

      Groot swerms jellievisse en ander gelatiendiere-wat soms honderde vierkante myl se oseaan beslaan-is onlangs in baie van die wêreld se grootste vakansie- en visbestemmings aangemeld. In hierdie onderhoud met Lily Whiteman van die National Science Foundation, bespreek die bekende "jellyologist" Monty Graham van die Dauphin Island Sea Lab in Alabama die oorsprong en impak van sulke swerms. (Let wel: jellievisse en ander gelatienagtige diere word hier "jellies" genoem.)

      Watter tipe skade het jellie-swerms aangerig?

      'Skade' kan as ekonomies of omgewingsbelangrik beskou word. Onlangse voorbeelde van jellieswerms wat sulke probleme veroorsaak het, sluit in:

      • Toerisme in Australië, waar dodelike boksjellies woon, en in die Middellandse See, waar brandende jellievisse gedurende die somer van 2008 baie strande gesluit het.
      • Baie belangrike visserye, insluitend die Golf van Mexiko, waar jellies gereeld nette, voëlvisgereedskap verstop of op eiers en larwes van vis prooi.
      • Akwakultuurbedrywighede word dikwels geraak. Een besondere voorbeeld was in 2007, toe 'n buitengewoon groot swerm jellievisse 'n salmplaas by Noord -Ierland feitlik uitgewis het.
      • Seebodemdiamantbedrywighede aan die kus van Namibië, waar jellies vakuumpype verstop het.
      • Kernkragaanlegte op baie plekke. Onlangs, in November 2008, het 'n jellieswerm inlaatpype by die Diablo Canyon-kragstasie verstop en daardeur 'n tydelike stillegging van die aanleg veroorsaak.

      Hoe dig is jellies in swerms saamgepak?

      In die meeste gevalle sou 'n digte swerm 'n paar diere in een kubieke meter water wees. In uiterste gevalle kan daar egter meer jellies as water wees. Sulke swerms kan 'n honderd myl of meer van die kuslyn op 'n slag aflê.

      Is jellie-swerms natuurlike verskynsels?

      Ja. Jellies het waarskynlik meer as 600 miljoen jaar in ons see geswem en geswem. As die omstandighede reg is, kan jellieswerms vinnig vorm. Dit blyk dat hulle dit doen vir seksuele voortplanting. Aangesien mans gamete (sperms) in die water moet vrylaat, moet hulle baie naby wyfies wees. Daarom is swermgedrag net 'n manier vir hulle om naby aan mekaar te wees.

      Neem jelliebevolkings toe?

      In sommige plekke neem jelliebevolkings toe, maar sulke toenames is streeksgebonde. Ons het nie bewyse dat daar 'wêreldwye' toenames is as gevolg van wêreldwye invloede nie, maar bewyse neem toe dat klimaatsverandering 'n uitwerking kan hê.

      Bevorder menslike omgewingsprobleme bevolkingsontploffings van jellies?

      Verskeie tipes omgewingsprobleme kan die vorming van jellieswerms bevorder. Hierdie probleme sluit in besoedeling, die oes van vis, die bekendstelling van nie-inheemse jelliespesies in nuwe habitatte, die toevoeging van kunsmatige substraat (soos visriwwe en verskeie buitelandse platforms) in die see en klimaatsverandering.

      Hoe kan klimaatsverandering bevolkingsontploffings van jellies bevorder?

      Hoër watertemperature kan die voortplanting van jellie bespoedig asook die groeiseisoen vir jellie verleng, 'n langer reproduksieseisoen kan meer jellies tot gevolg hê. Klimaatsverandering kan ook die hoeveelheid kos wat beskikbaar is vir jellie verhoog.

      Klimaatsverandering kan ook seestrome verander. Veranderde strome kan jellies-wat met strome dryf-na nuwe habitatte vervoer.

      Omdat klimaatsverandering 'n wêreldwye verskynsel blyk te wees, kan klimaatsverandering wêreldwye gevolge vir jellies hê. Maar ons weet regtig nog nie wat die besonderhede is rakende interaksies tussen klimaatsverandering en jelliebevolkings nie.

      In die lig van die oorvloed van jellies, hoekom weet ons nie meer daarvan nie?

      Mariene ekoloë het jellies tradisioneel beskou as blote oorlas wat die studie van werklik belangrike wesens belemmer het. As gevolg van sulke houdings het ekoloë tradisioneel baie moeite gedoen om jellies te vermy, eerder as om dit te bestudeer. Trouens, in die verlede, toe wetenskaplikes per ongeluk jellies in hul navorsingsnette vasgevang het, het hulle gereeld afskuwelike dinge aan jellies gedoen-soos om bleikmiddel oor hulle te gooi om dit weg te los sonder om die harde beeste wat hulle regtig wou bestudeer, te vernietig.

      Omdat jellies tradisioneel onderbestudeer is, het ons nie baie akkurate langtermynrekords van hul bevolkingsgroottes nie. Daarom kan ons op baie plekke nog nie met sekerheid sê of of hoeveel jelliebevolkingsgroottes kan verander nie.

      Kry jellies uiteindelik die respek wat hulle verdien?

      Die waardering vir die ekologiese belangrikheid van jellies het geleidelik toegeneem sedert die 1980's, toe jelliebevolkings in verskeie ekosisteme ontplof het, waaronder die Swart See. Meer wetenskaplikes bestudeer nou jellies op meer plekke as ooit tevore.

      Waarom is jellies besonder moeilik om te bestudeer?

      Jellie is broos, daarom word dit dikwels vernietig wanneer ons dit in nette probeer versamel. Dit is ook moeilik om jellies te bewaar omdat hul liggame deur baie soorte preserveermiddels vernietig word. Boonop is baie soorte jellies te groot of te klein om in gevangenskap grootgemaak te word.

      Is jy al ooit erg deur jellies gesteek terwyl jy dit ondersoek het?

      Ja, maar nie meer as 'n ongemaklike steek nie. Ek het wel kollegas wat in die hospitaal opgeneem is terwyl ek jellies bestudeer het.

      In light of the fact that jellies are difficult to study and the ocean is so complex, how can scientists identify the individual impacts of each type of environmental disturbance on jelly populations?

      By developing computer models of marine ecosystems. One of my main activities now is to help build such models, and then manipulate various factors in these models--such as water temperature or salinity and the size of fish harvests--in order to identify their relative influences on jelly populations.

      If some places have too many jellies, why don't people just eat them?

      Some jellies are eaten by humans and have long been considered a delicacy in some Asian countries. In addition, processed jellies are sold in some Asian food stores in the U.S.

      As long-lived, hardy and often abundant creatures, are jellies "the cockroaches of the sea?"

      Absolutely not! Jellies are much better than cockroaches! Jellies represent among the oldest living animals on Earth and if the past is prologue, these highly successful creatures will continue to thrive, even under the changing conditions of today's oceans. I have said before that most likely, cockroaches will be long gone when the last jelly swims in a lonely sea.

      For More Information:

      Visit the National Science Foundation's special online report on jelly swarms, Jellyfish Gone Wild: Environmental Change and Jellyfish Swarms at: http://www.nsf.gov/news/special_reports/jellyfish/index.jsp. A video of Monty Graham discussing jellyfish swarms is included in the report at http://www.nsf.gov/news/special_reports/jellyfish/swarms.jsp.


      Jellyfish researcher Monty Graham of the Dauphin Island Sea Lab.
      Krediet en groter weergawe

      An aerial view of a jelly swarm in the Gulf of Mexico.
      Krediet en groter weergawe

      Ondersoekers
      William Graham

      Related Institutions/Organizations
      Marine Environmental Sciences Consortium

      Liggings
      Alabama

      Total Grants
      $390,028


      Jellyfish researcher Monty Graham of the Dauphin Island Sea Lab.
      Krediet en groter weergawe

      An aerial view of a jelly swarm in the Gulf of Mexico.
      Krediet en groter weergawe


      Can jellyfish improve the Black Sea ecosystem? - Biologie

      Access this article and hundreds more like it with a subscription to Science World magazine.

      JELLY PACK: A bloom of moon jellyfish, which get their name from their circular shape

      CCSS: Reading Informational Text: 2

      Are people to blame for a growing number of jellyfish swarming the seas?

      ESSENTIAL QUESTION: What factors might cause a population of organisms to suddenly increase?

      What should have been a fun trip to the beach last June soon turned into a nightmare for thousands of visitors to Florida’s eastern coast. Over the course of two weeks, more than 3,000 beachgoers were stung by nettle and moon jellyfish. Luckily, no one was seriously injured. Although stings from these types of jellies can be extremely painful, they’re rarely deadly.

      Last June, visitors flocked to Florida’s eastern coast. It should have been a fun trip to the beach. But it soon turned into a nightmare for thousands of people. More than 3,000 visitors were stung by nettle and moon jellyfish over a two-week period. Luckily, no one was seriously hurt. Stings from these types of jellies can be extremely painful, but they’re rarely deadly.

      This map shows areas with increased sightings of jellyfish blooms, represented by red triangles and blue squares. Scientists are uncertain whether more blooms are in fact occurring or if people are just better at reporting them than in the past.

      This map shows areas with increased sightings of jellyfish blooms, represented by red triangles and blue squares. Scientists are uncertain whether more blooms are in fact occurring or if people are just better at reporting them than in the past.

      SOURCE: NATIONAL GEOGRAPHIC, LUCAS BROTZ, HYDROBIOLOGIA IMAGE: JIM MCMAHON/MAPMAN®

      This map shows areas with increased sightings of jellyfish blooms, represented by red triangles and blue squares. Scientists are uncertain whether more blooms are in fact occurring or if people are just better at reporting them than in the past.

      This map shows areas with increased sightings of jellyfish blooms, represented by red triangles and blue squares. Scientists are uncertain whether more blooms are in fact occurring or if people are just better at reporting them than in the past.

      SOURCE: NATIONAL GEOGRAPHIC, LUCAS BROTZ, HYDROBIOLOGIA IMAGE: JIM MCMAHON/MAPMAN®

      This is just one recent encounter between people and swarms of jellyfish, called blooms , in the worlds’ oceans. Reports of these incidents have been on the rise for the past few decades ( see Jellyfish Sightings ). Jellyfish blooms can cover thousands of square miles and cause all sorts of trouble. In places like Israel, Japan, the Philippines, Scotland, Sweden, and the U.S., the gelatinous animals have clogged intake pipes at power plants that pull in water from the ocean to cool machinery. That can cause the plants to temporarily shut down. Large masses of jellies also frustrate people who are fishing by damaging their nets and gumming up boat engines.

      “There are definitely more reports of jellyfish blooms from more locations,” says Mark Q. Martindale, a marine biologist at the University of Florida. He explains that scientists are unsure whether blooms are really increasing or if reporting of the occurrences has just improved. However, Martindale says changing climate patterns and human activities, like overfishing, could be affecting jellyfish numbers. That could result in larger blooms showing up more often closer to shores—and in places where they haven’t been spotted before.

      This is just one recent run-in between people and swarms of jellyfish in the worlds’ oceans. Reports of these events have been increasing for the past few decades (see Jellyfish Sightings). Swarms of jellyfish are called blooms. They can cover thousands of square miles and cause all sorts of trouble. Some power plants pull ocean water in through pipes to cool machinery. Jellyfish have clogged these pipes in places like Israel, Japan, the Philippines, Scotland, Sweden, and the U.S. That can cause the plants to shut down for a while. Large masses of jellies also make trouble for fishermen. The jellies damage fishing nets and gum up boat engines.

      “There are definitely more reports of jellyfish blooms from more locations,” says Mark Q. Martindale. He’s a marine biologist at the University of Florida. He explains that scientists aren’t sure why. Are blooms really increasing, or are they just being reported better? But Martindale says changing climate patterns could be affecting jellyfish numbers. So could human activities, like overfishing. That could result in larger blooms showing up more often, closer to shores, and in completely new places.


      Opsomming

      As a result of the fact that many of the jellyfish increases we are seeing at the local level are a likely symptom of local perturbations to the ecosystem, notwithstanding the global drivers of overfishing and climate change, it is only by resolving those local issues that we stand any chance of managing jellyfish fisheries or of bringing jellyfish populations back to “normal”. However, given that there is not just one “smoking gun” in most instances, and that the driving factors are inter-correlated and act synergistically, this may not be easy without a multi-pronged approach. For example, the increase in jellyfish (Mnemiopsis) abundance during the 1980s in the Black Sea is thought to have been brought about by the combined effects of overfishing, pollution, and ballast water transport of the invasive species. Yet by unintentionally starting to clean up eutrophication and by judicious management of fisheries (aided by a bio-control agent, Beroe), fish stocks have partially recovered and populations of the alien ctenophore have declined ( Kideys, 2002).

      The clean-up of the Black Sea appears to be the exception that demonstrates it is possible to clean-up a jellyfish problem and reverse, in part, a regime shift, because even with knowledge of the potential drivers of change, and a concerted effort to rectify this, there is no guarantee that we will resolve the problem. In the case where overfishing alone may have led to an increase in jellyfish, it could be argued that a better management of fish populations, with the return to pre-decline conditions, could resolve the problem of the abnormally large jellyfish populations. This simplistic line of argument assumes that the biomass that first went in the phytoplankton–crustaceans–fish pathway is now going in the phytoplankton–crustaceans–carnivorous jellyfish pathway ( Boero et al., 2008), and that the predator-pit created by jellyfish for fish can somehow be alleviated (as Fauchald, 2010). However, for the Benguella, which is perhaps one of the best present examples of the impacts of overfishing on jellyfish ( Roux et al., 2013), the biomass of pelagic finfish may simply not be there to rebuild. Even if there was a sufficient base to build from, however, it could not be done without an exhaustive and very costly effort to concurrently reduce the population of competing and predating jellyfish. This comes with its own bycatch and ecosystem risks, and uncertainties about the strength of the link between populations of medusae and polyps. It should also be realized that by the time these changes have been made, the system we want to return to has probably changed again and that we will never can go back!

      The problems experienced in the Inland Sea of Japan and the East China Sea seem far more intractable because not only are there the local issues of overfishing and pollution, but there is also extensive coastal development about which nothing can meaningfully be done. The global effects of ocean warming are obvious in parts of this region too ( Lin et al., 2005), which is outside local control. The overexploitation of fish populations is a global problem ( Swartz et al., 2010) and the removal of many species of fish is very likely releasing many species of jellyfish from both predation and competition. Jellyfish, in their turn, exacerbate our impact on fish by exerting predation on fish eggs and larvae and on the food of juveniles and adults ( Purcell and Arai, 2001). While the decrease in fish populations is undeniable, as demonstrated by the steady rise of aquaculture to satisfy commercial demands, the link between it and increasing jellyfish numbers is weak, if logical. We should not assume that eating more jellyfish, or even fishing them, will be an economically viable solution to our jellyfish problems, and it may in fact lead to unfulfilled expectations and unexpected results. After all, the economic implications of setting up an industrial jelly-fishery are wide, whereas the certainty of jellyfish availability so as to economically sustain the effort is weak.

      Indeed, there are far too many unknowns to simply assume that fishing medusae will negatively impact jellyfish populations without concomitant negative impacts to the wider ecosystem. Jellyfish have persisted relatively unchanged since the Cambrian and they are likely to be very deeply embedded within the communities and systems they occupy. However, they are not invulnerable to catastrophes, so decisions need to be made on a case-by-case basis. It would seem that a far more prudent approach would be to mitigate and minimize the anthropogenic impacts that are suspected of causing increasing jellyfish populations. At the same time, we should employ the precautionary principle and learn as much as we can about our collective impacts on the marine environment and the important roles that jellyfish play in ecosystems. Although humans are indeed “good” at overfishing, we hope that we have illustrated why we should not jump to overfishing jellyfish as a viable solution. While history does sometimes repeat itself, we should not be so bold to assume we can do so intentionally.


      "Trouble at Sea" - The Mnemiopsis Jellyfish Invasion

      The jellyfish in the photos didn't look like they'd pose a danger to swimmers. Thinly veined and translucent, they didn't have stinging tentacles trailing behind them or dramatic colors signaling danger. But Ferdinando Boero, a professor of zoology at the University of Salento in Italy, knew that they meant trouble nonetheless.

      The pictures, sent by a biologist in the northern Italian town of Lerici in July, marked the first time the species Mnemiopsis leidyi, a thumb-size jellyfish known as the sea walnut, had been documented in the western Mediterranean Sea. Native to the Atlantic coast of the U.S., Mnemiopsis was introduced to the Black Sea in the 1980s — most likely from the ballast water of oil tankers — and played an instrumental role in the collapse of the region's fisheries. "Now the question is, Will it do in the Mediterranean the same thing it did in the Black Sea?" Boero says. "It's harmless for [humans], but it can be deadly for the fish."

      The ominous discovery — the result of Boero's request that all Italians report their jellyfish sightings — came during a series of unusually prolific jellyfish seasons 
 over the past five years. This summer, jellyfish outbreaks forced numerous resorts along the Mediterranean coast to shut their beaches. In Corsica and Tuscany, several swimmers were wounded by Portuguese man-of-wars, jellyfish-like creatures with a potentially fatal sting. In Tunisia, a swarm of jellyfish engulfed a fish farm, killing the year's production of sea bass and sea bream.

      Off the coast of Israel, where tropical species have moved in through the Suez Canal, jellyfish floated in swarms more than 100 km long and 2 km wide. Blooms of Mnemiopsis, first documented off Israel last winter, clogged the filters of a desalination plant that supplies coastal communities with 100 million liters of water a day. At the height of the outbreak, water production at the plant dropped by more than a third as desperate workers tried to clear the filters.

      The reasons for the recent explosion in jellyfish numbers are many. The problems in the Black Sea occurred because Mnemiopsis had been introduced to an ecosystem that had already been severely overfished. In a healthy ecosystem, small fish keep the jellyfish population in check by eating their young. But when the fish population plummets, the tables are turned. By preying on the eggs and larvae of the few surviving fish, the jellyfish prevent them from replenishing their numbers and quickly take their place. "We're shifting from a fish to a jellyfish ocean," says Boero. "We're removing most of the fish, and nature doesn't like a vacuum."

      But overfishing is not solely to blame. The nutrients from fertilizer runoff and sewage suck oxygen from the lower layers of the ocean, creating an environment in which fish struggle but jellyfish thrive. Since 2000, there's been such an increase in numbers of Australian jellyfish in the oxygen-depleted waters of the Gulf of Mexico that shrimpers have been forced to hang up their nets during the swarm season in the summer. In the nutrient-rich waters off the coast of Japan, where jellyfish can grow to the size of refrigerators, a nuclear power plant was forced to lower production in 2006 when a mass of the creatures clogged its cooling system.

      Climate change, too, is likely playing a role. As ocean temperatures rise, jellyfish are reproducing faster, and tropical species are beginning to extend their range.


      Are jellyfish going to take over the oceans?

      Like a karmic device come to punish our planetary transgressions, jellyfish thrive on the environmental chaos humans create. Is the age of the jellyfish upon us?

      Barrel Jellyfish at Kynance Cove in Cornwall, UK. Photograph: Andrew Pearson/Alamy

      Barrel Jellyfish at Kynance Cove in Cornwall, UK. Photograph: Andrew Pearson/Alamy

      Last modified on Wed 14 Feb 2018 20.54 GMT

      Another British summer, another set of fear-mongering headlines about swarms of “deadly” jellyfish set to ruin your holiday. But news that jellyfish numbers may be rising carries implications far beyond the interrupted pastimes of the sunburnt masses.

      Like a karmic device come to punish our planetary transgressions, jellyfish thrive on the chaos humans create. Overfishing wipes out their competitors and predators warmer water from climate change encourages the spread of some jellies pollution from fertilisers causes the ocean to lose its oxygen, a deprivation to which jellyfish are uniquely tolerant coastal developments provide convenient, safe habitat for their polyps to hide. In addition, the great mixing of species transported across the world in the ballasts of ships opens up new, vulnerable ecosystems to these super-adaptors.

      “They’ve got this unique life cycle where they can tolerate harsh conditions and then rapidly thrive when conditions are favourable. So when a stressor like climate change or overfishing opens up a niche for them they can really take advantage of that and rapidly proliferate,” said Lucas Brotz, a researcher at the University of British Columbia. Not all species of jelly benefit, rather there tends to be a reduction in the diversity of species and vast, homogenous masses emerge.

      “They can make millions and millions of copies of themselves and clone asexually. That’s when you get these massive blooms. I think that’s the secret to the success of jellyfish, the reason they’ve been around for hundreds of millions of years.”

      Thousands of jellyfish are washed-up on Pembrey Sands near Llanelli, Carmarthenshire, Wales in June 2015. Photograph: Algis Motuza/Alamy

      The latest flurry of “jellyfish invasion” stories was spawned by an announcement by the UK’s Marine Conservation Society (MCS) that their annual survey of UK waters for 2015 was looking like being a ‘record-breaker’.

      The problem is there aren’t many records to break. The MCS survey has only run for 12 years, not enough to identify a strong trend. Further confusing the issue, the MCS study relies on members of the public for its data. Citizen science is a wonderful tool but adds extra uncertainty – the society admits it cannot be sure how much of the growth is due to more jellyfish and how much is people becoming aware of their survey and reporting to it.

      Even so, the charity’s jellyfish expert Dr Peter Richardson said climate change and overfishing were fundamentally changing the ocean.

      “At the same time we seem to be witnessing increases in jellyfish around the UK. Is this an anomaly, a coincidence, or are the jellyfish telling us something?” het hy gevra.

      Are these British blooms harbingers of the age of the jelly? Globally, jellyfish are little surveyed and their numbers vary wildly from year to year for reasons not entirely understood. Because of the paucity of historical records, jellyfish experts are hesitant about whether a global trend exists.

      But Priscilla Licandro, a researcher at the Sir Alister Hardy Foundation for Ocean Science, said in the few places where decent data exist, populations of jellyfish tend to be rising.

      “There is not very much reliable information, but from what we’ve got, at least at a regional level, there is an increase in the persistence and the occurrence,” she said. In the Mediterranean Sea, where records date back some 200 years, natural cycles of boom and bust have been replaced by a constant, large presence.

      “[In the Mediterranean] there have been changes in the last 15 to 20 years that haven’t been seen for two centuries,” she said. Similar increases in the northeastern Atlantic seem to support the MCS’s more anecdotal findings.

      The links between human activity and local jellyfish blooms are strong. In the Black Sea, invasive comb jellies dumped from the ballast of tankers have spawned deliriously and destroyed the region’s fishing industry. In the Sea of Japan, fertiliser run-off has left an oxygen-depleted sea where little other than jellies can thrive.

      But aside from these regional observations, Mark Gibbons, a zoologist at the University of the Western Cape, said the evidence to support a global trend was still patchy.

      “Whether there is strong evidence of a global increase in jellyfish populations [now] is difficult to answer. Certainly in some coastal systems there have been increases but in others there have not – or at least the background data with which to measure change are absent or scant, so it is hard to say,” he said.

      A lions mane jellyfish drifts in the shallows of Bonne Bay, Canada. Photograph: David Doubilet/NG/Getty Images

      Other researchers, including Steven Haddock from the Monterey Bay Aquarium Research Institute, believe the current observed rise may represent a natural cycle.

      “I have a collection of headlines dating back as far as 1906, and all through the decades, the numbers that people see are ‘unprecedented’,” he said. “In my opinion. there is very little evidence for a global trend that indicates we are due for a future ocean dominated by jellies. They have been in the seas for millions of years, blooming and busting.”

      But scientists agree that the continued abuse of our oceans is leading us down a road where fish and other marine animals fail and jellies win.

      “In all likelihood, owing to the factors that you have listed, we are going to see more jellyfish,” said Gibbons.

      However, said Brotz, “we don’t want to be too quick to say that jellyfish are this evil plague, or the cockroaches of the sea or anything like that. Jellyfish are these beautiful, amazing creatures that play a very important role in the ecosystem.”

      To vilify them would be to miss the ultimate lesson: that a future of oceans filled with swarms of gelatinous beasts will not be a jellyfish apocalypse, but a human one.


      Verwante

      Jaglavak, Prince of Insects

      Animal Magnetism

      Other Fish in the Sea

      It looks benign enough, but the North American gray squirrel has outcompeted the native red squirrel in England, causing its decline there.

      At the third level, the introduced species becomes dominant and alters or upsets the entire ecosystem. One of the most dramatic and damaging invasions of the past quarter century involves a single species of comb jellyfish, a jellyfish-like marine animal also known as a ctenophore ("ten-oh-for"). Looking like a small, translucent medusa, this willowy creature demonstrates the enormous impact that a small, apparently innocuous species can have in a new habitat.

      Native to estuaries along the western Atlantic coast from the northern United States to the Valdés peninsula in Argentina, Mnemiopsis leidyi (as this species of comb jellyfish is known scientifically) appeared in the Black Sea in 1982. It was almost certainly introduced by a ship that loaded Mnemiopsis-laden ballast water in the western Atlantic and then emptied its tanks in the Black Sea. At first, the ctenophore was misidentified, and not until 1989 did authorities recognize it as a species of Mnemiopsis and thus an invader.

      The species usually has moderate population densities in the western Atlantic, but its populations exploded in the Black Sea and the adjacent Azov Sea and Sea of Marmara. M. leidyi has invaded the entire Black Sea, a practically closed body of water that communicates with the Sea of Marmara and thus the Mediterranean through the Turkish strait of Bosporus.

      The comb jellyfish has recently arrived in the Caspian Sea via the Black Sea, where it triggered the catastrophic collapse of local fisheries.

      The Black Sea has two unusual features. On the one hand, it is naturally sterile at great depths there is no oxygen between 660 feet and the deepest regions, which surpass 6,600 feet. On the other hand, it is highly polluted, as it receives the great rivers of eastern Europe and Russia, which drain the effluent of many giant factories and large cities with inadequate sewage treatment. Indeed, the quantities of nutrients, insecticides, fungicides, herbicides, heavy metals, organic compounds, hydrocarbon derivatives, and radioactive waste found on the edges of the Black Sea near the deltas of the great rivers are all worthy of mention in the Guinness Book of World Records .

      Despite this unenviable situation, which would not seem conducive to life, the catch of pelagic fishes (primarily anchovy, sprat, and horse mackerel) had always been good. But when Mnemiopsis exploded in 1988—up to 500 individuals per cubic yard—and devoured all the zooplankton, including fish larvae, the entire pelagic ecosystem was profoundly modified, and the catch plummeted. The anchovy catch fell from 204,000 tons in 1984 to 200 tons in 1993 sprat from 24,600 tons in 1984 to 12,000 tons in 1993 horse mackerel from 4,000 tons in 1984 to zero in 1993. A simple little comb jellyfish caused more damage to the fishery than the various pollutants so often decried!

      Die Mnemiopsis population began to collapse in 1991 as its food base declined, but the comb jellyfish is still present, with drastic annual population fluctuations. Though we can reasonably hope for a reduction in pollution from the Danube, Dnieper, Don, and Dniester Rivers, what can we hope to do against Mnemiopsis, which has overthrown the entire pelagic ecosystem of the Black Sea (and has lately arrived in the Caspian Sea via rivers and canals connecting it to the Black)?

      Threat of threats

      At the fourth level, the introduced species affects several ecosystems, thus threatening an even larger swath of biodiversity. Regrettably, the number of invaders of this sort is growing. For the most part, they are species able to tolerate a wide variety of habitats, or those in such great densities that they disturb all the ecosystems surrounding the one they inhabit.

      The water hyacinth's beauty (top) belies its ability to choke off both standing and running bodies of water (above).

      Water hyacinth (Eichhornia crassipes) is one of the most widespread invaders worldwide. A century after its first introduction outside its native range, the Amazon basin, it infests numerous tropical lakes, estuaries, streams, and rivers. A beautiful plant that attracted botanists seeking ornamentals for botanical gardens, it was imported to a horticultural exposition in New Orleans in 1884. Visitors were impressed by its beauty and planted it in several water bodies.

      The aquatic ecosystems of the southeastern United States were then progressively colonized by vast, floating, dense carpets of water hyacinth. The economic repercussions, particularly interference with navigation, first drew attention, but the presence of an opaque covering of plants on the water surface and the eventual decomposition of dying plants devastated numerous aquatic ecosystems, both planktonic and on the bottom. At one time, water hyacinth dominated 123,500 acres of Florida waters. There it has been reduced to a minor problem, primarily by the use of chemicals and large floating mechanical reapers, but the plant remains a pest in many states, particularly Louisiana.

      Water hyacinth reached Africa in 1892, then Asia in 1894 (after being brought to a botanical garden in Indonesia). Today water hyacinth is present around the globe on thousands of miles of streams and rivers. It first appeared in great quantity in Lake Victoria in 1989 today it covers well over 12,000 acres and is spreading. It wreaks havoc with the commercial fishery, fouls boat engines and propellers, obstructs landing sites, and clogs cooling pipes for power plants, leading to massive blackouts. The impact on native species must be enormous but is largely unstudied. This insufficient scientific documentation of ecological impact is lamentably common for most ecosystems invaded by this plant.

      The water hyacinth's beauty (top) belies its ability to choke off both standing and running bodies of water (above).

      Caulerpa taxifolia, the killer alga, is a dominant, ubiquitous, persistent, and rapidly spreading introduced species. Having colonized a wide variety of habitats, it falls squarely in level four, the highest degree of threat to plants and animals. The fact that it appears to be a single individual, a clone, of a genotype unknown in nature makes it an exceptional and particularly unsettling case.

      Invading the world

      In the U.S., more than 7,000 introduced species (not counting microorganisms) are established in nature, of which perhaps 15 percent cause ecological or economic damage. Some recent cases are rapidly evolving. The cordgrass Spartina alterniflora of the Atlantic coast of the United States has invaded the soft-bottom coasts of California and Washington, completely transforming intertidal ecosystems. Kudzu (Pueraria montana), a Chinese vine, has spread through the forests of the Southeast and Hawaii, covering more than four million acres with a green curtain. The European green crab (Carcinus maenas) is invading the Pacific coast (and also Tasmania) in enormous numbers, with major impacts on coastal benthic food webs.

      Each invading species is a unique case, with characteristic impacts, degrees of dominance, and features of dispersal. Thus each invasion has been treated differently. But the succession of invasions, each dramatic in its own way, that spreads rabbits, rats, camels, horses, deer, birds, frogs, toads, snakes, fishes, insects, jellyfish, crustaceans, mollusks, starfish, sea urchins, dinoflagellates, macroalgae, ferns, and higher plants is dizzying.

      Even as the atlas of plant and animal pests continuously expands, legislation to stem this tide, while drastic in a few nations, is rare or nonexistent in the majority. The scientific illiteracy with respect to the global threat posed by invasive introduced species means that other ecological horrors are much more in the news. Insidious (because it seems natural), progressive, underestimated—this is nature of the blow that human-introduced species strike against biodiversity. Has it not already surpassed that caused by the sum of all chemical pollution?


      Kyk die video: MATRANG Медуза. Вечерний Ургант. (September 2022).