University of Zagreb. Faculty of Science. Department of Biology.
Abstract
Najveća prijetnja koraljima je proces globalnog zatopljenja jer povećanje temperature mora od samo 1-2ºC može uzrokovati njihovo izumiranje. Jedna od posljedica globalnog zatopljenja je zakiseljavanje oceana do čega dolazi zbog porasta koncentracije ugljikovog dioksida u atmosferi, a time i u oceanima. Kisela sredina uzrokuje razgradnju karbonata pa bi najranjiviji bili koralji i neke alge. Koncentracija atmosferskog CO2 ubrzano raste zbog ljudski-izazvane emisije, prvenstveno izgaranjem fosilnih goriva. Porast temperature oceana, jako UV-zračenje i podizanje razine mora još su neke od posljedica globalnog zatopljenja koje utječu na koralje. Prije 12 godina, zbog porasta temperature oceana došlo je do rekordnog izumiranja koralja. Zbog toga se smanjila raznolikost riba, a na nekim područjima je došlo i do lokalnog izumiranja ribljih vrsta te do pada u brojnosti vrsta. Simbiotske alge koje žive s koraljima, vršeći fotosintezu daju koraljima gorivo za izradu novog kostura. No kad su koralji pod termičkim stresom, oni gube alge i polako odumiru. Kad koralji izgube dovoljno algi, postaju bijeli što je nazvano „izbljeđivanje“. Koralji, poput jelenskog roga, Acropora, kolonije su koje su najranjivije kada su suočene s temperaturnim stresovima ili bolestima jer energiju koriste za brzi rast i reprodukciju i imaju manje u rezervi za svoj imunološki odgovor. Ključni je element imunološkog sustava koralja produkcija melanina koji pruža obranu protiv organizama koji uzrokuju bolest u koralja. Glavni faktori koji uzrokuju „izbjeljivanje“ koralja su: napadi koji uzrokuju bolesti i temperaturni stresovi. Globalno zatopljenje usporava obnavljanje ozona i time zatvaranje ozonskih rupa pa sve više opasnog zračenja dolazi do površine Zemlje. Organizmi grebena koriste različite mehanizme kako bi se obranili od UV svijetlosti. To su: „izbjeljivanje“, zaštita i popravak. Neki koralji kao što su Acropora i Pocillopora posjeduju pigmente koji apsorbiraju UV svjetlost. Koralji se moraju zaštititi od UV-zračenja jer ono inhibira fotosintezu. Porast razine mora utjecati će na ekosustav koraljnih grebena koji žive na dubinskoj granici rasta koralja, koji u uvjetima smanjenog osvjetljenja više neće moći održati rast, što će najvjerojatnije dovesti do smrti. Neki pak istraživači tvrde da porast razine mora zapravo može biti korisno, jer će novi uvjeti biti povoljni za vertikalni rast grebena. Koralji imaju mnoge mehanizme kako bi se prilagodili na stresove. Međutim, kad su oslabljeni, njihovi sustavi postaju ranjivi. Kada se unište, potrebno je više od 25 godina za popravak i obnovu čak i najmanjih koraljnih kolonija. Oporavak koralja od štetnih događaja ovisi o opsegu uništenja, blizini izvora za rekolonizaciju i povoljnim uvjetima staništa.The biggest threat to corals is the process of global warming because the increase in sea temperature of only 1-2 º C can lead to their extinction. One of the consequences of global warming, acidification of the oceans which occurs due to increased concentrations of carbon dioxide in the atmosphere, and consequently in the oceans. Acidic environment causes a breakdown of carbonates and the most vulnerable organisms would be corals and some algae. The concentration of atmospheric CO2 is growing rapidly due to human-caused emissions, primarily the burning of fossil fuels. The increase in ocean temperatures, strong UV-radiation and sea level rise are some of the consequences of global warming affecting coral. 12 years ago, due to rising ocean temperatures there was an unprecedented extinction of corals. Because of that, the diversity of fish has reduced, and in some areas has led to local extinction of fish species and a decrease in the number of species. Symbiotic algae that live with corals, carrying out photosynthesis in corals provide fuel for a new skeleton. But when the corals are under thermal stress, they lose their algae and slowly die. When corals lose enough algae, they become white, and that is called " bleaching ". Corals, like a deer horn, Acropora, colonies are most vulnerable when confronted with the temperature stress and diseases, because they use energy for rapid growth and reproduction and have less in reserve for their immune response. A key element of the immune system of coral production of melanin, which provides defense against organisms that cause disease in corals. The main factors that cause "bleaching" of corals are attacks that cause disease and temperature stress. Global warming slows the recovery of ozone and thereby close the ozone hole and all the more dangerous radiation coming to the Earth. Reef organisms use different mechanisms to defend themselves from UV- light. These are "bleaching", the protection and repair. Some corals such as Acropora and Pocillopora have pigments that absorb UV- light. Corals should be protected from UV- radiation because it inhibits photosynthesis. Sea levek rise will affect the ecosystem of coral reefs that live on the depth limit of coral growth, which in low light conditions will no longer be able to maintain growth, which will likely lead to death. However, some researchers argue that rising sea levels can actually be beneficial, because the new conditions will be favorable for the vertical growth of reefs. Corals have many mechanisms to adapt to stress. However, when they are weakened, their systems become vulnerable. When destroyed, it takes more than 25 years for repair and reconstruction of even the smallest of coral colonies. Coral recovery from the adverse event depends on the extent of destruction, sources close to recolonization and favorable conditions of habitat
