Invazivne vrste algi - Caulerpa taxifolia i Caulerpa recemosa

U Sredozemnom moru, veliki problem predstavljaju invazivne tropske vrste algi iz roda Caulerpa, u prvom redu Caulerpa taxifolia i Caulerpa racemosa. Navedene alge, dospjele namjernim ili nenamjernim unošenjem u more, donešene balastnim vodama, pričvršćene za trupove brodova ili sidro, ribarskim mrežama, važe za jednu od najvećih opasnosti za bioraznolikost mora.

Caulerpe su morske zelene alge, poznate kao najveći jednostanični organizmi koji mogu da narastu i do nekoliko metara. Građene su od stabalca, listića i korjenčića, a u zavisnosti od vrste alge različitog su oblika. Ono što je karakteristično za ove alge jeste brza regeneracija, jer ukoliko dođe do oštećenja, vrlo lako dolazi do brzog stvaranja citoplazmatskog čepa koji zatvara ranu. Zbog rapidnog rasta i odsutnosti prirodnog neprijatelja u ovim područjima, ove alge predstavljaju značajnu prijetnju morskom ekosistemu Mediterana.

Caulerpa taxifolia 

Caulerpa taxifolia

Poznata kao ''Tumor mora'', Caulerpa taxifolia je florescentno zelena makroalga, građena od puzajućeg stabalca i listića dužine od 5 do 65cm. Jedna je od 100 najgorih svjetskih invazivnih vrsta. Prvi put je primijećena u Sredozemnom moru 1984. godine, a pretpostavlja se da je dospjela slučajnim ispuštanjem iz akvarijuma Oceanografskog muzeja u Monaku. Alga Caulerpa taxifolia se najčešće prenosi na sidrima brodova ili ribarskim mrežama. Zahvaljujući mogućnosti brzog prilagođavanja na različite ekološke uslove, ova alga ima sposobnost razvijanja i opstanka na svim tipovima dna: pjeskovitom, stjenovitom i muljevitom dnu. Najdrastičnije promjene se dogode ukoliko se nastane na stjenovitom dnu jer se u tom slučaju autohtone vrste potpuno povuku.

Caulerpa racemosa 

Caulerpa recemosa

Tamnozelena alga Caulerpa racemosa, građena je poput svih algi iz roda Caulerpa, prepoznatljiva po  stabalcu sa listićima na kojima su sitne kuglaste izrasline. Dospjela je iz Crvenog mora u Sredozemlje gdje se iznenađujuće brzo proširila. U odnosu na algu Caulerpa taxifolia koja se prenosi isključivo sidrima i ribarskim mrežama, ova alga ima dodatni učinkovitiji način širenja. Njen glavni mehanizam širenja je uz pomoć talasa i snažnih morskih struja, pa je relativno moguće predvidjeti globalni smjer širenja alge. Caulerpa racemosa u vodu ispušta određene materije koje imaju negativan uticaj na biodiverzitet. Podjednako dobro razvija gustu mrežu isprepletanih stabalaca na kamenitom, pjeskovitom i muljevitom dnu, a najgušća naselja su na zahvaćenom stjenovitom dnu.

Širenje algi na velike udaljenosti najčešće je posljedica prenosa ljudskim djelovanjem. Uklanjanje invazivnih vrsta algi osjetljiv je posao koji obavljaju za to obučeni ronioci, obzirom da nestručno uklanjanje može da dovede do širenja algi i još veće štete. Najčešće metode uklanjanja i saniranja područja zahvaćenih ovim invazivnim vrstama su ručno skupljanje talusa, podvodnim sisaljkama, prekrivanje crnim plastičnim folijama. Kako je za razmnožavanje potreban mali dio alge, nijedna od ovih metoda uklanjanja nije konačna. Ipak, najdjelotvornija metoda je prekrivanje crnom plastičnom folijom koja sprečava prodor svjetlosti do alge i tako izaziva njeno uginuće.

Ono što je najveći problem kod uklanjanja ovih invazivnih vrsta algi jeste nedostatak prirodnih neprijatelja. Jedini zabilježen prirodni neprijatelj ovih vrsta jesu sredozemni puževi Oxynoe olivacea i Lobiger serradifalci, koji se hrane ovim algama. Međutim, ovi puževi nemaju brojnu populaciju, pa samim tim ne mogu značajno ni uticati na sprječavanje širenja ovih algi Sredozemnim morem. 

Nepravilno sidrenje, ispuštanje balastnih voda, bacanje smeća, buka, gliseri i razne ljudske aktivnosti vrlo su štetni za prirodnu okolinu. Potrebno je da svaki pojedinac preuzme odgovornost za svoje postupke kako bi se spriječilo trajno oštećenje. Neke od mjera predostrožnosti su:

• Kod sidrenja koristite tehnike i materijale koji smanjuju negativan utjicaj;

• Opremite plovilo sistemom za zadržavanje balastnih voda;

• Poštujte propise o ribolovu;

• Otpad odlažite u lukama, a ne u more. 

Praćenje razvoja algi i kontrola uticaja na autohtone vrste i ekosistem u cjelini, trebalo bi da bude glavni zadatak moderne ekologije i akvakulture. Potrebno je podići svijest pojedinca, raditi na međunarodnoj saradnji i uložiti više napora kako bi se pronašlo konkretno rješenje za ovaj problem.

Mediterranean invasive algae - Caulerpa taxifolia and Caulerpa racemosa

In the Mediterranean sea, the problem is invasive tropical species of Caulerpa algae, primarily Caulerpa taxifolia and Caulerpa racemosa. The mentioned algae, due to intentional or unintentional introduction into the sea, brought by ballast waters, attached to vessel's hull or anchors, by fishing nets, are considered to be one of the greatest threats to the biodiversity of the sea.

Caulerpa is sea green alga, known as the largest single organism that can grow up to several meters. They are made of the stem, leaves and roots, and depending on the type of algae they have a different shape. What is characteristic of these algae is rapid regeneration, because if damage occurs, it creates rapidly a cytoplasmic cap that closes the wound. Due to the rapid growth and absence of natural enemies in these areas, these algae are a significant threat to the marine ecosystem of the Mediterranean sea.

Caulerpa taxifolia

Caulerpa taxifolia

Known as the "Tumor of the Sea," Caulerpa taxifolia is a fluorescent green macroalga, built of crawling trees and leaves from 5 to 65 cm in length. It is one of the world's 100 worst invasive species. It was first spotted in the Mediterranean in 1984, and it is assumed that it was accidentally released from the Aquarium Oceanographic Museum in Monaco. Alga Caulerpa taxifolia is most often transmitted on ship anchors or fishing nets. Due to the possibility of rapid adaptation to different ecological conditions, this alga has the capacity to develop and survive on all types of bottom: sandy, rocky and muddy bottom. The most drastic changes occur on the rocky bottom because in this case, the indigenous species will withdraw completely.

Caulerpa racemosa

Caulerpa racemosa

The dark green alga Caulerpa racemosa, like all the algae of the Caulerpa genus, is recognizable by the tree with leaves with tiny balls. These algae came from the Red Sea to the Mediterranean where they spread very quickly. In relation to alga Caulerpa taxifolia, which is exclusively transmitted by anchors and fishing nets, this alga has an additional more efficient way of spreading. Its main spreading mechanism is with the help of waves and strong sea currents. Caulerpa racemosa releases certain substances that negatively affect the biological diversity of the sea. It is equally well developed by a dense network of twisted trees on the rocky, sandy or sandy bottom, and the most densely populated settlements are on the rocky bottom.

The proliferation of algae at long distances is most often the result of human transmission. Removing invasive algae species is a delicate task performed by trained divers, since unprofessional removal can lead to the spread of algae and even more damage. The most common methods of removing algae from the areas affected by these invasive species are manually collecting talus, underwater suckers, covering with black plastic foil. As a small part of the alga is needed for reproduction, so none of these removal methods is ultimate. However, the most effective method is to cover algae with a black plastic film that prevents light penetration into the algae and causes its death.
The biggest problem in removing these invasive algae species is the lack of natural enemies. The only recorded natural enemie of these species is the Mediterranean snail, Oxynoe olivacea and Lobiger serradifalci, which feed on these algae. However, these snails don't have a large population, so they can't prevent the spread of these algae to the Mediterranean Sea.

Improper anchoring, discharged ballast water, littering, noise and various human activities are very harmful to the natural environment. It is necessary that each individual takes responsibility for their actions in order to prevent irreparable damage. Some of the precautionary measures:

•        When anchoring, use techniques and materials that reduce the negative impact;
•        Equip the vessel with a system for retention of bilge water;
•        Respect the fishing regulations;
•        Dispose of waste in ports and not in the sea.

Monitoring the development of algae and controlling impacts on indigenous species and the ecosystem, should be the main task of modern ecology and aquaculture. It is necessary to raise awareness of the individual, to work on international cooperation and to make more efforts in order to find a concrete solution for this problem.