Fish, sharks, races, octopus and even dragons leaf. There are over 200 marine species that were killed by the flowering of a toxic alga, the “Karenia Mikimotoi”, which since last March has invaded the coasts of southern Australia. A “worrying” extermination, as confirmed by Brad Martin, head of the Ozfish project, an organization that deals with safeguarding marine habitats.
The toxic seaweed that invaded Australia
According to the data collected by Ozfish, out of 1,400 reports of deceased animals, almost half, i.e. 47%, concerned species of fish with rooted fins (such as scorpion fish, moon fish or leaf fish), while 26% were related to sharks and breeds. The cephalopods, such as squid, cuttlefish and octopus, represented 7% of the victims, while 6% were related to crabs, lobsters and prawns. The blooms of this particular seaweed are rare but have fatal effects, as they are able to release toxins and reduce oxygen in the affected waters, as explained by Martin: “Karenia creates a poor oxygen environment. A condition that marine animals simply cannot escape”.
In recent months, coastal communities and fish operators have reported thousands of beached and death creatures, some of which never seen before, if not in the sea depths. “The toxin – the experts explain – can suffocate fish by literally blocking the gills, can also cause internal bleeding, and act similarly to a neurotoxin, destroying the nervous system and causing anomalous behaviors. For this reason some fish and sharks have expressed unusual attitudes and many appear reddish. It seems the scene of a horror film”.
According to the Department for the Environment of Southern Australia (EPA), the algal proliferation is fueled by a prolonged wave of marine heat, with sea temperatures of about 2.5 degrees Celsius above average, combined with calm sea, weak wind and minimum wave motorcycle. A particular condition that has “helped” flowering to progress in recent months. Reported for the first time last March off the Fleurieu peninsula, the Killer algae then spread in the coastal areas of the south-east of the state, including the Gulf of San Vincenzo, the Yorke peninsula and the island of Kangaroo.
The effects of Karenia Mikimotoi
Karenia is lethal for marine fauna, while the effects on man are decidedly less serious, but still to be avoided. Contact with the seaweed can however cause skin irritation and respiratory problems. According to Ozfish experts, this “extermination” could have worrying long -term consequences. Especially for fishing, given that flowering has affected fish in all stages of life, from young people to adults of reproductive age, together with their natural prey. The Minister of the Environment of Southern Australia, Susan Close, said that several oysters farms and commercial collection activities had to stop because of the epidemic, calling it an unprecedented event: “It is a very serious seaweed flowering, with terrible effects on marine fauna. In some areas it has even come to 20 meters deep”.
The toxic alga was identified using the microscope and DNA analysis by Professor Shauna Murray, marine biologist at the University of Technology of Sydney: “In the world, about 100 species of harmful algae are known in the world, each with a specific toxic impact. Although it is not entirely clear, it is believed that Karenia Mikimotoi releases a reactive form of oxygen that It damages the branchic cells of the fish, which then kills them by suffocation “. “The current flowering – added Professor Murray – extends for about 150 kilometers, but it is not the largest recorded in Australia. In 2013, another kind of alga, the Alexandrium Catella, held the entire eastern coast of Tasmania, blocking aquaculture and fishing activities for almost four months”.
Karenia is a decidedly unusual behavior, as underlined by Professor Martina Doblin, oceanographer at the University of Technology of Sydney, specialized in harmful algal phenomena: “This alga can derive energy from both sunlight and feeding on other organisms. A double capacity that, together with temperatures, have allowed the flowering to expand. At low concentrations it is part of the food chain, but concentrations becomes a real threat, capable of reducing oxygen levels in the water “. A scourge that local authorities are trying to stem: as explained by the spokesperson of the Department for the Environment of Southern Australia, to disperse the algae would need strong western winds, but the current weather conditions in Australia have delayed the arrival of these currents.