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More than 200 marine species off the coast of South Australia (SA) have been killed by a weeks-long toxic algae explosion, in what conservationists have described as “a horror movie for fish”.<\/p>\n
The algal bloom – a rapid increase in the population of algae in water systems – has been spreading since March, growing to about 4,500 sq km (3,400 sq miles), or roughly the size of nearby Kangaroo Island.<\/p>\n
“It’s an unprecedented event, because the bloom has continued to build and build,” said Vanessa Pirotta, a wildlife scientist.<\/p>\n
Other scientists say the algae produces poisons which “act like a toxic blanket that suffocates” a wide range of marine life, including fish, rays and sharks.<\/p>\n<\/div>\n
Brad Martin, SA project manager for OzFish, a non-profit organisation that protects fishing habitats, said that while algal blooms are not uncommon, the “massive” scale of the current event has had a dramatic impact on marine life.<\/p>\n
Toxins produced by the algae can cause “gill and tissue damage” by attacking the red blood cells, Mr Martin told the BBC.<\/p>\n
The large density of the bloom also means that oxygen is being taken out of the water, “so we know that the fish are suffocating”.<\/p>\n
“It is like a horror movie for fish,” he said.<\/p>\n
The event has been widely documented by people sending in pictures of dead wildlife washed up on beaches.<\/p>\n<\/div>\n
The effect on sharks and rays has been particularly graphic, with large numbers washing up on beaches “bright red”, showing indications of haemorrhaging.<\/p>\n
A three-metre great white shark was among those found dead in recent weeks. <\/p>\n
Among the more than 200 species that have been killed, which range from the smallest of baby fish to great whites, some are more vulnerable than others. <\/p>\n
Reef species like crabs and pufferfishes have been the worst hit, as they are less mobile and can’t swim away from the toxic algae.<\/p>\n
While the algae isn’t harmful to humans, those exposed to high doses can experience skin irritation and respiratory symptoms such as coughing or breathing issues.<\/p>\n
The SA government has advised people to avoid swimming at beaches where there is discoloured water and foam.<\/p>\n
Algal blooms occur during sunny and warm conditions, and SA has had a marine heatwave since last September, with temperatures about 2.5 degrees warmer than average.<\/p>\n
Australia has also been experiencing unseasonably warm conditions since March, which has further driven the size and duration of the current algal bloom.<\/p>\n
The last time SA recorded a large event of this type of toxic algae was in 2014, according to the state’s environment and water department.<\/p>\n
The spread has also affected some commercial fisheries, which have pre-emptively closed harvest areas.<\/p>\n
Local coastal businesses have also seen a dip in visitors due to the sheer number of dead marine life washing up on shore. <\/p>\n
Meanwhile, researchers and the SA government are continuing to monitor the bloom as it moves west.<\/p>\n<\/div>\n