Freak monsoon-like weather conditions in north-eastern Australia pose a significant risk to corals including the Great Barrier Reef, according to new research.

The impact of abnormal quantities of floodwater reaching the sea causes the salinity of the ocean to drop, which in turn provokes a similar stress response in corals as extreme heating does, researchers from James Cook University and the University of Technology Sydney found.

The phenomenon known as “freshwater bleaching” can result in coral death, the scientists said.

Extreme and sudden changes in ocean salt concentration cause a biochemical response in corals similar to that seen during marine heatwaves, but in some ways it could be even more damaging, they added in the findings which were published in the journal BMC Genomics.

“Corals are sensitive organisms, known to only tolerate slight changes in their environment. Thriving in clear, sunlit waters - the majority of reef-building corals are found in tropical and subtropical waters with a salinity between 32 to 42 parts per thousand,” said senior author Professor David Miller. “During the recent flooding, there are reports that nearshore reefs were exposed to roughly half the normal ocean salinity.”

Dirty water threatens the Great Barrier Reef Show all 20 1 /20 Dirty water threatens the Great Barrier Reef Dirty water threatens the Great Barrier Reef Months after scientists warned that it is at greater risk than ever, the Great Barrier Reef is facing a new challenge: dirty water. AFP/Getty Dirty water threatens the Great Barrier Reef Run-off from the recent floods in Australia is spreading out from the coast with the potential to smother the fragile reef. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef The floodwater is thick with sediment from the shore and scientists fear that this may block out the sun, preventing photosynthesis for the algae that the coral relies on to survive. AFP/Getty Dirty water threatens the Great Barrier Reef Dr Frederieke Koon from the Australian Institute of Marine Science however, has told the BBC that the floodwater contains nutrients that have boosted algae growth in some areas, turning the water "a thick blanket of green". Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Despite such benefits in some areas, the fear is that the floodwater will contain pesticides that could prove extremely damaging and due to a lack of wind, it isn't dispersing. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Dr Koon added that "a bit of wind and wave action can break the plumes up quite quickly, but we have literally had no wind so they're just sitting there hanging". Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Fears over the future of the reef have been building in recent years, with the US National Oceanographic and Atmospheric Administration forecasting in October 2018 that the entire 130,000 miles square system is at high risk of bleaching. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef These aerial photos show the murky water spreading across the reef. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef A handout photo taken by Matt Curnock on February 13, off Townsville. 2019 and released on February 15 shows sediment (R) approaching Central Great Barrier Reef from recent unprecedented rain and flooding around Cape Cleveland, off Townsville. - Runoff from recent floods in northern Australia is flowing onto parts of the Barrier Reef, scientists said on February 14, starving coral of light and providing fodder for the predatory crown-of-thorns starfish. (Photo by MATT CURNOCK / Matt Curnock / AFP) / --EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / Matt Curnock" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESMATT CURNOCK/AFP/Getty Images AFP/Getty Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef A handout photo taken by Matt Curnock on February 13, off Townsville. 2019 and released on February 15 shows sediment (bottom) approaching Central Great Barrier Reef from recent unprecedented rain and flooding around Cape Cleveland, off Townsville. - Runoff from recent floods in northern Australia is flowing onto parts of the Barrier Reef, scientists said on February 14, starving coral of light and providing fodder for the predatory crown-of-thorns starfish. (Photo by MATT CURNOCK / Matt Curnock / AFP) / --EDITORS NOTE--- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / Matt Curnock" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVESMATT CURNOCK/AFP/Getty Images AFP/Getty Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. TPX IMAGES OF THE DAY Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters Dirty water threatens the Great Barrier Reef Sediment-filled water is seen in the Great Barrier Reef, Australia February 13, 2019 in this picture obtained from social media on February 15, 2019. MATT CURNOCK/TROPWATER JCU/via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. Matt Curnock / Reuters

“Our research shows that this kind of environmental change causes a shock response in corals that prevents normal cell function.”

To examine the impact floodwater entering coral seas may have, the researchers used the sequenced genome - a biological blueprint - of the common reef-building coral, Acropora millepora. Then they looked for changes in the coral’s biology.

“Using the sophisticated labs at the National Sea Simulator, we put both young and adult corals under a salinity stress test to see how they respond to differing salinity concentrations,” said co-author Dr Jean-Baptiste Raina. “We found that there was a common response between both coral life-stages - with the younger corals being more sensitive to low salinity conditions, but faring slightly better with exposure over time.”

The reaction was comparable to how corals react when exposed to warming sea waters.

“In general, we found that the coral’s cells launch a similar chemical response to reduced salinity as they do for heat stress,” Prof Miller said. “However, unlike the heat stress response, corals exposed to reduced salinity experience a complete collapse of their internal cellular protein balance, suggesting that their cells are in deep trouble.”

The findings come a few days after the Great Barrier Reef Marine Park Authority told a government committee there is a chance corals already damaged after being hit by mass bleaching in 2016 or 2017 could be damaged again by one of several impacts from the flooding disaster.

Other impacts include algal blooms which have erupted after fertilisers from farmland were washed into the sea. These form huge rafts of algae which block light from reaching the corals.

Earlier this month, floodwaters spread more than 37 miles offshore, dragging huge green clouds of algae over the reef.

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Meanwhile one million tons of sludge composed of industrial residues are to be dumped on the Great Barrier Reef, after Australian authorities circumnavigated a rule which bans dumping waste at the World Heritage-listed site.

The dumping licence, awarded due to a loophole for “port maintenance waste”, was described as “another nail in the coffin” for the beleaguered reef - the biggest living structure on Earth.