New research suggests that groundwater contamination is a significant source of pollution to the Great Barrier Reef, highlighting the need for new mitigation strategies.
What's happening?
The Great Barrier Reef is the largest living structure on Earth, stretching 1,429 miles off the coast of Queensland, Australia. Made up of nearly 3,000 individual reefs, it can be seen from space. However, the Great Barrier Reef is in danger from coral bleaching due to a warming planet.
Nitrogen runoff from farms also threatens the reef as it smothers corals and seagrass beds. An excess of nutrients in the water can cause algal blooms, promote outbreaks of coral-eating starfish, and promote fish disease.
Scientists have long thought that the pollution was primarily entering the reef system from rivers, but new research suggests that almost one-third of dissolved inorganic nitrogen and two-thirds of dissolved inorganic phosphorus in the reef's waters are due to groundwater contamination.
Why is the new data concerning?
The new research is concerning because it is unclear when the pollutants began making their way to the reef's waters.
According to lead author Douglas Tait, an expert on the chemistry of coastal waters at Southern Cross University, the chemicals could take decades to move from farms to underground aquifers before emerging from springs in the reef lagoon.
"This could just be the start of the front [of pollution] that is coming through," or it could be the tail-end, he told the Guardian. "We could have a significant problem realized in the coming decades."
The Great Barrier Reef is an important habitat for animals like sea turtles and crocodiles. It supports 134 species of sharks and rays and 400 different hard and soft corals.
The reef ecosystem also benefits people. Fishing and tourism here pumps $6 billion into the economy and supports around 69,000 Australian jobs.
What's being done about reef pollution?
It's not all bad news. Researchers recently discovered that coral cover increased by at least one-third in the northern and central parts of the Great Barrier Reef in 2022. In fact, they recorded more coral in these areas of the reef than any time in the past four decades.
Still, scientists have said that improving water quality in the reef system will give corals a better chance of recovering from bleaching events caused by a warming world. It will also help avert the negative outcomes associated with an excess of nutrients in the coral system, such as algal blooms.
So far, policymakers have been focused on cutting pollution to the reef from river catchments. Both state and federal governments have pledged hundreds of millions of dollars to improve water quality in the Great Barrier Reef.
Organizations like the World Wildlife Fund are advocating for laws that put legal caps on pollution and help farmers adopt cleaner practices. Plus, some scientists are working on a backup plan: preserving coral through deep freezing in hopes of one day replanting them in the ocean.
Tait said that the new research underscores a need to shift management approaches, however.
Stephen Lewis, a reef water quality expert at James Cook University, said that while the study's findings would not change the importance of training farmers to use fertilizers more efficiently, it could help policymakers to better target future funds.
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