A new study suggests that coral reefs, including the Great Barrier Reef, were not formed by a continuous process. The findings showed that changes in the sea level can impede the coral reefs' formation.
According to the NOAA website, coral reefs begin to form when coral larvae attach to rocks along the edge of islands or continents until they continuously grow and expand at a rate of 0.3 to 10 centimeters per year depending on the coral type. Scientists calculated that it will take 100,000 to 30 million years for a coral reef to fully form and that this is a continuous process.
But scientists at the University of Sydney's School of Geosciences challenged this belief by providing evidence that even minor changes in the sea level affects the reef's formation. They argued that the minor changes have deferred the growth of the coral reef and rock formation.
"We create a new narrative for how the Barrier Reef and other coral reefs came about and explain the importance of surprisingly small changes in sea level," said Associate Professor Jody Webster from the University of Sydney's School of Geosciences in a news release.
The researchers used radiocarbon dating to examine samples of sediment cores collected from the lagoons of the coral reef on One Tree Reef in the southern Great Barrier Reef. The sediment cores tell the amount of sand infilling while fossil samples from micro-atolls were used to calculate the sea level change.
"Most current models describe this infilling as a continual process, taking place over the past 6,000 years or mid-Holocene, the geological era dating to the present day, following the reef reaching present sea level," said Dr Ana Vila-Concejo, also from the School and an author of the study.
"Instead our research suggests that the majority of lagoon infilling occurred for only four thousand years and was 'turned off' by a relatively small sea level fall 2,000 years ago."
The researchers concluded that sea level changes brought by climate change can directly affect the formation of coral reefs, aside from known factors such as ocean acidification and pollution.
This study was published in the journal, Geology.
