Scientists strengthen global efforts to manage vulnerable marine habitats

A research team from King Abdullah University of Science and Technology has standardised a method for strengthening global efforts to manage vulnerable marine habitats.

Measuring calcium carbonate: Helping scientists monitor coral reef health

A blueprint for measuring calcium carbonate on the ocean floor could assist marine scientists in monitoring coral reef health, and in encouraging the observation of vulnerable marine habitats on a global scale.

Climate change and pollution from human activities are conclusively modifying a variety of marine habitats, particularly coral reefs. To assess and mitigate future negative impacts, ecologists must understand how these ecosystems are functioning in the present.

An indicator of coral reef health is how much calcium carbonate is produced over a certain period of time as shells and skeletons of marine animals accumulate on the ocean floor. The research team employed a unique method to measure the accumulation of calcium carbonate – they considered tiles on the seabed, which gradually become home to settling pioneering plants and animals. After a year, the researchers retrieved the tiles to see how much calcium carbonate had been collected and which living species were present.

“To understand how marine ecosystems are changing over space and time, we need to be able to compare data collected from different habitats,” explained Maggie Johnson, Marine Scientist. “But researchers employ a range of approaches or measure different variables, meaning that the data might not be directly comparable,” she adds. This makes it difficult to create a global picture of marine ecosystem health, and therefore makes it difficult to determine how the vulnerable marine habitats can be managed.

Collecting comparable data is critical in monitoring vulnerable marine habitats

Johnson and her colleagues have developed a standardised method for making and deploying calcification accretion units (CAUs), which is similar to settlement tiles. However, it is specifically utilised to measure calcium carbonate. The comprehensive ‘how-to’ guide provides detailed instructions for tile construction and CAU assembly, from material suppliers to measurements, as well as how to place and retrieve them. This will allow scientists to collect comparable data from coral and oyster reefs worldwide.

“Coral reefs cover less than 1% of the seafloor yet provide more than 25% of the ocean’s biodiversity,” said Johnson. “Much of this diversity comes from tiny critters living in the unseen cracks and crevices.” These hidden species, or ‘cryptic taxa,’ cannot be captured by visual surveys, but the CAUs include a small space for these tiny taxa to occupy.

“During collection, the tiles must be placed in zipped bags to keep the community of cryptic critters intact all the way to the lab,” added Johnson.

The guide advises immediate processing of the samples while the animals and plants are still alive. This involves taking high-resolution photographs later utilised for spotting species and microscope observations to count baby coral before a weak acid then removes the calcium carbonate.

“By weighing the tiles before and after decalcifying them, researchers can calculate how much calcium carbonate was deposited on that tile over a year,” noted Johnson. “This figure can help compare reef conditions in different parts of the world or how the health of one reef is changing over time.”

Thus, understanding the impacts of human actions on marine habitats will help researchers and governments in discovering methods that can aid in managing vulnerable marine habitats and mitigate the adverse effects. “This standardised and accessible approach will help promote collaboration and informed decision-making even when using data from all over the world,” concluded Johnson.


  1. Johnson, M.D., Price, N.N. & Smith J.E. Calcification Accretion Units (CAUS): A standardised approach for quantifying recruitment and calcium carbonate accretion in marine habitats. Methods in Ecology and Evolution Advance online publication, 11 April 2022.|article

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