Ocean acidification: The science of Papua New Guinea's carbon dioxide seeps


A healthy "control reef" at the study site in Milne Bay Province, Papua New Guinea.

Researchers from the Australian Institute of Marine Science (AIMS) are currently studying the shallow volcanic CO2 seeps in eastern Papua New Guinea (PNG) in Milne Bay Province to observe how ocean acidification (OA) is affecting the oceans. 

"These experiments and field trips are essential to study at first-hand what is occurring in nature when more and more CO2 from the atmosphere mixes with water," said AIMS research scientist, Dr Katharina Fabricius.

When CO2 from the atmosphere dissolves in water, it causes OA, slightly lowering the pH of the water and changing its carbonate chemistry. This in turn makes it harder for a range of marine animals to form their shells and skeletons.

A reef exposed to moderate carbon dioxide levels at the study site.

Over the past five years AIMS researchers have been studying the area, one of the few known CO2 seep sites in tropical coral reef ecosystems in the world. The scientists are, in effect, studying a snapshot of the centuries to come for our coral reefs if global warming continues.

"We have found that ocean acidification will select large boulder-like coral over structurally complex branching (leaf-like) corals, which are the home of many species like crabs, shrimps and sea stars. As a result, OA has a domino effect: as the habitat structure decreases, the animals that live and hide in their nook sand crannies find it far harder to survive, simply because they cannot hide from predators," explained Dr Fabricius. 

 

A reef exposed to high carbon dioxide concentrations at the study site.

Other ocean acidification research 

In addition to the field work, researchers at AIMS are also undertaking aquarium experiments in the new National Sea Simulator in Townsville in Queensland, to determine how the combined effects of elevated sea temperatures and OA effects corals and sponges.

"In this ‘cradle to grave' experiment we are testing how corals and sponges from different life stages – from babies right through to adults, respond to the cumulative pressures associated with climate change" explained AIMS research scientist, Dr Nicole Webster

Other research at AIMS has shown that ocean acidification causes a reduction in calcification of reef-building corals, which poses a significant threat to the survival of coral reefs around the world. They also found that the foraminifera, crustose coralline algae (CCA) and biofilms are affected by OA.