Tests conducted by researchers from University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS) and Curtin University have found that noise from seismic airguns used for marine oil and gas exploration significantly increases mortality in scallops.
Published in the US scientific journal Proceedings of the National Academy of Sciences, the study used field-based experiments over a three-year period to test the impact on scallops of exposure to compressed air guns used to explore for sub-seafloor deposits.
Lead author Dr Ryan Day said the research was undertaken to investigate the potential impact of seismic surveys on economically important fishery species.
As he explained, seismic tests did not result in immediate mortality in scallops, but mortality increased over time when comparing exposed and control scallops and impacts were also observed on the scallops’ behaviour, reflexes and physiology.
“Testing of scallops after seismic exposure showed a high likelihood that their immune systems and physiology were compromised due to a decline of haemocytes (blood cell analogues) and imbalances in haemolymph (blood analogue) biochemistry. The degree of exposure increased the risk of mortality significantly in scallops, and they showed compromised physiology over a chronic timeframe from which there were no signs of recovery over the course of our experiments,” Dr Day said.
Project leader Associate Professor Jayson Semmens said there were also significant changes in scallop behaviour and reflexes during and following seismic exposure, even 120 days after completion of the experimental sampling.
“The surviving scallops would have reduced tolerance to subsequent stressors, including environmental, nutritional and pathological stressors such as dredging or temperature changes.”
In an earlier paper, published in Nature Ecology and Evolution in June, the researchers found that exposure to seismic air gun signals increased the mortality rate of zooplankton by two-three times, causing a significant reduction in plankton biomass up to at least 1.2 km from the source.
