Whales stop singing and rock lobsters lose balance: How seismic surveys can harm marine life

Woodside Energy this week announced it would begin seismic testing of the Scarborough gas project on Australia’s west coast, before reversing the decision in the face of a legal challenge from Ndabuko’s owners.

Seismic testing is very controversial in marine areas. The Federal Regulator (National Offshore Petroleum Safety and Environmental Management Authority) is currently reviewing a proposal for seismic testing in the Otway Basin in Bass Strait, which conservationists have attracted more than 30,000 public submissions.

Seismic testing is also being carried out as part of “PEP11” (Petroleum Exploration Permit 11) along the coast of New South Wales, from Manly to Newcastle.

As marine biologists with expertise in research in this field, here we present the latest evidence from seismic research. It shows that there are many dangers to marine life, and many unanswered questions.

What is seismic research?

Marine seismic surveys are used to search for oil and gas, greenhouse gas reservoirs, and potential locations for wind farms.

Research uses air guns to create sound signals. These sound signals are powerful (loud, at high decibel levels) and “impulsive” (sharp, like a popping balloon). In the open ocean, sound waves can be detected thousands of kilometers from the source.

Sound can penetrate more than 10 kilometers under the sea. The way the signals reflect different sea levels can identify geological structures, including those that contain mineral deposits such as oil and gas. The sound waves are reflected back to acoustic receivers (hydrophones) that are towed behind the test vessel on cables known as streamers.

During the research, sound signals are generated every four to ten seconds, 24 hours a day, seven days a week. Surveys can last weeks or months, and cover thousands of miles of ocean. The proposal to study the Otway Basin, for example, covers 45,000 km².

Seismic research and marine life

The ability to fully evaluate the results of seismic testing in mammals is limited, because invasive methods are not feasible either procedurally or legally.

But there is a long history of research on whales and dolphins, because of their reliance on sound to communicate, find food and navigate.

Observations of marine mammals show that strong sounds such as those from seismic surveys can affect hearing, temporarily or permanently, depending on the depth, range and duration of exposure.

Noise pollution can mask communication, causing whales to sing louder or stop singing altogether, which can affect social interactions and interactions. Seismic surveys may alter the presence and abundance of marine mammal prey.

What about fish?

Fish also show a range of responses to seismic testing. Some fish show physical damage to their senses and signs of stress.

The behavior of fish can also change. Some are leaving traditional feeding or breeding grounds, raising concerns about the effects on fisheries or impacts on important prey species. It is also uncertain whether the fish will be able to find other suitable habitats if relocated over time.

Others may “habituate” or adapt to the exposure, increasing the risk of serious damage by spending more time in the test area.

Scallops, lobsters and plankton

Although invertebrates make up about 92% of marine species, the impact of marine noise on these species has only recently been studied. This indicated the possibility of injury.

In the prized southern lobster fishery, off the coast of Victoria, South Australia and Tasmania, exposure to seismic airguns damages a sensory organ that provides gravity and balance, such as the human inner ear. Affected lobsters may also be unable to right themselves when placed upside down, an idea that supports important behaviors such as fleeing predators.

Scallops have shown the worst effects, with four times higher mortality rates and a range of other fatal effects including altered behavior, impaired physiology and disruption of the immune system. As this species already has high natural and overfishing mortality rates, this additional pressure could be a major concern.

Invertebrates also make up a large proportion of the zooplankton community, a broad group of microscopic animals carried by ocean currents. It is food for a wide range of marine animals, from other zooplankton to small fish and whales.

In the first seismic air gun exposure test, a large proportion of the zooplankton died. The total mass is greatly reduced, at a distance of up to 1.2 km from the air gun.

Corroborating this result, another recent study of zooplankton found that exposure to seismic airguns 50 meters away led to increased mortality immediately after exposure. Plankton continued to die or suffer development for several days.

These effects, especially in the case of repeated exposures over the course of months within the same area, have the potential to negatively impact plankton communities that support marine food webs.

Difficulty predicting impacts

While the few studies available show exposure to earthquake research can harm animals, our ability to understand or predict what happens in the wild is still very limited.

Part of the problem is the conflicting results. For example, in one case, seismic survey exposure had no effect on the species of fish found in the area or their behavior. And a separate study of scallops found no mortality after earthquake exposure. These studies conflict with the findings we previously described, which occur frequently in science and highlight the need for more detailed research.

Only a few animal species have been studied so far, making it difficult to predict how some animals might be affected by earthquake testing. There are also limitations in study methods that limit our ability to understand real-world effects, such as animals living in captivity after exposure.

Sound behaves differently in water than in air. Water is denser, allowing sound to travel faster, farther and more slowly. The comparison between the “noise” of sounds in air and water is not straightforward.

While mounting evidence suggests that seismic research can harm marine species, much remains to be learned.