AE.org - website of the Acoustic Ecology Institute
newsCommunityResourcesSoundscapesAbout UsJoin Us
aeinews Home

Oysters and scallops: no ears, but they still hate loud ocean noises

Ocean, Seismic Surveys, shipping No Comments »

A recent line of research ups the ante on how widespread the impacts of human noise in the ocean may be. Oysters appear to suddenly and dramatically close up in response to low frequency noise at intensities that are relatively common—beginning at sound as levels as low as 120dB, and ramping up rapidly above 140dB. The figure at left shows how fast the shells closed at top and the degree of closing at bottom (from the minimal to maximal responses observed). Effects were strongest from 10-200Hz, a frequency range that includes shipping and seismic survey sounds.

While oysters, like many other shellfish and crustaceans, do not have ears, they are sensitive to vibrations; earlier oyster studies speculate that they may be responding to subtle seabed vibrations, though it’s also possible their tissues are responding to water-borne particle motion. Another recent paper looked at scallop behavior and mortality after exposure to airguns, and reports that negative effects were seen for months after exposure:

“Exposure to seismic signals was found to significantly increase mortality, particularly over a chronic (months postexposure) time scale, though not beyond naturally occurring rates of mortality. Exposure did not elicit energetically expensive behaviors, but scallops showed significant changes in behavioral patterns during exposure, through a reduction in classic behaviors and demonstration of a nonclassic “flinch” response to air gun signals. … Hemolymph (blood analog) physiology showed a compromised capacity for homeostasis and potential immunodeficiency, … with effects observed over acute (hours to days) and chronic (months) scales. … Given the scope of physiological disruption, we conclude that seismic exposure can harm scallops.”

As our colleagues at Ocean Conservation stress in their coverage of these new developments, all this is part of a rapidly expanding awareness of the ways that our noise compromises ocean life far beyond the whales and dolphins that were the focus of initial concern and research. Early this year saw the publication of a comprehensive review of the potential impacts of marine seismic surveys on fish & invertebrates. The authors point out that on many topics (fish catch rates, startle responses, tissue damage) results have been mixed/contradictory, with some studies finding negative impacts and others finding no response; their paper lays out key areas for future research that could begin to clarify these ambiguities.

The authors of a 2016 study on the effects of shipping and construction noise on lobsters and clams paint the picture quite clearly:

Tim Leighton, Professor of Ultrasonics and Underwater Acoustics and study co-author, said: “There has been much discussion over the last decade of the extent to which whales, dolphins and fish stocks, might be disturbed by the sounds from shipping, windfarms and their construction, seismic exploration etc. However, one set of ocean denizens has until now been ignored, and unlike these other classes, they cannot easily move away from loud man-made sound sources. These are the bottom feeders, such as crabs, shellfish and invertebrates similar to the ones in our study, which are crucial to healthy and commercially successful oceans because they form the bottom of the food chain.” Co-author Dr Chris Hauton, Associate Professor in Invertebrate Ecophysiology and Immune Function, added: “I think these findings raise the prospect that anthropogenic sounds in the marine environment are impacting marine invertebrate species in ways that have not been previously anticipated.”

The Leighton and Hauton study, using sound playbacks mimicking a ship at 100 yards and wind farm construction at 60 yards, found that both lobsters and clams changed their digging behaviors, and triggered changes in their overall activity level (lobsters increased, clams decreased); they found no marked effects on brittlestar activity.

Clearly, we are still in the early stages of understanding how our noises may be changing ocean ecosystems. In addition, the recent review paper affirms a longstanding concern that noise may act as a synergistic stressor, making animals more susceptible to other known stressors such as food shortages or rising ocean temperatures, noting that “Single stressors related to sound exposure may show no effects in isolation but when combined with other stressors effects may become pronounced.” New study designs are beginning to tease out these inter-relationships, giving researchers and ocean managers new tools that can move both science and policy forward in constructive ways.

Fishermen blasting “seal bombs” 30,000 times a month off Southern California

Ocean, Science No Comments »

They look small, about the size of a “cherry bomb” firecracker.  They’re legal, exempt from the Marine Mammal Protection Act thanks to their functional purpose: protecting fishermen’s nets from seals and cetaceans poaching their catches, including squid, anchovies, and tuna.

But they are loud and used freely in waters off southern California. Divers report physical pressure waves hitting them from up to a mile away; they’re audible in the water out to tens of kilometers and have been recorded by Scripps Acoustic Ecology Laboratory hydrophones 37,000 times a month at peak fishing season—up to 500 blasts an hour at times.

A recent article in Hakai Magazine delves into this little-known ocean noise issue. “The amount of use is alarming,” says Scripp’s Simone Baumann-Pickering. “We know the noise poses a potential threat.”  While earlier NOAA research with dolphin carcasses demonstrated they can cause physical damage at extremely close range (less than a meter), the Scripps team did not document any physical injuries, though they stress that behavioral impacts are likely.  Divers and whale watch captains confirm that whales tend to avoid areas where the seal-bombs are in use; yet fishermen counter with reports of dolphins and whales being unfazed by their use (keeping the uncertainty cycle spinning, conservationists speculate that such non-response could be related to deafness from previous exposure to this or other loud noise).

In an effort to move beyond the conflicting anecdotal report, the Scripps researchers are now looking more closely at the effects of the noise on Risso’s dolphins, a squid-loving species that is commonly exposed. As Baumann-Pickering affirms, “In science, you have to measure the effects.”

Note: Hakai Magazine, published by a foundation in British Columbia, is well worth being on the radar of any ocean lover.

 

SD county learns that 2000ft setbacks not quite enough

Wind turbines No Comments »

Clark County SD is in a legal battle over its decision to increase wind turbine setbacks from 2000ft to 3960ft (three-quarters of a mile). The Clark County Commission approved the 400MW Crocker Wind Farm, but based on local experience with a smaller wind farm, decided that more distance was needed between turbines and non-participating homes.  As reported by the Watertown Public Opinion:

County zoning rules originally called for a minimum 1,000-foot setback from residences, but according to Commissioner Francis Hass, the commission didn’t do enough homework before allowing a 2,000-foot minimum setback for the 11-tower Oak Tree Project built four miles north of the Clark a few years ago.

“We absolutely don’t want to kill wind energy,” Hass said. “We just didn’t look good enough when we put in the first set. Those towers are fine with the exception of being too close to a residence. “Towers do make noise, and when the weather is right they make a lot of noise.”

The wind company, Geronimo Energy, challenged this decision in court, and in August the court declined its motion for a partial summary judgement. Initial reporting suggested the County’s standards had been upheld, though a followup clarified that the judge simply ruled that he would not issue a determination until after a full hearing on all the challenges included in Geronimo’s claims. (There are some conflicting press reports on this; a September article says Geronimo has appealed to a higher court.)

Meanwhile, the state PUC continued its consideration of state permitting for the 200-turbine wind farm. A September hearing attracted both farmers eager to host turbines and local residents opposed to the project. A decision was expected in late January 2018, but in October, the PUC denied the application, saying that Geronimo’s plans were still too much in flux to proceed with the approval process, which by state law must be concluded within six months. The uncertainty was mostly related to negotiations with US Fish and Wildlife over land swaps and environmental impact assessments for about 40 of the turbine locations, leading to the submission of four different possible turbine configuration plans. However, the quicker than expected decision was triggered by an intervention request by opponents of the wind farm, which noted that the Clark County half-mile setback would necessitate the relocation of 35 further turbines.

Geronimo is free to resubmit its application once the turbine layout is finalized.