Understanding how ocean noise pollution impacts marine life, and to what extent, are high priorities for scientists. To date, ocean noise research and related policy developments have been largely focused on marine mammals. However, new science presented at the 4th International Conference on The Effects of Noise on Aquatic Life held in Dublin, Ireland, earlier this month, indicated that noise may also seriously threaten the ocean’s most diverse and abundant organisms: marine invertebrates.
Marine invertebrates (animals without a backbone) like mussels and clams, squid and cuttlefish, crabs and shrimp, make up over 75% of described marine species. They are a key component of all marine ecosystems, playing critical roles in essential ecological processes and forming the basis of marine food webs that support other marine life. Many commercially important fisheries increasingly rely on marine invertebrates – there were 1.5 times as many countries fishing for twice as many invertebrate taxa in 2004 compared to 1950.
From a scientist’s perspective, marine invertebrates are a very useful group of species to study to better understand the effects of ocean noise. Marine invertebrates can be easily kept in tanks and subjected to controlled and replicated experiments. By using controlled experiments, scientists can more confidently identify the specific impacts of noise on a particular species. The impacts revealed by the scientists presenting in Dublin were nothing short of striking.
Noise damages DNA and proteins. Researchers carefully carried out laboratory experiments that exposed blue mussels – a species harvested for food throughout the world – to playbacks of ship noise for up to 6 hours. They observed a significantly higher level of single-strand breaks in the DNA in the cells of mussels exposed to ship noise compared to those kept under ambient noise conditions. The degradation of the mussel’s DNA is thought to be related to an increase in chemicals produced by the mussel as a result of the stressful noise conditions.
A different research group reported damage to the structure of 37 proteins in one of the sensory receptors (called a ‘statocyst’) of the Mediterranean common cuttlefish after exposure to low-intensity, low-frequency sound. The observed changes are known to affect the physiology and the function of the receptor and therefore the sensory information received by the cuttlefish, which may compromise their survival and role in oceanic ecosystems.
Perception of noise as a predator. A number of scientists reported that marine invertebrates respond to noise in a similar way to predators. For long-fin squid, these behaviors ranged from inking (used to misdirect predators) and jetting (fleeing), to body pattern changes (intended to startle predators). Predator evasion behaviors are stress responses that can use up a lot of the animals’ energy and affect their health in the long-term. The common cockle – a small bi-valve mollusk that buries itself in the seabed to feed – responded to sound by retracting its feeding tubes and burying deeper into the sand. When the cockles do this they stop feeding, which may put their survival and ability to reproduce at risk.
There were also some fascinating anecdotal observations. A crowd favorite described how a hermit crab, after being subjected to sediment vibration similar to what would be experienced from pile driving (hammering large cement pillars into the seabed), would leave its shell and thoroughly inspect it before climbing back in, as if trying to determine the source of the disturbance. While this provided amusement in the lab, out in the ocean the hermit crab would be more vulnerable to predation without its protective shell.
While there is still a great deal to learn about the impacts of ocean noise on marine invertebrates, science clearly shows direct linkages between exposure to noise and changes in the physiology and behavior of a wide variety of species, which could possibly threaten their long-term survival. As such, marine invertebrates need to be afforded more consideration by both researchers and ocean noise policy-makers. In the United States, the recently-released NOAA Ocean Noise Strategy Roadmap is a promising tool that could be implemented to broaden NOAA’s practices to better address impacts to invertebrates, as well as fish and sea turtles that are also little studied.
It is high tide for marine invertebrates to take the stage.
To learn more about ocean noise and what you can do to help, visit the Sonic Sea website.