​​​​​​​It’s not just about marine mammals anymore: How ocean noise can harm marine ecosystems

The Skimmer on Marine Ecosystems and Management

Editor’s note: We’ve all read about how ocean noise can harm marine mammals. New research reveals that it can have profound impacts on lower trophic levels as well, with likely consequences for marine ecosystems. Catch up on the latest research with this month’s Skimmer.

A little background on sound in the ocean

Where all the ocean noise is coming from

How far does it go?

 

Bad things ocean noise does to marine animals

  • While research on the impacts of ocean noise on marine fish, reptiles, and invertebrates is still in its early stages, there have been several recent reviews (e.g., here, here, here, and here) of primary studies. (Editor’s note: You can watch a webinar on one of these reviews here it summarizes 115 studies of the impacts of anthropogenic ocean noise on 66 species of marine fish and 36 species of marine invertebrate.) These reviews found:
     
    • Developmental effects such as increased egg and larval mortality; delayed development; delays in metamorphosis and settling; slower growth rates; and bodily malformations.
       
    • Anatomical effects such as temporary or permanent hearing loss; cellular damage; temporary or permanent internal and external injuries; and even death.
       
    • Physiological effects such as increases in stress hormones; changes to metabolic rates, oxygen consumption, and heart rates; decreased immune response and resistance to disease; reduced energy reserves; and decreased reproductive rates.
       
    • Behavioral effects such as causing animals to avoid important habitat for days or years; alarm responses including hiding and flight; increased activity including moving faster, diving deeper, changing direction more frequently; increased time spent grooming nests; increased aggression; decreased anti-predator defensive behaviors; decreased nest digging and care of young; decreased courtship and spawning; decreased feeding; increases in errors or inefficiency in handling food; and uncoordinated schooling.
       
    • Masking effects (where sounds of interest are obscured by noise) such as reduced ability to use vocal communication; reducing detection distances for potential mates and predators; and reductions in larval settlement cues.

[Editor’s note: The lists above are a compilation of all impacts. Most studies found a limited number of impacts for a single or small number of species.]

  • To give a flavor for what individual studies found:
     
    • McCauley et al. (2000) observed that caged green and loggerhead turtles exposed to airgun noise increased their swimming speeds when sound intensity levels reached 166 dB and started behaving erratically when sound intensity levels reached 175 dB.
       
    • Sara et al. (2007) found that boat noise caused bluefin tuna to change direction and swim vertically toward the surface or bottom. It also disrupted school structure and coordination of swimming behavior and increased aggressive behavior. These effects could interfere with the accuracy of bluefin tuna migrations to spawning and feeding grounds.
       
    • André et al. (2011) found that exposure to relatively brief periods of moderate-intensity (peak levels of 175 dB), low-frequency noise caused “massive acoustic trauma, not compatible with life” in four cephalopod species (the European squid, European common cuttlefish, common octopus, and southern shortfin squid). The noise exposure damaged the sensory hair cells of their statocysts, organs that control their balance and orientation.
       
    • Aguilar de Soto et al. (2013) found that seismic survey noise caused significant developmental delays in New Zealand scallop larvae. In addition, nearly half of the larvae studied developed bodily abnormalities.
    • Nedelec et al. (2014) found that boat noise reduced successful development of sea hare embryos by 21% and increased mortality of recently hatched sea hare larvae by 22%.
       
    • Simpson et al. (2016) found that motorboat noise increased metabolic rates and decreased responsiveness to simulated predatory strikes in Ambon damselfish. In field experiments, more than twice as many damselfish were consumed by predators when motorboats were passing by, suggesting the potential for significant changes in trophic dynamics in areas with heavy boat traffic.
       
    • Solan et al. (2016) found that shipping and offshore construction (e.g., pile driving) noises changed the burrowing and bioirrigation (circulation of water within burrows) behavior of Norway lobster. Manila clams exposed to these same noises exhibited stress responses in which they moved to the sediment surface, closed their valves, and reduced movement. In addition to diminishing the growth and fitness of individuals, these responses reduce mixing and oxygenation of the upper layer of sediment and could affect seabed nutrient cycling, productivity, and biodiversity as well as fisheries productivity.
       
    • Wale et al. (2016) found that blue mussels exposed to ship noise reduced their filtration rates by 84% and had more breaks in their DNA, likely due to the production of stress-related chemicals.
       
    • Day et al. (2017) found that exposure to airgun noise in the field significantly increased mortality of commercial scallop. It also disrupted their typical behaviors and their reflexes during and after exposure and may have compromised their immune systems.
       
    • Fitzgibbon et al. (2017) found that seismic airgun noise suppressed the immune systems and harmed the nutritional condition of spiny lobsters for up to 120 days after exposure.
       
    • McCauley et al. (2017) found that noise from a single airgun decreased zooplankton abundance within a 1.2-km range (the maximum distance sampled) and caused a two- to three-fold increase in larval and adult zooplankton mortality.
       
    • Paxton et al. (2017) looked at fish abundance on two temperate reefs for three days before and three days during a nearby seismic survey. They found that fish abundance on the reef during evening hours – when fish utilization of the reef was highest prior to the seismic survey – declined by 78% once the seismic survey began. This change represents lost opportunities for reef fish to aggregate, forage, and mate.
       
    • Charifi et al. (2018) found that ship noise decreased feeding and growth rates in Pacific oysters by a factor of ~2.5 and represents a risk to ecosystem productivity.
       
    • Maud et al. (2018) found that boat noise decreased the ability of juvenile Ambon damselfish to learn to recognize predators, and that fish trained in the presence of boat noise had substantially higher mortality when placed in a natural setting.
       
    • Fakan and McCormick (2019) found that exposure to boat noise in a laboratory increased the heart rates and negatively affected the development of embryos of two coral reef damselfish species. The noise did not affect mortality rates for the embryos in the laboratory, but the physiological and morphological changes that were observed could affect mortality in the field or fitness in later life stages.

  • As evidenced by the reviews and studies described above, ocean noise can impact most of the key life functions of marine animals e.g., movement, migration, locating preferred habitat, locating and capturing food, feeding, growth, maturation, reproduction, care of young, response to predators, communication. These impacts, in turn, impair individuals’ growth, survival, and reproductive rates. And these impacts, in turn, affect populations – population size, biomass, age structure, spatial distribution, and genetic diversity – and communities of species and their interactions (including trophic linkages).
     
  • There is also now strong evidence (see the studies described above) that ocean noise negatively impacts ecosystem productivity and the provision of ecological services, including water filtration, sediment mixing, and nutrient cycling.
     
  • Finally, ocean noise has also been observed to negatively impact the fishing industry:
     

Are marine fish, reptiles, and invertebrates uniquely vulnerable to ocean noise?

Most studies of the impacts of ocean noise on marine animals have looked at marine mammals because of their reliance on sound for communication, feeding, and navigation. Marine fish, reptiles, and invertebrates are also vulnerable to the impacts of ocean noise, however – perhaps even uniquely vulnerable in some ways.

 

Why ocean noise research is so tricky

What we can do to make things better (or at least keep them from getting worse)

Examples of spatial management measures taken to protect marine mammal populations include a moratorium on military use of active sonar around the Canary Islands, moratoria on seismic surveys and seasonal vessel traffic in a marine mammal protection zone in the Great Australian Bight, and a moratorium on seismic surveys off the Bahia e do Espírito Santo in Brazil during the breeding season for humpback whales.


[1] A sound wave’s amplitude is the change in pressure as it passes a given point and is related to the amount of energy it carries. The sound wave’s power (measured in watts) is the amount of energy it carries per unit time. The sound wave’s intensity (measured in watts per square meter) is the amount of power transmitted through a specified area in the direction in which the sound is traveling and is a function of the wave’s amplitude. Sound intensity is often specified in decibels (dB) rather than watts per square meter, however. Decibels are 10 times the logarithm of the ratio of the intensity of a sound wave to a reference intensity, so they are a relative unit of measure rather than an absolute measure. Different reference levels are used for air and water, so decibels in air are not directly comparable to decibels in water.

[2] The auditory capabilities of different fish species vary dramatically. For example, fish species that do not have swim bladders are believed to sense particle motion and to sound pressure at a narrow range of frequencies, while fish with swim bladders that are closely connected to their ears are believed to be sensitive primarily to sound pressure but at a wide range of frequencies.

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