September 2019 (12:9)

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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.

Editor’s note: Heather Welch is a research associate with the University of California at Santa Cruz and the (US) NOAA Southwest Fisheries Science Center’s Environmental Research Division. The Skimmer spoke with her about her research, which focuses on understanding and planning for the spatial and temporal dynamics of large-scale marine processes.

The Skimmer: We last covered dynamic ocean management and dynamic ocean management tools in 2014. Can you tell us a bit about how the field has progressed since then?

One area of progress is that dynamic ocean management is now better located within the larger field of dynamic management, allowing us to borrow concepts and methodologies from more established disciplines. Weather science has been developing dynamic management tools such as weather forecasts and hurricane forecast tracks for over a century. While on land, established dynamic management tools track floods, wildfires, and disease outbreaks. Understanding the parallels between dynamic ocean management and dynamic management in other realms allows us to leverage lessons learned and avoid reinventing the wheel.

Another area of advancement is that dynamic ocean management tools are moving towards producing forecasts. Initially, tools were producing hindcasts and nowcasts, i.e., predicting where species were last month and where species are today, respectively. Now, dynamic ocean management tools are forecasting species distributions days to seasons in advance. For example, the Atlantic Sturgeon Risk Model predicts Atlantic sturgeon habitat one to three days in advance to help fishers avoid the bycatch of these endangered fish. A seasonal forecasting system in the Great Australia Bight predicts the distribution of Southern bluefin tuna several months into the future to help fishers efficiently locate and harvest their target species. These types of forecasts give end-users time to plan ahead for future conditions.

Lastly, dynamic ocean management is moving from single-species tools to multi-species tools that can address greater proportions of biodiversity. Single-species management was a natural starting point for the field, but established methodologies and technological advances now allow for more complex tools. For example, TurtleWatch helps fishers avoid the bycatch of loggerhead and leatherback turtles. On the US west coast, EcoCast helps fishers maintain their target catch of swordfish while avoiding the bycatch of loggerhead turtles, California sea lions, and blue sharks.

The Skimmer: Can you tell us about your new research and what you found?

As dynamic ocean management continues to shift towards multi-species management, decision support tools will be critical to help determine which areas to prioritize for protection. In a paper that we just published in Conservation Biology, we compared two decision support tools: the algebraic algorithm that underpins EcoCast and the simulated annealing algorithm that powers the reserve design software Marxan. While EcoCast’s algebraic algorithm was explicitly designed for dynamic ocean management and Marxan was developed as a conservation planning tool, Marxan has functionality (e.g., consideration of cost and boundary complexity) that could confer advantages over EcoCast. We compared the performance of both tools over time using a dynamic ocean management scenario for fisheries sustainability. We found that the relationship between EcoCast solutions and the underlying species distributions was more linear and less noisy, while Marxan solutions had more contrast between waters that were good to fish and poor to fish.

The Skimmer: When might a manager use one of these tools versus the other?

One of the biggest drivers of decision support tool selection is managers’ preferences for how species importance is assigned. In EcoCast’s algebraic algorithm, species importance is assigned relatively, e.g., species X is twice as important as species Y. In Marxan, species importance is assigned absolutely, e.g., protect 20% of species X’s habitat and 15% of species Y’s habitat.

Both decision support tools were designed to be responsive to changing management priorities. For example, a recent bycatch event might change management priorities. We found EcoCast’s algebraic algorithm was better able to reflect changing management priorities, meaning that it might be the more appropriate tool for management scenarios that emphasize flexibility. On the other hand, Marxan outperformed EcoCast’s algebraic algorithm as more species were added, meaning that it might be the more appropriate tool for management scenarios that aim to manage many species. Table 4 in the paper (figure below) outlines 10 considerations that could affect manager preference regarding tool selection.

The Skimmer: Are there other possible marine management situations where a dynamic Marxan might be useful?

Certainly. The dynamic configuration of Marxan could be useful to any dynamic ocean management scenario that aims to manage multiple features. These features might be species, hydrological events such as temperature anomalies or seasonal upwelling, or socio-economic factors such as fishing ground quality and shipping channel efficiency. In addition, Marxan will be particularly useful in dynamic ocean management scenarios where there is a cost constraint.

The Skimmer: What are your next steps for this research?

One area of future development will be moving towards dynamic marine protected areas. Most dynamic management scenarios produce continuous risk surfaces, e.g., bycatch risk in EcoCast or shipstrike risk in WhaleWatch. Moving towards binary open/closed areas is a logical next step. Doing this in a dynamic capacity, however, will require exploring trade-offs between protection levels and opportunity cost across time and ensuring that the locations of closed areas do not change drastically from day to day.

Secondly, Marxan is part of a family of decision support tools designed for conservation planning, and it would be worthwhile to explore how other tools such as Zonation, C-Plan, and prioritizr perform in a dynamic capacity.

In case you missed it, last month’s issue of The Skimmer featured original articles: