Good and bad ocean noise

Recently I noticed rumblings about ocean noise pollution. As you might have guessed it has major effects on the underwater ecosystem. And just like a horrible next-door neighbor, of course we didn’t notice we were making all that noise, officer.

The Bad: Horrible Neighbors

Science recently published a review article on The Soundscapes of the Anthropocene Ocean, in which they identify sound as an important modern “pollutant”:

…we call for it to be included in assessments of cumulative pressures on marine ecosystems. Compared with other stressors that are persistent in the environment, such as carbon dioxide emitted to the atmosphere or persistent organic pollutants delivered to marine ecosystems, anthropogenic noise is typically a point-source pollutant, the effects of which decline swiftly once sources are removed. The evidence summarized here encourages national and international policies to become more ambitious in regulating and deploying existing technological solutions to mitigate marine noise and improve the human stewardship of ocean soundscapes to maintain a healthy ocean.

The soundscape of the Anthropocene ocean, Duarte et al., Science, (2021).

An interesting point they make is how noise pollution is acute – once the noise stops, the pollution is gone. Unlike oil spills, the “clean-up” process can be as simple as shutting the hell up.

The full article is quite grokable and is worth the read, so I’ll link to it again here. In it they make both political and technical recommendations to help reduce anthropogenic ocean noise. Some of the more obvious recommendations include changing shipping routes, policing speed in sensitive ecological zones, and making international agreements regarding ocean pollution mandatory (most are voluntary). These solutions sound easy, but we know that getting a room full of people to agree on anything can be tough.

The technical solutions mentioned in the article are not exhaustive, but do point to some interesting angles of attack. Sound barriers are classic solutions used to insulate neighborhoods from highway noise (with sometimes questionable results), and similar principles can be used in oceans. Bubble curtains are an interesting solution that I had never heard of before, but seem to be a fairly good at controlling the movement of debris, contaminants, salt, oil, and sound through waterways (water transmits soundwaves better than air, and the agitation of water by air bubbles work together as a sort of “wall”). Other solutions ask for researchers to better understand and control the rumbling of ships. New polymer materials with better damping properties, electric motors, and a better understanding of cavitation can help shipping companies keep their boats quiet. But an important point: shipping companies are the ones held accountable for their oceanic pollution, not ship builders. So we again are brought back to the challenge of convincing a room full of people to agree on something.

The Good: Bringing Coral Reefs Back to Life

All this ocean noise talk reminded me of another paper I saw a while ago that I had never gotten around to digging into. The researchers (mostly from the UK and Australia) wanted to see what would happen if you started with a dead coral reef and made it sound like a happy, thriving coral reef. Would it come back to life?

Scientists know that coral reefs are an important and delicate ecosystem. They also know that when fish abandon a reef, it’s usually game over for the reef. When a reef is decaying, the sound and smell of the reef decays with it, which makes the reef even less attractive to fishies looking for a good time. It’s a positive feedback loop, when fish leave, the reef decays, which makes the reef unpleasant for fish, which makes more fish leave. (This kind of sounds like how hot new clubs work, or how they probably used to work…)

So, could scientists make a reef sound like a cool place to be, and thus, make it a thriving fish hotspot? To find out, scientists built 33 “dead” coral reefs near existing coral reefs. In sets of three, they gave their “dead” reefs a) a speaker that played healthy reef sounds, b) a speaker that did nothing, or c) no speaker. The result? The bumpin’ reefs were the place to be, and fish knew it.

The analysis took into account different types of fish and overall species diversity, but overall it appears that a reef that sounds good is significantly better at bringin’ fish to the yard. From the abstract:

Acoustic enrichment enhances fish community development across all major trophic guilds, with a doubling in overall abundance and 50% greater species richness.If combined with active habitat restoration and effective conservation measures, rebuilding fish communities in this manner might accelerate ecosystem recovery at multiple spatial and temporal scales. Acoustic enrichment shows promise as a novel tool for the active management of degraded coral reefs.

Acoustic enrichment can enhance fish community development on degraded coral reef habitat, Gordon et al., Nature Communications, (2019).

Important note, though: soundscapes are just one piece of the puzzle. A good DJ isn’t going to make up for a terrible atmosphere.

The ugly hopeful

For the Canadians in the room, you may be wondering what our government is doing about this issue, if anything. Well, Transport Canada issued a report on exactly that. They contracted Green Marine to carry out the research for the report. (Green Marine is managed by Green Marine Management Corporation, a not-for-profit organization. Members of the corporation are the leaders of companies participating in Green Marine’s environmental program (voting members) and marine industry associations based in Canada and the United States (non-voting members).)

The executive summary of the report basically says “it’s hard to know how much noise pollution is too much”. Good news, Frances Juanes from the University of Victoria in BC is a co-author on the big Science review linked at the top, and one of the goals of the review article was to collect the quantitative data that we do have to help start enacting change. So let’s get to work, eh?

So the conclusion? I guess I learned that we are screwing up the oceans in a million different ways I never would have considered, and one of those ways is sonically. But we can fight back, and one big data-driven collaboration that’s doing it is Ocean Networks Canada. This is a UVic initiative that just celebrated its 15-year anniversary of monitoring the coasts, providing real-time physical, chemical, biological and geological data to researchers at their own labs. If you are a student thinking of getting in on the fight, a good place to start would be checking out Ocean Networks Canada and seeing who’s involved and what they’re up to. For educators looking to incorporate some ocean science into their classrooms, they also offer plenty of resources and outreach opportunities.

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