Quiet Oceans

H. ampullatus, the Northern bottlenose Whale


As pointed out in one of the most important papers for marine science in decades (Duarte et al. 2020), during World War I and II, an unexpected benefit was observed: Fish populations rebounded after fishing boats were withdrawn from the oceans. The hiatus allowed fish stocks to replenish, likely delaying their collapse by decades. This recovery of marine life demonstrates the resilience within these communities. There is hope for the ocean yet. 

 

Did COVID create a similar situation? It turns out that the slowdown in shipping and ocean traffic generally quieted the oceans. What effects did this quieting have on overall ocean ecosystems?

 

In areas like the Hauraki Gulf Marine Park in New Zealand, boat traffic almost completely stopped, and underwater noise dropped by about 2/3 within 12 hours. This reduction expanded the communication ranges of fish and dolphins by up to 65%. Dolphins' calls can travel 1 mile (1.6 km) farther when not blocked by shipping noise. If we wander back to a time before global shipping, we would find an ocean that mainly consisted of animal sounds (biophony) and natural Earth sounds (geophony). Now, of course, human sounds (anthrophony) dominate, just as human influence dominates this planet to such a large extent. During peak snorkeling season, motorboat sounds on the coral reefs are constant during daylight hours. Historically, a similar noise reduction (post-9/11 in the Bay of Fundy) was linked to decreased stress in right whales.

 

For decades, we’ve worried about nets, climate change, and chemical spills. Now, we see that one of the most pervasive and overlooked pollutants is noise. From ship engines to seismic surveys, human-generated sounds have changed the ocean and compromised the abilities of marine denizens. Noise disrupts communication, foraging, and reproduction, and adverse effects don’t stop at the individual level; they expand, threatening population viability and ecosystem stability.

 

What we know:

Noise playback reduced nest digging and anti-predator defense in cichlids and caused male Spiny Chromis (Acanthochromis polyacanthus) to spend less time feeding, resulting in complete brood mortality in some nests. In toadfish, boat noise severely impeded communication required for attracting mates and repelling intruders.

Noise directly affects the most vulnerable life stages: eggs, embryos, and larvae. Damage sustained early in life has a “fundamental influence on population dynamics and resilience”. (Quote from the Nedelec et al. paper cited below).


More targeted noise is even more devastating; in experiments using an airgun, shots from a single seismic pulse were found to kill microscopic zooplankton, especially the young, creating a large area of death. Zooplankton are vital to the food web, grazing on microscopic algae and serving as a key food source for the entire ocean ecosystem. Larvae of larger organisms also fare poorly under direct noise; scallop larvae exposed to seismic airgun pulses in tanks exhibited significant developmental delays, with nearly fifty percent developing body malformations. Damage to young scallops obviously affects the overall scallop stock.


Noise directly interferes with the reproductive success of marine populations, particularly for species that rely on acoustic signals for mating or parental care for offspring survival. Long-term sound stress exposure on Atlantic cod broodstock in aquaculture facilities increases cortisol content in eggs. Cortisol is a stress hormone. Affected cod subsequently had lower fertilization rates and a greater than 50% decrease in viable egg productivity.


Experiments using boat noise reduced successful embryonic development in sea hares and simultaneously killed off over 20% of exposed larvae. For the Spiny Chromis, damselfish, Acanthochromis polyacanthus, chronic motorboat noise caused males guarding nests to have inappropriate and ineffective defensive behaviors. As a result, they spent less time feeding. Most critically, while all control nests survived, 32% of nests exposed to motorboat noise suffered 100% mortality.


Boat noise significantly reduces communication range in fish like the Lusitanian Toadfish, shrinking the distance that they can detect conspecific boat whistles. These sounds are critical for attracting mates and repelling rivals; masking them reduces reproductive success and throws off the evolutionary influence of sexual selection.


The Challenge of Chronic Noise vs. Ecosystem Function

Anthropogenic noise affects entire communities, reducing the time animals spend foraging and leaving them more vulnerable to predators. Damselfish, when exposed to boat noise, responded less often and more slowly to simulated predatory attacks. As a result, their natural predator consumed twice as many damselfish when motorboats were passing. Noise compromises anti-predator behavior in European eels, reducing their likelihood of startle responses by 50% and their startle latency by 25% when exposed to a simulated predator.

Noise pollution alters attention in prey species (e.g., sticklebacks), causing them to make more food-handling errors, thus decreasing their foraging efficiency. By affecting these crucial predator-prey dynamics, noise can compromise food-web stability and alter community structure.

The evidence indicates that noise is very bad, it…

1.    Cut cod spawning performance.

2.    Increased predation risk. 

3.    Disrupts food webs in general.

4.    Masks communication.

5.    Lowers offspring survival.

 

 

Noise, especially human-caused noise, is very BAD. Got it. The good news: If we reduce the noise before populations are devastated, things can bounce back. One way to do this is to increase the size of Marine Protected Areas (MPAs). And establish within MPAs more stringent traffic regulations. 

 

The recent reversal in the decline of the Northern Bottlenose Whale (Hyperoodon ampullatus) in the Gully MPA is partially attributed to the noise reduction within the Zone 1 (the highly protected region) of the MPA. By the way, if you don’t know this whale, take a look at the photo I used at the beginning of this post, what an awesome beasty. Fabulous.

 

Let me share one more photo of this fantastic whale; a screen capture from …I can’t believe I’m typing this,… TikTok: 

 

What an awesome-looking animal; the
Northern Bottlenose Whale. (TikTok capture).



Sources and Further Readings:

Adkins, F. 2020. Covid 2020: The year of the quiet ocean. BBC.

Beare D, Hölker F, Engelhard GH, McKenzie E, & Reid DG. 2010. An unintended experiment in fisheries science: a marine area protected by war results in Mexican waves in fish numbers-at-age. Naturwissenschaften 97: 797–808.

Duarte CM, Agusti S, Barbier E, Britten GL, Castilla JC, Gattuso J-P, Fulweiler RW, Hughes TP, Knowlton N, Lovelock CE, Lotze HK, Predragovic M, Poloczanska E, Roberts C, & Worm B. 2020. Rebuilding marine life. Nature. https://doi.org/10.1038/s41586-020-2146-7

Duarte CM, Chapuis L, Collin SP, Costa DP, Devassy RP, Eguiluz VM, Erbe C, Gordon TAC, Halpern BS, Harding HR, Havlik MN, Meekan M, Merchant ND, Miksis-Olds JL, Parsons M, Predragovic M, Radford AN, Radford CA, Simpson SD, Slabbekoorn H, ... Juanes F. 2021. The soundscape of the Anthropocene ocean. Science 371(6529). eaba4658. https://doi.org/10.1126/science.aba4658

Feyrer L, Walmsley SF, Stewart MA, MacNeil MA, & Whitehead H. 2025. Reversing decline: The impact of spatial conservation on endangered northern bottlenose whales. Journal of Applied Ecology62: 2464–2474. https://doi.org/10.1111/1365-2664.70122

Nedelec SL, Radford AN, Simpson SD, Nedelec B, Lecchini D, & Mills SC. 2014. Anthropogenic noise playback impairs embryonic development and increases mortality in a marine invertebrate. Scientific Reports 4: 5891. https://doi.org/10.1038/srep05891

Weilgart LS. 2018. The impact of ocean noise pollution on fish and invertebrates. Report for OceanCare, Switzerland.



Comments

Post a Comment

Popular posts from this blog

Northern Movements

Image
  Dusky Shark (from Blueplanetarchive.com) A recent science paper noted Dusky Sharks feeding on Gray Seals off Cape Cod.  The Dusky Shark, Carcharhinus obscurus , is a subtropical to temperate species that roams further north during the warm months; it is not known to enter the icy northern waters north of the Gulf of Maine. Expectably, they tend to be rare north of the New England coast. That was then; this is now. We have already entered a new world of warming.  Dusky Sharks can grow to be quite large, reaching lengths of over 3 meters, or more than 10 feet. They are feeders on fish, lots of fish, and will, apparently, also go in for those nice succulent seals. Thisis not something they were thought to feed on much. However, those cheeseburgers dotting the coastline, hauling out on rocks, must be a pleasant sight for a hungry shark.  The abundance of seals makes them a central target for shark species. These marine mammals are abundant in late August all along the ...
Read more

The Hoodwinker Sunfish

Image
  This month’s post is reminiscent of last month’s, more about toxins. However, let’s start with something different. The Ocean Sunfish, genus Mola , is odd-looking—it looks somewhat like a fish that has been cut in half. In addition, these species contain many superlatives. They are one of the largest bony fishes, reaching 3.3 meters and 2740 kg (6000 lbs). Females possess a remarkable reproductive capacity, producing more eggs than any known vertebrate, a staggering 300 million at a time. The little fish fry are tiny. The fry can grow up to 60 million times its original weight before reaching adult proportions, arguably the most extreme size growth of any vertebrate animal. In 2016, researchers sequenced the genome, discovering several genes that might explain its fast growth rate and large body size. Figure 1. Drawing of an adult  Ocean Sunfish, Mola mola . The Hoodwinker Sunfish, Mola tecta, is a species of Sunfish that has only recently come to light, discovered in 20...
Read more

An Ancient Snorkeler

Image
Long before dinosaurs thundered across the land, before even the first fish dared to sprout fins, an unassuming yet extraordinary creature roamed the ancient seas. It was...   a snail.   Yochelcionella  (yo-kel-see-oh-nell-uh ) is a tiny, enigmatic mollusk from the Cambrian period, which ended about 485 million years ago. Its shell is adorned with a delightfully perplexing feature, a tubular snorkel-like extension near its peak. Paleontologists are debating its function. Was it an inhalant siphon drawing in fresh, oxygen-rich water? Or an exhalant tube expelling spent deoxygenated currents? Perhaps, in an elegant evolutionary flourish, it did both! No matter the answer, this humble creature is a key to the great puzzle of molluscan evolution.   Yochelcionella  greenlandica,  stolen from   Atkins & Peel, 2008. The Cambrian was   a period where evolution tried out a vast diversity of body plans. Imagine an ocean floor teeming with newly evo...
Read more