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Human impacts

Noise Pollution Changes How Ocean Animals Grow

Paper: Fakan, E. P., & McCormick, M. I. (2019). Boat noise affects the early life history of two damselfishes. Marine Pollution Bulletin, 141(February), 493–500. https://doi.org/10.1016/j.marpolbul.2019.02.054

 

We never really experience silence. Take a minute to close your eyes and listen – to really listen- to everything around you. Maybe you hear other people talking, cars buzzing past you, birds chirping, or wind rustling tree leaves. I am the only person in a vacuous building right now but I am still surrounded by sound. The faint whirring of the air conditioner, a slight electrical hum coming from the computer in front of me, and the continuous click clicking of my fingers on the keyboard as I type this. Every place on earth is blanketed in sound, even when you slip below the waves and dive into the ocean.

The ocean itself is a relatively noisy place. There are pops and clicks from shrimps, the whooshing of waves overhead, and a chorus of other animals making noises and moving around in their environment. Sadly, just like on land, the ambient noise in the ocean is becoming increasingly less natural as humans continue to encroach on landscapes. Sound travels farther in water than in air so even smaller amounts of human-created (called anthropogenic) noise can spread across ocean habitats, polluting the natural soundscape. Anthropogenic noises like those created by boats, construction or oil and gas exploration and drilling create large disturbances that harm ocean animals – making it difficult for them to communicate, interrupting migration routes, and altering animal behaviors.

Noise pollution impacts the developing babies of fire clownfish (left) and spiny chromis (right). Images from wikimedia commons.

While studies have shown the adverse effects of noise pollution in adult animals, scientists still don’t know just how growing up and developing in the cacophony of human noises might impact animals. To learn more about noise pollution’s affect on younger individuals, a team of scientists at James Cook University in Australia investigated how boat noise impacts the development of embryonic fishes.

The scientists collected eggs from two species of fish commonly found in the Great Barrier Reef –the fire clownfish (Amphiprion melanopus) and the spiny chromis (Acanthochromis polyacanthus). They split the eggs from the two species into two different experimental groups. In one group, the eggs were exposed to a sound recording of the natural, ambient soundscape from the Great Barrier Reef. The other group, was exposed to a recording of a motor boat driving through a reef habitat every 5 min. Both groups of eggs were exposed to their respective sound recordings (ambient reef or ambient reef+boat) continuously for the experiment and the scientists monitored how the fish developed in their eggs.

The scientists found that the clownfish and chromis responded differently to the motor boat sound exposure, supporting the hypothesis that there is no one-size-fits-all approach to understanding how animals will respond to noise pollution. Different animals are equipped with different hearing abilities so we cannot expect they will all respond the same to noises.

Scientists measured the differences between the developing fishes that were exposed to the different soundscapes by measuring the size of the egg yolk in their eggs, their heart rate, and then how big they were upon hatching.  While the clownfish growth was not significantly affected by exposure to motor boat noises, the chromis were – individuals exposed to ambient reef+boat soundscapes were slightly larger at hatch, had larger eyes, and had smaller egg yolks through development. It is pretty incredible to think that noises heard during a fish’s development can have impacts on the way the fish develops and even looks after it is born. But it is even more important to consider the fact that egg yolks were smaller, appearing to diminish faster, when fish heard boat noises. Egg yolks are the developing fish’s food source, which it relies on until it has grown large enough to catch its own food. If the yolk reserves are eaten up too quickly, the baby fish may starve to death later.

Once baby fish hatch from their eggs (bottom), they rely on their yolk sac (outlined in the dotted line) for energy until they can find and eat food on their own. Image modified from wikimedia commons

Despite their variable responses, there was one commonality in the response both the clownfish and chromis had to motor boat noises. The individuals of both species that were exposed to the ambient reef+boat sound recording had a higher heart rate than the fishes exposed to the normal ambient reef sound recording. On average, the fish that heard boat noises had a 10% increase in their heart rate, which indicates the motor boat noise stressed those fish out.

While short periods of stress is not altogether harmful, longer more chronic stress can have disastrous health impacts and may be a problem for animals that are still growing and developing. The continuous noise pollution may have damaging effects on reef fish. In this lab study, the boat noises did not appear to decrease the fishes’ ability to survive; however, that may not be the case in a less controlled, natural environment where a stressed fish could easily become a meal for a passing predator. This study shows animals are affected by the noises we create and pump into their habitats from the very beginning of their lives. Essentially, our noise pollution could be shaping the development of animals – we still don’t know the consequences of this.

Different animals respond to these anthropogenic noise disturbances in different manners. Some, like the clownfish in this study, may not be drastically impacted, but others like the chromis, marine mammals, or other animals that rely heavily on sound to navigate, communicate, and find food could be disastrously impacted by this constant and increasing bombardment with unnatural noises. Unfortunately, we continue to make more noise but we still know little about how noise pollution will impact all of these animals.

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