Post provided by Karen de Jong
Most people assume that research equipment is expensive and complicated. But, it doesn’t need to be and the noise egg is a perfect example of this. It consists of a watertight container (as used by scuba divers) and the buzzer from a cellphone and does exactly what it says: it produces low frequency noise. This allows researchers to test the effect of noise on underwater life. It is a small, simple and cheap device that anyone can build.
Why Test Effects of Noise?
Underwater noise is rapidly increasing due to, for example, boat traffic and offshore wind farms. This can lead to stress for animals and difficulties in communication. Just as people have a hard time communicating in a noisy pub, animals may struggle to get their messages across when background noise is high. A nice description of how animals use sound and how noise may affect this can be found at www.dosits.org
While there is some knowledge on the effect of noise on large aquatic animals, we still know very little about how fish and other small aquatic animals are affected. Such knowledge is vital for management of protected areas. It’s also important to know whether wind farms and boat traffic can affect reproduction in populations of underwater resources such as fish and mussels. The answers to these questions are likely to be species specific, so we’ll need data on a large number of species in different habitats.
The Noise Egg
With the development of the noise egg we aimed to suggest a simple device that is much cheaper than underwater speakers, and could be used by research groups all over the world to test effects of noise on species that are important in their particular system.
The robustness of the conclusions from an experiment depend, to a large extent, on the number of replicates. If you test the effects of noise on 3 animals, your results are more likely to be affected by chance variations between individuals than if you use 30 animals. Because the noise egg is cheap and easy to build it will allow for ample replication for most studies.
The noise produced by the noise egg only travel a few meters, so it can be used in the natural environment to target certain individuals without affecting a larger area. The housing and the properties of the noise could be adapted to each study, but the basic design is so simple anyone could build it on their kitchen table. We hope it will produce a wealth of knowledge on this subject.
In collaboration with research institutes in several European countries, we have used the noise egg to test effects of noise on several species of fish (see below). For more information on our acoustic work: www.karendejong.nl
Effects of Noise on Reproductive Behaviour in the Corkwing Wrasse
Karen Bussmann, Karen de Jong and Anne-Christine Utne Palm
For my Master’s thesis, I used the noise egg to investigate the effects of continuous noise on the corkwing wrasse (Symphodus melops) in a bay in Norway. The corkwing wrasse is a common coastal fish of the family Labridae that occurs at rocky coasts from Morocco up to Norway. This genus has hardly ever been investigated in terms of acoustics and vocal communication and this will be the first study to examine the influence of noise on reproductive behaviour in Labrids.
The beautifully coloured territorial males of the corkwing wrasse build nests out of different kinds of algae in which several females can spawn sequentially. They provide brood care till the eggs hatch and then they construct a new nest and start their breeding cycle over again. Sneaker males, which mimic the appearance of females, often group up with them and try to steal fertilizations.
The species is acoustically very active with several different calls. Therefore, it is potentially vulnerable to masking (the perceptual interference of one sound by another). I’ll also be investigating stress responses which influence things like nest building behaviour or the interactions of the fish. I am looking at the effects of noise on their communication, but also their reproductive behaviour in general.
To do this study with underwater speakers would have been much more expensive and complicated, while the noise egg was cheap and very easy to deploy in the field.
Effects of Noise on Reproductive Behavior in Two Species of Gobies
Karen de Jong, Clara Amorim, Paulo Fonseca, Adrian Klein and Katja Heubel
We tested the effect of noise on male and female reproductive behavior in two closely related gobies: the two-spotted goby (Gobiusculus flavescens) and the painted goby (Pomatoschistus pictus). The two-spotted goby we studied at SAMS in Scotland and the painted goby at the University of Lisbon, Portugal.
Gobies are small marine fish. The males of the species build and defend a nest and take care of the eggs until they hatch. They are often key species in their ecosystems and an important food source for many of the larger fish. They’re much prettier than you would think at first sight and they have a very sexy courtship song.
Because of its small size, the noise-egg was easy to use in our experimental aquariums. Also, because it ran for up to five days on one battery, we could let the animals acclimatise to the noise before testing the effect on their behaviour.
We found that males of both species produced fewer courtship calls in a noisy environment. Painted goby females spawned less and with different males in the noisy treatment. If females choose different males to reproduce with this could lead to changes in male characteristics in the population over time. We presented these results at the fourth International Conference on “The Effects of Noise on Aquatic Life”; our conference paper can be found here.
Effects of Noise on Reproductive Success of Two-Spotted Gobies in the Field
Karen de Jong and Anne-Christine Utne Palm
Because laboratory studies inherently limit the number of mates an individual can choose from, we are also testing the effect of noise on the reproductive success of two-spotted gobies in the field using artificial nests, or nest boxes if you like. Here we simply test whether we get fewer eggs in our nest boxes at noisy sites compared to quiet sites. This would suggest that these fish prefer quiet sites to reproduce. For this study, it was very important that the noise did not reach our quiet sites, which was possible because the noise field of the egg only extends to a few meters.
We hope we have given a good impression of what we use the noise egg for in the lab and in the field, but of course many other applications can be thought of. For example, we have just started to use the egg to test the propagation of different sound frequencies in shallow bays. Because the noise-egg is cheap and very simple to build we hope it can be useful to many other researchers studying noise in aquatic environments.
To find out more about the noise egg, read our Methods in Ecology and Evolution article ‘The noise egg: a cheap and simple device to produce low-frequency underwater noise for laboratory and field experiments’. As this is an Applications article, it’s freely available to everyone.