Podcast: How marine life responds to underwater noise

Shoal of fish

2 September 2014 by Richard Hollingham

This week in the Planet Earth podcast, Steve Simpson and Rick Bruintjes of the University of Exeter and HR Wallingford describe a huge experiment to find out how man-made, underwater noise affects cod, plaice, crabs and other marine life.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Richard Hollingham: This time in the Planet Earth podcast, an unusual large scale experiment to investigate how fish respond to underwater noise. I'm Richard Hollingham and I'm at the offshore renewable energy catapult at Blythe, just north of Newcastle. A beautiful sunny and you can hear an awful lot of seagulls around and this is a form ship yard, still docks here, and the one I'm looking at is full of water but it is slung with ropes and cables and beside it is a tractor, and that's important. I'm joined by marine biologist, Steven Simpson, from the University of Exeter and Rick Bruintjes who is funded by NERC's knowledge transfer programme. Steve, what is this experiment?

Steve Simpson: So, this is probably the biggest fish tank you have ever seen. It is basically a step up from about three years of research where we've been looking at impacts of noise on marine fish and invertebrates to the real world. So, we've now got a fish tank, that you are looking at, that is 80 metres long, 20 metres wide, three metres deep and in it we've got cod, we've got plaice, we've got crabs, all getting on with their day to day business, and we're looking at the impact particularly pile driving noise has on these animals. Pile driving offshore is used during construction so, for example, building wind farms and there is a lot of concern or uncertainty about how much impact that pile driving noise would have on the animals in the marine environment. So we've built an experimental piling rig which is, as you have mentioned, the tractor attached to a tractor. It's a small pile driver banging on a three metre long steel pipe which is then set into the sediment. We've got three metres of sediment at the bottom of this dry dock.

Richard Hollingham: So, Rick, just talk me through the whole experiment here. We've got a sense of what's going on. What are all the ropes and wires slung across the dock here, or as Steve says, this giant fish tank?

Rick Bruintjes: The ropes and the wires at the moment are there to actually make recordings of the noise. They are underwater hydrophones or underwater microphones called hydrophones and so we can pick up the noise that we create during the pile driving and with all the fish we put in they have like a little tack, and this tack pings at a very, very high frequency, so with all the hydrophones we have across this dock they can hear this tack and therefore we know exactly where the fish are on an accuracy of approximately 20 centimetres.

Richard Hollingham: The tractor is not working at the moment, that's also part of the experiment. You do some pile driving for a certain period of time and then some time off.

Steve Simpson: That's right. So we're going with two hours of pile driving, two hours without pile driving and this is running for two solid days of piling, after which we then are able to look at the movement based on the pingers. We also have heart rate monitors so we can look at heart rate. We've got accelerometers that measure the tail beat of some of the fish in the arena and we're able to look at their behaviour and their physiological condition during the piling to compare it against periods when we are not piling.

Richard Hollingham: And I think we can listen to some of that piling now and what they're hearing under water.

Steve Simpson: What we're really interested in here is that previous studies have used playback of pile driving using underwater speakers, but a lot of the energy is being transferred directly into the sediment, so with this piling rig that we've built we are able to not only look at the acoustic conditions within the water column up in mid water but also how that sound is propagated through the sediment and certainly for the plaice and the crabs that are sitting on the seabed that is much more important than what is happening up in mid-water.

Richard Hollingham: And, Rick, this builds on previous studies but nothing on this scale.

Rick Bruintjes: So one of the main interesting things and the main question, which is a very simple question that nobody has really answered this is, do fish avoid noise, and using this really large scale aquarium we should actually be able to tell if the fish go away from the noise, they will swim away from it, or are attracted by noise or do anything else because they might freeze because of the noise, or they might double their swimming speed, they might hold them all together and this of course can actually be a negative effect but it doesn't not necessarily have to be a negative effect.

Richard Hollingham: Now, as well as the dock here and the tractor by the side with the pile going down into the water, there are several containers along here, shipping containers, and they are full of your equipment. So you are monitoring the sounds recording with the hydrophones and may be we can head in here because there's another part of the experiment that is being put together.

Rick Bruintjes: Okay, so this is one of our shipping containers.

Richard Hollingham: Right, let's head inside. Now, as you would expect an awful lot of equipment down here and a little bit of water on the floor because you are dealing with fish. This is the most curious thing! On the bench here is a basket from a deep fat fryer attached to some rope and inside that basket instead of chips there is a plastic tub with a lid on... so, Fiona, you're an undergraduate working on this and what on earth is this?

Fiona: In each container we're going to put a crab or maybe a mussel and then we're going to lower this into the dock. We're going to fill each container with water and then from that before we put it in we will measure the oxygen content of the water, we will put it into the dock and set the piling off and then bring it up at the end and then again when we've taken it out measure the oxygen content afterwards and then we will get an indication of how much oxygen the crab or the mussel has been using and then we can work out from that the metabolic rate and so obviously during the piling noise if there has been more oxygen used that means it has got a higher metabolic rate so it indicates that is probably more stressed, for example, and then we can compare that to the ambient as well. Hopefully we will get some good results. I know it looks crazy but I think it will work - I'm hoping it will work.

Richard Hollingham: Back out through the shipping container door - and looking at this it is a vast tank - if you can imagine it as a fish tank but on the scale of the sorts of projects that are going on offshore, all the way round the British coast this is still quite small isn't it, but you can get enough from this?

Steve Simpson: I think we get two things from this. We are able to look at animals moving naturally, so not confined in a small tank arena. We're able to much more closely replicate the acoustic conditions, including in the sediment, the seabed, but we're also trialling the types of equipment technologies that we could take to that offshore environment and that's really our longer term ambition to see whether the pinger systems that we can use to localise the animals could be used in a larger off-shore environment, to see how the heart rate monitors, the accelerometers on the animals can be used perhaps in a sea-pen or even with totally free living animals.

Richard Hollingham: Rick, this is increasingly relevant as we're seeing more and more off-shore, particularly wind generation, around the UK but around coasts across Europe and the world in other places.

Rick Bruintjes: Yeah, that is correct. The UK at the moment is definitely one of the frontiering in offshore wind energy. As we speak there are large areas where the piles are being piled in the bottom for wind energy which is a very, very good thing. However, the noise that is actually made by that is very, very loud because you have to imagine that the piles they use for a large wind turbine and wind turbines can now be up to 180 to 200 metres high, so the piles that they use are on average five to ten metres diameter, and to get these into the bottom you have to have a very big hammer and it makes a lot of noise. We know that noise is very important but how important yet, well that is still to be found out.

Richard Hollingham: But, Steve, this research is vitally important given the state of the industry and the amount of these wind turbines being built into the sea.

Steve Simpson: Absolutely and I think the UK stands to be a global lead on offshore renewal energy. We are certainly a small island surrounded by energy-rich waters, whether it is tidal and wave or wind, but at the moment we've just got this issue that the uncertainty that the noise might have on certain species of animal, be they fish or invertebrates, means that industry has held up sometimes. So what we hope to be doing is generating the evidence that can reduce the uncertainty about how important noise is on particular species, on particular life stages, so that offshore renewal energy can be an important part of our energy budget in the future and I guess the nice thing about working with noise as a pollutant is that we could stop it, we could stop it now, we could stop it tomorrow, we can control noise in a way we can't control temperature, ocean acidification, chemical pollutants, microplastics, so it means you could choose simply not to make noise during a spawning season or to redirect a shipping lane if you've got a sensitive biological event, and by trying to provide the evidence that could help that decision making to take place we may soon be able to accelerate the deployment of renewable energy which is important if we're ever to meet our 2020 and 2050 obligations for carbon dioxide emissions.

Richard Hollingham: Steve Simpson and Rick Bruintjes - thank you both very much. I'll take some pictures which you can find on Planet Earth online, Facebook and Twitter feeds. And that's the Planet Earth podcast from the Natural Environment Research Council. From the dock here in Blythe, I'm Richard Hollingham, thanks for listening.