As I write and as you read, we are both acutely aware of our environments. Like me, you may hear the pigeons on your roof, a loud car passing by, or the sound of a neighbour hoovering in the middle of a workday. All that we know trickles down from our ability to process this sensory information. The ability to interpret sound is particularly important, and it would be an understatement to say that the world is a noisy place.
Given that it covers about 70% of our planet’s surface, the ocean is naturally a sound-rich environment. Above and beneath the surface of the water you could encounter such sounds as crashing waves, intense winds and storms, whale frequencies or dolphin vocalizations, and even the slightest sound of snapping shrimp. However, you wouldn’t only encounter natural noises.
Measuring human-generated sound in the ocean
As the International Quiet Ocean Experiment (IQOE) points out, in the past few hundred years, human activity has changed the sound field in the ocean. We have reduced sources of biological sound in the ocean by fishing noise-producing species, and we have added human-generated sound to the ocean with the development of industrial activities such as motorized ships or oil extraction.
The IQOE is “an international scientific programme to promote research, observations, and modelling to improve understanding of ocean soundscapes and effects of sound on marine organisms”. Developed in 2011 and formally launched in 2015, the project is co-sponsored by the Partnership for Observation of the Global Oceans (POGO) and the International Science Council’s Scientific Committee on Oceanic Research (SCOR). As explained by the Experiment’s founders, five fundamental questions underpin the IQOE:
1. How have human activities affected the global ocean soundscape compared with natural changes over geologic time?
2. What are the current levels and distribution of sound in the ocean?
3. What are the trends in sound levels across the global ocean?
4. What are the current effects of anthropogenic sound on important marine animal populations?
5. What are the potential future effects of sound on marine life?
These questions of how the increase of sound in the ocean could affect organisms have sparked an interest in many scientists and small-scale research groups, and the IQOE aims to bring scientists together in a large-scale international project of coordinated research.
“International research projects like IQOE – which coordinate efforts of national scientists -bring several benefits to the community of scientists involved. One important benefit I would like to highlight is the ability for the international community to agree on standard procedures for observations and/or research. IQOE has promoted the development of the Ocean Sound Software for Making Ambient Noise Trends Accessible (MANTA), which will allow scientists to process observations of ambient ocean sound from different locations to make them comparable. The Alfred Wegener Institute in Bremerhaven, Germany, is establishing the Open Portal to Underwater Sound (OPUS) to archive and serve MANTA-processed data. Without MANTA and OPUS, it would be impossible to create international databases of ambient ocean sound and to determine whether there are trends in sound levels.”, says Edward R. Urban Jr, Project Officer for the IQOE.
The difficulty to understanding ocean soundscapes is that measuring tools aren’t always available, not to mention that hydrophones (underwater microphones) have historically been scattered and isolated. Efforts to quantify and compare what sound levels cause harm to marine life and where in the ocean these levels could be the most damaging have therefore been hindered. Nonetheless, the IQOE has encouraged the deployment of hydrophones worldwide and called for the development of standard procedures on the international scale. The effects of these efforts are notable, as the number of hydrophones globally has dramatically increased in recent years. As Ed Urban informs us, “we are probably up to about 250 hydrophones now [that have agreed to be included in our database], although there are hydrophones being activated and deactivated all the time.”
Taking advantage of the COVID-19 pandemic “natural experiment”
During 2020 the COVID-19 pandemic resulted – among other things – in travel restrictions and a global economic slowdown. ‘Noisy’ activities such as “shipping, tourism and recreation, fishing and aquaculture, energy exploration and extraction, naval and coast guard exercises, offshore construction, and port and channel dredging” all decreased during 2020, as pointed out by a recent article in Eos. The pandemic has therefore provided a unique opportunity to explore how a sudden reduction in human activities, followed by global economic slowdown, affects levels of ocean sound. The IQOE, with the ocean observing community, is working to identify the global network of “civilian-operated, passive acoustic hydrophones” that can be used to measure the impact of the pandemic on sound in the ocean. For the IQOE, the pandemic arrived at a fortuitous time, as it can now help us gather understanding on the extent to which human-generated noise impacts ocean species.
Originally, the IQOE Science Plan had designated 2022 as “the Year of the Quiet Ocean”. Indeed, “a main premise of IQOE has been to study ocean sound and its effects on marine organisms without adding sound to the ocean, to look for opportunities to observe the effects of natural or human-caused changes in ocean sound, such as changes in the routes of shipping lanes, port building, development of wind farms, etc. We were hoping around 2022 to find a way to create voluntary reductions in ocean sound for a day or week. When we observed how much the COVID-19 pandemic affected human activities in the ocean, the IQOE Science Committee decided to declare 2020 the International Year of the Quiet Ocean, recognizing that it is unlikely that a voluntary reduction in activity for a short period would produce as significant an effect. We hope through data analysis made possible by MANTA and OPUS to focus analysis on the effects of the pandemic on ocean sound by comparing 2019 data with data from 2020. It is harder to determine how the reductions in ocean sound reported in some peer-reviewed papers affected marine organisms, although it should have increased their ability to communicate as the levels of “masking sound” were decreased.” (Ed Urban).
2020 did provide an unprecedented opportunity for the IQOE and “papers now appearing do show that the pandemic has decreased sound levels in some areas”, says Urban. However, Ed Urban also points out that he has “heard from some scientists that they saw no impact, and in some areas an increase in sound from pleasure boats. It will be important to determine what factors controlled whether sound decreased or not (e.g., distance from major shipping lanes, depth of hydrophones, pandemic closure policies of the country where the hydrophones are deployed, etc.). It may be difficult to directly ascribe changes in organisms’ behaviour to the noise decreases, but it will be interesting to see what is possible. Even if there are correlations between changes in sound levels and animal behaviour, it is hard to prove causation”, explains Edward Urban.
Nonetheless, remaining difficulties and the questions that arise from them will be investigated by the IQOE, to help explore areas that are still poorly understood. The International Science Council, as the global voice for science, will be following the outcomes and findings of the IQOE Project in the coming years – keep an eye on our ocean content here.
Image: Listening to sounds captured by an underwater hydrophone (Jeremy Potter NOAA/OAR/OER via Flickr).