Research Profile | María Renee Contreras Merida | Marine Science & Climate Change

"As the public becomes aware of the impact that several activities we carry out in the ocean have on marine fauna, they can become part of the solution."
4th November 2021
María Renee Contreras Merida, one of our Master in Marine Science and Climate Change students, spoke to us about her research project, characterising the continuous noise caused by shipping activity, of both commercial and recreational vessels present in the Bay of Gibraltar.

Describe your MSc project?

My dissertation project consists of the characterisation of the continuous noise caused by shipping activity, of both commercial and recreational vessels present in the Bay of Gibraltar. Sound is considered as a source of pollution in terms of it being an energy input from human activities (commonly known as underwater noise). This underwater noise can be categorised as impulsive (e.g. drilling, oil extraction) and continuous (e.g. shipping); depending on the time scale it persists. An increase in low-frequency noise, mainly form shipping activity, has been increasing since the nineteenth century due to the marine traffic and industry growth. Several international regulations continue to develop, as regional and local legislations are being implemented to regulate pollutants and achieve a Good Environmental Status. To monitor and manage vessel noise, the Marine Strategy Framework Directive –MSFD- created a descriptor (11.2), where it mandates member states to ensure underwater noise levels do not surpass good environmental status thresholds.
These guidelines have been adopted by the OSPAR Commission and complemented with an Ecosystem Approach process at a Mediterranean level by the Barcelona Convention. A common approach to underwater noise is using passive acoustic measurements, undertaken by hydrophone deployment methodologies. Gibraltar is considered to be a relevant marine area due to its rich diversity in species and habitats. However, it is also a well transited marine route, with likely elevated continuous underwater noise that impact the marine fauna and ecosystems. Currently there is no sufficient evidence to assess underwater noise trends in such relevant areas, therefore this project aims to develop an underwater noise baseline of the Bay of Gibraltar.
To achieve this, I carried out the deployment of an EA-SDA-14 hydrophone by a bottom-mooring system with a sub-surface buoy in the No-fishing, no anchoring zone of Seven sisters in Rosia Bay. As the hydrophone recorded the acoustic data, observational information from different vessel types was gathered to identify in the noise source in the recordings. Based on the obtained results, recommendations for management and mitigation of underwater noise in this area will be formulated.

What type of research has it involved and what skills have you learned?

Example of a crude oil tanker with bulk carrier in background (Commercial Vessels).

This research contains a mixture between both quantitative and qualitative data, by obtaining the noise levels within the bay through the measure of sound pressure level, as well as describing the source of noise to the best of the possibilities with the data provided by direct observation and literature research. I have gained research skills with the development of the experimental design and a critical literature review to help identify relevant information on continuous noise (shipping), the impacts of underwater noise in the marine fauna, ecosystems and their interactions. I have also improved on my searching skills to gather information on the different methodologies used to gather the acoustic data, hydrophone deployment, the frequencies to study, statistical analysis that need to be carried out and how to implement mitigation and legislation recommendations after the obtained results.
Other relevant skills I gained range from technical support of hydrophone maintenance; mission configuration on an online software; analysis of acoustic data by using an acoustic software (Audacity) an passive acoustic measurement guide (PAMGuide); interpretation and creation of spectrograms; to the use of more in depth statistical software’s as R and Primer7.

Were there any partners/stakeholders on your project?

The main stakeholder involved with this project is the Department of Environment, Sustainability, Climate Change and Heritage –DESCCH-, of the Government of Gibraltar. The DESCCH supported by lending the hydrophone to carry out the acoustic recordings, as well as providing help with carrying out both the Pilot study and the main project’s deployment methodology in the area of Seven Sisters in Rosia Bay.
There is also a partnership with a world leader researcher of underwater noise, PhD. Nathan Merchant, as he kindly accepted on becoming my second supervisor and provided help in the acoustic analysis using his PAMGuide.

Example of bulk carriers (Commercial Vessels).

Why should the public know about this topic?

A relevant source of underwater noise are recreational vessels such as fishing boats, jet skies, sailboats, yachts, etc. As the public becomes aware of the impact that several activities we carry out in the ocean have on marine fauna, they can become part of the solution in reducing the noise levels, as well as supporting the legislations that can come out of this to help improve the health of the ocean.

Spectrogram displays of frequency of underwater noise within the Bay of Gibraltar (2021).

A and B are two different ways of displaying noise frequencies i.e. both Power Spectral Density (PSD) and Third Octave levels (TOLs) Spectrograms of high peak underwater noise recorded during a weekend at midday. The red areas at the start of the spectrogram are attributed to an oil tanker dropping anchor and activity towards end of the recording (after 150 secs) (Commercial vessels).

The high frequency noise at 50 secs is attributed to a fishing vessel passing close to the hydrophone (recreational vessels).

What is the wider impact of your research?

The results obtain from this dissertation will help elucidate the levels of noise that are ranging in the Bay of Gibraltar. From there, it can prove to be a useful tool in guiding the DESCCH in the creation of any possible regulation and legislation that would need to be taken into consideration to achieve a good environmental status and minimise the impacts of underwater noise on the marine fauna.

Example of a law enforcement launch.

Comments from Head of School

Ocean Health includes how noisy the marine environment and is attributed to both commercial and recreational marine traffic.
All Marine Science students at UniGib are taught that their research matters and is of benefit to society. Maria’s research is a great example of how ecological research can influence marine policy, management, and ultimately, conservation. Maria’s work has led to the first characterisation of underwater noise within the Bay of Gibraltar. The research has been conducted with HMGoG Department of the Environment (DESCCH) and UK Government (Cefas).
Dr Awantha Dissanayake, BSc, MSc, PhD
  • MSc

    Master in Marine Science & Climate Change

    Designed and delivered by expert academics and scientists, this full or part-time interdisciplinary programme blends theoretical study with practical, field-based work. You will cover specialist subject areas and gain the skills required to tackle the complex issues associated with the sustainable development of marine ecosystems.[...]

    1 Year

    No Placement option

    Full Time

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