by Pablo Pla Caro LAB-UPC
This news article is part of Issue 2 of our annual newsletter, which chronicles our research in 2022. To view more articles describing our research progress from our second year, read the newsletter in full here.
Above: the AquaVib with the large steel acoustic chamber mounted.
Vibrations are perceived in one way or another by every living being on Earth. Under certain conditions, these vibrations can propagate long distances through an elastic medium (such as air or water) and generate pressure waves, tightly related to the motion of the tiny particles that constitute the medium.
Acoustic pressure has been used as a unique metric to study the possible negative impacts of anthropogenic underwater noise on aquatic organisms. It is only fairly recently that a new question has arisen which could assist naval, offshore and shipping industries towards quieter oceans:
Are underwater organisms more sensitive to these pressure fluctuations or to the motion of the particles?
Committed to addressing this challenge, researchers at the Laboratory of Applied Bioacoustics (LAB), from the Universitat Politècnica de Catalunya, BarcelonaTech (UPC), have concentrated their efforts in the past two years to design and build a unique experimental laboratory setup: the AquaVib.
Above: Researchers Marta Solé (right) and Pablo Pla (left) using the AquaVib setup.
Supported by a firm structure anchored to a thick reinforced concrete platform, a pair of heavy electrodynamic shakers cap both ends of the three interchangeable acoustic chambers equipped with different sensors to measure acoustic pressure, particle motion, temperature and dissolved oxygen in a regulable seawater flow. Within the central chamber, aquatic organisms can be exposed to controlled vibroacoustic cues with characteristics similar to those radiated by ships navigating our oceans, from regular fishing boats to the largest cargo ships with 400 meter long hulls and over 200 gigatons in weight.
The design of the AquaVib is conceived in a way that the rate between the acoustic pressure and the motion of the water particles can be set at two different configurations, allowing to assess their contributions separately. The combination of control over these two sound variables, an automated regulation of the water temperature and dissolved oxygen contents, and the possibility for visual inspection through the transparent chamber, provides the LAB-UPC team with a multimodal approach to investigate possible physiological, pathological and ultrastructural effects of the exposed organisms to each of these two sound components.
Above: Mussels exposed to controlled vibroacoustic cues in the transparent acoustic chamber.
Preliminary experiments with mussels (Mytilus edulis.) and Norway lobsters (Nephrops norvegicus) have served to fine-tune the system and to define, in collaboration with SATURN partner TNO, adequate test protocols as a rigid basis for this cutting-edge approach. In the upcoming year, the LAB-UPC group will study four different species of marine invertebrates that are considered of interest due to their major role in aquatic ecosystems and for their commercial importance. Our ultimate goal is to identify and quantify possible risks, and acute and long-term impacts on marine invertebrates directly related to the exposure to underwater radiated noise from shipping, assessing particle motion andacoustic pressure effects separately. This work will contribute to defining the most effective mitigation measures and marine spatial planning developed by the SATURN consortium, which aims to improve current maritime policies.