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Ref.: Int. Conf. on the Effects of Noise on Aquatic Life, Prague (Czech Rep).
June-July 2025
Abstract:
The exploration of deep-sea resources has been on the waiting for decades. Until recently the
economic viability and the fear of environmental impact have hampered the industrial development
set off. However, deep-sea technological tools are now getting in place and the start of the
extensive exploitation phase seems ineluctable and only a few years away, at most. It is therefore
of paramount importance to provide a framework and adequate tools for environmental impact
monitoring. TRIDENT is an EU Horizon initiative aiming at contributing to a sustainable exploitation
of seabed mineral resources, by developing a reliable, transparent and cost-effective system for
prediction and continuous environmental impact monitoring of exploration and exploitation activities
in the deep-sea (Silva et al. 2023). Among other disturbance parameters addressed under
TRIDENT, stands noise and vibration produced by seabed exploration machinery and associated
platforms, risers, pumps and support ships. The extent of noise impact depends on a variety of
factors, among which the intensity, frequency and location of the noise source, on the sound
pressure level distribution in space and time and, ultimately, on the receptor species acoustic
characteristics and their spatial distribution (Spadoni et al, 2025). This paper addresses this
concern through a noise risk assessment study carried out at Tropic Seamount (TSM) TRIDENT
test site that encompasses, in one hand, the estimation of the sound distribution field through a
noise model duly calibrated with real-time acoustic measurements gathered near, mid and in the
far-field of the exploitation site. And, on the other hand, uses a MAXENT model fed in with field
observations over 5 years as well as environmental data, for estimating habitat suitability (HS)
distribution of noise sensitive cetacean species in the area. At this stage a sea trial was carried out
in June 2024 to establish a risk baseline due to shipping noise, prior to any seabed exploitation. As
expected from previous studies that show an increase of HS around seamounts (Correia et al.
2021), experimental data show a baseline mild risk centered on the TSM and decreasing to the
borders of the 400 x 400 km target area. The risk field obtained with a simulated deep-sea mining
source positioned near the SOFAR channel axis, which coincides with the top of the TSM, shows a
dramatic risk increase even at the border of the area. A proposal for the usage of risk assessment
and acoustic threshold for real-time exploitation monitoring is made.