Identification of the Noise Hotspots For Marine Mammals In The Indian Ocean Region.


This research project aims at identifying noise hotspots and areas of potential conflicts with vulnerable marine mammals’ habitats in the Indian Ocean Region. The global aim of this project is to gather baseline knowledge of noise-producing shipping activities. Areas accumulating noise-producing activities (noise hotspots) are pointed out, with a focus on zones overlapping with important marine mammals’ habitats. The results have revealed several noise hotspots overlapping important marine mammals’ habitats.

The research study states the two different noises that the marine environment experience- impulsive noise and continuous low-frequency noise. It further notes that marine mammals, especially cetaceans, are highly vocal and dependent on sound for almost all aspects of their lives, e.g. food-finding, reproduction, communication, detection of predators/hazards, and navigation. They are thus likely sensitive to anthropogenic noise. The work attempts to study and map variations in the ambient noise levels corresponding to the fluctuations in the surface parameters and shipping traffic.

Key highlights
  • Vulnerable marine mammals (IOR): There are many marine mammals in the Indian Ocean region whose condition, as stated by IUCN, is vulnerable or endangered.
  • Marine Environment (important for mammals): One of the characteristics of low-frequency sound is that it can travel relatively long distances without much attenuation (reduction in level).
  • Spatial-temporal mapping (way of implementation): The work attempts to study and map variations in the ambient noise levels corresponding to the fluctuations in the surface parameters and shipping traffic.
  • Noise and noise-mammals interaction hotspots: The audibility maps were limited to the area that had previously been surveyed for marine mammals.
Key Challenges
  • Data collection- Indian ocean Region: Indian ocean region covers 20 lakh square kilometer, but only less than 20 % of the ocean have been studied. There is a lot to discover, including data for the many marine mammals that are not appropriate, their habitat, threats in the IOR, etc.
  • Finding the audible acoustic energy: The audible acoustic energy is the audibility of the shipping on a marine mammal. While dividing the chosen sites into small cells and fetching the ship source spectra.
  • Lack of Precise data noise mapping at each pixel: Many sound sources are simply missing from this estimate of cumulative ship noise energy. The most important of these missing sources in our noise maps is small boat traffic.
Conclusions drawn from the study

It is hoped that the efforts of this study could serve three important purposes

    • As a current best estimate of the co-occurrence of marine mammals and chronic ocean noise levels in the Indian Ocean region, regions for conservation, management, and mitigation,
    • As a framework for making predictions about the consequences likely to result from increased noise levels as various parts of the coast are subject to industrial development applications, or conversely as places where ship-quieting technologies may be most useful,
    • As a simple M-weighting method that could be used anywhere that a variety of marine mammal species may be at risk from chronic anthropogenic noise.

“A demonstrator system for real-time noise monitoring has been built up in an important conservation area where noise due to anthropogenic sources has been recognized to be a threat to a marine mammal. The project has the potential to become a helpful tool for implementing conservation, management, and mitigation policies.”

Shobhit Mehta and Dr (Cdr) Arnab Das