Fishing in troubled waters
Sound is essential for communication between all living beings. While soft chatter indicates a cheerful atmosphere, high noise levels signify signs of disturbance. SHASHWAT GUPTA RAY reports on two different studies related to sounds observed underwater off the coast of Goa and their implications on marine life, especially fish, which are essential for the people of Goa. While the first study deals with the issue of marine noise pollution caused by human activities, the other establishes a direct link between variations in the sound emitted by fish and the change in temperature underwater.
Although the harmful impact of noise pollution on land is well documented, the general public knows very little about the impact of marine noise pollution caused by human activities.
Now, a study has been carried out by researchers at BITS Pilani, Goa campus, in which noise levels were recorded underwater off the coast of Goa. The study revealed high levels of underwater anthropogenic noise caused by human activities such as movement of ships, tourist activities and construction activities, namely the construction of bridges, among others. This is going to have a long term impact on the availability of fish in Goa.
The research was conducted by Commodore (Retired) K Laxmi Narasimha Chary in pursuit of his PhD, under the supervision of Dr (Prof) Mukund K Deshmukh and Dr (Prof) Nitin Sharma at the Department of Electrical and Electronic Engineering, BITS , Pilani KK Birla Goa Campus, is the very first attempt to develop a comprehensive marine soundscape at the marine site near the coast of Goa.
“The marine site is characterized in terms of measured values of existing noise levels and corresponding frequencies, as well as their variation over time of day, month, season and year. I undertook the study as part of my doctoral thesis to develop an underwater soundscape in shallow tropical coastal waters near the Grande Island Biodiversity Site,” Commodore Chary told the Herald.
Many challenges were encountered when taking underwater measurements of sound levels as part of the study.
“Main was the monsoon weather. No underwater measurements could be made from May to October due to rough seas and damaged instruments. This is the first underwater soundscape developed based on long-term measurements in Indian waters,” said the veteran Indian Navy officer.
This will be helpful in monitoring the human-made underwater noise pollution in the marine environment which is increasing and threatening marine life. Noise from ships, fishing and tourist boats can be monitored and noise regulations can be implemented near Grande Island to protect marine life.
“Goa’s coastline provides livelihoods to fishing communities, and care should be taken to ensure that fish species are not threatened by underwater noise pollution. The marine ecosystem of estuaries must also be protected from underwater noise pollution. Noise maps should be generated for biodiverse areas to monitor underwater noise pollution,” he said.
A marine soundscape is essentially a complete representation of the sound (or noise) levels existing in an underwater environment. The study of soundscapes is an emerging field of research that attempts to provide important baseline information about environmental conditions as well as the biological composition of the underwater environment.
The measurements were carried out on the site using three distinct innovative methods. The measurement site is located near the archipelago of Grade Island near the coast of Goa, about 16 km west of Dabolim International Airport.
“The measurements were recorded over a long period, spanning many years. It turns out that the noise measured is mainly low frequency noise ranging from near zero to 10 kHz, which confirms the presence of various biophonic sources, including a variety of fish, snapping shrimp, dolphins, nearby of the site,” said Dr. Deshmukh, who was the research guide for the study.
It can be noted that the archipelago of Grande Island is recognized worldwide as the site of biodiversity. In addition, the existence of higher noise levels in the 10 Hz to 10 kHz range is recorded at the site, confirming that noise levels due to anthropogenic sources such as shipping and ship traffic and off-shore constructions, etc., regularly contribute to the soundscape of the site.
“The trends in noise levels measured at the site clearly show that noise levels due to anthropogenic sources are increasing over the measurement period and these may interfere with the frequencies used by aquatic species for their sustenance. It is well known that excessive and constant noise levels can be fatal to the aquatic ecosystem as it hinders communication between marine animals and in the long term can pose a major threat to the existence of a biodiverse marine site. near Big Island. Archipelago,” said the head teacher.
It may be noted that unlike environmental regulatory practices in advanced countries such as the United States, Europe, New Zealand and Australia, the inclusion of underwater noise in the environmental impact assessment environment in India is of recent origin.
“There is an urgent need to measure underwater noise levels and establish baseline soundscapes for the site. To this end, it is possible to develop suitable measurement schemes using available technologies and suitable formats of soundscapes for standardization.
“Additionally, there is a wide scope for the development of computer models based on artificial intelligence for the prediction of short and long-term noise levels, using the data generated by extensive measurements. Current research highlights the need to continue efforts in this direction,” he said.
National Institute of Oceanography Emeritus Scientist Bishwajit Chakraborty, an authority on marine soundscapes, said fish behavior was affected due to noise created by human activities.
“Due to the constant noise pollution, the communication system breaks down and their ears are affected. Their otolith bone is negatively affected, degrading the fish’s auditory system. The impact is already visible on the ground. For example, off the coast of Goa, you find that the fish go up at night and go down during the day. It affects their reproduction through noise as they cannot hear mating calls to each other,” Dr Chakraborty said.
According to him, this will cause fish species to move from their current location in search of a more peaceful environment, which will lead to the unavailability of fish that are currently found.
“In addition, fish are important members of aquatic ecosystems and indicators of water quality. said Dr. Chakraborty.
NIO Director Sunil Kumar Singh said there are different types of fish found underwater that produce different types of sounds to communicate with each other.
“Their sound frequency is very low. The source level and frequency of signals generated by human activities are very harmful to their biology. Their daily activity is affected since noise pollution acts as a barrier in their communication process. It will also affect fish productivity,” Dr Singh said.
International Quite Ocean Experiment (IQOE) is an international research, observation and modeling program to characterize the ocean sound field to promote understanding of sound on marine life initiated from 2016 with funding from the Sloan Foundation at the SCOR (Scientific Committee on Ocean Research).Dr Chakraborty represented India on the founding committee of IQOE (2016-2018).