Communication signals threaten marine habitat

Commnuication and navigation beacons.

Back in the mid 1970’s Physical Oceanographer Walter Munk was evaluating the acoustical transmission characteristics of the ocean “sound channel” – an isothermal layer in the deep ocean that baleen whales use for long distance communication.

His visionary work in this field developed into a 1991 experiment called the “Heard Island Feasibility Test” which produced the first sound that was literally heard around the world – under water.

The utility of this ocean feature for long distance communication was something Dr. Munk had been advancing ever since 1978 when he proposed a “Sea Net” – an acoustic based ocean internet system that could be used – and heard around the world.

It was along this trajectory that the “Acoustic Thermography of Ocean Climates” (ATOC) was proposed, and then deployed in 1992 despite the misgivings many of us had about projecting very loud sounds throughout the entire Pacific Basin.

ATOC turned out to be relatively benign, but for me it was the harbinger of things to come; where all manner of acoustic signals would be used for research, military, and industrial communication –crowding out the important bio-acoustic signals of marine animals.

The signals and technologies continued to develop, and it was in 2000 with a US Navy proposal of a long distance sonar system called “SURTASS” (which would ensonify the entire ocean with military noise) that the public became aware of the problem.

Public hearings were conducted, lawsuits filed, and demonstrations ensued. It was in the midst of this gambit that the Bahamas Stranding occurred – alerting us all that despite the assurances of our Navy that there was indeed a problem.

It is the continuous association between military operations and marine mammal strandings that has kept the Ocean Noise Pollution issue in the public conversation. While most of this conversation orbits around military sonar and seismic surveys, the exponential advance of other acoustical communication and navigation signals threatens to seriously compromise the marine bio-acoustic habitat.

This link describes one such signal, but there are many others being developed and deployed for research, industrial, and military applications.

While some of these signals may not be pernicious – even while overlapping some odontocete communication and bio-sonar bands, it would be good to know this prior to saturating biologically significant habitat with sounds generated by expensive equipment.

Tools to make this determination is one of OCR’s banner projects which we hope to complete this year pending support from funding agencies.

When we do complete these tools it will be none too soon, as underwater communication systems are springing up like mushrooms all over the sea.

Stay tuned!