How loud is the ocean now?

 

A few years back we worked on a modeling exercise to explore the historic noise levels in the ocean prior to the industrialization of the ocean, which began around the turn of the last century when fossil fuel came onto the bounding waves. Prior to the fossil-fuel era human-driven noise in the ocean was pretty minimal (creaking hulls and squeaking oarlocks mostly).

Our study focused on the biological noise contribution of the great whales, which we found to be a significant contributor to the pre-industrial noise in the ocean. If our models are close approximations the ocean was noisier back in 1820 than it is today. But the models and data we have today is largely drawn up using shipping data. There are many new sources of noise unaccounted for in these models.

Williams et. al. noise opportunity sitesThese newer sources are also associated with fossil fuel; from seismic surveys to extraction and production processes. None of this industrial fossil-fuel-associated noise is modeled – at least for public consumption, so the existing models are based on available data, still mostly from shipping data.

But a recent (and excellent) paper out by Maglio, Pavan, Castellote, and Frey looks at the contributions from shipping, energy, civil engineering, and military sources to come up with a more comprehensive and systematic model. These data are being represented on an Ocean Noise Map Website. Like the NOAA “CetSound/SoundMap” the application informs us of how human enterprise is “lighting up the ocean” with noise.

It is a good thing that the ocean noise issue is increasingly being framed in terms of acoustical habitats. We are coming out of an era where individual noise sources have only being assessed for potential impacts on their own and not systematically included as a contributing element of an entire marine soundscape.

The conversation is deepening. In place of evaluating a specific noise in the context of how it relates to a specific exposure threshold, noise impacts are beginning to be evaluated from the standpoint of the receivers (marine animals). This allows for consideration of cumulative impacts, concurrent noise exposures, and how the habitat is compromised by the introduction of unnatural noise.

In this context a recent paper has been published by Rob Williams et. al. that looks at Marine Protected Areas (MPAs) with a noise focus with a plan to “move beyond single-species management and begin to make some predictions about influences of noise on ecological communities.” The authors suggest that “opportunity sites” be used for MPSs to leverage the conservation benefits of quitter areas.

It remains to be seen how this work gets integrated into marine spatial planning, particularly in light of the fact that at least in the Norther Hemisphere these “opportunity sites” are becoming fewer and farther between. But that the conversation is expanding into systematic views of marine habitats is an encouraging advancement in conservation biology.