Quantifying Loss of Acoustic Communication Space for Right Whales in and around a U.S. National Marine Sanctuary

Abstract

The effects of chronic exposure to increasing levels of human-induced underwater noise on marine animal populations reliant on sound for communication are poorly understood. We sought to further develop methods of quantifying the effects of communication masking associated with human-induced sound on contact-calling North Atlantic right whales (Eubalaena glacialis) in an ecologically relevant area (~10,000 km(2) ) and time period (peak feeding time). We used an array of temporary, bottom-mounted, autonomous acoustic recorders in the Stellwagen Bank National Marine Sanctuary to monitor ambient noise levels, measure levels of sound associated with vessels, and detect and locate calling whales. We related wind speed, as recorded by regional oceanographic buoys, to ambient noise levels. We used vessel-tracking data from the Automatic Identification System to quantify acoustic signatures of large commercial vessels. On the basis of these integrated sound fields, median signal excess (the difference between the signal-to-noise ratio and the assumed recognition differential) for contact-calling right whales was negative (-1 dB) under current ambient noise levels and was further reduced (-2 dB) by the addition of noise from ships. Compared with potential communication space available under historically lower noise conditions, calling right whales may have lost, on average, 63-67% of their communication space. One or more of the 89 calling whales in the study area was exposed to noise levels ≥120 dB re 1 μPa by ships for 20% of the month, and a maximum of 11 whales were exposed to noise at or above this level during a single 10-min period. These results highlight the limitations of exposure-threshold (i.e., dose-response) metrics for assessing chronic anthropogenic noise effects on communication opportunities. Our methods can be used to integrate chronic and wide-ranging noise effects in emerging ocean-planning forums that seek to improve management of cumulative effects of noise on marine species and their habitats.

North Atlantic right whale Eubalaena glacialis occurrence in offshore wind energy areas near Massachusetts and Rhode Island, USA

“…Other abbreviations and additional details of the study area are shown in Fig. 1 E. glacialis communicate less in the presence of elevated sound levels, and physiological stress is increased (Hatch et al 2012, Rolland et al 2012). Increased stress levels may contribute to reduced fecundity, suppressed immunity and reduced reproductive rates .…”

“…In addition, noise generated by ship traffic decreases the ability of E. glacialis to hear each other (Clark et al 2007, Hatch et al 2012, may change behavior (Parks et al 2011), and can increase stress hormones in E. glacialis (Rolland et al 2012). E. glacialis also face environmental stressors such as algal toxins, climate-driven ocean changes, and reduced prey availability , Doucette et al 2012, Fortune et al 2013.…”

Assessing the risk of chronic shipping noise to baleen whales off Southern California, USA

“…Estimates of the loss of acoustic communication space can be a valuable tool for assessing risk caused by low-frequency, chronic noise (Clark et al 2009, Hatch et al 2012. Spatially explicit risk assessments have also been conducted using spatial representations of species habitats and underwater noise generated by human activity.…”

Underwater Ambient Noise in a Baleen Whale Migratory Habitat Off the Azores

“…The production and reception of baleen whale vocalizations have been associated to vital biological processes such as feeding, mating, group cohesion and social interaction (e.g., Payne and Webb, 1971;Dudzinski et al, 2002) which make these animals especially vulnerable to this source. Noise in the environment can limit the range for successful detection of signals through masking, thus significantly affecting the acoustic communication in large whales (Samaran et al, 2010;Ponce et al, 2012;Hatch et al, 2012;Erbe et al, 2015). Blue whales (Balaenoptera musculus) have shown increased source levels of their D calls (<100 Hz) as well as increased multiple callers when ships are nearby (McKenna, 2011;Melcón et al, 2012) and North Atlantic right whales (Eubalaena glacialis) call louder with increasing background noise levels (Parks et al, 2010).…”