A threatened beluga (Delphinapterus leucas) population in the traffic lane: Vessel-generated noise characteristics of the Saguenay-St. Lawrence Marine Park, Canada
Study area showing the six sites in and around the Saguenay-St. Lawrence Marine Park (dashed border), and the positions of the transmitting (black dots) and recording (white dots) vessels during the sound propagation experiments.
(a) Modeled and experimental functions used to apply M-weighting and C-weighting filters, respectively [dashed portion of C-weighting function was extrapolated from Finneran and Schlundt (2011), Eq. (4)] (b) 1/12 octave sound pressure levels (SPLBB) per site. (c) The median, minimum and maximum 1/12 octave SPLBB at the noisiest (EMB) and quietest (CAC) sites.
Site-specific median (line), 75% (box), 90% (whisker), and 95% (point) broadband (white boxes), M-weighted (light gray boxes), and C-weighted (dark gray boxes) SPL (dB re 1 μPa) estimated at six sites in the St. Lawrence Estuary from June to September, 2005.
(a) Vessel occurrence (mean number of vessels observed per 10 min visit) and (b) estimated mean vessel distance (km) by vessel category and site measured in the St. Lawrence Estuary between 06:00 and 18:00 from June to September, 2005.
Regressions of the median SPLBB (white dots), SPLM (gray dots), and SPLC (black dots) on the amount of (a) ferry traffic (mean occurrence × mean distance−1) and (b) RHIB traffic per site excluding the data from EMB (points beyond regression lines; see text). Asterisks denote significant regressions at p < 0.05.
Median RMS SPL (dB re 1 μPa) measured at six sites in the St. Lawrence Estuary from June to September 2005: (a) broadband (0.01–23.0 kHz), (b) M-weighted (mid-frequency cetacean), and (c) C-weighted (bottlenose dolphin).
(a) Transmission loss (dB re 1 μPa) of pure tones (3.0 kHz) over distance from source (km) with field measurements (dots), fitted model (solid line) and 95% CI (dashed lines) from Eq. (1), individually at each of five sites in the St. Lawrence Estuary, and for all sites (other frequencies are similar but are not shown).
(a) Spreading loss coefficients (dB re 1 μPa) with 95% CI from Eq. (1) fitted to received levels of pure-tones (1.0–6.0 kHz) over distance from source as measured during sound propagation experiments at each of five sites in the St. Lawrence Estuary.
Vessel noise signature of approaching vessels: (a) container ship, Canmar Venture and (b) large RHIB; (c),(d) the broadband, M-weighted and C-weighted RMS SPL (dB re 1 μPa) over time for each approaching vessel (CPA = closest point of approach); and (e),(f) 1/12 octave broadband sound levels (solid line) of approaching vessels at CPA relative to a beluga audiogram (dashed line) illustrating approximate audible (above) and inaudible (below) frequencies.
Mean and median (± range) RMS broadband (0.01–23.0 kHz) SPLBB, median (± range) M-weighted SPLM, median (± range) C-weighted SPLC and percentage of summer daytime hours (between 06:00 and 18:00) that the mean SPLBB was measured above 110 and 120 dB re 1 μPa, respectively, at each site.
Monthly large commercial vessel passages between Les Escoumins pilot station and Ile Rouge in 2004 and 2005, and local whale-watching vessel passages (twice the number of recorded round trips) in 2004 from the Canadian Coast Guard (INNAV) database.
Correlation coefficients (r 2) for linear regressions between broadband, M-weighted and C-weighted SPL per site, and mean traffic (mean occurrence × mean distance−1) of each vessel type (regressions exclude EMB site; significant regressions at p < 0.05 are in bold).
Median broadband (0.01–23.0 kHz), M-weighted [mid-frequency cetacean (Southall et al., 2007d)] and C-weighted [bottlenose dolphin (Finneran and Schlundt, 2011)] SPL (dB re 1 μPa RMS) with 25 and 75 percentiles and range measured at six sites in the St. Lawrence Estuary from June to September 2005.
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