Characterization of underwater sounds produced by hydraulic and mechanical dredging operations

Abstract

Sound recordings were made of two dredging operations at hydrophone depths of 3 and 9.1 m at distances up to 1.2 km from the source in shallow waters (<15 m) of New York Harbor. Sound sources included rock fracturing by a hydraulic cutterhead dredge and six distinct sources associated with a mechanical backhoe dredging operation during rock excavation. To place sound emitted from these dredges in perspective with other anthropogenic sounds, recordings were also made of several deep-draft commercial vessels. Results are presented as sound pressure levels (SPLs) in one-third octave versus range across the 20 Hz to 20 kHz frequency band. To address concerns for protection of fishery resource occupying the harbor, SPL were examined at frequency bands of 50-1000 Hz and 100-400 Hz, the ranges where the majority of fishes without hearing specializations detect sound and the range of greatest sensitivity, respectively. Source levels (dB re 1 μPa-1 m rms) were back calculated using fitted regression (15LogR). The strongest sound sources (180-188.9 dB) were emitted by commercial shipping. Rock fracturing produced a source level of 175 dB, whereas six distinct sources associated with rock excavation had source levels ranging from 164.2 to 179.4 dB re 1 μPa-1 m (rms).

Effect of construction-related activities and vessel traffic on marine mammals

“…Few studies have explicitly investigated the impact of dredging, rock trenching or rock dumping on marine mammals. The noise emitted during these types of activities is most likely broadband, with most energy below 1 kHz (Reine et al 2014) and is therefore unlikely to cause damage to the auditory systems of marine mammals (e.g. Kaste lein et al 2002).…”

The marine soundscape of the Perth Canyon

“…Anthropogenic sources include seismic exploration (Erbe and King, 2009;Greene and Richardson, 1988), pile driving (Erbe, 2009), dredging (Reine et al, 2014), petroleum production operations (Erbe et al, 2013;Wyatt, 2008), equipment such as sonars, echosounders, acoustic tags and pingers (Ainslie, 2010;Erbe and McPherson, 2012), explosions (Soloway and Dahl, 2014), as well as ships of all sizes (Erbe, 2002(Erbe, , 2013aRoss, 1976;Scrimger and Heitmeyer, 1991). Propeller cavitation is typically the strongest source of ship noise from large vessels and exhibits a broadband spectrum, amplitude modulated at the propeller blade rate (i.e.…”

A critical analysis of the direct effects of dredging on fish

“…Several published studies exist that have quantified dredging sounds from hydraulic and mechanical dredging (e.g. Reine, Clarke, & Dickerson, ; Reine, Clarke, Dickerson, & Wikel, ; Thomsen, McCully, Wood, White, & Page, ). The available evidence indicates that dredging scenarios do not produce intense sounds comparable to pile driving and other in‐water construction activities, but rather lower levels of continuous sound at frequencies generally below 1 kHz.…”

“…Despite the necessity of dredging for industrial development, its potential impacts on the environment are of particular concern as multiple potential stressors associated with dredging activities have been well documented. Chief among these are sediment stress (suspended and deposited), release of toxic contaminants, hydraulic entrainment and noise pollution (Figure ; McCook et al ., ; Reine & Clarke, ; Reine, Clarke, & Dickerson, ; Reine, Clarke, Dickerson, & Wikel, ; Wilber & Clarke, ). Although there are significant dredging operations undertaken across a range of aquatic environments, and an increasing body of literature documenting dredging‐related effects on fish is available (e.g.…”

“…If both the exposures and responses are accurately assessed, appropriate risk management measures can be identified to balance the need to construct and maintain coastal infrastructure with adequate protection of vulnerable species and valuable finfish fishery resources. This review and meta‐analysis synthesizes and characterizes the known direct effects on fish from exposures to the most commonly cited potential stressors associated with dredging: sediment, release of toxic contaminants, hydraulic entrainment and noise (McCook et al ., ; Reine & Clarke, ; Reine, Clarke, & Dickerson, ; Reine, Clarke, & Dickerson, ; Reine, Clarke, Dickerson, & Wikel, ; Wilber & Clarke, ), with an emphasis on exposures relevant to dredging processes.…”