why noise from small boats is important to quantify -...
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The missing noise metric:Why noise from small boats is important to quantify
Line Hermannsen1,2, Lonnie Mikkelsen2, Jakob Tougaard2, Magnus Wahlberg3 and Peter T. Madsen1,4
1) Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark, 2) Marine Mammal Research, Department of Bioscience, Aarhus University, 4000 Roskilde, Denmark,
3) Marine Biological Research Centre, University of Southern Denmark, Kerteminde, Denmark, 4) Murdoch University Cetacean Research Unit (MUCRU), Murdoch University, Murdoch, Australia
References1. Miller, L.J., Solangi, M. and Kuczaj, S. (2008). “Immediate response of Atlantic bottlenose dolphins to high-speed personal watercraft inthe Mississippi Sound,” in J. Mar. Biolog. Assoc. U.K., 88(6), pp. 1139-1143. 2. Jensen, F.H., Bejder, L., Wahlberg, M., Soto, N.A., Johnson, M.,and Madsen, P.T. (2009). “Vessel noise effects on delphinid communication,” in Mar. Ecol. Prog. Ser. 395, pp. 161–175. 3. Williams R., BainD.E., Ford J.K.B., Trites A.W. (2002). “Behavioural responses of male killer whales to a ‘leapfrogging’ vessel,” in J. Cetacean Res. Manag. 4,pp. 305–310. 4. Merchant, N.D, Witt, M.J., Blondel, P., Godley, B.J., Smith, G.H. (2012). “Assessing sound exposure from shipping in coastalwaters using a single hydrophone and Automatic Identification System (AIS) data,” in Mar. Pollut. Bull. 64, pp. 1320–1329. 5. Erbe C.,Williams R., Sandilands D., Ashe E. (2014). “Identifying Modeled Ship Noise Hotspots for Marine Mammals of Canada’s Pacific Region,” inPLoS ONE 9(3): e89820. doi:10.1371/journal.pone.0089820.
Estimating noise impacts on marine life: Why noise from small vessels matters
Large vessels (> 300 gross tonnage)Large vessels (> 300 gross tonnage)
Steps to determine vessel noise levels (NL) and assess impacts on marine lifeSteps to determine vessel noise levels (NL) and assess impacts on marine life
VesselPosition, speed, type, size etc.
EnvironmentWater depth,
sound speed profile, sea bottom type etc.
Source level (SL)How much noise does the vessel emit?
Transmission loss (TL)How is the vessel noise absorbed
and attenuated by the environment?
NL = SL – TLHow much vessel noise exists at a certain distance from the vessel?
Measured/modelledMeasured/modelled
Measured/modelledMeasured/modelled
Hearing Sensitivity
Which sounds are audibleto the study species?
Noise exposureWhat is the noise exposure of thestudy animal?
ImpactWhat are the noise
effects on the study animal?
Weighting functionsWeighting functions
Passenger vesselsPassenger vessels
Automatic Identification System (AIS)mandatory by International law (IMO)
”Small” vessels (< 300 gross tonnage; e.g. recreational vessels/leisure crafts)”Small” vessels (< 300 gross tonnage; e.g. recreational vessels/leisure crafts)
AIS voluntary and not commonly used
Pictures not to scalePictures not to scale
Large vessels (> 300 gross tonnage)
Steps to determine vessel noise levels (NL) and assess impacts on marine life
VesselPosition, speed, type, size etc.
EnvironmentWater depth,
sound speed profile, sea bottom type etc.
Source level (SL)How much noise does the vessel emit?
Transmission loss (TL)How is the vessel noise absorbed
and attenuated by the environment?
NL = SL – TLHow much vessel noise exists at a certain distance from the vessel?
Measured/modelled
Measured/modelled
Hearing Sensitivity
Which sounds are audibleto the study species?
Noise exposureWhat is the noise exposure of thestudy animal?
ImpactWhat are the noise
effects on the study animal?
Weighting functions
Passenger vessels
Automatic Identification System (AIS)mandatory by International law (IMO)
”Small” vessels (< 300 gross tonnage; e.g. recreational vessels/leisure crafts)
AIS voluntary and not commonly used
Pictures not to scale
AcknowledgementsA huge thanks to the volunteers Mia, Pernille, Emil and Peter, andto Hans & co. from Sletterhage lighthouse for all their help withfieldwork. Also thanks to K. Beedholm for helpful analytical advice.
BackgroundVessels are the most widespread source ofanthropogenic underwater noise world-wide. Current methods to modelunderwater noise pollution from vessels usetracking data from AIS as a proxy forshipping intensity and thereby noise load(4,5). However, since only large ships arerequired to carry AIS, underwater noise incoastal areas with many small recreationalboats may be largely underestimated.
ResultsPeaks in noise levels correlated well withvessels passing close to the recordingstation (Fig. 1). Some vessels causedelevations in noise in the 2 kHz band, butnot in 63 Hz and 125 Hz bands (Fig. 1).Noise in the 2 kHz band correlatedconsiderably better with distance tonearby small boats (Fig. 3) than to AIS-registered vessels (Fig. 2). Noise levels wereaffected by boat speed (Fig. 3).
Study Area and MethodsVessels were tracked in Aarhus Bay, Denmark (5-15 mwater depth) in June-July 2015. Small motor-drivenboats (n=106) were tracked with theodolite from a highpoint (47 m above sea level) in Beaufort sea statesbelow 2. Larger vessels were tracked by AIS (source:Danish Maritime Authority). Concurrently, underwaternoise was recorded with a stationary acoustic logger(SoundTrap, oceaninstruments.co.nz) deployed at 10 mdepth and sampling at 288 kHz. Noise was quantified inthree third-octave bands; around 63 Hz and 125 Hzfollowing the European Marine Strategy FrameworkDirective and around 2 kHz following a recommendationof the BIAS project. This study was made in parallel withanother study, where harbour porpoises were tracked bytheodolite. Small boats were therefore only trackedduring periods, where no porpoises were seen.
BackgroundVessels are the most widespread source ofanthropogenic underwater noise world-wide. Current methods to modelunderwater noise pollution from vessels usetracking data from AIS as a proxy forshipping intensity and thereby noise load(4,5). However, since only large ships arerequired to carry AIS, underwater noise incoastal areas with many small recreationalboats may be largely underestimated.
ResultsPeaks in noise levels correlated well withvessels passing close to the recordingstation (Fig. 1). Some vessels causedelevations in noise in the 2 kHz band, butnot in 63 Hz and 125 Hz bands (Fig. 1).Noise in the 2 kHz band correlatedconsiderably better with distance tonearby small boats (Fig. 3) than to AIS-registered vessels (Fig. 2). Noise levels wereaffected by boat speed (Fig. 3).
Study Area and MethodsVessels were tracked in Aarhus Bay, Denmark (5-15 mwater depth) in June-July 2015. Small motor-drivenboats (n=106) were tracked with theodolite from a highpoint (47 m above sea level) in Beaufort sea statesbelow 2. Larger vessels were tracked by AIS (source:Danish Maritime Authority). Concurrently, underwaternoise was recorded with a stationary acoustic logger(SoundTrap, oceaninstruments.co.nz) deployed at 10 mdepth and sampling at 288 kHz. Noise was quantified inthree third-octave bands; around 63 Hz and 125 Hzfollowing the European Marine Strategy FrameworkDirective and around 2 kHz following a recommendationof the BIAS project. This study was made in parallel withanother study, where harbour porpoises were tracked bytheodolite. Small boats were therefore only trackedduring periods, where no porpoises were seen.
AimTest correlations between
underwater noise levels and presence of vessels with and without AIS
Figure 1. Recorded underwater noise levels in third-octave bands 63 Hz,125 Hz and 2 kHz (two top plots) and the distance to nearby AIS-registeredvessels and theodolite tracked boats (bottom plot) during one field day(Beaufort sea state 0.5-1). Orange arrows mark noise levels during the passagesof four small boats at close range.
Figure 1. Recorded underwater noise levels in third-octave bands 63 Hz,125 Hz and 2 kHz (two top plots) and the distance to nearby AIS-registeredvessels and theodolite tracked boats (bottom plot) during one field day(Beaufort sea state 0.5-1). Orange arrows mark noise levels during the passagesof four small boats at close range.
ConclusionSmall boats without AIS contributed significantly tonoise levels in a coastal habitat at frequencies ofrelevance for marine mammals. Therefore, in coastalareas with many small boats noise models based onlyon AIS-registered vessels may severely underestimatenoise loads and thereby also underestimate noiseimpacts on the marine environment.
Impact assessment
Small vessels are mainly in coastal waters Potential overlap with important breeding, mating or resting grounds for marine animalsSmall vessels often move at high speed Increased noise levels – has been linked to avoidance (1) and decreased communication range (2) in odontocetesSmall vessels move unpredictably Erratic movements of boats have been shown to increase negative effects on odontocetes (3)Small vessels are mainly present in fair weather (low wind, low sea state and no rain) High relative contribution to ambient noise levels
Figure 2. Noise levels in a 2 kHz third-octave band as a function of distanceto AIS-registered vessels of different speeds (see colour bar). Only the closestmoving AIS-registered vessel within line of sight from the acoustic recorder in seastates below Beaufort 2 were plotted (n=486). Ambient noise levels are plotted aspercentiles during the entire recording period (all sea states).
Figure 2. Noise levels in a 2 kHz third-octave band as a function of distanceto AIS-registered vessels of different speeds (see colour bar). Only the closestmoving AIS-registered vessel within line of sight from the acoustic recorder in seastates below Beaufort 2 were plotted (n=486). Ambient noise levels are plotted aspercentiles during the entire recording period (all sea states).
FundingThis project was funded partly by theBIAS project (EU LIFE11 ENV/SE/000841;www.bias-project.eu) and partly byEnergiNet.dk. The recording equipmentwas funded by a grant from the DanishResearch Council to PTM. Marinebioacoustics.com facebook.com/MarineBioacoustics
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Figure 3. Noise levels in a 2 kHz third-octave band as a function of distanceto theodolite tracked boats of different types and speeds (see colour bar). Note thatsmall boats were only tracked, whenever no porpoises were in sight. Ambient noiselevels are plotted as percentiles during the entire recording period (all sea states).
Figure 3. Noise levels in a 2 kHz third-octave band as a function of distanceto theodolite tracked boats of different types and speeds (see colour bar). Note thatsmall boats were only tracked, whenever no porpoises were in sight. Ambient noiselevels are plotted as percentiles during the entire recording period (all sea states).