CEDA Underwater sound in relation to dredging Dr. Frank Thomsen DHI Group
Underwater sound and dredging http://www.dredging.org/, special thanks to Anna Csiti 23 4 2013 2
Outline Sound and marine life Effects of sound on marine life Mitigation Policy Conclusions 23 4 2013 3
Sound Acoustic pressure: SPL (db) = 20 log 10 (P/P 0 ) P 0 underwater = 1 µpa; P 0 air = 20 µpa Pitch: Hz = cycles / s (pitch) 23 4 2013 4
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Water is an ideal medium for sound Sound is more than four times faster underwater compared to air and there is less attenuation 23 4 2013 6
Marine life is noisy! 23 4 2013 7
Use of sound Communication Navigation Eavesdropping Foraging Stunning prey 23 4 2013 8
Detection Masking Response Hearing loss, injury 23 4 2013 9
Marine mammal hearing 160 140 SPL (db re 1 µpa) 120 100 80 60 40 20 0.01 0.1 1 10 100 Frequency (khz) Bottlenose dolphin (Johnson 1967) Risso's dolphin (Nachtigall et al. 1995) Striped dolphin (Kastelein et al. 2003) Killer whale (Szymanski et al. 1999; Behaviour) Killer whale (Szymanski et al. 1999; ABR) Harbour porpoise (Kastelein et al. 2002) 23 4 2013 10
Fish hearing Pressure Detection Particle Motion Detection 23 4 2013 11
Fish hearing 160 150 140 130 SPL (db re 1 µpa) 120 110 100 90 80 70 60 50 10 100 1000 Bass (Nedwell et al. 2004) Cod (Offut 1974) Cod (Hawkins & Myrberg 1983) Dab (Hawkins & Myrberg 1983)) Bass (Nedwell et al. 2004) Herring (Enger 1967) Pollack (Chapman 1973) Pollack (Chapman & Hawkins 1969) Atlantic Salmon (Hawkins & Johnstone 1978) Little Skate (Casper et al. 2003) 23 4 2013 12
Marine sound sources Boyd et al. 2008 23 4 2013 13
Seismic surveys > 256 db re 1µPa (peak to peak) at 1 m < 1 khz (see OSPAR 2009) 23 4 2013 14
Offshore wind 228 db re 1µPa peak 257 db re 1µPa (peak to peak) at 1 m < 1kHz Werner Piper 23 4 2013 15
Military activities Military, private and research > 220 db re 1µPa at 1 meter LF, MF and HF Activities classified 23 4 2013 16
Shipping Small leisure crafts and boats < 50 m Variable output: 160 175 db re 1µPa at 1 m - < 1kHz - > 10 khz Medium sized ships 50 100 m 165 180 db re 1µPa a 1 m -< 1 khz Werner Piper Large vessels > 100 m 180 > 190 db re 1µPa a 1 m - < 200 Hz (see OSPAR 2009) 23 4 2013 17
Dredging Excavation of sediment from a sea, river or lake bed and the handling and transport of the excavated sediments and soils to a placement site elsewhere Construction and maintenance of ports and waterways, dikes and other infrastructures Reclamation of new land Flood and storm protection and erosion control by maintaining river flows and by nourishing beaches Extraction of mineral resources from underwater deposits, particularly sand and gravel, to provide raw materials for the construction industry Environmental remediation of contaminated sediments. 23 4 2013 18
Dredger types and noisy activities Cutter suction dredgers (CSD), trailing suction hopper dredgers (TSHD), grab dredgers (GD) backhoe dredgers (BHD) Activities generating sound: Dredging excavation Dredging vessels during transport Dredged material placement 23 4 2013 19
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New TSHD investigations 1 De Jong et al. 2009 Maasvlakte 2, Port of Rotterdam 23 4 2013 22
260 Detection of pile driving 1 m 200 db re 1µPa 100 80 km 20 100 1,000 10,000 100,000 Frequency [Hz] (Thomsen et al. 2006) 23 4 2013 23
Detection of dredging sound 18 160 16 150 14 140 Detection distance (km) 12 10 8 6 130 120 110 100 db re 1 µpa rms 4 90 2 80 0 10 2 10 3 10 4 10 5 10 670 Frequency (Hz) 23 4 2013 24
Response Age Condition Source Channel Sex Social state Properties duration transient / continuous Behavioural state Season 23 4 2013 25
Response of fish to seismic surveys Significant decline in herring catch rate during and after seismic exposure 5 days to recover Effects 20 nm Vertical movement in some species Pearson et al. 1992; Engas et al. 1996; Slotte et al. 2004 23 4 2013 26
Documented effects of dredging ( Lutz von der Heyde) Gray and bowhead whales avoid areas of dredging activity (reviewed by Richardson et al. 1995) Harbour porpoises leave areas during sand extraction. The reactions were relatively short term however (Diederichs et al. 2010) 23 4 2013 27
1 Sound Frequency Duration Source level Duty cycle +++ + PCAD Model (NRC 2005) Behavioural change 2 Orientation Breathing Vocalising Diving Resting Avoidance Mother infant spatial rel. ++ + Life function affected Survival Breeding Migration Feeding Growth Predator resp. Nurturing + 3 Vital rates Survival Maturation Reproduction + 0 Population effects Population growth rate Population structure Transient dynamics Sensitivity Elasticity Extinction probability + 4 +++ 23 4 2013 28
Masking potential of shipping sound Whales Fish Seals & Sea Lions Toothed Whales 200 k 1 Hz 10 Hz 100 Hz 1 khz 10 khz 100 khz Shipping Southall & Hatch in OSPAR 2009 23 4 2013 29
Consequences Theoretical consequences of masking Southall & Hatch in OSPAR 2009 23 4 2013 30
Hearing loss, injury TTS studies in a few marine mammal and fish species Depending on sound type, duration and pressure Cumulative exposure important 23 4 2013 31
Repeated exposure BioConsult / Itap 2008 23 4 2013 32
Mitigation Acoustic devices (e.g. Pinger) Equipment Design (e.g. pile sleeves) Timing Bubble curtain Monitoring of safety zones (visual and acoustic) Research Ramp up / soft start Nehls et al. 2007 23 4 2013 33
Cumulative impacts 23 4 2013 34
Marine Strategy Framework Directive Chronic exposure to continuous low frequency sound Masking and potentially stress in marine mammals and fish 23 4 2013 35
MSFD Indicator 11.2.1 Trends in the ambient noise level within the 1/3 octave bands 63 and 125 Hz (centre frequency) (re 1μPa RMS; average noise level in these octave bands over a year) measured by observation stations and/or with the use of models if appropriate 23 4 2013 36
Conclusions 1 Underwater sound is important for many marine life Man made underwater sound can impact marine life in various ways and over various spatial scales A lot of gaps still exist on impacts of underwater sound on marine life Mitigation measures are being developed and policy has picked up the issue 23 4 2013 37
Conclusions 2 Dredging comes with lower sound pressure levels compared to other activities (e.g. pile driving) Behavioural impacts and masking possible TTS to consider at long exposures Injury unlikely More studies on dredging sounds and effects on marine life are needed 23 4 2013 38
Thanks to: Fabrizio Borsani, Douglas Clarke, Anna Csiti, Christ de Jong, Pim de Wit, Frederik Goethals, Martine Holtkamp, Astrid Kramer, Helmut Meyer, Kevin Reine, Frederik Roose, Elena San Martin, Philip Spadaro, Gerard van Raalte, George Yesu Vedha Victor, Anders Jensen. 23 4 2013 39