marine noise pollution
Post on 25-May-2017
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According to the UN Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP):Marine pollution is the introduction by man, directly or indirectly, of substances or energy to the marine environment resulting in deleterious effects such as: hazards to human health; hindrance of marine activities, including fishing;impairment of the quality for the use of seawater, and reduction of amenities.IS MARINE NOISE POLLUTION?So technically - yes
Light availability in the oceans decrease with depth
little light below 200m, so hearing becomes a more important sense than sight
Sound also travels faster (1500 m/s vs 330 m/s) in water and can travel greater distances
Because of the distances and directions that sound can travel in it has a wide geographical range WHY IS UNDERWATER NOISE IMPORTANT?
Research off of Point Sur, California comparing sound levels between 1963-65 and 1994-2001 discovered:INCREASE OF UNDERWATER NOISEA 10 dB increase in noise levels= x 10 increase in noise in 33 yearsThis increase in noise was primarily due to human activities in the oceans [Wenz, 1968; Andrew et al., 2002]
Sound is biologically important for the survival of many marine species:CommunicationNavigationFinding foodPredator detectionFinding mates/breeding [Parsons & Dolman (2003)]
WHY IS UNDERWATER NOISE IMPORTANT?
Natural phenomenon in the marine environment that produce noise include:NATURAL SOURCES OF UNDERWATER NOISEwaveswindsurf (104 dB)lightningprecipitation (rain 55-85 dB) earthquakesNoise from earthquakes dominate frequencies below 100Hz, but rain and wave sounds dominate higher frequenciesanimals (fish, shrimp, marine mammals)
Shipping is one of main sources of man-made sound in the marine environment. Other sources includeSOURCES OF MAN-MADE NOISEAir guns used in oil & gas explorationFish finders and depth soundersSound sources used in oceanographic researchPredator deterrent devices (seal scrammers)DredgingMilitary activities [Parsons et al. (2003)]Oceanic windfarms
In general, older vessels produce more noise than newer ones and larger vessels produce more than smaller ones Lower frequency noises produced by shipping also travel further than higher frequency noises e.g. the noise from a supertanker (@ 6.8 Hz) could be detected 139 - 463 km away. [Gordon and Moscrop (1996); Ross, (1976)]SHIPPING
but even the noise from a small 70 hp outboard engine [142 dB; 400 Hz-4 kHz] could be detected 50 m away.[Stewart et al., (1982)]
Shipping typically produces frequencies below 1 kHz - although frequencies above 1 kHz can be produced Species such as baleen whales may be most susceptible to these low frequency sounds.SHIPPING
Type of vesselFrequency (kHz)Source level (dB re 1mPa)Reference650cc Jetski0.8-50.075-125Evans and Nice, (1996)Rigid inflatable6.3152Malme et al., (1989)7m outboard motor boat0.63156Malme et al., (1989)Fishing boat0.25-1.0151Greene, (1985)Fishing trawler0.1158Malme et al., (1989)Tug pulling empty barge0.0371.05.0166164145Buck and Chalfant, (1972)Miles et al., (1989)Tug pulling loaded barge1.05.0170161Miles et al., (1989)34m (twin diesel engine) workboat0.63159Malme et al., (1989)Tanker (135m)Tanker (179m)Supertanker (266m)Supertanker (340m)Supertanker (337m)0.430.060.0080.0070.007169180187190185Buck and Chalfant, (1972);Ross, (1976);Thiele and dengaard, (1983)Containership (219m)Containership (274m) Freighter (135m)0.0330.0080.041181181172Buck and Chalfant, (1972); Ross, (1976); Thiele and dengaard, (1983)
To determine the location of oil and gas deposits under the sea bed seismic surveys are conducted.
These surveys produce high intensity sounds which penetrate the seabed, the echo of these sounds, upon analysis, telling the oil companies the structure of the sea bed and positions of probable fossil fuel deposits.
Depending on method being conducted, seismic surveys can produce sound of frequencies ranging from 5 Hz to 200 kHz, at levels of 225 to 270 dB OIL AND GAS EXPLORATION
Summary of sound frequencies produced by seismic surveys and their source level [Greene & Moore (1995); Perry (1998)]
ActivityFrequency range (kHz)Source Level (dB re 1 Pa)Seismic surveys i) High Resolution Pingers, side-scanner ii) Low resolution Airguns Sleeve exploder Vibroseis
The sounds produced by seismic surveys can be detected more 3000 miles from their source [Nieukirk et al. (2004)] Researchers trying to record cetaceans in the mid-Atlantic found that whale calls were frequently being smothered and masked by the high levels of continuous sound produced by seismic surveys [Nieukirk et al. (2004)]
Sperm whales have been observed exhibiting a startle reaction 2km away from a seismic survey [Stone (2003)] SEISMIC SURVEYS
Seismic surveys have also been linked to whale stranding events: in 2002, two Cuviers beaked whales stranded on the Isla San Jose (Gulf of California) coincident with seismic surveys from the research vessel Maurice Ewing. [Malakoff, (2002)] It is possible that seismic surveys have caused cetacean strandings in other areas, such as the Galpagos Islands [Palacios et al. (2004)] But marine mammals arent the only marine life effected by seismic surveysSEISMIC SURVEYS
A study by Norway's Institute of Marine Research showed that trawl catch rates of haddock and cod fell by 45-70% over a 2,000 square mile area - while seismic surveys were being conducted. Catch rates did not increase during 5 days surveyed after the air guns stopped. [Engas, et al. 1993] Another study by showed damage to fish ears by seismic surveys - beginning at 160 dB[MacCauley et al. 2000]Unusual numbers of giant squid were also found dead and stranded on beaches in large numbers at the same time seismic surveys were being conducted [MacKenzie, (2004)]
Marine vessels have a variety of pieces of equipment which produce high levels of sound the most common being echo-sounders and fish-finders, both of which analyze received sound echoes from either fish or the seabed. This equipment can produce substantial levels of underwater soundFor example:220-230 dB for side scan sonar (50-500 kHz); 180dB+ for depth sounders (12kHz+); 200-230 dB for bottom profilers (100Hz-160 kHz) 180-200 dB for navigational transponders (7-60kHz) [Greene and Moore, (1995)].
FISH FINDERS AND DEPTH SOUNDERS
Oceanographers frequently use high intensity sound sources during their research -including seismic surveysHowever, one of the most infamous was the Acoustic Thermometry of the Ocean Climate (ATOC) project The ATOC project was designed to detect changes in oceanic temperatures using a high intensity, low frequency sound source. The project was initially to have two transmitters - Kauai, Hawaiian Islands - Monterey Bay National Marine Sanctuary, California.After public protest - the California sound source was relocated to the Pioneer Seamount, outside of, but close to, the Monterey Bay Sanctuary area. OCEANOGRAPHIC RESEARCH
To investigate the potential impacts of the ATOC sound source on cetaceans in 1991 a field test (209-219 db) was conducted on Heard Island, in the Antarctic. While the low frequency sound source was operating researchers monitored a 70km by 70km area of ocean: Although long-finned pilot whales (Macrorhynchus melas) and sperm whales (Physeter macrocephalus) were acoustically detected nearly a quarter of the time when the sound source wasnt operating- there were no acoustic detections of these species at all when the sound system was on. [Bowles et al. (1994)] ATOC
Despite the results of the Heard Island test, the ATOC project continued, albeit with a quieter (195 dB) source level than used in the Heard Bay test. Effects of the system were still reported:In Kauai, distances and durations between surfacings increased in humpback whales (Megaptera novaeangliae) exposed to ATOC (received levels = 98-109 dB) [Frankel & Clark (1998); Frankel & Clark (2000)]Also - whales were statistically significantly further away when the sound source was on, than when the sound source was off [Frankel & Clark (2002)]ATOC
These results were also echoed by researchers conducting aerial surveys in the Californian site: humpback whales, and sperm whales, where sighted significantly further away from the ATOC sound source when it was turned on [Calambokidis (1998)] But despite this ATOC was considered to have no short or long-term biologically significant effectThis attitude was criticized in a US National Research Council report - the marine mammal research program associated with the ATOC project was insufficient and had not adequately conducted research into whether there had indeed been short or long-term effects on marine mammals, or their biological significance [National Research Council (2000)]The ATOC project stopped in 1999 but the sound source was reused in 2002 - North Pacific Acoustic Laboratory Program (NPAL)ATOC
Fish farms are frequently predated by seals, sealions and other marine predators To prevent marine marine mammals or other predators from approaching fish farm sites, many companies have resorted to using Acoustic Harassment Devices (AHDs) or seal-scrammers-to scare away predators, or even cause pain AHDs typically produced mid to high frequency sounds (1.8 kHz 103 kHz) with a peak source level of up to 193 dB [Lepper et al. (2004) ]There are several studies ha