Low frequency sound found to cause lesions in sensory organs of squid, octopus and cuttlefish.
Noise pollution in the oceans has been shown to cause physical and behavioral changes in marine life, especially in dolphins and whales, which rely on sound for daily activities. However, low frequency sound produced by large scale, offshore activities is also suspected to have the capacity to cause harm to other marine life as well.
Spanish researchers examining the effects of ocean noise pollution on different species of cephalopods have shown that exposure to low frequency sound can cause lesion that has been linked to squid deaths in the wild.
Giant squid, for example, were found along the shores of Asturias, Spain in 2001 and 2003 following the use of airguns by offshore vessels and examinations eliminated all known causes of lesions in these species, suggesting that the squid deaths could be related to excessive sound exposure.
Michel André, Technical University of Catalonia in Barcelona, and colleagues examined the effects of low frequency sound exposure—similar to that caused by the use of airguns by offshore vessels—in four cephalopod species.
All of the exposed squid, octopus and cuttlefish exhibited massive acoustic trauma in the form of severe lesions in their auditory structures.
The researchers exposed 87 individual cephalopods—specifically, Loligo vulgaris, Sepia officinalis, Octopus vulgaris and Illex coindeti—to short sweeps of relatively low intensity, low frequency sound between 50 and 400 Hertz (Hz) and examined their statocysts. (Statocysts are fluid-filled, balloon-like structures that help these invertebrates maintain balance and position—similar to the vestibular system in the inner ears of mammals. )
Immediately following exposure to low frequency sound, the cephalopods showed hair cell damage within the statocysts. Over time, nerve fibers became swollen and, eventually, large holes appeared—these lesions became gradually more pronounced in individuals that were examined several hours after exposure. In other words, damage to the cephalopods' auditory systems emerged immediately following exposure to short, low intensity sweeps of low frequency sound.
All of the individuals exposed to the sound showed evidence of acoustic trauma, compared with unexposed individuals that did not show any damage.
"If the relatively low intensity, short exposure used in our study can cause such severe acoustic trauma, then the impact of continuous, high intensity noise pollution in the oceans could be considerable," said André. "For example, we can predict that, since the statocyst is responsible for balance and spatial orientation, noise-induced damage to this structure would likely affect the cephalopod's ability to hunt, evade predators and even reproduce; in other words, this would not be compatible with life."
The effect of noise pollution on marine life varies according to the proximity of the animal to the activity and the intensity and frequency of the sound. However, with the increase in offshore drilling, cargo ship transportation, excavation and other large-scale, offshore activities, it is becoming more likely that these activities will overlap with migratory routes and areas frequented by marine life.
Sauti ya masafa ya chini imepatikana kusababisha majeraha katika viungo vya hisia vya squid, octopus na cuttlefish. Uchafuzi wa kelele katika bahari huathiri tabia za wanyama wa baharini, hasa pomboo na nyangumi, ambao hutegemea sauti katika shughuli zao za kila siku. Hata hivyo, sauti ya masafa ya chini inayotokana na shughuli kubwa za pwani pia inashukiwa kuwa na uwezo wa kusababisha madhara kwa maisha mengine ya baharini pia. Watafiti wa Uhispania ambao wamechunguza athari za uchafuzi wa kelele wa bahari kwa spishi tofauti za cephalopods wameonyesha kuwa kuambukizwa kwa sauti ya masafa ya chini kunaweza kusababisha uharibifu ambao umehusishwa na vifo vya squid katika mazingira ya asili. Kwa mfano, kalamu kubwa zilipatikana kwenye pwani ya Asturias, Hispania, mnamo 2001 na 2003 kufuatia matumizi ya bunduki za hewa na meli za pwani, na uchunguzi uliondoa sababu zote zinazojulikana za majeraha katika spishi hizi, ikidokeza kwamba vifo vya kalamu vinaweza kuhusiana na mfiduo wa sauti kupita kiasi. Michel, Chuo Kikuu cha Ufundi cha Catalonia huko Barcelona, na wenzake walichunguza athari za mfiduo wa sauti ya masafa ya chini - sawa na ile inayosababishwa na matumizi ya bunduki za hewa na meli za pwani - katika spishi nne za cephalopod. Kwa mfano, kwa mfano, squid, octopus na cuttlefish walioharibiwa na maambukizi ya sauti, walipata majeraha makubwa ya kusikia. Watafiti hao waliweka viumbe 87 vya aina ya cephalopod - hasa Loligo vulgaris, Sepia officinalis, Octopus vulgaris na Illex coenidae - kwenye sauti za chini za frequency za 50-400 Hz na kuchunguza statocysts zao. (Statocysts ni umajimaji-kujazwa, balloon-kama miundo ambayo kusaidia hawa invertebrates kudumisha usawa na nafasi - sawa na mfumo vestibular katika masikio ya ndani ya mamalia.) Mara tu baada ya kuathiriwa na sauti ya masafa ya chini, cephalopods zilionyesha uharibifu wa seli za nywele ndani ya statocysts. Baada ya muda, nyuzi za neva zilivimba na, hatimaye, mashimo makubwa yakaonekana - majeraha hayo yakawa wazi zaidi hatua kwa hatua kwa watu waliochunguzwa saa kadhaa baada ya kuambukizwa. Kwa maneno mengine, uharibifu wa mfumo wa kusikia wa cephalopods ulitokea mara tu baada ya kuambukizwa kwa sauti fupi, ya chini ya nguvu ya sauti ya chini ya mzunguko. Watu wote waliokabiliwa na sauti walionyesha dalili za majeraha ya sauti, ikilinganishwa na watu wasio na sauti ambao hawakuonyesha uharibifu wowote. "Ikiwa kiwango cha chini cha sauti, na kuambukizwa kwa muda mfupi, kinaweza kusababisha majeraha makubwa ya sauti, basi athari za uchafuzi wa kelele wa kuendelea na nguvu kubwa katika bahari zinaweza kuwa kubwa. """ "Kwa mfano, tunaweza kutabiri kwamba, kwa kuwa statocyst ni wajibu wa usawa na mwelekeo wa nafasi, uharibifu wa kelele kwa muundo huu pengine kuathiri uwezo wa cephalopods kuwinda, kuepuka wawindaji na hata kuzaliana; kwa maneno mengine, hii itakuwa si sambamba na maisha. """ Athari za kelele kwenye maisha ya baharini hutofautiana kulingana na ukaribu wa mnyama na shughuli na nguvu na mzunguko wa sauti. Hata hivyo, kwa kuongezeka kwa uchimbaji wa pwani, usafirishaji wa meli za mizigo, uchimbaji na shughuli nyingine za pwani za kiwango kikubwa, inawezekana zaidi kwamba shughuli hizi zitajipinda na njia za uhamiaji na maeneo yanayotembelewa na maisha ya baharini.