Page 16 - Special Issue

bioacoustic Monitoring Contributes
to an Understanding of Climate Change
ocean because logistics have prevented scientists from acidi- fying the large volumes of seawater necessary to observe de- creases in absorption.
In addition to the decrease in sound absorption, the reduc- tion in ocean pH may affect oceanic animals in other ways. Larval fish are thought to rely on sensory cues such as ol- faction and hearing for predator avoidance and for localiz- ing reef settlement sites. Noisy reefs indicate the presence of predators, so most larval fish will avoid these noisy sites.
2 LFiagruvrael 1c:loRwangfiesohf rpereadreicdtedinglwobaatel rmsewanithsureflaecveatemdpCerOaturlesv(eilns
The global average surface ocean pH is approximately 8.0,
but continued solution of CO2 in the water is expected to
reduce pH by 0.3 or more by the end of the century (Orr
et al., 2005). Climate projections estimate future CO2 will
decrease the open ocean pH by 0.3 units or more in the next
100 years, resulting in a decrease of sound absorption, par-
Celsius) based on the 2007 IPCC climate models. Temperatures are
carbon dioxide environments did not avoid the noise. Figure adapted
did not avoid noisy sites; instead, they demonstrated no pref-
The reduction of sound absorption in the ocean means that
predicted to increase between 1 and 4 degrees Celsius between the
from Simpson et al. (2011).
erence for sites depending on noise level (Figure 3; Simpson
sounds, both natural and anthropogenic, will travel farther. The increase in anthropogenic sound levels will contribute
years 2000 and 2100.
et al., 2011). This suggests that ocean acidification may result
sponses from auditory nuclei in the brain varied with hous-
in a breakdown of predator avoidance among fish species by
dSiosurunpdtinagtuthraelilryaabtitleitnyutaotedsetiencthaendocloeacnal,izaensdouthnids saocuourcsetisc.
absorption is dependent on temperature, pressure, salinity
fanrdeascihdwitya. Thteisrnsatpurealcaitetesnuation can be further affected
Pbyrecdhiacntignegs tihnepiHm.pFaigcturoef 2cliilmluasteractehsatnhgaet othnefdresphewndateenrcsepoen-
caibesoirsptmionreanddiffipcHultc.hThanegessizneoonflimneaanrylyfrdeesphewnadtienrgsyosntepmHs
iasnbdeslowuntdhefrreeqsuoeluntciyo.nThofeGlelftobpalnCelismhoatwesMhowdetlhse(GabCsMorsp)-,
wtiohnic(hincdoBn)stbreatinwseetnhea paHccuorfa7c.5y aonfdc8l.i5mcahteanpgreosjnecotniolinseafrolyr
tahcersoesseanvfrieroqnumenecnytrsa(nHgoebfrdoamy a5n0d0 HLozutogh1,02k0H11z)..CAhdadnigteiosnin-
ally, unlike the relatively homogenous oceans, freshwater
systems are enclosed and habitat specific. Because climate
models predict droughts in some regions and heavier rainfall
in others, we cannot create a unifying prediction as to how
climate change will impact freshwater species (Hobday and
Lough, 2011). For example, streams associated with melt-
ing glaciers may increase in flow and volume as the planet
warms, whereas lakes and ponds in other regions may desic-
cate as those environments experience droughts. Increased
temperatures can result in a decrease in aquatic mixing and
turnover, resulting in stratified regions with hypoxic condi-
more noise to the ocean. These changes can impact the
Figure 2: Left panel shows the absorption (in dB) at 10 km for pH values that their songs travel several kilometers (Payne and by altering species distribution, behaviors, and viability.
t(i7o.5nsanadnd8.l5o)waspaHf.uAnctidonifiocfaftrieoqnueonfcfyr.eThshewraigthetrpsaynsteelmshsowissptrhe-absorp-
As discussed above for aquatic species, studying these im-
dtiiocnte(din, bduBt)iattis1n0oktmknatowtwnoifrseiqgunenificcieasn0t.5chaanndg5eskiHnzsofournpdHavba-lues 7.5
Webb, 1971). Because these animals use songs to communicate with members of their own species, an
from 8.5. (Miller et al., 2014).
pacts in terrestrial species is also not trivial, because these
sorption will occur due to the small size of most freshwater systems. Clearly more data are needed.
acidification-caused reduction in sound absorption
ticularly for low frequencies, by as much as 40% in 100 years
Figure 3: Effect of carbon dioxide concentration on auditory be- (Brewer and Hester, 2009; Hester et al., 2008).
havior of juvenile clownfish. Fish reared in ambient CO2 conditions avoided simulated predator noise, whereas fish reared in elevated
saltwater species
ing temperature (Wysocki et al., 2009); at high temperatures,
acoustic communication behaviors of many marine species,
thresholds increased and hearing sensitivity decreased. The
including invertebrates, fishes, and marine mammals. We
magnitude of these changes varied between the two species,
already know that anthropogenic noise impacts the acous-
and was further affected by how long the fishes were kept at a
tic behavior of marine mammals. In noisy environments,
particular temperature. These results have particular impli-
whales lengthen the duration of their communication sounds
cations for how fishes may respond to climate change. First,
(Miller et al., 2000; Foote et al., 2004), increase the intensi-
temperature will not affect the hearing sensitivity of all spe-
ties of these sounds (Au et al., 1985; Parks et al., 2011), and
cies to the same degree, and second, if animals can acclimate
adjust their sound frequencies (Au et al., 1985). Increased
to temperature variations, then the negative consequences
ambient noise levels can lead to other changes in be-
of increased temperature on hearing sensitivity may be less-
havior, such as aborting foraging dives (Aguilar Soto
ened (Wysocki et al., 2009).
et al., 2006; Cox et al., 2006). These results highlight the negative implications of reduced sound absorp-
effect on Aerially
tion, but potentially there could be positive effects of
Communicating Animals
reduced sound absorption. Baleen whales produce
Climate change impacts terrestrial species as well as aquatic
low-frequency communication sounds that travel
species. Changes in temperature (Figure 1- see page 9), pre- long distanc2es. These whales currently take advan-
cipitation, and CO levels, combined with the increased
tage of low-attenuation regions of the ocean (SOFAR
climatic variability caused by global warming, can initi-
channels), occasionally singing in these regions so
ate or exacerbate habitat loss and thus affect biodiversity
impacts vary between different habitats (tropical and tem-
may be beneficial to them because it will allow them
perate zones, high and low elevations; Navas, 1996; Deutsch
An additional factor to consider in predicting the impact
to remain in communication over longer distances.
absorption that depend on pH occur for frequencies below 3
et al., 2008), and between different species (longer-lived sRpeegcairedslseusschofawshbeirthdesrmreadyubcedaffabescoterdptinonaidsihffaerrmenfutlmoranbnener- tehfiacniasl,hsormteer-ilnivedstsigpaetcoiers dsuiscahgraeseinovsecrtws;hŞeetkhercoiocğelauneatcaidl.-, 2ifi0c1a2t)i.onBewcialul sresouflthienccohmapnlgeexsitiynanabdsvoarrpitaiboinlitlyarogfedeiffneoruegnht htoabciatuastse manedastuhreabdlieffcehreantgelisfethhaitswtoirllieasffoecf tsapneicmieaslsli(vJionsgepinh tahnedseChaiubi,t2at0s1, 0w).eAstdidllitdionnaollty,kint oiswimwhpiocrhtasnptetcoieps owiniltl oacu-t cthliamt attheesaendpraedaicptiotonsaacrheabnagseedhaarboiutantd, wtheiocrhetwicilalldciaslpceurlsae- toioontshaenrdhanboitaetxs,paenridmwenhtiacthiomn.ayThgeosexptriendcitc.teThd icshiasnwgehserine asonuimndal abbiosoacrpoutisotnicshcaavne pyleatytaombaejoermrpoilrei,cbaolltyh tbeystperdoviniditnhge
on climate change in freshwater environments is the effect
kHz, and the maximum difference in absorption for a range
of ambient temperature on the auditory system. Fishes are
of 10 km is approximately 2 dB. The right panel shows how
ectotherms that regulate their body temperature by refer-
the absorption between a frequency of 500 Hz and 5 kHz
ence to external temperature, rather than by internal physi-
changes nonlinearly across a pH range from 7.5 to 8.5. For
ological setpoints. The water temperature at which animals
a pH value of 7.5, the difference in absorption between the
were housed affects the hearing sensitivities of two species
low (500 Hz) and high (5 kHz) tone is approximately 2.5 dB,
of catfish, the channel catfish (Ictalurus punctatus) and the
but at a pH value of 8.5 the difference in absorption may be
tropical catfish (Pimelodus pictus). Thresholds of neural re-
as high as 4.5 dB (Miller et al., 2014).
16 | Acoustics Today | Spring 2020, Special Issue 10 | Acoustics Today | Summer 2014
Reprinted from volume 10, issue 3
| 9