Baleen whales influence their ecosystems through immense prey consumption and nutrient recycling
. It is difficult to accurately gauge the magnitude of their current or historic ecosystem role ...without measuring feeding rates and prey consumed. To date, prey consumption of the largest species has been estimated using metabolic models
based on extrapolations that lack empirical validation. Here, we used tags deployed on seven baleen whale (Mysticeti) species (n = 321 tag deployments) in conjunction with acoustic measurements of prey density to calculate prey consumption at daily to annual scales from the Atlantic, Pacific, and Southern Oceans. Our results suggest that previous studies
have underestimated baleen whale prey consumption by threefold or more in some ecosystems. In the Southern Ocean alone, we calculate that pre-whaling populations of mysticetes annually consumed 430 million tonnes of Antarctic krill (Euphausia superba), twice the current estimated total biomass of E. superba
, and more than twice the global catch of marine fisheries today
. Larger whale populations may have supported higher productivity in large marine regions through enhanced nutrient recycling: our findings suggest mysticetes recycled 1.2 × 10
tonnes iron yr
in the Southern Ocean before whaling compared to 1.2 × 10
tonnes iron yr
recycled by whales today. The recovery of baleen whales and their nutrient recycling services
could augment productivity and restore ecosystem function lost during 20th century whaling
.
Ecological relationships of krill and whales have not been explored in the Western Antarctic Peninsula (WAP), and have only rarely been studied elsewhere in the Southern Ocean. In the austral autumn ...we observed an extremely high density (5.1 whales per km(2)) of humpback whales (Megaptera novaeangliae) feeding on a super-aggregation of Antarctic krill (Euphausia superba) in Wilhelmina Bay. The krill biomass was approximately 2 million tons, distributed over an area of 100 km(2) at densities of up to 2000 individuals m(-3); reports of such 'super-aggregations' of krill have been absent in the scientific literature for >20 years. Retentive circulation patterns in the Bay entrained phytoplankton and meso-zooplankton that were grazed by the krill. Tagged whales rested during daylight hours and fed intensively throughout the night as krill migrated toward the surface. We infer that the previously unstudied WAP embayments are important foraging areas for whales during autumn and, furthermore, that meso-scale variation in the distribution of whales and their prey are important features of this system. Recent decreases in the abundance of Antarctic krill around the WAP have been linked to reductions in sea ice, mediated by rapid climate change in this area. At the same time, baleen whale populations in the Southern Ocean, which feed primarily on krill, are recovering from past exploitation. Consideration of these features and the effects of climate change on krill dynamics are critical to managing both krill harvests and the recovery of baleen whales in the Southern Ocean.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This article evaluates Southall et al. (2007) in light of subsequent scientific findings and proposes revised noise exposure criteria to predict the onset of auditory effects in marine mammals. ...Estimated audiograms, weighting functions, and underwater noise exposure criteria for temporary and permanent auditory effects of noise are presented for six species groupings, including all marine mammal species. In-air criteria are also provided for amphibious species. Earlier marine mammal hearing groupings were reviewed and modified based on phylogenetic relationships and a comprehensive review of studies on hearing, auditory anatomy, and sound production. Auditory weighting functions are derived for each group; those proposed here are less flattened and closer to audiograms than the Southall et al. M-weightings. As in Southall et al., noise sources are categorized as either impulsive or non-impulsive, and criteria use multiple exposure metrics to account for different aspects of exposure. For continuous (non-impulsive) noise sources, exposure criteria are given in frequency-weighted sound exposure level (SEL, given in units relative to 1 microPa.sup.2-s or (20 microPa.sup.2)-s for water and air, respectively). Dual exposure metrics are provided for impulsive noise criteria, including frequency-weighted SEL and unweighted peak sound pressure level (SPL, given in units relative to 1 microPa or 20 microPa for water and air, respectively). Exposures exceeding the specified respective criteria level for any exposure metric are interpreted as resulting in predicted temporary threshold shift (TTS) or permanent threshold shift (PTS) onset. Scientific findings in the last decade provide substantial new insight but also underscore remaining challenges in deriving simple, broadly applicable quantitative exposure criteria for such diverse taxa. These criteria should be considered with regard to relevant caveats, recommended research, and with the expectation of subsequent revision. Key Words: hearing, marine mammals, noise exposure, TTS, PTS, weighting, criteria
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Many baleen whales undertake annual fasting and feeding cycles, resulting in substantial changes in their body condition, an important factor affecting fitness. As a measure of lipid-store body ...condition, tissue density of a few deep diving marine mammals has been estimated using a hydrodynamic glide model of drag and buoyancy forces. Here, we applied the method to shallow-diving humpback whales (Megaptera novaeangliae) in North Atlantic and Antarctic feeding aggregations. High-resolution 3-axis acceleration, depth and speed data were collected from 24 whales. Measured values of acceleration during 5 s glides were fitted to a hydrodynamic glide model to estimate unknown parameters (tissue density, drag term and diving gas volume) in a Bayesian framework. Estimated species-average tissue density (1031.6 ± 2.1 kg m-3, ±95% credible interval) indicates that humpback whale tissue is typically negatively buoyant although there was a large inter-individual variation ranging from 1025.2 to 1043.1 kg m-3. The precision of the individual estimates was substantially finer than the variation across different individual whales, demonstrating a progressive decrease in tissue density throughout the feeding season and comparably high lipid-store in pregnant females. The drag term (CDAm-1) was estimated to be relatively high, indicating a large effect of lift-related induced drag for humpback whales. Our results show that tissue density of shallow diving baleen whales can be estimated using the hydrodynamic gliding model, although cross-validation with other techniques is an essential next step. This method for estimating body condition is likely to be broadly applicable across a range of aquatic animals and environments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Marine mammals consume large quantities of microplastic particles, likely via trophic transfer (i.e., through prey who have consumed plastic) and direct consumption from seawater or sediment. ...Microplastics have been found in the stomachs, gastro-intestinal tracts, and feces of cetaceans and pinnipeds. Translocation of ingested microplastics has been documented in other organs of several aquatic species, but has not been examined in marine mammals. Marine mammals have highly specialized lipid-rich tissues which may increase susceptibility to lipophilic microplastics. Here we demonstrate the occurrence of microplastics, ranging in size, mass concentration, and particle count concentration from 24.4 μm – 1387 μm, 0.59 μg/g – 25.20 μg/g, and 0.04 – 0.39 particles/g, respectively, in four tissues (acoustic fat pad, blubber, lung, & melon) from twelve marine mammal species inclusive of mysticetes, odontocetes, and phocids. Twenty-two individuals were examined for microplastics using a combination of Raman spectroscopy and pyrolysis gas chromatography with mass spectrometry. Overall, 68% of individuals had at least one microplastic particle in at least one of the four tissue types, with the most common polymer and shape observed being polyethylene and fibers, respectively. These findings suggest some proportion of ingested microplastics translocate throughout marine mammal bodies posing an exposure risk to both marine mammals and people. For people, exposure could be directly through consumption for those who rely on marine mammals as food and indirectly to peoples globally who consume the same prey resources as marine mammals. Some individuals examined represent samples obtained over two decades ago, suggesting that this process, and thus exposure risk, has occurred for some time.
Display omitted
•Internalized microplastics translocate to marine mammal organs, notably blubber.•Samples containing microplastics spanned over two decades.•68% of samples contained at least one microplastic particle.•The most common polymer & shape observed were polyethylene & fibers, respectively.•Use of complimentary methods allowed for both mass and count concentrations.
For many marine organisms, especially large whales that cannot be studied in laboratory settings, our ability to obtain basic behavioral and physiological data is limited, because these organisms ...occupy offshore habitats and spend a majority of their time underwater. A class of multisensor, suction-cup-attached archival tags has revolutionized the study of large baleen whales, particularly with respect to the predatory strategies used by these gigantic bulk filter feeders to exploit abundant oceanic resources. By integrating these data with those from other disciplines, researchers have uncovered a diverse and extraordinary set of underwater behaviors, ranging from acrobatic diving maneuvers to extreme feeding events during which whales engulf volumes of prey-laden water that are much larger than their own body. This research framework not only improves our knowledge of the individual performance and behavior of these keystone predators but also informs our ability to understand the dynamics of complex marine ecosystems.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Animal behaviour can provide valuable information for wildlife management and conservation. Studying the detailed behaviour of marine mammals involves challenges not faced by most animal behaviour ...researchers due to the size, mobility and lack of continuous visibility of these animals. We describe several methods developed by marine mammal scientists to study behaviour, primarily of cetaceans, focusing on technological advances: unmanned aerial systems (UAS), satellite-linked telemetry, passive acoustics and multisensor high-resolution acoustic recording tags. We then go on to explain how the data collected by these methods have contributed to and informed conservation actions. We focus on examples including: satellite data informing the interactions between cetaceans and offshore oil and gas development; passive acoustics used to track distributions of several species of cetaceans, including their movements near shipping lanes; and high-resolution acoustic recording tags used to document responses of cetaceans to anthropogenic activities. Finally, we discuss recent efforts to link animal behaviour to individual fitness and, particularly for behavioural disturbances, to population-level consequences, which can be helpful for informing conservation efforts. The infusion of technological advancements into studies of cetacean behaviour combined with emerging analytical techniques brings us to the next 20+ years of studying these animals. These developments will improve our capabilities in areas such as testing whether their behaviour adheres to traditional behavioural theory, and will certainly assist the guiding of conservation efforts.
•Technological advances provide new insights into marine mammal behaviour.•We highlight four areas of technological advances.•Aerial systems, radiotelemetry, passive acoustics and acoustic recording tags.•These methods allow comparison between marine mammal behaviour and theory.•These crucial data are helping to inform conservation applications.
Among the many factors that influence the cardiovascular adjustments of marine mammals is the act of respiration at the surface, which facilitates rapid gas exchange and tissue re-perfusion between ...dives. We measured heart rate (
) in six adult male bottlenose dolphins (
) spontaneously breathing at the surface to quantify the relationship between respiration and
, and compared this with
during submerged breath-holds. We found that dolphins exhibit a pronounced respiratory sinus arrhythmia (RSA) during surface breathing, resulting in a rapid increase in
after a breath followed by a gradual decrease over the following 15-20 s to a steady
that is maintained until the following breath. RSA resulted in a maximum instantaneous
(i
) of 87.4±13.6 beats min
and a minimum i
of 56.8±14.8 beats min
, and the degree of RSA was positively correlated with the inter-breath interval (IBI). The minimum i
during 2 min submerged breath-holds where dolphins exhibited submersion bradycardia (36.4±9.0 beats min
) was lower than the minimum i
observed during an average IBI; however, during IBIs longer than 30 s, the minimum i
(38.7±10.6 beats min
) was not significantly different from that during 2 min breath-holds. These results demonstrate that the
patterns observed during submerged breath-holds are similar to those resulting from RSA during an extended IBI. Here, we highlight the importance of RSA in influencing
variability and emphasize the need to understand its relationship to submersion bradycardia.
1. Since the last thorough review of the effects of anthropogenic noise on cetaceans in 1995, a substantial number of research reports has been published and our ability to document response(s), or ...the lack thereof, has improved. While rigorous measurement of responses remains important, there is an increased need to interpret observed actions in the context of population-level consequences and acceptable exposure levels. There has been little change in the sources of noise, with the notable addition of noise from wind farms and novel acoustic deterrent and harassment devices (ADDs/AHDs). Overall, the noise sources of primary concern are ships, seismic exploration, sonars of all types and some AHDs. 2. Responses to noise fall into three main categories: behavioural, acoustic and physiological. We reviewed reports of the first two exhaustively, reviewing all peer-reviewed literature since 1995 with exceptions only for emerging subjects. Furthermore, we fully review only those studies for which received sound characteristics (amplitude and frequency) are reported, because interpreting what elicits responses or lack of responses is impossible without this exposure information. Behavioural responses include changes in surfacing, diving and heading patterns. Acoustic responses include changes in type or timing of vocalizations relative to the noise source. For physiological responses we address the issues of auditory threshold shifts and 'stress', albeit in a more limited capacity; a thorough review of physiological consequences is beyond the scope of this paper. 3. Overall, we found significant progress in the documentation of responses of cetaceans to various noise sources. However, we are concerned about the lack of investigation into the potential effects of prevalent noise sources such as commercial sonars, depth finders and fisheries acoustics gear. Furthermore, we were surprised at the number of experiments that failed to report any information about the sound exposure experienced by their experimental subjects. Conducting experiments with cetaceans is challenging and opportunities are limited, so use of the latter should be maximized and include rigorous measurements and or modelling of exposure.
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