Developing an Underwater Sound Recorder: The Long and Short (Time) of It...
TL;DR: A brief history of the sound recorders’ development and characteristics is presented, some examples of the information they have provided and future direction for their next generation are presented.
Abstract: Passive acoustic recording of marine noise has advanced considerably over recent years. For a long time, a lack of widely available technology limited the acquisition of long-term acoustic data sets to a small number of large, cabled installations mostly restricted to military use. For other users, recordings were limited by the available technology to short snapshots of minutes to possibly days of data at a time. As technology has improved, passive acoustic monitoring has shown marine soundscapes are filled with biotic and abiotic sounds that occur on a range of often unpredictable timescales. Thus, snapshot recordings can lead to biased data. In 1999, the Centre for Marine Science and Technology, together with Australia’s Defence Science and Technology Organisation, began developing remote underwater sound recorders to increase the duration and quality of recordings. As time passed, the sound recorders were developed significantly, have been deployed over 600 times at a variety of Australian and international locations and have identified a plethora of biological, geophysical and anthropogenic sound sources. This paper presents a brief history of the recorders’ development and characteristics, some examples of the information they have provided and future direction for their next generation.
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TL;DR: An overview of the literature on vessel noise impacts on marine mammals shows that studies have been patchy in terms of their coverage of species, habitats, vessel types, and types of impact investigated, and the biological significance of observed responses is mostly unknown.
Abstract: The number of marine watercraft is on the rise—from private boats in coastal areas to commercial ships crossing oceans. A concomitant increase in underwater noise has been reported in several regions around the globe. Given the important role sound plays in the life functions of marine mammals, research on the potential effects of vessel noise has grown—in particular since the year 2000. We provide an overview of this literature, showing that studies have been patchy in terms of their coverage of species, habitats, vessel types, and types of impact investigated. The documented effects include behavioural and acoustic responses, auditory masking, and stress. We identify knowledge gaps: There appears a bias to more easily accessible species (i.e., bottlenose dolphins and humpback whales), whereas there is a paucity of literature addressing vessel noise impacts on river dolphins, even though some of these species experience chronic noise from boats. Similarly, little is known about the potential effects of ship noise on pelagic and deep-diving marine mammals, even though ship noise is focussed in a downward direction, reaching great depth at little acoustic loss and potentially coupling into sound propagation channels in which sound may transmit over long ranges. We explain the fundamental concepts involved in the generation and propagation of vessel noise and point out common problems with both physics and biology: Recordings of ship noise might be affected by unidentified artefacts, and noise exposure can be both under- and over-estimated by tens of decibel if the local sound propagation conditions are not considered. The lack of anthropogenic (e.g., different vessel types), environmental (e.g., different sea states or presence/absence of prey), and biological (e.g., different demographics) controls is a common problem, as is a lack of understanding what constitutes the ‘normal’ range of behaviours. Last but not least, the biological significance of observed responses is mostly unknown. Moving forward, standards on study design, data analysis, and reporting are badly needed so that results are comparable (across space and time) and so that data can be synthesised to address the grand unknowns: the role of context and the consequences of chronic exposures.
171 citations
TL;DR: This work provides a summary of the brief history of using passive acoustics to assess marine biodiversity and community structure, a critical assessment of the challenges faced, and outline recommended practices and considerations for acoustic biodiversity measurements.
Abstract: Ecosystems and the communities they support are changing at alarmingly rapid rates. Tracking species diversity is vital to managing these stressed habitats. Yet, quantifying and monitoring biodiversity is often challenging, especially in ocean habitats. Given that many animals make sounds, these cues travel efficiently under water, and emerging technologies are increasingly cost-effective, passive acoustics (a long-standing ocean observation method) is now a potential means of quantifying and monitoring marine biodiversity. Properly applying acoustics for biodiversity assessments is vital. Our goal here is to provide a timely consideration of emerging methods using passive acoustics to measure marine biodiversity. We provide a summary of the brief history of using passive acoustics to assess marine biodiversity and community structure, a critical assessment of the challenges faced, and outline recommended practices and considerations for acoustic biodiversity measurements. We focused on temperate and tropical seas, where much of the acoustic biodiversity work has been conducted. Overall, we suggest a cautious approach to applying current acoustic indices to assess marine biodiversity. Key needs are preliminary data and sampling sufficiently to capture the patterns and variability of a habitat. Yet with new analytical tools including source separation and supervised machine learning, there is substantial promise in marine acoustic diversity assessment methods.
63 citations
TL;DR: Six fish choruses identified around Lizard Island exhibited distinctive spatial and temporal patterns from 2014 to 2016, indicating that particular sites may represent important habitat for fish species, such as fish spawning aggregations sites.
Abstract: The coral reefs surrounding Lizard Island in the Great Barrier Reef have a diverse soundscape that contains an array of bioacoustic phenomena, notably choruses produced by fishes. Six fish choruses identified around Lizard Island exhibited distinctive spatial and temporal patterns from 2014 to 2016. Several choruses displayed site fidelity, indicating that particular sites may represent important habitat for fish species, such as fish spawning aggregations sites. The choruses displayed a broad range of periodicities, from diel to annual, which provides new insights into the ecology of vocalising reef fish species and the surrounding ecosystem. All choruses were affected by one or more environmental variables including temperature and moonlight, the latter of which had a significant influence on the timing and received sound levels. These findings highlight the utility of passive acoustic tools for long-term monitoring and management of coral reefs, which is highly relevant in light of recent global disturbance events, particularly coral bleaching.
23 citations
TL;DR: In this article, an upwelling index of seasonally integrated seabed water temperature across seven seasons was used to predict the seasonal variance in whale presence and the strength of this correlation was reduced by population growth of whales.
Abstract: Passive acoustic recorders set around Australia since 2004 have been used to study blue whales Calls from New Zealand pygmy blue whales occur predominantly eastward of Bass Strait (1458° E), calls from Eastern Indian Ocean pygmy blue whales (EIO PB) west of Bass Strait, while Antarctic blue whale calls occur along the entire southern Australian coast The only location all calls have been detected within a short space of time in the same season is Bass Strait, where inter-species mixing commonly occurs The EIO PB shows three migratory stages: "southbound" from November to January during which whales travel down the Western Australian coast; "southern Australian" where animals spread across the Indian and Southern Oceans spanning longitudes from 74° to 146° E down to at least a latitude of 55° S searching for food and feeding; then a northern migration where they return north to Indonesian waters post April-August Along the southern Australian coastline EIO PB whales are more often detected towards the east, favouring an area where late summer to autumn upwelling occurs mostly over ~ 134-145° E longitude Receivers on the shelf break south of Portland (1412° E) showed 10–181 times greater EIO PB whale calling when integrated over their three month season than at sites located around the Great Australian Bight to the west Within a season the Portland site did not show consistency of EIO PB whale presence or number of calling individuals, but when the number of calling individuals was integrated across a season and correlated with an upwelling index of seasonally integrated seabed water temperature across seven seasons, the upwelling index predicted 83% of the seasonal variance in whale presence The strength of this correlation will be reduced by population growth of whales By correcting EIO PB whale call rates for a variety of population growth rate values, we found a 43% growth rate for the population proportion visiting the Portland area, gave the maximum regression, correlation coefficient of r2= 90% Time averaged levels of squared pressure produced at the upper chorus frequency of the Antarctic blue whale z-call and received via deep sound channel propagation at Portland showed a 126% increase rate This is indicative of population growth rate for Antarctic blue whales using waters south of Australia, although the value of using pressure squared in this fashion and the assumptions underlying the technique need to be explored
21 citations
TL;DR: Changes in respiration rate were of a similar magnitude to changes in baseline groups being joined by other animals suggesting any change group energetics was within their behavioural repertoire, and the reduced progression southwards in response to the active treatments, was below typical migratory speeds.
Abstract: Despite concerns on the effects of noise from seismic survey airguns on marine organisms, there remains uncertainty as to the biological significance of any response. This study quantifies and interprets the response of migrating humpback whales (Megaptera novaeangliae) to a 3130 in3 (51.3l) commercial airgun array. We compare the behavioural responses to active trials (array operational; n = 34 whale groups), with responses to control trials (source vessel towing the array while silent; n = 33) and baseline studies of normal behaviour in the absence of the vessel (n = 85). No abnormal behaviours were recorded during the trials. However, in response to the active seismic array and the controls, the whales displayed changes in behaviour. Changes in respiration rate were of a similar magnitude to changes in baseline groups being joined by other animals suggesting any change group energetics was within their behavioural repertoire. However, the reduced progression southwards in response to the active treatments, for some cohorts, was below typical migratory speeds. This response was more likely to occur within 4 km from the array at received levels over 135 dB re 1 µPa2s.
20 citations
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TL;DR: In this article, correlations between indices of the Southern Oscillation (SO) and areal average rainfall for 107 Australian rainfall districts for the period December 1932 to November 1974 have been calculated.
Abstract: Correlations between indices of the Southern Oscillation (SO) and areal average rainfall for 107 Australian rainfall districts for the period December 1932 to November 1974 have been calculated. Simultaneous correlations between the SO and rainfall show a clear annual cycle with the best relationship occurring in spring (September-November). The season with the weakest relationship is summer (December-February). In all seasons, seasonal rainfalls in some parts of Australia are significantly correlated with the SO in the preceding season. The strongest lag correlations occur with spring rainfall, which for some areas is also significantly correlated with the SO two seasons (six months) earlier. Correlations were also calculated with the data divided into two subseries from 1932 to 1953 and from 1954 to 1974. These calculations suggest a westward shift with time of the correlation pattern, associated with substantial changes in the magnitude of the correlations in some areas. Some speculations on t...
604 citations
TL;DR: McVicar et al. as discussed by the authors developed Australia-wide 0.01 resolution daily u grids by interpolating measurements from an expanded anemometer network for 1975-2006.
Abstract: [1] Near-surface wind speeds (u) measured by terrestrial anemometers show declines (a ‘stilling’) at a range of midlatitude sites, but two gridded u datasets (a NCEP/NCAR reanalysis output and a surface-pressure-based u model) have not reproduced the stilling observed at Australian stations. We developed Australia-wide 0.01 resolution daily u grids by interpolating measurements from an expanded anemometer network for 1975–2006. These new grids represented the magnitude and spatialvariability of observed u trends, whereas grids from reanalysis systems (NCEP/NCAR, NCEP/DOE and ERA40) essentially did not, even when minimising the sea-breeze impact. For these new grids, the Australianaveraged u trend for 1975–2006 was 0.009 m s 1 a 1 (agreeing with earlier site-based studies) with stilling over 88% of the land-surface. This new dataset can be used in numerous environmental applications, including benchmarking general circulation models to improve the representation of key parameters that govern u estimation. The methodology implemented here can be applied globally. Citation: McVicar, T. R., T. G. Van Niel, L. T. Li, M. L. Roderick, D. P. Rayner, L. Ricciardulli, and R. J. Donohue (2008), Wind speed climatology and trends for Australia, 1975 – 2006: Capturing the stilling phenomenon and comparison with near-surface reanalysis output, Geophys. Res. Lett., 35, L20403,
370 citations
TL;DR: Evidence is provided that there are significant differ- ences in the spectral and temporal composition of ambient sound associated with different coastal habitat types over relatively short spatial scales.
Abstract: There is evidence that ambient underwater sound is used by some pelagic larval reef fishes and decapods as a guide to direct them toward coastal areas. It would be advantageous to these organisms if they were also able to use sound to remotely identify suitable settlement habitats. However, it is unknown whether different coastal habitats produce different sounds that would be capable of providing distinctive cues for larvae. This study identified marked differences in the char- acteristics of ambient underwater sound at 3 distinct types of coastal habitat: a macroalgal-dominated reef, a sea urchin-dominated reef, and a sandy beach. The sea urchin-dominated reef habitat pro- duced sound that was significantly more intense overall in a biologically important frequency band (800 to 2500 Hz), compared with that from macroalgal-dominated reefs and beach habitats. The sound produced by snapping shrimp also exhibited marked differences among habitat types, with the sea urchin-dominated reef having significantly more snaps than the macroalgal-dominated reef or beach habitat. Many of the differences in the sound produced by the 2 reef habitats became more apparent at dusk compared with noon. This study provides evidence that there are significant differ- ences in the spectral and temporal composition of ambient sound associated with different coastal habitat types over relatively short spatial scales. An acoustic cue that conveys both directional and habitat quality information that is transmitted considerable distances offshore would have the poten- tial to be of immense value to the pelagic larval stage of a coastal organism attempting to remotely locate a suitable habitat in which to settle.
179 citations
TL;DR: In this article, observations of biological choruses in the ambient noise of tropical waters of the east Indian Ocean, the west Pacific Ocean, and the Timor Sea near Australia are described.
Abstract: Observations of biological choruses in the ambient noise of tropical waters of the east Indian Ocean, the west Pacific Ocean, and the Timor Sea near Australia are described. These choruses occurred for a few hours at a time and had most energy at frequencies between 400 Hz and 4 kHz, with spectral peaks mainly at 800 Hz, 1.6–2 kHz, and 3 kHz. During choruses, noise spectrum levels rose up to 30 dB above the usual background noise. Statistics of occurrence of the evening choruses indicate that they would occur on most, if not all evenings at the locations of measurement and are probably fairly widespread in and near shallow waters of the region. As well as these regular evening choruses, there were also transitory choruses which were observed at various times of day over periods of a few days but not before or after. Possible sources of the choruses are discussed. There are at least three sources of the regular evening choruses, possibly fish or sea urchins. Some of the transitory choruses, spectrally similar to the regular choruses, were composed of intense clicking sounds, apparently from sperm whales.
120 citations
TL;DR: In this article, the authors used passive acoustic data collected from the Integrated Marine Observing System (IMOS) at Rottnest Island in Western Australia to characterize and quantify the marine soundscape between 5 and 3000 Hz.
95 citations