Soundscapes of the Southern Ocean: Passive Acoustic Monitoring in the Weddell Sea
The Southern Ocean provides an important habitat for marine mammals, both residential and migratory, yet long term studies of their habitat usage are hampered by the region’s seasonal inaccessibility. To overcome this problem, two autonomous underwater passive acoustic recorders were deployed in the...
| Main Authors: | , , , , , , |
|---|---|
| Format: | Conference Object |
| Language: | unknown |
| Published: |
2013
|
| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/32687/ https://epic.awi.de/id/eprint/32687/1/Soundscapes-of-the-southern-ocean.pdf https://hdl.handle.net/10013/epic.41248 https://hdl.handle.net/10013/epic.41248.d001 |
| Summary: | The Southern Ocean provides an important habitat for marine mammals, both residential and migratory, yet long term studies of their habitat usage are hampered by the region’s seasonal inaccessibility. To overcome this problem, two autonomous underwater passive acoustic recorders were deployed in the Weddell Sea in 2008 to collect multiyear passive acoustic data. The recorders were retrieved in 2010 and the acoustic recordings were analyzed in terms of broad- and narrow-band noise. Noise in this context is defined as the acoustic energy not assignable to a specific singular source. It comprises both biotic as well as abiotic components. Noise levels were determined by selecting the quietest 10 s of each 5 min recording to exclude energetic contributions from nearby singular acoustic sources. The respective sound pressure levels (SPL) and spectra were correlated with time series of environmental covariates. The ambient noise levels of both recorders were found to be highly variable in time, ranging from 102 to 115 dB re 1 μPa (broadband SPL 5th and 95th percentile), and were correlated with the sea ice cover and wind speed. The annual variation of the ice cover caused a bimodal distribution of broadband SPL. In winter the SPL mode was 106 dB re 1 μPa. By contrast, storms over the open ocean in summer resulted in an SPL mode of 111 dB dB re 1 μPa. Variation in the ambient noise spectra could be correlated to wind speed and ice coverage. The acoustic presence of several mysticete (Antarctic blue whale, Balaenoptera musculus intermedia, fin whale, Balaenoptera physalus) and pinniped (leopard seal, Hydrurga leptonyx, crabeater seal, Lobodon carcinophaga) species created distinct bands in the spectra that contributed considerably to ambient noise levels. Comparison of the timing of these noise bands between the two acoustic data sets revealed offsets in the occurrence of acoustic activity between both recorders, suggestive of marine mammal latitudinal migration. At 66°S (the northern recorder position) fin whales were ... |
|---|