Dynamics of soundscape in a shallow water marine environment: A study of the habitat of the Indo-Pacific humpback dolphin

Abstract

The underwater acoustic field is an important ecological element for many aquatic animals. This research examines the soundscape of a critically endangered Indo-Pacific humpback dolphin population in the shallow water environment off the west coast of Taiwan. Underwater acoustic recordings were conducted between late spring and late fall in 2012 at Yunlin (YL), which is close to a shipping lane, and Waisanding (WS), which is relatively pristine. Site-specific analyses were performed on the dynamics of the temporal and spectral acoustic characteristics for both locations. The results highlight the dynamics of the soundscape in two major octave bands: 150-300 Hz and 1.2-2.4 kHz. The acoustic energy in the former frequency band is mainly associated with passing container vessels near YL, while the latter frequency band is from sonic fish chorus at nighttime in both recording sites. In addition, large variation of low frequency acoustic energy throughout the study period was noticed at WS, where the water depths ranged between 1.5 and 4.5 m depending on tidal cycle. This phenomenon suggests that besides certain sound sources in the environment, the coastal soundscape may also be influenced by its local bathymetry and the dynamics of the physical environment.

Indo-Pacific humpback dolphin occurrence north of Lantau Island, Hong Kong, based on year-round passive acoustic monitoring

“…In the present study it cannot be determined if low detection rates at locations and periods with high noise indicate avoidance, lower rates of signaling, or lower detectability of signals. However, high noise levels from shipping and other anthropogenic activities are important habitat variables to monitor, as they may have adverse impacts on humpback dolphins either in the acute sense or over the long term (e.g., Wang et al, 2014;Guan et al, 2015;Li et al, 2015).…”

Improving biodiversity assessment via unsupervised separation of biological sounds from long-duration recordings

“…In this study, we primarily used a median power spectrum to demonstrate the application of PC-NMF. With a long-term spectrogram, a biological chorus, which occurs periodically, can be easily observed 31 . Below, we describe the methodology of using PC-NMF to separate biological sounds with strong periodicity from a long-term spectrogram.…”

Spatial and Temporal Variation in the Acoustic Habitat of Bottlenose Dolphins (Tursiops aduncus) within a Highly Urbanized Estuary

“…This agrees with findings of previous studies. Soundscape studies in New Zealand (Radford et al, 2010), Pacific Panama (Kennedy et al, 2010), the U.S. east coast (Rice et al, 2014) and Taiwan (Guan et al, 2015) have also noted site-specific sound fields at locations several kilometers apart, generally as the result of biotic or anthropogenic activities. Additionally, there was considerable temporal variation within sites.…”

“…Given that the underwater soundscape contains sounds driven by weather conditions, environmental variables, and the presence of both marine fauna and human activities, it follows that an acoustic habitat will not be static in its composition. Consequently, whilst generalizations may be made about the acoustic characteristics of some underwater environments, many marine habitats will also display spatial and temporal variability in their acoustic components (Parks et al, 2009;Radford et al, 2010;McWilliam and Hawkins, 2013;Rice et al, 2014;Erbe et al, 2015;Guan et al, 2015;Marley et al, 2016a). Thus, to understand the role acoustic characteristics may play in driving the habitat use of cetaceans, there is a need to quantify the marine soundscape over large areas and across long periods of time.…”

“…Such baseline studies involve describing the habitat in terms of prominent sound sources, levels of acoustic energy in particular frequency bands, and patterns of ambient and anthropogenic noise (e.g., Parks et al, 2009;Erbe et al, 2014;Rice et al, 2014;Guan et al, 2015). Once identified, the acoustic characteristics of critical cetacean habitats can be further examined to determine the potential impact of man-made noise.…”