MEES Theses and Dissertations

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Browsing MEES Theses and Dissertations by Subject "Acoustics"

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    Ambient sound affects movement and calls of bottlenose dolphins
    (2021) Fandel, Amber Desneige; Bailey, Helen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Abundant oceanic shipping and more frequent and intense storms are increasing sound levels in aquatic habitats. Understanding how changing soundscapes affect protected species, especially those that use sound to communicate and navigate, is critical. This study utilizes passive acoustic monitoring to investigate the effects of changing ambient sound levels on bottlenose dolphin (Tursiops truncatus) movements, spatial utilization, and social calls in the Mid-Atlantic Bight, USA. By localizing dolphin whistles, I determined that their habitat use changed under higher ambient sound levels and that these elevated sound levels caused dolphins to alter the acoustic characteristics of their calls. The acoustic characteristics of individually identifiable calls (signature whistles) also varied between the sites and regions in which they were recorded. As changes in the underwater soundscape continue in the future, these findings will help inform resource managers about how protected marine mammals may be affected by anthropogenic activities and sounds.
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    SPATIAL AND TEMPORAL DYNAMICS OF THE CHESAPEAKE BAY SEA NETTLE
    (2018) Shahrestani, Suzan; Bi, Hongsheng; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The jellyfish Chrysaora chesapeakei forms large summer blooms in Chesapeake Bay, and has substantial ecological and economic impacts on local ecosystems. Limited information on this species is mostly due to difficulties collecting spatial information on jellyfish in dynamic coastal ecosystems. Spatial gaps of C. chesapeakei were addressed by applying a multi-scale approach across life stages and within a source-sink context, reflected by the ecology and habitat utilization of C. chesapeakei. An Adaptive Resolution Imaging System (ARIS, SoundMetrics, Inc.) was used to collect high-resolution data on medusae in 2016 and 2017, within a Patuxent River waterscape. Polyp settlement plates were deployed at eight sites to understand the distributional range of the sessile benthic stage in Chesapeake Bay, but polyps successfully overwintered at only one of the sites, indicating that settlement alone was insufficient to explain C. chesapeakei dispersal to new habitat. Using high-resolution sonar data, a multi-scale spatial analysis was conducted to understand medusae dispersion and abundance. Medusae were three times more abundant in 2017 than in 2016. However, differences in water-column concentration were not apparent at the fine-scale (<5m) where medusae were randomly dispersed in both years. At the mesoscale (10km), spatial dependency was observed in both years, with more transport of jellyfish to dispersal habitat in the high-abundance year (2017). Overall, polyp settlement and overwintering survival in potential habitat seem to control the spatial distribution of C. chesapeakei at the Bay-wide scale while medusae appear responsible for mesoscale dispersal to new habitat, demonstrating high dispersal to sink habitat in a high-density year and low dispersal in a low-density year.