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      Underwater Chatter for the Win: A First Assessment of Underwater Soundscapes in Two Bays along the Eastern Cape Coast of South Africa

      , ,
      Journal of Marine Science and Engineering
      MDPI AG

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          Abstract

          In 2014, the South African government launched ‘Operation Phakisa’ under which port developments play a significant role in supporting ocean economic growth. These developments will likely increase vessel traffic to and from South African ports, making it imperative to monitor for changes in underwater sound budgets with potential negative effects on marine life. However, no soundscape studies have been conducted around South Africa, resulting in an absence of baseline measurements. This study provides a first description of the underwater soundscape in St. Francis Bay and Algoa Bay, Eastern Cape. Soundscape measurements identified major soundscape contributors, temporal patterns in broadband sound levels, and underlying environmental drivers. Applicability of modelled vessel noise and wind noise maps to predict large-scale spatial variation in sound budgets was assessed. Our study shows that sounds from biological sources and wind dominated at all recording sites, with fish choruses driving temporal patterns as a function of time of year and position of the sun. Sound from vessels was present at all sites but most notable in long-term spectral levels measured in Algoa Bay. Sound propagation models predicted a further increase in the contribution of vessel noise towards shipping lanes and east Algoa Bay. Our study provides a building block to monitor for shifts in sound budgets and temporal patterns in these two bays under a developing ocean economy. Furthermore, our study raises concerns that vessel noise is likely a significant contributor in shallow waters elsewhere along the South African coast where vessel density is known to be higher (i.e., Durban and Cape Town).

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          The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2)

          The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) is the latest atmospheric reanalysis of the modern satellite era produced by NASA’s Global Modeling and Assimilation Office (GMAO). MERRA-2 assimilates observation types not available to its predecessor, MERRA, and includes updates to the Goddard Earth Observing System (GEOS) model and analysis scheme so as to provide a viable ongoing climate analysis beyond MERRA’s terminus. While addressing known limitations of MERRA, MERRA-2 is also intended to be a development milestone for a future integrated Earth system analysis (IESA) currently under development at GMAO. This paper provides an overview of the MERRA-2 system and various performance metrics. Among the advances in MERRA-2 relevant to IESA are the assimilation of aerosol observations, several improvements to the representation of the stratosphere including ozone, and improved representations of cryospheric processes. Other improvements in the quality of MERRA-2 compared with MERRA include the reduction of some spurious trends and jumps related to changes in the observing system, and reduced biases and imbalances in aspects of the water cycle. Remaining deficiencies are also identified. Production of MERRA-2 began in June 2014 in four processing streams, and converged to a single near-real time stream in mid 2015. MERRA-2 products are accessible online through the NASA Goddard Earth Sciences Data Information Services Center (GES DISC).
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            The Problem of Pattern and Scale in Ecology: The Robert H. MacArthur Award Lecture

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              The soundscape of the Anthropocene ocean

              Oceans have become substantially noisier since the Industrial Revolution. Shipping, resource exploration, and infrastructure development have increased the anthrophony (sounds generated by human activities), whereas the biophony (sounds of biological origin) has been reduced by hunting, fishing, and habitat degradation. Climate change is affecting geophony (abiotic, natural sounds). Existing evidence shows that anthrophony affects marine animals at multiple levels, including their behavior, physiology, and, in extreme cases, survival. This should prompt management actions to deploy existing solutions to reduce noise levels in the ocean, thereby allowing marine animals to reestablish their use of ocean sound as a central ecological trait in a healthy ocean.
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                Author and article information

                Contributors
                (View ORCID Profile)
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                Journal
                Journal of Marine Science and Engineering
                JMSE
                MDPI AG
                2077-1312
                June 2022
                May 28 2022
                : 10
                : 6
                : 746
                Article
                10.3390/jmse10060746
                d19b7635-73da-450c-b7fc-a22f3f51b2da
                © 2022

                https://creativecommons.org/licenses/by/4.0/

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