Equipping an underwater glider with a new echosounder to explore ocean ecosystems

Abstract

Mobile autonomous platforms are revolutionizing our understanding of ocean systems by providing a solution for the four-dimensional observation problem faced in the ocean. The sensors commonly used in autonomous platforms, however, leave a large gap in our observations of the food chain between primary producers and large predators. Echosounders have the potential to fill this gap. Here, we present details of a new, commercially available quantitative scientific echosounder specifically designed to meet the challenges of deployment in autonomous platforms, including those of relatively low power and small size, while providing data comparable to systems deployed from ships. We detail the integration into a Slocum glider of this echosounder and both upwardand downward-looking transducers to provide guidance for those considering similar efforts. We also identify key features of the system and the challenges that must be overcome to ensure collection of high-quality data. The most important feature of the integrated glider is that it carries instruments capable of providing depth profiles of bio-optical and environmental variables that are synoptic with the echosounder data. On a dive-by-dive basis, we can use these co-located data to quantify relationships between the acoustic, bio-optical, and environmental data. A field deployment of the echosounder-equipped glider elucidated the processes driving diel migration in zooplankton and nekton in Monterey Bay, emphasizing the novel science questions that can be addressed using contemporary means of accessing the sea and new, integrated tools for describing the habitat and its inhabitants.

Arctic Marine Data Collection Using Oceanic Gliders: Providing Ecological Context to Cetacean Vocalizations

“…More recently, such sensors have been integrated onto gliders that can measure presence, abundance, and distribution, of higher trophic level organisms, e.g., fish and cetaceans (Baumgartner and Fratantoni, 2008;Ferguson et al, 2010;Klinck et al, 2012;Meyer-Gutbrod et al, 2012;Baumgartner et al, 2013;Marques et al, 2013;Send et al, 2013;Suberg et al, 2014;Cauchy et al, 2020). However, only a few studies have focused on deployments with simultaneous measurements of physical and biological components using gliders (e.g., Suberg et al, 2014;Benoit-Bird et al, 2018), particularly in terms of monitoring higher trophic organisms such as cetaceans. The purpose of this work is to show the capabilities of gliders in oceanic deployments and investigate cetacean ecology and background noise, while concurrently recording seawater characteristics and lower trophic-level features.…”

Autonomous vehicle surveys indicate that flow reversals retain juvenile fishes in a highly advective high‐latitude ecosystem

“…Traditionally, acoustic surveys have relied on trawl sampling of species and size composition to convert acoustic backscatter into abundance estimates (Simmonds and MacLennan 2005). Recent advances in the integration of echosounders into autonomous platforms have increased our ability to measure acoustic backscatter remotely over long periods (Greene et al 2014; Mordy et al 2017; Benoit‐Bird et al 2018; Ohman et al 2019). We used the endurance of the saildrones to collect a large number of acoustic observations over an extended period of time which would have been prohibitively expensive and logistically difficult using ships.…”

Globally Consistent Quantitative Observations of Planktonic Ecosystems

“…Multi-sensor fusion efforts have the potential for wider application through the use of autonomous platforms, which resolves the limited range issue of high frequency acoustics. While bio-acoustic instruments have only begun to be deployed over long periods of time on autonomous platforms (Powell and Ohman, 2015a,b), we expect that strong development and wide use of these instruments will be seen in the next decade (Benoit-Bird et al, 2018).…”