A system of coordinated autonomous robots for Lagrangian studies of microbes in the oceanic deep chlorophyll maximum

Zhang, Yanwu; Ryan, John P.; Hobson, Brett; Kieft, Brian; Romano, Anna E.; Barone, Benedetto; Preston, Christina M.; Roman, Brent; Raanan, Ben Yair; Pargett, Douglas; Dugenne, Mathilde; White, Angelicque E.; Freitas, Fernanda Henderikx; Poulos, Steve; Wilson, Samuel T.; DeLong, Edward F.; Karl, David M.; Birch, James M.; Bellingham, James; Scholin, Christopher A.

doi:10.1126/scirobotics.abb9138

Cited by 40 publications

(29 citation statements)

References 71 publications

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“…The ability to generate energy-efficient trajectories that take advantage of the inherent motions of a background flow field has significant implications for monitoring large bodies of water with intelligent mobile sensors [ 1 – 3 ], furthering our understanding of the climate and natural ecosystems [ 4 – 6 ]. Developments in this area also present economic opportunities for cost reduction in industries that rely heavily on maritime transport and shipping.…”

Section: Introductionmentioning

confidence: 99%

Finite-horizon, energy-efficient trajectories in unsteady flows

2022

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Intelligent mobile sensors, such as uninhabited aerial or underwater vehicles, are becoming prevalent in environmental sensing and monitoring applications. These active sensing platforms operate in unsteady fluid flows, including windy urban environments, hurricanes and ocean currents. Often constrained in their actuation capabilities, the dynamics of these mobile sensors depend strongly on the background flow, making their deployment and control particularly challenging. Therefore, efficient trajectory planning with partial knowledge about the background flow is essential for teams of mobile sensors to adaptively sense and monitor their environments. In this work, we investigate the use of finite-horizon model predictive control (MPC) for the energy-efficient trajectory planning of an active mobile sensor in an unsteady fluid flow field. We uncover connections between trajectories optimized over a finite-time horizon and finite-time Lyapunov exponents of the background flow, confirming that energy-efficient trajectories exploit invariant coherent structures in the flow. We demonstrate our findings on the unsteady double gyre vector field, which is a canonical model for chaotic mixing in the ocean. We present an exhaustive search through critical MPC parameters including the prediction horizon, maximum sensor actuation, and relative penalty on the accumulated state error and actuation effort. We find that even relatively short prediction horizons can often yield energy-efficient trajectories. We also explore these connections on a three-dimensional flow and ocean flow data from the Gulf of Mexico. These results are promising for the adaptive planning of energy-efficient trajectories for swarms of mobile sensors in distributed sensing and monitoring.

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Section: Introductionmentioning

confidence: 99%

Finite-horizon, energy-efficient trajectories in unsteady flows

2022

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“…The tracking capability enables observation of phytoplankton communities within a patch while it is moving. In that moving frame of reference, simultaneous observations of environmental conditions capture the processes that drive changes in the phytoplankton community within the patch, similar to a Lagrangian study of microbial communities in the deep chlorophyll maximum layer in an open-ocean eddy [21]. These methods advance understanding of the factors that cause the growth and decline of marine phytoplankton populations.…”

Section: Discussionmentioning

confidence: 99%

“…While tracking a phytoplankton patch, an AUV can make some of the essential environmental measurements required to understand phytoplankton ecology. Additionally, a Tethys-class LRAUV can carry a robotic autonomous molecular analytical instrument to acquire samples and then preserve or process those samples in real time [21], [22]. Such augmentation of onboard sensing is an important technological capability for advancing plankton research.…”

Section: Discussionmentioning

confidence: 99%

Finding and Tracking a Phytoplankton Patch by a Long-Range Autonomous Underwater Vehicle

Zhang

Godin

Kieft

et al. 2022

IEEE J. Oceanic Eng.

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Phytoplankton (microscopic algae) play an important role in marine ecology. Resulting from a combination of physical, chemical, and biological processes, the distribution of phytoplankton is patchy, particularly in coastal marine ecosystems. Patches of high chlorophyll represent areas where enhanced primary productivity and biogeochemical cycling can occur. The scientific goal is to place observations within these biological hotspots to enable more extensive characterization of the environment and plankton populations. Aerial or satellite remote sensing can detect optical signal originating from phytoplankton within a limited depth range only near the ocean surface, and application of remote sensing is limited by atmospheric clarity. To observe the development of patchy phytoplankton communities in situ, we need the ability to locate and track individual patches. In this article, we present a method for an autonomous underwater vehicle (AUV) to autonomously find and climb on a positive horizontal gradient of chlorophyll to locate and track a phytoplankton patch. In two experiments in 2021, a Tethys-class long-range AUV autonomously located and tracked phytoplankton patches in southern Monterey Bay, CA, USA. The experiments demonstrated effectiveness of the method and pointed to the need for increased onboard adaptiveness in autonomous patch finding and tracking.

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“…Bioregions have also been defined in offshore Australian (Department of the Environment and Heritage, 2006), UK (Chaniotis et al, 2020), South African (Livingstone et al, 2018) and Canadian waters (Burt et al, 2018). Multiple national and international seabed mapping projects are underway, including efforts to map the entire seafloor by 2030 (Wölfl et al, 2019); technology innovations promise to deliver increasingly accurate biophysical data (e.g., Zhang et al, 2021). This ongoing global acquisition of data, together with sophisticated theoretical and modelling approaches, invites both a flexible and adaptive management approach that can incorporate new information within a systematic planning framework.…”

Section: Monitoringmentioning

confidence: 99%

How to Meet New Global Targets in the Offshore Realms: Biophysical Guidelines for Offshore Networks of No-Take Marine Protected Areas

et al. 2021

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Networks of no-take marine protected areas (MPAs), where all extractive activities are prohibited, are the most effective tool to directly protect marine ecosystems from destructive and unsustainable human activities. No-take MPAs and MPA networks have been globally implemented in coastal seas, and their success has been significantly enhanced where science-based biophysical guidelines have informed their design. Increasingly, as human pressure on marine ecosystems is expanding further offshore, governments are establishing offshore MPAs—some very large—or MPA networks. Globally, there are growing calls from scientists, non-government organisations, and national governments to set global conservation targets upwards of 30%. Given that most of the ocean is found either in the high seas or offshore within national Exclusive Economic Zones, large offshore MPAs or networks of MPAs must be a major component of these global targets for ocean protection. However, without adequate design, these offshore MPAs risk being placed to minimise conflict with economic interests, rather than to maximise biodiversity protection. This paper describes detailed biophysical guidelines that managers can use to design effective networks of no-take MPAs in offshore environments. We conducted a systematic review of existing biophysical design guidelines for networks of MPAs in coastal seas, and found consistent elements relating to size, shape, connectivity, timeframes, and representation of biophysical features. However, few of the guidelines are tailored to offshore environments, and few of the large offshore MPAs currently in place were designed systematically. We discuss how the common inshore design guidelines should be revised to be responsive to the characteristics of offshore ecosystems, including giving consideration of issues of scale, data availability, and uncertainty. We propose 10 biophysical guidelines that can be used to systematically design offshore networks of MPAs which will also contribute to the global goal of at least 30% protection globally. Finally, we offer three priority guidelines that reflect the unique conservation needs of offshore ecosystems: emphasising the need for larger MPAs; maximising the inclusion of special features that are known and mapped; and representing minimum percentages of habitats, or, where mapped, bioregions. Ultimately, MPA guidelines need to be embedded within an adaptive management framework, and have the flexibility to respond to emerging knowledge and new challenges.

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A system of coordinated autonomous robots for Lagrangian studies of microbes in the oceanic deep chlorophyll maximum

Cited by 40 publications

References 71 publications

Finite-horizon, energy-efficient trajectories in unsteady flows

Finite-horizon, energy-efficient trajectories in unsteady flows

Finding and Tracking a Phytoplankton Patch by a Long-Range Autonomous Underwater Vehicle

How to Meet New Global Targets in the Offshore Realms: Biophysical Guidelines for Offshore Networks of No-Take Marine Protected Areas

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