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Abstract Trait-based simplifications of plankton community structure require accurate assessment of trait values as expressed in situ. Yet planktonic organisms live suspended in a fluid medium and often bear elongate appendages, delicate feeding structures, and mucous houses that are badly damaged upon capture or removal from the fluid environment. Fixatives further distort organisms. In situ imaging of zooplankton from a fully autonomous Zooglider reveals a suite of trait characteristics that often differ markedly from those inferred from conventionally sampled plankton. In situ images show fragile feeding appendages in natural hunting postures, including reticulate networks of rhizopods, feeding tentacles of cnidarians, and tentilla of ctenophores; defensive spines and setae of copepods; intact mucous houses of appendicularians; and other structures that are not discernible in conventionally collected zooplankton. Postures characteristic of dormant copepods can be identified and the presence of egg sacs detected. Intact, elongate diatom chains that are much longer than measured in sampled specimens are resolvable in situ. The ability to image marine snow, as well as small-scale fluid deformations, reveals micro-habitat structure that may alter organismal behaviour. Trait-based representations of planktonic organisms in biogeochemical cycles need to consider naturally occurring traits expressed by freely suspended planktonic organisms in situ.
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Resolving abrupt frontal gradients in zooplankton community composition and marine snow fields with an autonomous Zooglider
Abstract An autonomousZooglidernavigated across the California Current Front into low salinity, minty waters characteristic of the California Current proper in both summers of 2019 and 2021. Diving to 400 m depth,Zooglidertransited another near‐surface frontal gradient somewhat inshore. These frontal gradients were generally associated with changes in intensity, size composition, and Diel Vertical Migration responses of acoustic backscatterers. They were also associated with pronounced changes in zooplankton community composition, as assessed by a shadowgraph imaging Zoocam. Zoocam detected a decline in concentrations of copepods, appendicularians, and marine snow in the offshore direction, and an overall shift in community structure to a higher proportion of carnivorous taxa (and, in 2019, of planktonic rhizaria). No taxon was consistently elevated at all the peak frontal gradients, but appendicularians, copepods, and rhizarians sometimes showed front‐related increases in concentration. Such frontal gradient regions represent relatively abrupt transitions to different communities of planktonic organisms and suspended marine snow particles, with consequences for predator–prey relationships and the dominant vectors of particle export into subsurface waters.
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- PAR ID:
- 10584570
- Publisher / Repository:
- Wiley Periodicals
- Date Published:
- Journal Name:
- Limnology and Oceanography
- ISSN:
- 0024-3590
- Subject(s) / Keyword(s):
- Ocean fronts Autonomous Underwater Vehicle Plankton Imaging Bioacoustics Zooplankton Diel Vertical Migration Machine Learning
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/lno.12642
