An autonomous, in situ light-dark bottle device for determining community respiration and net community production
An autonomous, in situ light-dark bottle device for determining community respiration and net community production
Date
2018-03
Authors
Collins, James R.
Fucile, Paul D.
McDonald, Glenn
Ossolinski, Justin E.
Keil, Richard G.
Valdes, James R.
Doney, Scott C.
Van Mooy, Benjamin A. S.
Fucile, Paul D.
McDonald, Glenn
Ossolinski, Justin E.
Keil, Richard G.
Valdes, James R.
Doney, Scott C.
Van Mooy, Benjamin A. S.
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Keywords
Respiration
Community metabolism
Aquatic microbial ecology
Autonomous instrumentation
Optodes
Dissolved oxygen
Ocean observing
Community metabolism
Aquatic microbial ecology
Autonomous instrumentation
Optodes
Dissolved oxygen
Ocean observing
Abstract
We describe a new, autonomous, incubation-based instrument that is deployed in situ to
determine rates of gross community respiration and net community production in marine and aquatic
ecosystems. During deployments at a coastal pier and in the open ocean, the PHORCYS
(PHOtosynthesis and Respiration Comparison-Yielding System) captured dissolved oxygen fluxes
over hourly timescales that were missed by traditional methods. The instrument uses fluorescence-quenching optodes fitted into separate light and dark chambers; these are opened and closed with
piston-like actuators, allowing the instrument to make multiple, independent rate estimates in the
course of each deployment. Consistent with other studies in which methods purporting to measure
the same metabolic processes have yielded divergent results, respiration rate estimates from the
PHORCYS were systematically higher than those calculated for the same waters using a traditional
two-point Winkler titration technique. However, PHORCYS estimates of gross respiration agreed
generally with separate incubations in bottles fitted with optode sensor spots. An Appendix describes
a new method for estimating uncertainties in metabolic rates calculated from continuous dissolved
oxygen data. Multiple successful, unattended deployments of the PHORCYS represent a small step
toward fully autonomous observations of community metabolism. Yet the persistence of unexplained
disagreements among aquatic metabolic rate estimates — such as those we observed between rates
calculated with the PHORCYS and two existing, widely-accepted bottle-based methods — suggests
that a new community intercalibration effort is warranted to address lingering sources of error in
these critical measurements.
Description
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography-Methods 16 (2018): 323-338, doi:10.1002/lom3.10247.