FIRe glider: Mapping in situ chlorophyll variable fluorescence with autonomous underwater gliders

Abstract

Nutrient and light availability regulate phytoplankton physiology and photosynthesis in the ocean. These physiological processes are difficult to sample in time and space over physiologically and ecologically relevant scales using traditional shipboard techniques. Gliders are changing the nature of data collection, by allowing a sustained presence at sea over regional scales, collecting data at resolution not possible using traditional techniques. The integration of a fluorescence induction and relaxation (FIRe) sensor in a Slocum glider allows autonomous high‐resolution and vertically‐resolved measurements of photosynthetic physiological variables together with oceanographic data. In situ measurements of variable fluorescence under ambient light allows a better understanding of the physical controls of primary production (PP). We demonstrate this capability in a laboratory setting and with several glider deployments in the Southern Ocean. Development of these approaches will allow for the in situ evaluation of phytoplankton light stress and photoacclimation mechanisms, as well as the role of vertical mixing in phytoplankton dynamics and the underlying physiology, especially in remote locations and for prolonged duration.

Single-Turnover Variable Chlorophyll Fluorescence as a Tool for Assessing Phytoplankton Photosynthesis and Primary Productivity: Opportunities, Caveats and Recommendations

“…In ship-board laboratories, discrete samples can be analyzed individually, or data can be continuously acquired from a flowthrough seawater supply (e.g., Behrenfeld et al, 2006). Truly in-situ data acquisition can also be achieved using instruments deployed on depth-profiling packages, towed platforms (e.g., Moore et al, 2003) or autonomous platforms, including moorings, floats, and gliders (e.g., Fujiki et al, 2008;Carvalho et al, 2020). Whereas continuous data collection provides advantages of high frequency measurement, discrete analysis allows for better control and optimization of experimental protocols for individual samples (e.g., light-response curves, NPQ-relaxation, tuning of ST protocols, and blank correction).…”

“…Over the past decades, significant progress has been made in the use of ST-ChlF methods in aquatic ecosystems. Developments in sensor technology have greatly improved measurement sensitivity, with current instruments able to collect robust data in the most oligotrophic waters and from autonomous platforms (Lin et al, 2016;Carvalho et al, 2020). At the same time, new approaches to interpret ST-ChlF data in terms of phytoplankton photo-physiology and taxonomic composition allow for a better understanding of the environmental and taxonomic factors driving variability in derived parameters.…”

Exploring Variability of Trichodesmium Photophysiology Using Multi-Excitation Wavelength Fast Repetition Rate Fluorometry

“…FRRf observations of phytoplankton have been used principally to examine the effects of physiological stress, such as nutrient limitation (Behrenfeld et al, 2006;Schuback et al, 2016;Hughes et al, 2018b). Recently, FRRf has also been used for the characterization of light absorption (Silsbe et al, 2015), for interpreting phytoplankton photophysiological processes in the context of phytoplankton community structure (Carvalho et al, 2020;Gorbunov et al, 2020;Hughes et al, 2020), and for describing primary productivity (e.g., Smyth et al, 2004;Fujiki et al, 2008;Cheah et al, 2011;Wei et al, 2020;Zhu et al, 2016Zhu et al, , 2017Zhu et al, , 2019Hughes et al, 2018b;Schuback et al, 2021).…”

“…This has even extended to autonomous deployment across all major oceans via research vessels, buoy systems, and glider platforms (Falkowski et al, 2017;Carvalho et al, 2020;Ryan-Keogh and Thomalla, 2020).…”

Phytoplankton Photophysiology Utilities: A Python Toolbox for the Standardization of Processing Active Chlorophyll-a Fluorescence Data

“…Commercial fast repetition rate or fluorescence induction relaxation instruments exhibit large dynamic ranges in detection sensitivity suitable for application to eutrophic and oligotrophic systems (Röttgers, 2007). The ability to measure multiple parameters such as the functional absorption cross section and electron transport kinetics (Kolber et al, 1998;Gorbunov and Falkowski, 2004;Röttgers, 2007); as well as the capacity to collect measurements in the laboratory (Fujiki et al, 2007;Mckew et al, 2013;Schuback et al, 2015), connected to a flow-through aquatic water system (Behrenfeld et al, 2006;Houliez et al, 2017) or in-situ (Moore et al, 2003;Suggett et al, 2006b;Fujiki et al, 2008Fujiki et al, , 2011, including on autonomous platforms (Carvalho et al, 2020), are also advantageous features of this type of instrumentation.…”