Abstract
Trace metal micronutrients are integral to the functioning of marine ecosystems and the export of particulate carbon to the deep ocean. Although much progress has been made in mapping the distributions of metal micronutrients throughout the ocean over the last 30 years, there remain information gaps, most notable during seasonal transitions and in remote regions. The next challenge is to develop in situ sensing technologies necessary to capture the spatial and temporal variabilities of micronutrients characterized with short residence times, highly variable source terms, and sub-nanomolar concentrations in open ocean settings. Such an effort will allow investigation of the biogeochemical processes at the necessary resolution to constrain fluxes, residence times, and the biological and chemical responses to varying metal inputs in a changing ocean. Here, we discuss the current state of the art and analytical challenges associated with metal micronutrient determinations and highlight existing and emerging technologies, namely in situ chemical analyzers, electrochemical sensors, passive preconcentration samplers, and autonomous trace metal clean samplers, which could form the basis of autonomous observing systems for trace metals within the next decade. We suggest that several existing assets can already be deployed in regions of enhanced metal concentrations and argue that, upon further development, a combination of wet chemical analyzers with electrochemical sensors may provide the best compromise between analytical precision, detection limits, metal speciation, and longevity for autonomous open ocean determinations. To meet this goal, resources must be invested to: (1) improve the sensitivity of existing sensors including the development of novel chemical assays; (2) reduce sensor size and power requirements; (3) develop an open-source “Do-It-Yourself” infrastructure to facilitate sensor development, uptake by end-users and foster a mechanism by which scientists can rapidly adapt commercially available technologies to in situ applications; and (4) develop a community-led standardized protocol to demonstrate the endurance and comparability of in situ sensor data with established techniques. Such a vision will be best served through ongoing collaborations between trace metal geochemists, analytical chemists, the engineering community, and commercial partners, which will accelerate the delivery of new technologies for in situ metal sensing in the decade following OceanObs’19.
Highlights
Bioactive micronutrient metals are essential for cell functions and mediate vital biochemical reactions by acting as cofactors in many enzymes and as centers to stabilize enzymes and protein structures (Sunda, 2012)
In addition to core biogeochemical variables (e.g., T, S, O2, nitrate, Chl-a), we suggest that an ideal autonomous observing system for trace metal micronutrients would include the capability to measure total dissolved concentrations of Fe, Co, Cu, Mn, and Zn with detection limits suitable for openocean determinations and field endurance spanning from a month to 1 year depending on the deployment environment (Table 1)
We describe a series of tangible outcomes, that should be the focus of research and development efforts in the decade following OceanObs’19
Summary
Bioactive micronutrient metals are essential for cell functions and mediate vital biochemical reactions by acting as cofactors in many enzymes and as centers to stabilize enzymes and protein structures (Sunda, 2012). Over the past 30 years, from the pioneering work of John Martin on Fe limitation (Martin and Fitzwater, 1988; Martin and Gordon, 1988) to the ongoing GEOTRACES program that is mapping the distributions and investigating the biogeochemistry of trace elements and their isotopes throughout the ocean (Schlitzer et al, 2018), the database of discrete observations for Fe and other bioactive trace metals has grown by three orders of magnitude and encompasses observations in all ocean basins (Tagliabue et al, 2017 and references therein) These sampling efforts have greatly improved our understanding of micronutrient cycling, but are not sufficient to constrain the key processes underpinning metal micronutrient cycling and associated biological responses. This lack of understanding cascades into an incomplete representation of ocean Fe cycling in the global models used to project the impacts of change in Fe-limited regions (Tagliabue et al, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
