the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
A step towards measuring connectivity in the deep-sea: elemental fingerprints of mollusk larval shells discriminate hydrothermal vent sites
Christophe Pecheyran
Fanny Claverie
Cécile Cathalot
Marjolaine Matabos
Yoan Germain
Olivier Rouxel
Didier Jollivet
Thomas Broquet
Thierry Comtet
Abstract. Deep-sea hydrothermal-vent systems are under investigation for base and precious metal exploitations. The impact of mining will depend critically on the ability of larval dispersal to connect and replenish endemic populations. However, assessing connectivity is extremely challenging, especially in the deep sea. Here, we investigate the potential of elemental fingerprinting of mollusc larval shells to discriminate larval origins between multiple hydrothermal sites in the Southwest Pacific Ocean. The gastropod Shinkailepas tollmanni represents a suitable candidate as it uses capsules to hold larvae before dispersal, which facilitates sampling. Multielemental microchemistry was performed using cutting-edge femtosecond laser ablation Inductively Coupled Plasma Mass Spectrometry analysis to obtain individual measurements on 600 encapsulated larval shells. We used classification methods to discriminate the origin of individuals from 14 hydrothermal sites spanning over 3,500 km, with an overall success rate of 70 %. When considering less sites within more restricted areas, reflecting dispersal distances reported by genetic and modelling approaches, the success rate increased up to 86 %. We conclude that individual larval shells register site-specific elemental signatures that can be used to assess their origin. These results open new perspectives to get direct estimates on population connectivity from the geochemistry of pre-dispersal shell of recently settled juveniles.
Vincent Mouchi et al.
Status: open (until 20 Oct 2023)
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RC1: 'Comment on egusphere-2023-1324', Lisa Levin, 12 Aug 2023
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Review of Mouchi et al. A step towards measuring connectivity in the deep sea.General comments:
This work represents an important first step in the application of trace-elemental fingerprinting to deep-sea hydrothermal vent connectivity. The authors have selected a suitable test species and studied an impressive array of sites (14). I think this effort is a precursor to many important applications.
Although the authors present deep seabed mining as the key motivator , I would argue that there are many additional reasons for wanting to know about connectivity of vents – from basic science, to biodiversity conservation (30x30 goals), to addressing consequences of climate change on connectivity (e.g., Mitarai’s work in Levin et al. 2020 DOI: 10.1111/gcb.15223), vent roles in the carbon cycle etc. I would encourage at least mention of these other motivators. Within the mining realm, in addition to understanding consequences of mining disturbance, the authors should point out the importance of connectivity data to the designation of no-mining protected areas (APEIs) and also reference zone PRZ and IRZ (preservation and impact) designation.
Please consider adding to the end of the introduction a paragraph that clearly lays out the goals or objectives of the research. This could be in the form of questions, hypotheses or other… but should frame the science around the data presented in the paper. E.g., does the water chemistry of ‘habitat water’ differ among vent sites where S. tollmanni egg capsules occur? What elements are key to distinguishing sites? Does the trace element signatures of S. tollmanni larval shell reflect the habitat water chemistry? Are there specific sites or scales of connectivity where the application of trace elemental fingerprinting to the vent systems is likely to most reliable? What elements are key to this distinction? Some of these questions show up as the headings in the results section – but should be presented earlier.
Tell us a little bit more about the study species Shinkailepas tollmanni – its distribution, and its host Iffremeria distribution. Is the relationship obligate? Is anything known about depth ranges, longevity, development time, feeding mode, planktonic duration? How does its life history affect inferences about connectivity? Will information about mollusc/gastropod connectivity be relevant to other vent taxa – what will or won’t?
Consider discussion which of the study sites are targeted for mining, and which might serve as source populations. IUCN has red listed some species like the scaly foot snail based on their limited occurrence primarily in areas targeted for mining. I realize you don’t have any source or sink data generated yet but it might be useful to explain how this precursor work can lead to analyses that inform identification of vulnerable species.
Specific comments.
Title – please only hyphenate deep sea when it is used as a double adjective. Here it is a noun and should not be hyphenated.
Abstract: Line 19. The presence of capsules not only facilitates sampling, it means the embryos develop in a fixed location – and form carbonates whose trace elemental signature could reflect that location.
Line 30 – Even vent sites on mid ocean ridges far from coastlines are of interest to commercial mining (ISA contracts on Mid Atlantic Ridge and Southwest Indian Ridge).
Line 65 – replace ‘minute’ with a more accurate indication of size…. 100 micron?
Line 72 – replace ‘which carbonate shells ‘with ‘whose carbonate shells’
Line 263 Simmonds et al. should come out of the parentheses.
Note that Levin 2006 (doi:10.1093/icb/icj024) in discussing future directions for larval dispersal studies in a larval dispersal review wrote How much larval exchange occurs within and among reducing ecosystems such as vents, seeps, and whale falls? Analysis of short-term larval exchange among seep or hydrothermal vent ecosystemsmight be tractable if these impart distinct trace element signatures to larval shells.
I think this paper is really the first to tackle this problem. (17 years later).
Fig. 4 and 5 caption. Indicate what the lighter and darker shades of blue and red mean.
The supplemental information needs a table of contents as it is extensive.
Table S4 should replace the ‘,’ with decimal points.
The comparison of habitat water to larval shell chemistry should be included in the main paper.
Overall this is a significant contribution in need of relatively minor revision.
Citation: https://doi.org/10.5194/egusphere-2023-1324-RC1
Vincent Mouchi et al.
Vincent Mouchi et al.
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