Flipping for Food: The Use of a Methane Seep by Tanner Crabs (Chionoecetes tanneri)

Sarah Seabrook,Andrew R Thurber,Fabio C De Leo

doi:10.3389/fmars.2019.00043

Sarah Seabrook, Andrew R Thurber + Show 1 more

Open Access

https://doi.org/10.3389/fmars.2019.00043

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Abstract

Methane seep habitats are widespread chemosynthesis-based ecosystem that span continental margins and interact with surrounding marine systems. With many of these habitats occurring below 200m, seeps can serve as an important source of nutrients in otherwise food limited deep-sea environments. However, the potential for marauding megafauna to assimilate seep derived nutrition has been difficult to quantify. Here, we provide the first evidence of a commercially harvested species, Chionoecetes tanneri (tanner crab), assimilating chemosynthetic production. Although bulk isotope analysis of C. tanneri tissue indicated no quantifiable incorporation of seep-derived carbon or sulfur (mean δ13C, -18.5‰; mean δ34S, 19.5‰), depletions in 13C (δ13C as light as -38.8 ‰) were noted in fatty acid (FA) compounds. In addition, diagnostic biomarkers for seep bacteria, including 16:16 and 18:18c FA’s, were found to have been assimilated by C. tanneri. Futher supporting a trophic link between the seep and the C. tanneri, seep associated bacteria and archaea were, in certain cases, the dominant taxa in the gut contents of the crab. This work provides the first insights into a link between seep production and deep-sea ecosystem services, specifically fisheries production. In addition, it reveals a methodological bias that could exist in some trophic studies where bulk isotopes under-represent the role of seep nutrition in the diet of marauding animals.

Highlights

Deep-sea habitats provide a range of ecosystem goods and services to society (Armstrong et al, 2010; Thurber et al, 2014)
We found multiple lines of evidence that demonstrated that the C. tanneri were grazing upon seep nutrition, it was not reflected in bulk isotopic measurements
The fatty acid (FA) signatures revealed a dominance of photosynthetically derived carbon in the crab tissue, there were multiple bacterial FAs associated with chemosynthetic processes and instances of depletion in 13C associated with methane-derived carbon within particular FAs

Summary

Introduction

Deep-sea habitats provide a range of ecosystem goods and services to society (Armstrong et al, 2010; Thurber et al, 2014). Facilitated chemosynthetic production in deep-sea habitats, such as methane seeps can produce an abundant supply of food and support dense faunal communities (Levin, 2005; Cordes et al, 2010). The role these habitats serve for surrounding ecosystems and society remains largely unknown (Levin et al, 2016). We identify the unexpected use of chemosynthetic production by a commercially harvested species, Chionoecetes tanneri (tanner crab), identifying a novel link between seep ecosystems, fisheries, and humans Through this we discover unexpected methodological biases that could have obscured quantification of export production from seep ecosystems in previous studies

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