MEPS 571:245-251 (2017)  -  DOI: https://doi.org/10.3354/meps12138

NOTE
Variation in δ13C and δ15N values suggests a coupling of host and symbiont metabolism in the Symbiodinium-Cassiopea mutualism

Christopher J. Freeman1,*, Elizabeth W. Stoner2, Cole G. Easson3, Kenan O. Matterson3, David M. Baker4

1Smithsonian Marine Station, 701 Seaway Drive, Fort Pierce, Florida 34949, USA
2Loxahatchee River District, 2500 Jupiter Park Drive, Jupiter, Florida 33458, USA
3Department of Biology, University of Alabama at Birmingham, 1300 University Blvd, Birmingham, Alabama 35294, USA
4The Swire Institute of Marine Science, School of Biological Sciences, University of Hong Kong, Hong Kong, PR China
*Corresponding author:

ABSTRACT: While the ‘upside-down’ jellyfish Cassiopea xamachana feeds heterotrophically, its energy requirements are likely met through its symbiosis with the dinoflagellate symbiont Symbiodinium. To investigate the potential coupling of host and symbiont metabolism within C. xamachana, we assessed whether variation in the isotope values (δ13C and δ15N) of photosymbiont-rich oral arm tissue was reflected in bell tissue, which is predominately composed of thick animal mesoglea. Samples were collected from 5 geographically disparate sites, including a site influenced by anthropogenically-derived nutrients. Oral arm δ13C values were variable across sites, reflecting varying inputs of marine, terrestrial, and seagrass-derived carbon. Low (<0‰) δ15N values of oral arm tissue at the 4 non-impacted sites suggests nitrogen derived from nitrogen fixation, while high (~6‰) δ15N values from the impacted site suggests the assimilation of 15N-enriched sources like sewage. Oral arm δ13C and δ15N values accounted for ~75 and 25% of the variation in bell δ13C and δ15N values. The translocation of symbiont-derived carbon and nitrogen to the host was also supported by evidence of trophic enrichment, with bell tissue enriched on average by 1.7 and 3.4‰ compared to oral arm tissue for δ13C and δ15N, respectively. These data support the contention that microbial symbionts within Cassiopea are critical to productivity and nutrient cycling in oligotrophic systems, but also raise important questions about whether symbiont metabolism spurs Cassiopea growth and proliferation at sites with chronic anthropogenic nutrient inputs, where higher abundances can have negative effects on local fauna and flora.


KEY WORDS:Symbiosis · Jellyfish · Cassiopea · Stable isotopes · Caribbean · Anthropogenic nutrients


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Cite this article as: Freeman CJ, Stoner EW, Easson CG, Matterson KO, Baker DM (2017) Variation in δ13C and δ15N values suggests a coupling of host and symbiont metabolism in the Symbiodinium-Cassiopea mutualism. Mar Ecol Prog Ser 571:245-251. https://doi.org/10.3354/meps12138

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