C14 and N15 isotopes in rocks and animals from methane seep hard substrate ecosystems from R/V Atlantis AT15-44 in the Pacific, off Costa Rica from 2009-2009 (Seep Carbonate Ecology CROCKS II project)

<p>Average stable isotopic signatures (d15N and d13C) for carbonate rocks and animals collected during AT 15-44 at various methane seep sites on the Costa Rica margin. The values are averages, not actual measurements.&nbsp; Researchers needing the raw data should seek them from [e-mail].</p>

<p>Animal tissues were sorted, processed and analysed according to methods in Levin &amp; Mendoza.<br />
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Levin, L. A. &amp; Mendoza, G. (2007) \"Community structure and nutrition of deep methane seep macroinfauna from the Aleutian Margin and Florida Escarpment, Gulf of Mexico.\"&nbsp; Mar. Ecol. 28, 131-151. (doi:10.1111/j.1439-0485.2006.00131.x)<br />
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For further information, see:<br />
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Lisa A. Levin, Victoria J. Orphan, Greg W. Rouse, Anthony E. Rathburn, William Ussler III, Geoffrey<br />
S. Cook, Shana K. Goffredi, Elena M. Perez, Anders Waren, Benjamin M. Grupe, Grayson Chadwick and<br />
Bruce Strickrott.(2012) \"A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems\" Proc. R. Soc. B published online 7 March 2012. doi: 10.1098/rspb.2012.0205</p>

<p>From Final Report:</p>

<p>At Costa Rica, carbonate organic matter content was high (0.5 to 3.5%).&nbsp; Organic matter in the carbonates had d 13C signatures of -65o/oo to -23o/oo indicating a varied methane contribution to the C pool. Faunal isotopic signatures ranged broadly, from -101o/oo to -10o/oo for d13C and -12 to +18 for d 15N.&nbsp;&nbsp; They revealed strong trophic resource partitioning among mollusk and polychaete species. A broad range of d 13C&nbsp; signatures reflect use of a variety of microbial food resources, often within a single rock.&nbsp; Very light d 13C signatures (mean -92o/oo, n=18) in an abundant dorvilleid polychaete (Dorvillea sp.) in the most sulfidic carbonates provides evidence of a carbonate endolithofauna that may rely primarily on archaeal carbon. Intense grazing of rocks by lepetopsid limpets&nbsp; many with isotopic evidence for methane-derived C, apparently exerts strong top-down control on the distribution of protists and smaller invertebrates.<br />
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At Hydrate Ridge, inorganic d13C values of carbonates ranged from -26o/oo to -54o/oo, whereas the rock organic d13C spanned a much broader range (from -19o/oo to -71o/oo.).&nbsp; Within a rock the two values were not correlated and there were no significant isotopic differences on average between active and inactive carbonates, although inactive values were less variable.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Natural abundance animal carbon isotope signatures ranged from -17o/oo to -88o/oo, with average values of animals (per rock) showing no significant difference between active and inactive sites (P-0.232). However, carbonate d13C org (P=0.002) and d15N (animal P=0.005) were isotopically lighter on rocks designated as active, relative to those designated as inactive.<br />
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