C/¹²C ratios in marine invertebrates from reducing sediments: confirmation of nutritional importance of chemoautotrophic endosymbiotic bacteria

The carbon isotope composition (δ¹³C ‰) of the tissues of benthic invertebrates usually ranges from −16 to −20. In contrast we report that several common bivalve molluscs belonging to the superfamily Lucinacea and several small species of Pogonophora show much greater depletions, ranging from −23 to...

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Bibliographic Details
Published in:Marine ecology. Progress series (Halstenbek) 1986-02, Vol.28 (3), p.233-240
Main Authors: Spiro, B., Greenwood, P. B., Southward, A. J., Dando, P. R.
Format: Article
Language:English
Subjects:
Animals
Bacteria
Bicarbonates
Carbon isotopes
Carbonates
Hydrothermal vents
RESEARCH PAPERS
Sediments
Sulfur
Symbionts
Symbiosis
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Summary:The carbon isotope composition (δ¹³C ‰) of the tissues of benthic invertebrates usually ranges from −16 to −20. In contrast we report that several common bivalve molluscs belonging to the superfamily Lucinacea and several small species of Pogonophora show much greater depletions, ranging from −23 to −31 in the bivalves and from −35 to −46 in the pogonophores. These bivalves and pogonophores live in reducing sediments where the concentration of dissolved sulphide is low, usually < 1 μM. The gills of the bivalves and the trophosome tissue of the pogonophores contain intracellular or sub-cuticular bacteria. The bacteria are autotrophs, as shown by ribulosebisphosphate carboxylase activity of extracts of the bacteria-containing tissues. Comparisons of the δ¹³C values of the bacteria-containing regions and the rest of the tissues indicate substantial transfer of organic carbon, half or more of the nutritional needs of the hosts. The organic carbon is produced by fixation of CO₂ by the autotrophic bacteria, which oxidize reduced inorganic compounds, notably sulphide, to obtain energy for the process. Similar depletions of ¹³C were previously reported for other autotrophic symbiont-containing bivalves that live in habitats where dissolved sulphide concentrations are 2 or 3 orders of magnitude higher than in the sediments analysed here. This form of nutrition, involving symbiosis with autotrophic bacteria, is evidently not dependent on high levels of dissolved sulphide and appears to be widespread in calcareous reducing sediments of the shelf and continental slope.
ISSN:0171-8630
1616-1599