Symbiotic anemones can grow when starved: nitrogen budget for Anemonia viridis in ammonium-supplemented seawater |
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Authors: | J M Roberts P S Davies L M Fixter |
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Institution: | (1) Division of Environmental and Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, Scotland, GB;(2) Division of Biochemistry and Molecular Biology, University of Glasgow, Glasgow G12 8QQ, Scotland, GB |
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Abstract: | The ability of endosymbioses between anthozoans and dinoflagellate algae (zooxanthellae) to retain excretory nitrogen and
take up ammonium from seawater has been well documented. However, the quantitative importance of these processes to the nitrogen
budget of such symbioses is poorly understood. When starved symbiotic Anemonia viridis were incubated in a flow-through system in seawater supplemented with 20 μM ammonium for 91 d under a light regime of 12 h light at 150 μmol photons m−2 s−1 and 12 h darkness, they showed a mean net growth of 0.197% of their initial weight per day. Control anemones in unsupplemented
seawater with an ammonium concentration of <1 μM lost weight by a mean of 0.263% of their initial weight per day. Attempts to construct a nitrogen budget showed that, over
a 14 d period, ≃40% of the ammonium taken up could be accounted for by growth of zooxanthellae. It was assumed that the remainder
was translocated from zooxanthellae to host. However, since the budget does not balance, only 60% of the growth of host tissue
was accounted for by this translocation. The value for host excretory nitrogen which was recycled to the symbionts equalled
that taken in by ammonium uptake from the supplemented seawater, indicating the importance of nitrogen retention to the symbiotic
association.
Received: 23 December 1997 / Accepted: 12 September 1998 |
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