� 1999, by the American Society of Limnology and Oceanography, Inc. The fate of nitrogen in the Orbulina universa foraminifera–symbiont system determined by nitrogen isotope analyses of shell-bound organic matter
To trace the flow of nitrogen through the foraminifera–symbiont system, juvenile specimens of the symbiontbearing planktonic foraminifera, Orbulina universa were collected by SCUBA divers off the coast of Santa Catalina Island, California, and grown in filtered seawater solutions spiked with 15N-lab...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.6016 http://www.aslo.org/lo/toc/vol_44/issue_8/1968.pdf |
| Summary: | To trace the flow of nitrogen through the foraminifera–symbiont system, juvenile specimens of the symbiontbearing planktonic foraminifera, Orbulina universa were collected by SCUBA divers off the coast of Santa Catalina Island, California, and grown in filtered seawater solutions spiked with 15N-labeled nitrate. Our work isolated each pathway of this symbiotic system to determine the amount of nitrogen translocated to the foraminifera from its endosymbionts and its captured diet. Our model results show that when the nitrate uptake by the symbionts is at a maximum, between 50 and 57 % of the foraminiferal nitrogen was translocated from the symbionts and the remainder was derived from the captured diet. In nitrate-deficient environments, when the symbiont nitrate uptake was at a minimum, �90–100 % of the nitrogen was transferred to the foraminifer by the symbionts from the recycled nitrogen (NH 4) pool. In nitrate-deficient conditions, the primary role of the captured diet may be to provide the system with phosphorous. Highly efficient nutrient use is particularly important to the foraminifera–symbiont system, especially when nutrient concentrations are low. The results indicate a limited correlation between the isotopic composition of the NO in the culture solutions and the �15N values of the foraminifera. However, the �15 � 3 N values of the |
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