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Ammonium enhancement of dark carbon fixation and nitrogen limitation in symbiotic zooxanthellae: Effects of feeding and starvation of the sea anemone Aiptasia pallida
Author(s) -
Cook Clayton B.,
MullerParker Gisèle,
D'Elia Christopher F.
Publication year - 1992
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1992.37.1.0131
Subject(s) - zooxanthellae , sea anemone , biology , algae , photosynthesis , botany , ammonium , cnidaria , coelenterata , anemone , nitrogen fixation , zoology , coral , symbiosis , ecology , chemistry , bacteria , genetics , organic chemistry
The nutrient status of algae symbiotic with marine invertebrates is controversial. We assessed the nitrogen status of zooxanthellae symbiotic with the sea anemone Aiptasia pallida using NH 4 + enhancement of dark C fixation; enhancement increases with N limitation in other microalgae. Freshly isolated symbionts obtained from laboratory populations of known feeding history and from field populations were assayed: NH 4 + enhancement depended on the nutritional history of the host anemones. Zooxanthellae from well‐fed laboratory populations showed little enhancement of dark 14 C fixation by NH 4 + , while mean dark enhancement ratios (NH 4 + rates: seawater rates) exceeded 2.3 for zooxanthellae from anemones unfed for 1–6 weeks. Photosynthetic rates of the isolated algae declined with starvation. V D′ : V L , an index which includes both dark NH 4 + enhancement and photosynthesis, increased markedly with time since feeding. Three of four field samples of A. pallida yielded zooxanthellae with dark enhancement ratios similar to those of fed laboratory populations; V D′ : V L values were somewhat higher. Symbionts from anemones collected on a fourth date had a mean enhancement ratio of 2.88, and V D′ : V L values similar to those from laboratory anemones that had not fed for 1–2 weeks, indicative of increased N limitation.