NUTRIENT-UPTAKE KINETICS OF FRESHLY ISOLATED ZOOXANTHELLAE
NUTRIENT-UPTAKE KINETICS OF FRESHLY ISOLATED ZOOXANTHELLAE
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DOI：
10.1007/bf00405998
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发表时间：
1983-01-01
期刊：
影响因子：
2.4
通讯作者：
WEBB, KL
中科院分区：
文献类型：
--
作者：
DELIA, CF;DOMOTOR, SL;WEBB, KL
Zooxanthellae of the species Gymnodinium (= Symbiodinium) microadriaticum freshly isolated from a variety of hosts (Zoanthus spp., Tridacna crocea, Seriatopora hystrix, Montastrea annularis, Porites furcata and Stylophora pistillata) in the tropical Pacific Ocean and the Caribbean Sea exhibited saturation uptake kinetics when incubated in seawater enriched with nitrate, nitrite or ammonium. Half-saturation constants (Ks) for nitrate ranged from 0.23-3.14 .mu.M, for nitrite from 0.23-7.15 .mu.M and for ammonium from 5.03-21.99 .mu.M. Maximum specific uptake rates (Vmax) for ammonium (1.05-2.79 d[day]-1) exceeded those for both nitrate (not detectable to 0.54 d-1) and nitrite (not detectable to 0.67 d-1). Light did not affect the uptake rate of any substrate tested, nor did the addition of ammonium in concentrations up to 20 .mu.M reduce the rate of nitrate uptake at Vmax, but nitrite uptake was inhibited by the addition of nitrate to the medium. The inhibition of nitrite uptake by nitrate could not be described either as competitive or non-competitive. Although maximum specific uptake rates obtained for ammonium appear to exceed maximum potential specific growth rate in terms of N of the algae, the actual growth potential of the algae must be limited not only by nutrient concentrations to which they are exposed, but also by the percentage of assimilated N that they translocate to their host. Uptake rates obtained for isolated zooxanthellae are similar to those obtained previously for intact coral-zooxanthellae symbioses. Nutrient uptake by intact zooxanthellae-host symbioses occurs by diffusion down a concentration gradient created by localized substrate depletion by the zooxanthellae in host tissue.
