Imbalanced coral growth between organic tissue and carbonate skeleton caused by nutrient enrichment
Imbalanced coral growth between organic tissue and carbonate skeleton caused by nutrient enrichment
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DOI：
10.4319/lo.2007.52.3.1139
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发表时间：
2007-05
影响因子：
4.5
通讯作者：
Yasuaki Tanaka;T. Miyajima;I. Koike;T. Hayashibara;H. Ogawa
中科院分区：
文献类型：
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作者：
Yasuaki Tanaka;T. Miyajima;I. Koike;T. Hayashibara;H. Ogawa
在实验室条件下，研究了适度营养富集（NO3−:<5µmol L−1,PO43‐：<0.3µmol L−1）对虫黄酸珊瑚（Acropora pulchra）光合作用和钙化两种碳(C)固定速率的影响。将珊瑚枝条在营养条件下孵育3个不同时期（0、5、10 d），观察组织生物量和虫黄酸叶绿素a （Chl a）浓度的变化。接下来，将孵育的珊瑚同时转移到含有13C标记的溶解无机碳的营养物枯竭的海水中，以测定净光合作用和钙化率。在10天的富集过程中，单位表面积的Chl a浓度增加了2.6倍，净光合速率也被刺激到类似的水平（2.8倍）。在此期间，宿主珊瑚和虫黄藻的组织生物量大约增加了一倍。另一方面，钙化率只增加了1.3倍，这表明即使是适度的营养负荷也会导致藻类光合活性的单方面增强。有机碳与骨骼碳的固碳比大于结构碳，且随着Chl a浓度的增加，这种不一致性越来越大。增加的光合产物可能会过度储存在有机组织和/或释放到周围的海水中。
Effects of moderate nutrient enrichment (NO3− : <5 µmol L−1, PO43‐ : <0.3 µmol L−1) on two carbon (C) fixation rates (photosynthesis and calcification) of the zooxanthellate coral Acropora pulchra were investigated under laboratory conditions. The coral branches were incubated in the nutrient condition for three different periods (0, 5, 10 d) to observe changes in tissue biomass and zooxanthellate chlorophyll a (Chl a) concentration. Next, the incubated corals were simultaneously transferred to nutrient‐depleted seawater containing 13C‐labeled dissolved inorganic carbon to assay net photosynthesis and calcification rates. Chl a concentration per unit surface area increased 2.6‐fold for the 10‐d enrichment, and net photosynthetic rates were also stimulated up to a similar level (2.8‐fold). Tissue biomass of the host coral and zooxanthellae was approximately doubled during the period. On the other hand, calcification rates only increased 1.3‐fold, suggesting that even moderate nutrient loading resulted in one‐sided enhancement of the algal photosynthetic activity. The measured C fixation ratios of organic C: skeletal C were higher than the structural ratios, and the inconsistency became greater as Chl a concentration increased. The increased photosynthetic products could be excessively stored in the organic tissue and/or released into the ambient seawater.