Carbon and nitrogen utilization in two species of Red Sea corals along a depth gradient: Insights from stable isotope analysis of total organic material and lipids
Carbon and nitrogen utilization in two species of Red Sea corals along a depth gradient: Insights from stable isotope analysis of total organic material and lipids
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DOI：
10.1016/j.gca.2009.06.018
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发表时间：
2009-09-15
影响因子：
5
通讯作者：
Shemesh, Aldo
中科院分区：
文献类型：
--
作者：
Alamaru, Ada;Loya, Yossi;Shemesh, Aldo
我们研究了两种常见的红海珊瑚(水鞘珊瑚和黄花珊瑚)对碳和氮的利用，它们的群体形态和息肉大小不同，沿深度梯度向下延伸到60m。我们描述了珊瑚组织和藻类共生体的C/N比和碳、氮稳定同位素组成的变化。我们还测定了从珊瑚组织和藻类共生体中提取的脂肪组分的碳同位素组成，以揭示宿主珊瑚用于脂肪合成的碳源的变化。结果表明，对于这两个物种，动物组织、藻类共生体和脂肪组分中的(13)C随着深度的增加而减少7-8ppm。然而，与以前的报道相反，珊瑚组织和藻类共生体的Delta(13)C值之间的差异并不随深度增加而增加。两种珊瑚组织和藻类共生体的Delta(15)N值与深度无关，表明这些珊瑚的异养能力不随深度增加而增加。与所有深度的整个组织的Delta(13)C值相比，组织脂类的Delta(13)C值平均消耗了-3.5‰。藻类脂肪的Delta(13)C值平均消耗了千分之二。与整个虫黄藻在所有深度的增量(13)C相比，这表明两个共生伙伴之间沿着整个梯度进行了高效的碳循环。脂质的耗竭归因于脂肪合成过程中的分级机制。此外，与组织脂的增量(13)C相比，两个物种的藻类脂的增量(13)C值都较富集。在鱼腥藻中，组织脂和藻脂的Delta(13)C值之差随着深度的增加呈线性增加，表明在20米以下，珊瑚用于脂肪合成的碳源从自养转变为异养。然而，在福寿螺中，这一平均差异大约是浅雌蕊的4倍，并且在整个深度梯度上是恒定的，这表明福寿螺利用异养获得的碳来合成脂肪，而不考虑深度。总体而言，在整个梯度上，褐飞虱表现出丰富的增量(13)C和增量(15)N值，而雌鱼则表现出丰富的增量(15)N值。我们将这些差异归因于这两个物种之间的形态差异(即菌落形态、组织厚度和息肉大小)，以及在所有深度都有较高的异养/自养比率。雌鱼组织中的C/N值随水深的增加而降低，而鱼体中的C/N值基本不变。这反映了在所有的深度，大的多倍体的Favus具有更高的异养能力。(C)2009爱思唯尔有限公司。保留所有权利。
We examined the utilization of carbon and nitrogen in two common Red Sea coral species (Stylophora pistillata and Favia favus), differing in colony morphology and polyp size, along a depth gradient down to 60 m. We describe the changes in C/N ratios and in the stable isotope composition of carbon and nitrogen of coral's tissue and algal symbionts. We also measured the carbon isotopic composition of the lipid fraction extracted from both coral tissue and algal symbionts in order to reveal the changes in the carbon source utilized by the host coral for lipid synthesis.The results show that for both species, delta(13)C decreases by 7-8 parts per thousand in animal tissue, algal symbionts and in the lipid fractions as depth increases. However, in contrast to previous reports, the difference between delta(13)C values of coral tissue and algal symbionts does not increase with depth. delta(15)N values of coral tissue and algal symbionts in both species do not correlate with depth suggesting that the heterotrophic capacity of these corals does not increase with depth. delta(13)C values of tissue lipids were depleted by an average of -3.5 parts per thousand compared to delta(13)C of the entire tissue at all depths. delta(13)C values of algal lipids were depleted by an average of similar to 2 parts per thousand. compared to delta(13)C of the entire zooxanthellae at all depths, indicating high efficiency of carbon recycling between the two symbiotic partners along the entire gradient. The depletion of lipids is attributed to the fractionation mechanism during lipid synthesis. In addition, for both species, delta(13)C values of algal lipids were enriched compared with delta(13)C of tissue lipids. In S. pistillata, the difference between delta(13)C values of tissue lipids and algal lipids increased linearly with depth, indicating a change in the sources of carbon utilized by the coral for lipid synthesis below 20 m from an autotrophic to a heterotrophic source. However, in F favus, this average difference was similar to 4 times larger compared to shallow S. pistillata and was constant along the entire depth gradient, suggesting that F favus uses heterotrophically-acquired carbon for lipid synthesis regardless of depth. Overall, F. favus exhibited enriched delta(13)C and delta(15)N values compared to S. pistillata along the entire gradient. We attribute these differences to both morphological differences (i.e. colony morphology, tissue thickness and polyp size) between the two species and to a higher heterotrophy/autotrophy ratio in F favus at all depths. The C/N ratio in S. pistillata tissue decreased with increasing water depth whereas in F favus it remained constant. This reflects a higher heterotrophic capacity in the large polyped F favus, at all depths. (C) 2009 Elsevier Ltd. All rights reserved.