Calcareous green alga in the genus Halimeda are important contributors to the marine carbonate budget. Dongsha Island is located in the northernmost South China Sea and is a seagrass-dominated ecosystem with intermixed Halimeda macroloba patches, making it an excellent system to better examine the extent of carbonate contribution by H. macroloba in such an ecosystem. To this end, we examined the standing stock and actual CaCO3 contribution of H. macroloba in the seagrass-dominated ecosystem (herein Dongsha Island) and compared them with those in Halimeda-dominated ecosystems. The density, growth rate, calcification rate and CaCO3 content of H. macroloba at four life stages were investigated. The mean density of H. macroloba was around 8.82 ± 1.57 thalli m−2 and the estimated standing stock was 61,740 to 72,730 thalli. Thalli produced 1 to 2 new segments day−1, giving a growth rate of 0.003 ± 0.001 g dry weight thallus−1 day−1. Calculated algal biomass and annual areal production were 0.03 g m−2 and 9.66 g m−2 year−1. In each square metre of this area, H. macroloba produced 8.82 to 17.64 new segments day−1, accumulating 0.002 ± 0.001 g CaCO3 thallus−1 day−1 or around 6.44 g CaCO3 m−2 year−1. Mean CaCO3 content was 0.32 ± 0.05 g thallus−1. As expected, the growth rate and CaCO3 production of H. macroloba in Dongsha Island were lower than in other studies from Halimeda tropical ecosystems. Overall, this work provides the baseline of carbonate production of H. macroloba in Dongsha Island and relevant systems where the ecosystem is dominated by seagrasses.

中文翻译：

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南海东沙环礁主岛东沙岛热带海草为主的生态系统中大叶海藻的活量和CaCO3贡献

钙质绿藻属哈利梅达是海洋碳酸盐预算的重要贡献者。东沙岛位于南海最北端，是一个以海草为主、混杂的生态系统。大叶藻补丁，使其成为更好地检查碳酸盐贡献程度的优秀系统大叶海棠在这样的生态系统中。为此，我们检查了常备库存和实际 CaCO3的贡献大叶海棠在以海草为主的生态系统（此处为东沙岛）中，并与哈利梅达- 主导的生态系统。密度、生长速率、钙化速率和 CaCO33内容大叶海棠在四个生命阶段进行了调查。平均密度大叶海棠约为 8.82 ± 1.57 thalli m-2估计常备存量为 61,740 至 72,730 塔利。Thalli 每天生产 1 到 2 个新片段-1, 生长速率为 0.003 ± 0.001 g 干重菌体-1日-1. 计算出的藻类生物量和年面积产量为 0.03 gm-2和 9.66 克-2年-1. 在这个面积的每一平方米里，大叶海棠每天产生 8.82 到 17.64 个新段-1, 累积 0.002 ± 0.001 g CaCO3菌体-1日-1或约 6.44 克 CaCO3米-2年-1. 平均碳酸钙3含量为 0.32 ± 0.05 g 菌体-1. 正如预期的那样，增长率和 CaCO3的产品大叶海棠东沙岛低于其他研究哈利梅达热带生态系统。总体而言，这项工作提供了碳酸盐生产的基线大叶海棠以海草为主的东沙岛及相关系统。