ABSTRACT: Seaweed farming is widely perceived as one of the most environmentally benign types of aquaculture activity. In the past 10 yr, global seaweed production has doubled and reached 31.8 million t. Farmed seaweed also has important functions in local ecosystems. We focus on the production, bioavailability, and bacterial degradation rates of dissolved organic carbon (DOC) from cultured kelp Saccharina japonica. Semi in situ incubations in 2 growing seasons were conducted to estimate DOC production, and laboratory incubations were used to determine bioavailability and decay rates of DOC from cultured kelp. Results showed that DOC production was 6.2-7.0 mg C (g dry wt)^-1 d^-1 in the growing seasons, and the proportion of DOC in net primary production was 23.7-39.1%. The decomposition rate of DOC was 4 ± 1% d^-1 and 9 ± 1% d^-1 in January and April, respectively. About 37.8% remained as refractory DOC after 150 d incubation. It was calculated that the total DOC from kelp in Sanggou Bay was approximately 11.3 times of that from phytoplankton for the whole bay (144 km²). Our results suggest that more than half of the bioavailable DOC will be exported out of the bay to potentially support the wider food chain through bacterial uptake. Cultured kelp is therefore an important source of DOC in the embayment, contributes to the coastal DOC pool and provides a potential pathway for carbon dioxide sequestration.

中文翻译：

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养殖海藻糖藻中的溶解有机碳：产量，生物利用度和细菌降解率

摘要：海藻养殖被广泛认为是对环境最有益的水产养殖活动之一。在过去的10年中，全球海藻产量翻了一番，达到3180万吨。养殖海藻在当地生态系统中也具有重要功能。我们专注于养殖海带糖精的产量，溶解性有机碳（DOC）的生产，生物利用度和细菌降解率。在两个生长季节中进行半原位温育以估计DOC的产生，并使用实验室温育确定培养的海藻中DOC的生物利用度和腐烂率。结果表明DOC产量为6.2-7.0 mg C（g干重）^-1 d ^-1在生长期，DOC在净初级生产中所占的比例为23.7-39.1％。1月和4月DOC的分解速率分别为4±1％d ^-1和9±1％d ^-1。150 d孵育后仍保留约37.8％的难溶DOC。据计算，在整个沟港（144 km ²），桑沟湾海带的总DOC约为浮游植物的11.3倍。我们的结果表明，超过一半的可生物利用的DOC将被出口到海湾之外，以潜在地通过细菌吸收来支持更广泛的食物链。因此，养殖海带是该区中DOC的重要来源，有助于沿海DOC库，并为封存二氧化碳提供了潜在途径。