Molecular observational tools are great for characterizing the composition and genetic endowment of microbial communities, but cannot measure fluxes, which are critical for the understanding of ecosystems. To overcome these limitations, we use a mechanistic inference approach to estimate dissolved organic carbon (DOC) production and consumption by phytoplankton operational taxonomic units (OTUs) and heterotrophic prokaryotic amplicon sequences variants (ASVs), and infer carbon fluxes between members of this microbial community from Western English Channel time-series data. Our analyses focus on phytoplankton spring and summer blooms, as well as bacteria summer blooms. In spring blooms, phytoplankton DOC production exceeds heterotrophic prokaryotic consumption, but in bacterial summer blooms heterotrophic prokaryotes consume 3 times more DOC than produced by the phytoplankton. This mismatch is compensated by heterotrophic prokaryotic DOC release by death, presumably from viral lysis. In both types of summer blooms, large amounts of the DOC liberated by heterotrophic prokaryotes are re-used through internal recycling., with fluxes between different heterotrophic prokaryotes being at the same level as those between phytoplankton and heterotrophic prokaryotes. Contextualized, internal recycling accounts for approximately 75% and 30% of the estimated net primary production (0.16 vs 0.22 and 0.08 vs 0.29 μmol l−1 d−1) in bacteria and phytoplankton summer blooms, respectively, and thus represents a major component of the Western English Channel carbon cycle. We conclude that internal recycling compensates for mismatches between phytoplankton DOC production and heterotrophic prokaryotic consumption, and we encourage future analyses on aquatic carbon cycles to consider fluxes between heterotrophic prokaryotes, specifically internal recycling.

中文翻译：

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异养原核生物的内部碳循环补偿了浮游植物生产和异养消耗之间的不匹配


分子观测工具对于表征微生物群落的组成和遗传禀赋非常有用，但无法测量通量，而通量对于理解生态系统至关重要。为了克服这些限制，我们使用机械推理方法来估计浮游植物操作分类单元（OTU）和异养原核扩增子序列变体（ASV）的溶解有机碳（DOC）生产和消耗，并推断该微生物群落成员之间的碳通量来自西英吉利海峡时间序列数据。我们的分析重点是浮游植物春季和夏季的繁殖，以及细菌夏季的繁殖。在春季水华中，浮游植物产生的 DOC 超过异养原核生物的消耗，但在细菌夏季水华中，异养原核生物消耗的 DOC 是浮游植物产生的 3 倍。这种不匹配可以通过死亡时异养原核生物 DOC 的释放来补偿，推测是来自病毒裂解。在这两种类型的夏季水华中，异养原核生物释放的大量 DOC 通过内部循环被重新利用，不同异养原核生物之间的通量与浮游植物和异养原核生物之间的通量处于同一水平。在细菌和浮游植物夏季水华中，内部循环分别约占估计净初级生产力的 75% 和 30%（0.16 vs 0.22 和 0.08 vs 0.29 μmol l−1 d−1），因此代表了细菌和浮游植物夏季水华的主要组成部分。西英吉利海峡碳循环。 我们得出的结论是，内部循环补偿了浮游植物 DOC 生产和异养原核生物消耗之间的不匹配，并且我们鼓励未来对水生碳循环的分析考虑异养原核生物之间的通量，特别是内部循环。