Plastic marine debris is known to harbor a unique microbiome (termed the “plastisphere”) that can be important in marine biogeochemical cycles. However, the temporal dynamics in the plastisphere and their implications for marine biogeochemistry remain poorly understood. Here, we characterized the temporal dynamics of nitrifying communities in the plastisphere of plastic ropes exposed to a mangrove intertidal zone. The 39-month colonization experiment revealed that the relative abundances of Nitrospira and Candidatus Nitrosocosmicus representatives increased over time according to 16S rRNA gene amplicon sequencing analysis. The relative abundances of amoA genes in metagenomes implied that comammox Nitrospira were the dominant ammonia oxidizers in the plastisphere, and their dominance increased over time. The relative abundances of two metagenome-assembled genomes of comammox Nitrospira also increased with time and positively correlated with extracellular polymeric substances content of the plastisphere but negatively correlated with NH4+ concentration in seawater, indicating the long-term succession of these two parameters significantly influenced the ammonia-oxidizing community in the coastal plastisphere. At the end of the colonization experiment, the plastisphere exhibited high nitrification activity, leading to the release of N2O (2.52 ng N2O N g−1) in a 3-day nitrification experiment. The predicted relative contribution of comammox Nitrospira to N2O production (17.9%) was higher than that of ammonia-oxidizing bacteria (4.8%) but lower than that of ammonia-oxidizing archaea (21.4%). These results provide evidence that from a long-term perspective, some coastal plastispheres will become dominated by comammox Nitrospira and thereby act as hotspots of ammonia oxidation and N2O production.

中文翻译：

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沿海塑料球中 comammox Nitrospira 和 Ca. Nitrosocosmicus 的时间富集


众所周知，塑料海洋垃圾含有一种独特的微生物组（称为“塑料圈”），它在海洋生物地球化学循环中可能很重要。然而，人们对塑料圈的时间动态及其对海洋生物地球化学的影响仍然知之甚少。在这里，我们表征了暴露于红树林潮间带的塑料绳塑料圈中硝化群落的时间动态。39 个月的定植实验显示，根据 16S rRNA 基因扩增子测序分析，Nitrospira 和 Candidatus Nitrosocosmicus 代表的相对丰度随着时间的推移而增加。宏基因组中 amoA 基因的相对丰度表明 comammox Nitrospira 是塑料圈中占主导地位的氨氧化剂，并且它们的优势性随着时间的推移而增加。Comammox Nitrospira 的两个宏基因组组装基因组的相对丰度也随时间增加，与质体层的细胞外聚合物含量呈正相关，但与海水中的 NH4+ 浓度呈负相关，表明这两个参数的长期连续显著影响了沿海质体层的氨氧化群落。在定植实验结束时，塑料圈表现出高硝化活性，导致在 3 天的硝化实验中释放 N2O （2.52 ng N2O N g-1）。预测的 comammox Nitrospira 对 N2O 产生的相对贡献 （17.9%） 高于氨氧化细菌 （4.8%），但低于氨氧化古细菌 （21.4%）。 这些结果提供了证据，从长期来看，一些沿海塑料圈将以 comammox Nitrospira 为主，从而成为氨氧化和 N2O 产生的热点。