Lakes and reservoirs play key roles in global carbon cycling, especially as a carbon sink. Enrichment of nutrients in lakes and reservoirs (eutrophication) and rising global temperatures favors the proliferation of bloom-forming cyanobacteria. Harmful blooms of cyanobacteria (cyanoHABs) alter carbon and nutrient cycling in freshwater ecosystems. Some evidence suggests the introduction or establishment of invasive mussel species (i.e., Dreissena spp.) also favor cyanoHAB formation through selective filter feeding, a process through which they may also impact biogeochemical processes including carbon cycling and sequestration. However, few studies have considered the combined effects of invasive mussels and cyanoHABs on carbon and nitrogen cycling in freshwater ecosystems. Here, we examined microbial community composition and biogeochemical attributes (including carbon and nitrogen stable isotopes) in eutrophic lakes, reservoirs, and rivers in western Ohio, eastern Indiana, and northern Kentucky during the cyanobacterial bloom period of the summer of 2015. Our samples include both sites impacted by invasive mussels and those where invasive mussels have not yet been observed. Based on 16S and 18S rRNA gene sequence analysis, we found that cyanobacterial and algal communities varied across sites and were most closely related to habitat (sediment or water column sample) and site, regardless of the presence of invasive mussels or other environmental factors. However, we did find evidence that invasive mussels may influence both carbon and nitrogen cycling. While the results are based on a single time point sampling, they highlight the interactions of multiple environmental stressors in aquatic ecosystems and the critical need for more temporally intensive studies of carbon and nutrient cycling in bloom- and mussel-impacted waters.

中文翻译：

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德莱森入侵和未入侵的美国中西部湖泊和水库中氰基HABs期间的碳和氮循环

湖泊和水库在全球碳循环中发挥着关键作用，尤其是作为碳汇。湖泊和水库中营养物质的富集（富营养化）和全球气温上升有利于形成水华的蓝藻的增殖。蓝藻（cyanoHABs）的有害大量繁殖改变了淡水生态系统中的碳和养分循环。一些证据表明，入侵贻贝物种（即 Dreissena spp.）的引入或建立也有利于通过选择性滤食形成 cyanoHAB，在这一过程中它们也可能影响生物地球化学过程，包括碳循环和封存。然而，很少有研究考虑入侵贻贝和氰基HABs对淡水生态系统中碳和氮循环的综合影响。这里，我们检查了 2015 年夏季蓝藻爆发期间俄亥俄州西部、印第安纳州东部和肯塔基州北部富营养化湖泊、水库和河流中的微生物群落组成和生物地球化学属性（包括碳和氮稳定同位素）。我们的样本包括两个地点受入侵贻贝和尚未观察到入侵贻贝的影响。基于 16S 和 18S rRNA 基因序列分析，我们发现蓝藻和藻类群落因地点而异，并且与栖息地（沉积物或水柱样本）和地点的关系最密切，无论是否存在侵入性贻贝或其他环境因素。然而，我们确实发现了侵入性贻贝可能影响碳和氮循环的证据。虽然结果基于单个时间点采样，