Recent cyanobacterial blooms in otherwise unproductive lakes may be warning signs of impending eutrophication in lakes important for recreation and drinking water, but little is known of their historical precedence or mechanisms of regulation. Here, we examined long‐term sedimentary records of both general and taxon‐specific trophic proxies from seven lakes of varying productivity in the northeastern United States to investigate their relationship to historical in‐lake, watershed, and climatic drivers of trophic status. Analysis of fossil pigments (carotenoids and chlorophylls) revealed variable patterns of past primary production across lakes over two centuries despite broadly similar changes in regional climate and land use. Sediment abundance of the cyanobacterium Gloeotrichia, a large, toxic, nitrogen‐fixing taxon common in recent blooms in this region, revealed that this was not a new taxon in the phytoplankton communities but rather had been present for centuries. Histories of Gloeotrichia abundance differed strikingly across lakes and were not consistently associated with most other sediment proxies of trophic status. Changes in ice cover most often coincided with changes in fossil pigments, and changes in watershed land use were often related to changes in Gloeotrichia abundance, although no single climatic or land‐use factor was associated with proxy changes across all seven lakes. The degree to which changes in lake sediment records co‐occurred with changes in the timing of ice‐out or agricultural land use was negatively correlated with the ratio of watershed area to lake area. Thus, both climate and land management appeared to play key roles in regulation of primary production in these lakes, although the manner in which these factors influenced lakes was mediated by catchment morphometry. Improved understanding of the past interactions between climate change, land use, landscape setting, and water quality underscores the complexity of mechanisms regulating lake and cyanobacterial production and highlights the necessity of considering these interactions—rather than searching for a singular mechanism—when evaluating the causes of ongoing changes in low‐nutrient lakes.

中文翻译：

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“新的”蓝藻花并不新鲜：两个世纪的湖泊生产与冰盖和土地利用有关

在其他没有生产力的湖泊中，最近出现的蓝细菌水华可能是警告信号，表明对娱乐和饮用水很重要的湖泊即将发生富营养化，但鲜为人知的是它们的历史先例或调控机制。在这里，我们研究了来自美国东北部七个生产力不同的湖泊的一般和特定生物的营养代表的长期沉积记录，以研究它们与历史湖心，分水岭和营养状况的气候驱动因素的关系。对化石颜料（类胡萝卜素和叶绿素）的分析显示，尽管区域气候和土地利用方面的变化大体相似，但两个多世纪以来，整个湖泊过去的初级生产模式各不相同。蓝藻gloeotrichia的沉积物丰富，在该地区最近出现的花朵中常见的一种大型，有毒的固氮类群表明，这不是浮游植物群落中的新类群，而是存在了几个世纪。整个湖泊中，丰富的gloeotrichia的历史差异很大，并且与大多数其他具有营养状态的沉积物代理并没有始终如一的联系。冰盖的变化最经常与化石色素的变化同时发生，而流域土地利用的变化通常与格劳氏菌的变化有关尽管没有七个气候或土地利用因素与全部七个湖泊的代理变化相关联，但水量仍然很高。湖泊沉积物记录的变化与结冰或农业土地使用时间的变化同时发生的程度与流域面积与湖泊面积之比呈负相关。因此，尽管这些因素影响湖泊的方式是由流域形态来介导的，但气候和土地管理似乎在这些湖泊的初级生产调节中起着关键作用。加深对气候变化，土地利用，景观设置，