Sediment cores from 12 locations throughout the Laurentian Great Lakes basin were analyzed for geochemical indicators of primary production. Sediment analytes included organic and inorganic contents, carbonates, sediment accumulation rates, total organic carbon and nitrogen concentrations, carbon and nitrogen isotope composition, and trends in spectroscopically inferred chlorophyll a (and its main diagenetic products). When multiple indicators were considered, production records related to recent cultural eutrophication and catchment activities were clear in the paleorecords. Indicators derived from loss-on-ignition (organic and inorganic content) were strongly associated with periods of human settlement in the catchments that increased overall sediment loads to the lakes. The ratio of carbon to nitrogen tracked catchment inputs of carbon, especially during periods of watershed development in western Lake Superior. Sediment records such as chlorophyll a and δ 13 C org appear to be reliable indicators of trends in past algal abundance, particularly in Lake Erie, which has a well-known history of higher production and cultural eutrophication. These analytes also correlated well with past measured water quality surrogates for lake primary productivity and stressor data such as human populations in adjacent watersheds. A comparison among indicators revealed that several show redundancy as good proxies of production or productivity, though context was important. For instance, heavier isotopes of carbon and nitrogen are often prescribed as sedimentary indicators of lake productivity, but these two analytes were negatively correlated in Lake Superior, possibly due to long-term increases in cyanobacteria or changes in the nitrogen source. An increase in sediment carbonates can indicate summer blooms of cyanobacteria (a phenomenon that was clearly apparent in Lake Ontario) or catchment erosion. To make convincing geochemical inferences of primary production in the Great Lakes, it is recommended that a weight of evidence be built through the use of multiple indicators.

中文翻译：

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Laurentian Great Lakes 的长期初级生产趋势：地球化学方法的比较

分析了整个 Laurentian Great Lakes 盆地 12 个地点的沉积物岩心，以确定初级生产的地球化学指标。沉积物分析物包括有机和无机含量、碳酸盐、沉积物积累率、总有机碳和氮浓度、碳和氮同位素组成，以及光谱推断叶绿素 a（及其主要成岩产物）的趋势。当考虑多个指标时，与近期文化富营养化和流域活动相关的生产记录在古记录中很清楚。源自燃烧损失（有机和无机含量）的指标与人类在集水区定居的时期密切相关，这增加了湖泊的总体沉积物负荷。碳氮比跟踪集水区碳输入，特别是在苏必利尔湖西部的流域开发时期。叶绿素 a 和 δ 13 C org 等沉积物记录似乎是过去藻类丰度趋势的可靠指标，特别是在伊利湖，该湖有着众所周知的高产量和文化富营养化历史。这些分析物还与过去测量的湖泊初级生产力和压力源数据（例如邻近流域的人口）的水质替代指标密切相关。指标之间的比较表明，尽管背景很重要，但有几个指标显示冗余是生产或生产力的良好代表。例如，碳和氮的较重同位素通常被规定为湖泊生产力的沉积指标，但这两种分析物在苏必利尔湖中呈负相关，可能是由于蓝藻的长期增加或氮源的变化。沉积物碳酸盐的增加可能表明夏季蓝藻大量繁殖（这种现象在安大略湖中很明显）或集水区侵蚀。为了对五大湖的初级生产做出令人信服的地球化学推断，建议通过使用多个指标来建立证据权重。