Data from: Daphniid zooplankton assemblage shifts in response to eutrophication and metal contamination during the Anthropocene

Human activities during the Anthropocene result in habitat degradation that has been associated with biodiversity loss and taxonomic homogenization of ecological communities. Here we estimated effects of eutrophication and heavy metal contamination, separately and in combination, in explaining zooplankton species composition during the past 125–145 years using analysis of daphniid diapausing egg banks from four lakes in the northeastern USA. We then examined how these community shifts influenced patterns of diversity and homogenization. Analysis of past lake production (via subfossil pigments) and metal contamination (via sedimentary metals) demonstrated that eutrophication alone (19–39%) and in combination with metal pollution (17–54%) explained 36–79% of historical variation in daphniid species relative abundances in heavily fertilized lakes. In contrast, metal pollution alone explained the majority (72%) of historical variation in daphniid assemblages at the oligotrophic site. Several species colonization events in eutrophying lakes resulted in increased species richness and gamma diversity through time. At the same time, daphniid assemblages in three eutrophied lakes became more similar to each other (homogenized), but this pattern was only seen when accounting for species presence/absence. We did not observe consistent patterns of divergence between the assemblages in the eutrophying lakes and the low-nutrient reference site. Given the pervasive nature of fertilization and metal pollution, and the sensitivity of cladocerans to these factors, we suggest that many inhabited lake districts may already exhibit similar patterns of daphniid assemblage shifts.

人类世（Anthropocene）时期的人类活动会引发生境退化，而生境退化已被证实与生物多样性丧失及生态群落的分类群均质化（taxonomic homogenization）紧密关联。本研究通过对美国东北部四座湖泊的枝角类（daphniid）休眠卵库（diapausing egg banks）展开分析，评估了125至145年间富营养化（eutrophication）与重金属污染（heavy metal contamination）单独及联合作用对浮游动物物种组成的影响；随后进一步探究了这些群落结构转变如何作用于多样性格局与均质化过程。通过亚化石色素（subfossil pigments）分析重建湖泊历史生产力、通过沉积金属（sedimentary metals）分析评估重金属污染程度后，研究结果显示：在受高强度施肥影响的湖泊中，单独的富营养化可解释枝角类物种相对丰度历史变异中的19%~39%，其与重金属污染的联合作用可解释17%~54%，二者共计解释了36%~79%的历史变异；与之相对，在寡营养位点（oligotrophic site），仅重金属污染就解释了枝角类群落72%的历史变异。富营养化湖泊中发生的多次物种定殖事件，随时间推移提升了群落的物种丰富度与伽马多样性（gamma diversity）。与此同时，三座富营养化湖泊的枝角类群落彼此间相似度显著提升（即发生均质化），但该格局仅在纳入物种存在/缺失数据时才能被观测到。本研究未发现富营养化湖泊与低营养参考位点的枝角类群落间存在一致的分化格局。鉴于施肥与重金属污染的普遍性，以及枝角类（cladocerans）对这类环境扰动的敏感性，我们推测全球诸多受人类活动影响的湖泊区域，或已呈现出类似的枝角类群落转变格局。