North Temperate Lakes LTER: Phytoplankton - Madison Lakes Area 1995 - current

Phytoplankton samples for the 4 southern Wisconsin LTER lakes (Mendota, Monona, Wingra, Fish) have been collected for analysis by LTER since 1995 (1996 Wingra, Fish) when the southern Wisconsin lakes were added to the North Temperate Lakes LTER project. Samples are collected as a composite whole-water sample and are preserved in gluteraldehyde. Composite sample depths are 0-8 meters for Lake Mendota (to conform to samples collected and analyzed since 1990 for a UW/DNR food web research study), and 0-2 meters for the other three lakes. A tube sampler is used for the 0-8 m Lake Mendota samples; samples for the other lakes are obtained by collecting water at 1-meter intervals using a Kemmerer water sampler and compositing the samples in a bucket. Samples are taken in the deep hole region of each lake at the same time and location as other limnological sampling. Phytoplankton samples are analyzed by PhycoTech, Inc., a private lab specializing in phytoplankton analyses (see data protocol for procedures). Samples for Wingra and Fish lakes are archived but not routinely counted. Permanent slide mounts (3 per sample) are prepared for all analyzed Mendota and Monona samples as well as 6 samples per year for Wingra and Fish; the slide mounts are archived at the University of Wisconsin - Madison Zoology Museum. Phytoplankton are identified to species using an inverted microscope (Utermohl technique) and are reported as natural unit (i.e., colonies, filaments, or single cells) densities per mL, cell densities per mL, and algal biovolume densities per mL. Multiple entries for the same species on the same date may be due to different variants or vegetative states - (e.g., colonial or attached vs. free cell.) Biovolumes for individual cells of each species are determined during the counting procedure by obtaining cell measurements needed to calculate volumes for geometric solids (e.g., cylinders, spheres, truncated cones) corresponding to actual cell shapes. Biovolume concentrations are then computed by mulitplying the average cell biovolume by the cell densities in the water sample. Note that one million cubicMicrometers of biovolume PerMilliliter of water are equal to a biovolume concentration of one cubicMillimeterPerMilliliter. Assuming a cell density equal to water, a cubicMillimeterPerMilliliter of biovolume converts to a biomass concentration of one milligramPerLiter. Sampling Frequency: bi-weekly during ice-free season from late March or early April through early September, then every 4 weeks through late November; sampling is conducted usually once during the winter (depending on ice conditions). Number of sites: 4
Several taxonomic updates have been made to this dataset February 2013, see methods for details.

威斯康星州南部4个长期生态研究（Long-Term Ecological Research, LTER）湖泊（门多塔湖、莫诺纳湖、温格拉湖、菲什湖）的浮游植物样本，自1995年起由LTER团队收集用于分析（温格拉湖、菲什湖的样本收集始于1996年）——彼时威斯康星州南部湖泊被纳入北温带湖泊LTER研究项目。
样本以混合全水样的形式采集，并以戊二醛固定。门多塔湖的混合采样深度为0~8米（以匹配1990年起由威斯康星大学/自然资源部开展的食物网研究中采集与分析的样本标准），其余三座湖泊的混合采样深度则为0~2米。门多塔湖0~8米深度的样本采用管式采水器采集；其余湖泊的样本则通过凯默勒采水器（Kemmerer water sampler）按1米间隔取水，随后在桶中混合制成混合样。
所有样本均采集自各湖泊的深水区，且采样时间与地点与其他湖沼学采样活动保持一致。浮游植物样本由专门从事浮游植物分析的私营实验室PhycoTech, Inc.进行分析（具体操作流程参见数据规程）。温格拉湖与菲什湖的样本仅完成归档，未进行常规计数。
针对所有完成分析的门多塔湖与莫诺纳湖样本，均制作永久玻片标本（每样本3片）；温格拉湖与菲什湖则每年选取6份样本制作玻片。所有玻片标本均存档于威斯康星大学麦迪逊分校动物学博物馆。
浮游植物物种鉴定采用倒置显微镜结合乌特莫尔法（Utermohl technique）完成，报告指标包括每毫升水体的自然单位（即群体、丝状体或单细胞）密度、每毫升水体的细胞密度，以及每毫升水体的藻类生物体积密度。同一日期下同一物种的多条记录，可能源自不同的变种或营养生长状态——例如群体附着态与游离单细胞状态。
每个物种的单个细胞生物体积，在计数流程中通过测量细胞尺寸后，采用与细胞实际形态匹配的几何体（如圆柱体、球体、截头圆锥体）体积公式计算得到。随后通过平均细胞生物体积乘以水样中的细胞密度，计算得到生物体积浓度。请注意，每毫升水体中100万立方微米的生物体积，等同于1立方毫米每毫升的生物体积浓度。假设细胞密度与水体密度相当，则1立方毫米每毫升的生物体积浓度可换算为1毫克每升的生物量浓度。
采样频率：无冰期（3月下旬至4月初至9月上旬）每两周采样一次，9月上旬至11月下旬每四周采样一次；冬季通常采样一次（具体视冰况而定）。采样点位数量：4个。
2013年2月，该数据集完成了多项分类学更新，详细信息参见方法部分。