Phytoplankton Species Composition, Abundance and Cell Size in San Francisco Bay: Microscopic Analyses of USGS Samples Collected 1992-2014

This Data Release makes available measurements of phytoplankton species composition, abundance and cell size made on samples collected in San Francisco Bay (CA) from April 1992 through March 2014. Phytoplankton samples were collected at 31 stations along a 145-km transect where the variability of salinity, temperature, turbidity and nutrient concentrations reflected a broad range of environmental factors that regulate phytoplankton growth and abundance (station map on ScienceBase homepage). Whole water samples were preserved with acid Lugol’s solution, and 2 to 50 ml aliquots were settled in chambers for 6 to 24 hours (Utermöhl 1958). Phytoplankton cells were then counted and identified using a phase-contrast inverted microscope at 125x magnification, all cells greater than 30 μm diameter were enumerated. Cells smaller than 30 μm were counted at 1250x magnification; following the APHA (1989) strip count method, at least 100 cells of the most numerous taxon were counted. Cell volumes were estimated from measured linear dimensions and geometric formulas that varied with cell shapes. Phytoplankton samples representing 923 distinct date, station and depths were included. The 16,442 entries in this dataset include 609 different taxa within 11 functional groups. Diatoms dominated the total biovolume contributed by each functional group (77%) followed by dinoflagellates (14%) and cryptophytes (4.5%). The top 5 species contributing to the summed biovolume in all samples were: Thalassiosira punctigera, Chaetoceros socialis, Ditylum brightwellii, Thalassiosira rotula and Noctiluca scintillans. By frequency of occurrence, the top 5 species were: Teleaulax amphioxeia, Nannochloropsis spp., Plagioselmis prolonga var. nordica, Skeletonema costatum and Thalassiosira eccentrica. APHA. (1989). Standard methods for the examination of water and wastewater, 17th edn. American Public Health Association, Washington, DC Utermöhl H. (1958). Zur Vervollkommnung der quantitativen Phytoplankton-Methodik. Mitt Int Verh Theor Angew Limnol 9:1-38

本数据集发布提供了1992年4月至2014年3月期间，于加利福尼亚州旧金山湾采集的样本中浮游植物（phytoplankton）物种组成、丰度及细胞尺寸的测量数据。研究人员沿145公里的调查断面设置了31个采样站位，该断面的盐度、温度、浊度及营养盐浓度的变化范围覆盖了调控浮游植物生长与丰度的各类环境因子（站位地图见ScienceBase官网首页）。
采集的全水样采用酸性鲁哥氏液（acid Lugol’s solution）固定，随后取2至50毫升的分样置于沉降室中沉降6至24小时（Utermöhl 1958）。随后使用相差倒置显微镜，以125倍放大倍率对浮游植物细胞进行计数与鉴定：对直径大于30微米的所有细胞进行全数计数；直径小于30微米的细胞则以1250倍放大倍率计数，并遵循美国公共卫生协会（APHA, 1989）的条带计数法，至少完成占比最高的分类单元的100个细胞计数。
细胞体积通过测量得到的线性尺寸，结合适配不同细胞形态的几何公式进行估算。本数据集涵盖了923组包含不同日期、站位与水深的浮游植物样本，共计16442条记录，隶属于11个功能类群下的609个分类单元。
各功能类群贡献的总生物体积中，硅藻（diatoms）占比最高（77%），其次为甲藻（dinoflagellates，14%）与隐藻（cryptophytes，4.5%）。所有样本中，总生物体积贡献排名前五的物种依次为：斑点海链藻（Thalassiosira punctigera）、社会角毛藻（Chaetoceros socialis）、布氏双尾藻（Ditylum brightwellii）、旋转海链藻（Thalassiosira rotula）及夜光藻（Noctiluca scintillans）。按出现频率排序，排名前五的物种依次为：泰勒定鞭金藻（Teleaulax amphioxeia）、微拟球藻属（Nannochloropsis spp.）、延长异弯藻北欧变种（Plagioselmis prolonga var. nordica）、中肋骨条藻（Skeletonema costatum）及偏心海链藻（Thalassiosira eccentrica）。
参考文献：
1. 美国公共卫生协会（APHA）. (1989). 水和废水检验标准方法（第17版）. 美国公共卫生协会，华盛顿哥伦比亚特区
2. Utermöhl H. (1958). 定量浮游植物研究方法的完善. 国际理论与应用湖沼学学会会报（Mitt Int Verh Theor Angew Limnol）9:1-38