National Coral Reef Monitoring Program: Benthic Cover Derived from Analysis of Benthic Images Collected during Stratified Random Surveys (StRS) across the Hawaiian Archipelago in 2013 (NCEI Accession 0159140)

The data described here result from benthic photo-quadrat surveys conducted along transects at stratified random sites across the Hawaiian archipelago in 2013 as a part of Rapid Ecological Assessment (REA) surveys for corals and fish. Benthic habitat imagery were quantitatively analyzed using the Coral Point Count with Excel extensions (CPCe; Kohler and Gill, 2006) software. In general, images are analyzed to produce three functional group levels of benthic cover: Tier 1 (e.g., hard coral, soft coral, macroalgae, turf algae, etc.), Tier 2 (e.g., Hard Coral = massive, branching, foliose, encrusting, etc.; Macroalgae = upright macroalgae, encrusting macroalgae, bluegreen macroalgae, and Halimeda, etc.), and Tier 3 (e.g., Hard Coral = Astreopora sp, Favia sp, Pocillopora, etc.; Macroalgae = Caulerpa sp, Dictyosphaeria sp, Padina sp, etc.). A stratified random sampling (StRS) design was employed to survey the coral reef ecosystems throughout the U.S. Pacific regions. The survey domain encompassed the majority of the mapped area of reef and hard bottom habitats in the 0-30 m depth range. The stratification scheme included island, reef zone, and depth in all regions, as well as habitat structure type in the Main Hawaiian Islands. Sampling effort was allocated based on strata area and sites were randomly located within strata. Sites were surveyed using photo-quadrats along transects to collect benthic imagery to ultimately produce estimates of relative abundance (percent cover), frequency of occurrence, benthic community taxonomic composition and relative generic richness. The StRS design effectively reduces estimate variance through stratification using environmental covariates and by sampling more sites rather than sampling more transects at a site. Therefore, site-level estimates and site to site comparisons should be used with caution.本数据集源自2013年针对夏威夷群岛全域分层随机样点沿样带开展的底栖样方摄影调查，该调查作为珊瑚与鱼类快速生态评估（Rapid Ecological Assessment, REA）的一部分实施。底栖生境影像采用带Excel扩展工具的珊瑚点计数法（Coral Point Count with Excel extensions, CPCe；Kohler与Gill，2006）软件进行定量分析。通常，影像分析将生成三个功能组层级的底栖覆盖度数据：一级（如硬珊瑚、软珊瑚、大型藻类、表层藻类等）、二级（如硬珊瑚分为团块状、分枝状、叶状、壳状等；大型藻类分为直立大型藻类、壳状大型藻类、蓝绿大型藻类以及仙掌藻属（Halimeda）等）、三级（如硬珊瑚包括星孔珊瑚属（Astreopora sp.）、蜂巢珊瑚属（Favia sp.）、杯形珊瑚属（Pocillopora）等；大型藻类包括蕨藻属（Caulerpa sp.）、球囊藻属（Dictyosphaeria sp.）、团扇藻属（Padina sp.）等）。 本次全美太平洋海域珊瑚礁生态系统调查采用分层随机抽样（Stratified Random Sampling, StRS）设计。调查范围覆盖了水深0-30米范围内绝大多数已测绘的礁体与硬质底质生境区域。分层方案在所有海域涵盖岛屿、礁区与水深维度，主夏威夷群岛还额外纳入生境结构类型维度。抽样强度依据各分层单元的面积进行分配，样点在各分层单元内随机布设。各调查样点通过沿样带布设底栖样方的方式采集影像，最终生成相对丰度（盖度百分比）、出现频率、底栖生物群落分类组成以及属级相对丰富度的估算值。 分层随机抽样设计通过利用环境协变量进行分层，以及增加样点数量而非单样点内的样带数量，有效降低了估算方差。因此，在使用样点级估算值以及开展样点间对比时需谨慎行事。