Surveys of Octocoral communities, benthic cover and environmental factors on coral reefs of Hong Kong

All surveys were carried out by the principal researcher using Rapid Ecological Assessment. The dataset comprises 41 surveys from 21 reef locations, recording 42 species in 23 genera (dominated by azooxanthellate taxa).On each reef, 1-3 sites were surveyed with up to 5 transects (usually 200-300m long, 1-3m wide for 10-15 minutes) per site at pre-defined depths (1-3m, 3-8m, 8-13m, 13-18m and reef flat).Taxa recorded: octocorals (soft corals, gorgonians, sea fans, sea whips, sea pens, leather corals, arborescent octocorals, blue coral, stoloniferans), black and wire coral. Note that species are mostly at generic level.Site variables comprise: visibility (a modified Secchi technique - estimating maximum visible distance of a bright object in metres); depth; exposure (very exposed, protected, exposed, moderate); orientation (E, NNE, etc.); formation (Point, Face, Bay/Inlet, Channel); slope angle (assigned to 5° categories); flowspeed (estimated by 5 timings of the traveling speed of suspended particles along a ruler at cm/second); wave exposure (0=sheltered to 4=very exposed); sediment deposit (0=none, 1=thin layer, 2=considerable, 3=thick layer); rubble % cover; sand % cover.Visual estimates of overall abundance (percent cover) were estimated in 2.5% increments from 1-10%, 5% increments from 10-30% and 10% increments over 30%). Categories are: hard corals, soft corals, dead coral, turf algae, coralline algae, macroalgae (conspicuous macroalgae - Halimeda and sargassum - were recorded separately), and total percent cover including sand and silt.Octocoral genera (in some cases species) were given a taxon abundance ranking (0=absent, 1=rare, 2=uncommon, 3=common, 4=abundant, 5=dominant).Zooxanthellate and azooxanthellate richness was calculated based on the numbers of octocoral taxa with (or without) zooxanthellae.Where applicable, samples taken for taxonomic purposes are noted .Site locations: Bokhara Rocks, Breakers Rock, Fo Shek Chau, Junk Bay, Kung Chau, Lo Chau Pak Poi, Long Ke Wan, Luk Chau, Luk Chau Wan, North Ninepin, Pak Shau, Ping Chao, Po Toi, Sham Wan, South Ninepin, Tai Tau Chau, Waglan. To survey the cover of the main benthic groups, richness and abundance of octocorals in the reefs of Hong Kong and related spatial and water quality gradients.Because roughly half Octocorals have photosynthetic symbionts they are ideal to assess how biodiversity is related to spatial and environmental factors, and photosynthetic symbionts and energy supply.To examine principal drivers of biodiversity, community composition, and ranges ofcoral reef benthos. Comparable data are held for the Great Barrier Reef, Palau, Papua New Guinea, Torres Strait, and Rowley Shoals (WA).A subset of the data has been provided to the Ocean Biogeographic Information System (OBIS, http://www.iobis.org/OBISWEB/DisplayMetaData.jsp?content=meta/1462.html).

本研究所有调查均由首席研究员采用快速生态评估（Rapid Ecological Assessment）方法开展。本数据集涵盖来自21个珊瑚礁点位的41次调查记录，共记录23个属的42个物种，类群以不含虫黄藻的类群（azooxanthellate taxa）为主。每个珊瑚礁布设1-3个调查样点，每个样点设置最多5条样带（通常长200-300米、宽1-3米，调查时长10-15分钟），调查覆盖预设水深梯度：1-3米、3-8米、8-13米、13-18米以及礁坪。记录类群包括八放珊瑚（octocorals，含软珊瑚、柳珊瑚、海扇、海鞭、海笔、皮革珊瑚、树状八放珊瑚、蓝珊瑚、匍匐类群）以及黑珊瑚与铁丝珊瑚。需注意，本次记录的物种多数仅鉴定至属级水平。样点环境变量包括：能见度（采用改良塞氏盘法——以米为单位估算明亮物体的最大可视距离）、水深、暴露度（分为极暴露、受保护、暴露、中等四个等级）、朝向（东、东北偏北等）、地形类型（岬角、坡面、海湾/入口、水道）、坡度（划分为5°区间类别）、流速（通过5次测量悬浮颗粒沿标尺移动的速度估算，单位为厘米/秒）、波浪暴露度（0为遮蔽，4为极暴露）、沉积物沉积量（0为无沉积，1为薄层沉积，2为较厚沉积，3为厚层沉积）、碎石覆盖率百分比以及沙质覆盖率百分比。底栖生物总丰度（以盖度百分比计）采用视觉估算：1%-10%区间以2.5%为增量，10%-30%区间以5%为增量，30%以上区间以10%为增量。分类类别包括：硬珊瑚、软珊瑚、死亡珊瑚、皮藻、珊瑚藻、大型藻类（其中大型可见藻类——仙掌藻属（Halimeda）和马尾藻属（Sargassum）——单独记录），以及包含沙和粉沙在内的总盖度百分比。八放珊瑚的属（部分案例鉴定至物种水平）被赋予类群丰度等级：0=未出现，1=罕见，2=少见，3=常见，4=丰茂，5=优势类群。含虫黄藻（zooxanthellate）与不含虫黄藻的类群丰富度，基于八放珊瑚类群中是否带有虫黄藻的数量计算得出。若适用，为分类学研究采集的样本均已标注说明。调查点位如下：博卡拉岩（Bokhara Rocks）、布雷克斯岩（Breakers Rock）、斧洲（Fo Shek Chau）、将军澳（Junk Bay）、贡洲（Kung Chau）、螺洲排白排（Lo Chau Pak Poi）、浪茄湾（Long Ke Wan）、鹿洲（Luk Chau）、鹿洲湾（Luk Chau Wan）、北九柱岛（North Ninepin）、白沙洲（Pak Shau）、平洲（Ping Chao）、蒲台岛（Po Toi）、深湾（Sham Wan）、南九柱岛（South Ninepin）、大鸦洲（Tai Tau Chau）、横澜岛（Waglan）。本数据集旨在调查香港珊瑚礁区域主要底栖类群的盖度、八放珊瑚的丰富度与丰度，以及相关空间梯度与水质梯度变量。由于约半数八放珊瑚携带光合共生体，因此该类群是评估生物多样性与空间、环境因子以及光合共生体和能量供给之间关系的理想研究对象。本数据集用于探究珊瑚礁底栖生物的生物多样性、群落组成及其分布范围的主要驱动因子。大堡礁、帕劳、巴布亚新几内亚、托雷斯海峡以及罗利沙洲（西澳大利亚州，WA）均存有可比数据集。本数据集的一个子集已提交至海洋生物地理信息系统（Ocean Biogeographic Information System，OBIS，http://www.iobis.org/OBISWEB/DisplayMetaData.jsp?content=meta/1462.html）。