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，共记载23个属的42个物种，类群以无虫黄藻（azooxanthellate）类群为主。每个珊瑚礁布设1-3个调查样点，每个样点按预设水深梯度（1-3m、3-8m、8-13m、13-18m以及礁坪）设置最多5条样带（样带通常长200-300m、宽1-3m，调查时长10-15分钟）。本次调查记载的类群包括：八放珊瑚（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、匍匐八放珊瑚）以及黑珊瑚和丝珊瑚。需说明：本次记录的物种大多仅鉴定至属级水平。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、水动力暴露等级（分为极暴露、受保护、暴露、中等4类）、朝向（东、东北偏北等）、地形类型（岬角、崖壁、海湾/入口、水道）、坡度（划分为5°区间等级）、流速（通过5次测量悬浮颗粒沿直尺移动的速度估算，单位为厘米/秒）、波浪暴露等级（0=遮蔽，4=极暴露）、沉积物沉积状况（0=无沉积，1=薄层沉积，2=中等沉积，3=厚层沉积）、碎石盖度百分比、沙质盖度百分比。底栖生物总丰度（盖度百分比）采用目视估算法：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。调查类别包括：硬珊瑚、软珊瑚、死亡珊瑚、藻席、珊瑚藻、大型藻类（其中大型显眼藻类——仙掌藻（Halimeda）和马尾藻（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（部分类群鉴定至种）被赋予类群丰度等级：0=缺失，1=罕见，2=少见，3=常见，4=丰富，5=优势类群。有虫黄藻（zooxanthellate）和无虫黄藻八放珊瑚的物种丰富度，分别基于携带（或不携带）虫黄藻的八放珊瑚类群数量计算得到。如有需要，用于分类学研究的采集样本均已标注。样点位置如下：博卡拉岩（Bokhara Rocks）、断礁（Breakers Rock）、斧洲（Fo Shek Chau）、将军澳（Junk Bay）、弓洲（Kung Chau）、螺洲白排（Lo Chau Pak Poi）、浪茄湾（Long Ke Wan）、鹿洲（Luk Chau）、鹿洲湾（Luk Chau Wan）、北果洲（North Ninepin）、白洲（Pak Shau）、平洲（Ping Chao）、蒲台岛（Po Toi）、深湾（Sham Wan）、南果洲（South Ninepin）、大头洲（Tai Tau Chau）、横澜岛（Waglan）。本数据集旨在调查香港周边珊瑚礁海域主要底栖类群的盖度、八放珊瑚的物种丰富度与丰度，以及相关空间梯度和水质梯度特征。由于约半数八放珊瑚携带光合共生体，因此该类群是探究生物多样性与空间、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。本研究同时旨在探究珊瑚礁底栖生物群落的生物多样性、群落组成及分布范围的主要驱动因子。澳大利亚大堡礁、帕劳、巴布亚新几内亚、托雷斯海峡以及罗利沙洲（西澳州）拥有与之可比的同类数据集。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）。