Coral communities at Scott Reef and Rowley Shoals, Western Australia

In August/September 1993, surveys of coral community composition and structure were carried out at Scott Reefs (North Scott Reef and South Scott Reef) and two reefs in the Rowley Shoals group (Mermaid Reef and Clerke Reef).Coral communities were surveyed at a total of 94 sites, using a semi-quantitative visual survey method and a subset of these sites were surveyed using a video belt transect technique. Sites were areas of around 100-300 m², arranged along cross-reef profiles on the reef flats in a depth range of 0.5-2 m and on the slopes or adjacent reef floor at 4-6 m and 8-12 m. Aerial photography was used to assist in selection of study areas.During each visual survey a detailed list of coral species was made and the relative abundance of each taxa, as a percentage of total macro-benthos, was estimated. The site descriptors recorded were maximum and minimum depth (measured); and subjective estimates of the following: slope; percentage cover of hard substrate; percentage cover of major benthic groups (hard coral, soft coral, macro algae and sponge); percentage cover of substratum categories (platform; large blocks; small blocks; rubble; gravel; sand). An additional 4 sites were surveyed, without recording detailed species lists.A Sony Hi 8 video camera was used to film five replicate 20 m long belt transects about 40 cm wide, within each of the 3 depth ranges, in a sub-set of the sites used for visual surveys. Estimates of percent cover of hard coral, soft coral, algae and bare substratum were made using point sampling of the video tape. At 25 regularly spaced pauses along each video tape, the identity of each item under five points marked on the screen of the TV monitor (one near each corner and one in the centre) was recorded. Percent cover estimates were used to estimate the heterogeneity of the bottom cover as a basis for designing an appropriate sample protocol for a future monitoring program. The visual surveys were carried out to determine whether recognisable, taxonomically consistent assemblages of coral species occurred at the shallow water study sites and to determine the approximate spatial extent of these corals. The surveys were also used to provide detailed taxonomic descriptions of the coral communities at the sites where the video transects were recorded. These surveys were the first quantitative assessments of coral community structure on northwest Australian offshore reefs, previous coral surveys being largely concerned with taxonomic and biogeographic problems.The information collected during this survey formed the basis of of site selection for the subsequent long-term monitoring project.

1993年8月至9月，研究团队于斯科特礁（Scott Reefs，含北斯科特礁、南斯科特礁）以及罗利沙洲群（Rowley Shoals group）的两座礁体——美人鱼礁（Mermaid Reef）与克拉克礁（Clerke Reef）开展了珊瑚群落组成与结构调查。本次调查共布设94个点位，采用半定量目视调查法（semi-quantitative visual survey method）开展普查，其中部分点位辅以视频带状样带法（video belt transect technique）进行补充采样。点位面积约100~300平方米，沿礁坪的跨礁剖面布设，水深覆盖0.5~2米的礁坪区域，以及4~6米、8~12米的斜坡或邻近礁底区域。研究区域的遴选借助了航空摄影手段。

每次目视调查均会记录详细的珊瑚物种名录，并估算各分类群占大型底栖生物（macro-benthos）总丰度的百分比。记录的点位参数包括实测的最大、最小水深，以及以下项目的主观估算值：坡度、硬质基底覆盖率、主要底栖类群（硬珊瑚、软珊瑚、大型藻类、海绵）的覆盖率，以及基底类型（台地、大块礁体、小块礁体、碎石、砾石、沙）的覆盖率。另有4个点位仅开展调查，未记录详细物种名录。

在部分目视调查点位中，针对3个水深区间，各使用索尼Hi 8（Sony Hi 8）摄像机拍摄5条重复的20米长、宽约40厘米的带状样带视频。通过对录像带的点采样估算硬珊瑚、软珊瑚、藻类与裸露基底的覆盖率：在每条录像带的25个均匀间隔停顿点处，对电视监视器屏幕上标记的5个点（四角各1个、中心1个）下方的物体进行识别。利用覆盖率估算值评估底栖覆盖的异质性，为未来监测项目设计适配的采样方案提供依据。

本次调查的核心目标包括：探明浅水研究点位是否存在可识别的、分类学一致的珊瑚物种组合，并确定此类珊瑚群落的大致空间分布范围；同时为开展视频样带调查的点位提供珊瑚群落的详细分类学描述。本调查是澳大利亚西北海域离岸礁体珊瑚群落结构的首次定量评估，此前的珊瑚调查大多聚焦于分类学与生物地理学问题。本次采集的所有数据，为后续长期监测项目的点位遴选提供了核心依据。