Broadscale survey of coral condition on the reefs of the Easter Group of the Houtman Abrolhos Islands

Anthropogenic activities that occur at the Abrolhos Islands include commercial lobster and line fishing and tourism. Impacts such as physical damage from diving, anchoring deployment of lobster pots and influence of land-based activities could cause changes to coral condition. The possible effects of human activities on coral reefs were noted as potential issues during management and stakeholder workshops (Fisheries WA 1998; Chubb et al. 2002; Webster et al. 2002). This survey broadly addressed potential impacts on the coral reefs by estimating coral cover, coral bleaching, coral disease, coral damage, and the abundance of the corallivores; Acanthasterplanci starfish and Drupella snails. Eight research sites were selected, including reefs in the Rat Island group, Suami Island group and Leo Island group and surveyed from the 16th to 21st of February 2004. At each site three 50 metre belt transects were videoed and a GPS reading taken at the start of each site. Transects were laid parallel to the reef crest at a depth of appropriately 4 - 6 m. The video transects were analysed using AVTAS (AIMS Video Analysis System), (Christie et al, 1996). The health of the corals 2 m either side of the transect line were examined and the following potential impacts assessed and quantified: Bleaching: The severity of bleaching on individual colonies and the proportion of colonies affected was estimated. Disease: Five categories of coral disease were recorded including, black band disease, white syndrome, skeletal eroding band, brown band and pink spot. The species infected and the number colony displaying disease symptoms were recorded. Corallivores: The levels of the damage and incidence of starfish and snails were counted at each site. Coral Damage: The extent and severity of coral damage was recorded.

Abrolhos群岛（Abrolhos Islands）的人类活动包括商业龙虾捕捞、延绳钓渔业与旅游业。潜水作业造成的物理损伤、锚泊操作、龙虾笼布设以及陆基活动的影响，均可能改变珊瑚的生存状态。在管理方与利益相关方研讨会中，人类活动对珊瑚礁的潜在影响已被列为重点关切问题（西澳渔业局[Fisheries WA]1998；Chubb等人2002；Webster等人2002）。

本次调查通过估算珊瑚覆盖率、珊瑚白化程度、珊瑚病害状况、珊瑚损伤情况以及食珊瑚生物的丰度——棘冠海星（Acanthaster planci）与食珊瑚螺（Drupella snails）——，全面探讨了人类活动对珊瑚礁的潜在影响。本次研究共选定8个研究样地，涵盖拉特群岛群（Rat Island group）、苏阿米群岛群（Suami Island group）与利奥群岛群（Leo Island group）的珊瑚礁，并于2004年2月16日至21日完成野外调查。

在每个样地内布设3条50米带形样带，进行视频录制，并在每个样地的起始点记录GPS坐标。样带平行于礁冠布设，水深约4至6米。视频样带数据采用AVTAS（澳大利亚海洋科学研究所视频分析系统，AIMS Video Analysis System，Christie等人1996）进行分析。研究人员对样带两侧2米范围内的珊瑚健康状况开展检查，并对以下四类潜在影响进行评估与量化：
1. 珊瑚白化：估算单个珊瑚群落的白化严重程度以及受白化影响的群落占比；
2. 珊瑚病害：记录5类珊瑚病害，包括黑带病（black band disease）、白色综合征（white syndrome）、骨骼侵蚀带病（skeletal eroding band）、棕色带病（brown band）与粉斑病（pink spot），并记录受感染的珊瑚种类以及出现病害症状的珊瑚群落数量；
3. 食珊瑚生物：统计各研究样地内棘冠海星与食珊瑚螺的种群损伤程度及发生频次；
4. 珊瑚损伤：记录珊瑚损伤的范围与严重程度。