Effects of damselfish on corals at Britomart Reef, Great Barrier Reef

A series of photographs were taken of experimental conditions over a two-year period and analysed using digitizing techniques to determine direct and indirect effects of fish grazing, damselfish territoriality, and external bioerosion of dead coral substratumPieces of the freshly killed plating coral Pachyseris speciosa were placed under four experimental conditions on Britomart Reef: (1) within cages designed to exclude grazing fish; (2) within the territories of the damselfish Hemiglyphidodon plagiometopon; (3) beneath shade-tops to control for a decrease in light; and (4) outside damselfish territories, fully exposed to fish grazing.Three replicates (A, B, C) were conducted for each set of conditions, placed on the reef 9-11 m deep, and time-lapse photographs taken.Of the 12 plates, 3 subsets were exposed for 8, 12, 24 months.A parallel study was run at the same location and time using the same experimental design to examine the effects of fish grazing on coral recruitment. The number of competitive interactions and successful outcomes (for coral) were recorded between Acropora spat and other sessile epibiota (green alga - Palmophyllum sp.; Foram; red algae - Ceramium procumbens, Centroceras clavulatum, Gracilariopsis rhodotricha, Polysiphonia subtilissima; bryozoans; filamentous green algae; sessile polychaete - sandy tube). To determine the relationship between fish grazing, damselfish territoriality, and external bioerosion of dead coral substratum. Taxa: scarids (parrotfish); ;acanthurids (surgeonfish); small fish (Pomacentrus molluccensis, blennies); small invertebrates (pagurid and galatheid crabs - Galathea subsquamata). Three categories of borers were identified: Cliothosa hancocki; other sponges (Cliona viridis complex); and 'worms' (included polychaetes and sipunculids - Cleosiphon aspergillum).Coral recruit taxa: Acroporidae (Acropora, Seriatopora hystrix); Caryophylliid or Pectiniid (A); Fungiidae (Fungia A?, B, Compound Fungiid A); Faviid A; Mussid (A, B, C); Oculinidae (Galaxea?); Pocilloporidae (Stylophora?, possibly Pocillipora); Poritidae (Alueopora?, Porites probably P. andrewsi); Unidentified.

在两年期间，研究人员对实验条件拍摄了一系列照片，并利用数字化技术分析，以确定鱼类摄食、雀鲷领地行为（damselfish territoriality）及死珊瑚基质外部生物侵蚀（external bioerosion）的直接和间接效应。研究将新鲜杀死的板状珊瑚厚丝珊瑚（Pachyseris speciosa）片段放置在Britomart礁的四种实验条件下：（1）置于旨在排除摄食鱼类的网笼内；（2）置于雀鲷Hemiglyphidodon plagiometopon的领地内；（3）置于遮荫顶下以控制光照减少；（4）置于雀鲷领地外，完全暴露于鱼类摄食。每组条件设置三个重复（A、B、C），放置于礁区9-11米深处，并进行延时摄影。在12块珊瑚板中，3个子集分别暴露8、12、24个月。同期在同一地点采用相同实验设计开展并行研究，以探究鱼类摄食对珊瑚补充（coral recruitment）的影响。记录了鹿角珊瑚幼体（Acropora spat）与其他固着附生生物（如绿藻Palmophyllum sp.、有孔虫（Foram）、红藻Ceramium procumbens、Centroceras clavulatum、Gracilariopsis rhodotricha、Polysiphonia subtilissima、苔藓虫、丝状绿藻、固着多毛类——沙管虫）之间的竞争互作次数及珊瑚的成功存活结果。为明确鱼类摄食、雀鲷领地行为及死珊瑚基质外部生物侵蚀之间的关系，研究涉及以下类群：鹦嘴鱼（scarids，俗称parrotfish）；刺尾鱼（acanthurids，俗称surgeonfish）；小型鱼类（如摩鹿加雀鲷Pomacentrus molluccensis、鳚类）；小型无脊椎动物（如寄居蟹pagurid、铠甲虾galatheid crabs——亚鳞真铠甲虾Galathea subsquamata）。研究识别出三类钻孔生物（borers）：Cliothosa hancocki；其他海绵（如绿穿孔海绵复合体Cliona viridis complex）；以及'蠕虫'类（包括多毛类polychaetes和星虫类sipunculids——曲霉状管星虫Cleosiphon aspergillum）。珊瑚补充类群包括：鹿角珊瑚科Acroporidae（如鹿角珊瑚属Acropora、尖枝列孔珊瑚Seriatopora hystrix）；Caryophylliid或Pectiniid科（类型A）；石芝珊瑚科Fungiidae（如Fungia属A?、B、复合Fungiid A）；蜂巢珊瑚科Faviid（类型A）；褶叶珊瑚科Mussid（类型A、B、C）；眼珊瑚科Oculinidae（疑似Galaxea属）；杯形珊瑚科Pocilloporidae（疑似Stylophora属，可能为Pocillipora属）；滨珊瑚科Poritidae（疑似Alueopora属、滨珊瑚属Porites，可能为P. andrewsi）；以及未鉴定类群。