The role of bacteria on surfaces of coralline algae in settlement of crown-of-thorns starfish (Acanthaster planci) on the Great Barrier Reef

Field and laboratory experiments were undertaken during the spawning period of Acanthaster planci (November to January) to examine substratum preferences of larvae; and the effect of extracts from crustose coralline algae (CCA), the role of bacteria from the coralline algae Lithothamnium pseudosorum, and certain known chemicals on settlement rates.These experiments were conducted at Lizard Island and in the laboratory at the Australian Institute of Marine Science (with samples obtained from Davies Reef). Lizard Island experiment variablesSubstratum selection (no choice, choice of substrata offered) - L. pseudosorum (Lp); scratched (Lps); undamaged (Lpn); Neogoniolithon foslei (Nf); Peyssonellia sp. (Pe); Porolithon onkodes PO); coral rubble (RU); ceramic tile (Ti).Bioassays with CCA and extracts of Lithothamnium pseudosorum - settlement on CCA shards variously treated and on coral blocks perfused with extracts of CCA (use of mesh barriers, boiled shards, dialysis tubing etc.)Bioassays with coral blocks fouled for 9 d, and on coral blocks perfused with extracts from coral rubble.Chemical induction using 5 concentrations of GABA (¿-amino butyric acid) and 4 of K+ [potassium].AIMS experiment variables:Bioassays with CCA and extracts of Lithothamnium pseudosorum - settlement on scratched and unscratched L. pseudosorum, within-plant variation, microhabitat selection.Bacterial induction, the effects of antibiotics - the inductive ability of untreated and antibiotic-treated L pseudosorum, and of L. pseudosorum shards.Bioassays with epiphytic bacteria isolated from L. pseudosorum. To examine the ability of various natural substrata, including CCA, to induce settlement of Acanthaster planci.To determine whether the morphogens associated with highly inductive substrata might be bacterial in origin and, if so, to isolate and identify particular strains that induce settlement.To examine the relationship between the spatial distribution of inducers on reefs to patterns in Acanthaster planci outbreaks and to the paucity of juvenile starfish in shallow water on the Great Barrier Reef. The first research in which bacteria have been implicated in induction by CCA.Coralline algae species: Lithothamnium pseudosorum, Mesophyllum purpurescens, Mesophyllum syrphetodes, Neogoniolithon foslei, Paragoniolithon conicum, Porolithon onkodes.Isolates (10 strains):, Alcaligenes, Alteromonas/Pseudomonas, Alteromonas /Pseudomonas /Alcaligenes, Flavobacterium, Photobacterium, Vibrio.

在棘冠海星（Acanthaster planci）产卵期（11月至1月）开展野外与实验室实验，旨在探究其幼虫的基质偏好；以及壳状珊瑚藻（crustose coralline algae, CCA）提取物、珊瑚藻Lithothamnium pseudosorum所附细菌的作用，与若干已知化学物质对附着率的影响。这些实验于蜥蜴岛（Lizard Island）及澳大利亚海洋科学研究所（Australian Institute of Marine Science）实验室开展（样本取自戴维斯礁）。

蜥蜴岛实验变量：
基质选择（无选择、提供基质选择）——L. pseudosorum（Lp）；划痕（Lps）；未损伤（Lpn）；Neogoniolithon foslei（Nf）；Peyssonellia sp.（Pe）；Porolithon onkodes（PO）；珊瑚碎石（RU）；陶瓷砖（Ti）。
CCA与Lithothamnium pseudosorum提取物的生物测定（bioassays）——经不同处理的CCA碎片及灌注CCA提取物的珊瑚块上的附着情况（使用网状屏障、煮沸碎片、透析管等）。
9天污损珊瑚块及灌注珊瑚碎石提取物的珊瑚块的生物测定。
使用5种浓度的γ-氨基丁酸（gamma-aminobutyric acid, GABA）与4种浓度的钾离子（potassium, K+）进行化学诱导。

AIMS实验变量：
CCA与Lithothamnium pseudosorum提取物的生物测定——划痕与未划痕L. pseudosorum上的附着、植株内变异、微生境（microhabitat）选择。
细菌诱导及抗生素的影响——未处理与经抗生素处理的L. pseudosorum及L. pseudosorum碎片的诱导能力。
从L. pseudosorum分离的附生细菌的生物测定。

研究目标：
探究包括CCA在内的多种天然基质诱导棘冠海星附着的能力。
确定与高诱导性基质相关的形态发生素（morphogen）是否源自细菌；若然，则分离并鉴定诱导附着的特定菌株。
探究礁体上诱导物的空间分布与棘冠海星暴发模式及大堡礁浅水区幼海星稀少现象之间的关系。

首次揭示细菌参与CCA诱导作用（induction）的研究。

珊瑚藻种类：Lithothamnium pseudosorum、Mesophyllum purpurescens、Mesophyllum syrphetodes、Neogoniolithon foslei、Paragoniolithon conicum、Porolithon onkodes。
分离菌株（10株）：Alcaligenes、Alteromonas/Pseudomonas、Alteromonas/Pseudomonas/Alcaligenes、Flavobacterium、Photobacterium、Vibrio。