Small scale distribution of bioeroding sponges in shallow water at Orpheus Island, Great Barrier Reef

Five permanent 100m transects were established in the southern corner of Little Pioneer Bay, Orpheus Island. The transects, placed perpendicular to the coast, extended from the sandy zone, which is dry at low tide, across the reef flat. A quadrat with 0.5m sides, divided into 25 x 100 cm² quadrats was placed on the substrate along the whole length of each transect. The area of sponge tissue was estimated by counting the 100 cm² quadrats in which sponge tissue occurred. Due to the difficulty in identifying species in the field, seven species or groups of species were distinguished along the transects. These were: encrusting beta-form Cliona orientalis; brown alpha-form sponges (including the alpha-form of Cliona orientalis); brown to orange alpha-form sponges (includes Pione vastifica, Pione caesia and Bernatia vermifera); yellow to orange sponges (includes Cliona celata and Cliothosa hancocki); Aka mucosa; Zyzzya criceta; and others.Substrate characteristics were also recorded along the transects by counting the number of 100 cm² quadrats with over 50% of a given substrate. The substrate categories included: sand; rubble; rock; mud; dead top coral; coral material pavement; soft corals (mainly Sarcophyton); branching corals (Porites cylindrica, Millepora sp. and Porites rus); massive Porites colonies; various live corals; and funnel shaped corals. These characteristics were used to define zones along the transects. The zones were: sand flat; mixed zone (sand, rubble, dead top coral); coral pavement; branching corals; live coral reef relief; and soft coral belts. The amount of exposed calcium carbonate substrate suitable for settlement of bioeroding sponges was recorded. This study was initiated to address the lack of ecological data on bioeroding sponges in the Pacific. The objective was to determine small-scale distribution patterns of bioeroding sponges in shallow water across a reef flat and to examine the relationship between distribution patterns and substrate availability, exposure during low tide and water depth.

本研究在奥费斯岛（Orpheus Island）小先锋湾（Little Pioneer Bay）南侧区域布设了5条固定的100米样带。该样带与海岸垂直布设，从退潮时裸露的沙质带起始，横跨礁坪延伸。沿每条样带的全长，在底质上布设边长0.5米的样方，该样方被划分为25个100平方厘米的小样方。通过统计有海绵组织存在的100平方厘米小样方数量，估算海绵组织的覆盖面积。由于野外难以准确鉴定物种，研究沿样带区分出7个物种或物种类群，分别为：包壳型β型东方穿贝海绵（Cliona orientalis）、棕色α型海绵（包含东方穿贝海绵的α型）、棕至橙色α型海绵（涵盖Pione vastifica、Pione caesia及Bernatia vermifera）、黄至橙色海绵（涵盖Cliona celata与Cliothosa hancocki）、黏膜阿卡海绵（Aka mucosa）、环纹齐兹海绵（Zyzzya criceta）以及其他类群。研究同时沿样带记录底质特征：统计某类底质覆盖占比超过50%的100平方厘米小样方数量。底质类别包括：沙质、碎石、岩石、泥质、死亡造礁珊瑚顶部、珊瑚砾石坪、软珊瑚（主要为肉芝软珊瑚属Sarcophyton）、分枝状珊瑚（包括柱形多孔珊瑚Porites cylindrica、千孔珊瑚属Millepora sp.及Porites rus）、块状多孔珊瑚群落、多种活珊瑚以及漏斗形珊瑚。基于上述底质特征，研究将样带划分为以下生境带：沙质滩、混合带（沙质、碎石、死亡造礁珊瑚顶部）、珊瑚砾石坪、分枝状珊瑚带、活珊瑚礁隆起带以及软珊瑚带。本研究同时记录了可供生物侵蚀海绵附着的裸露碳酸钙底质面积。本研究旨在填补太平洋海域生物侵蚀海绵生态数据匮乏的空白，目标为明确浅水区礁坪上生物侵蚀海绵的小型空间分布格局，并探究其分布格局与底质可利用性、退潮暴露时长以及水深之间的关联。