Depletion of suspended particulate matter over coastal reef communities dominated by zooxanthellate soft corals, Great Barrier Reef

Measurements were carried out at the southern ends of the Pelorus and Fantome Channels (between 2 adjacent islands in the Palms Group) where the reefs are 50-150 m wide and over the sand bottom (more towards the middle of the channels).Current meters were deployed at 6 m depth (averaging 120 readings every 10th minute over 3-4 days. Relative flow was measured using plaster blocks: 2 blocks beneath each current meter, and 10 blocks across each reef perpendicular to the flow left for 24 hr (2 tidal cycles).Water samples were taken from 5-8 m depths upstream of the reefs, repeated downstream, and at the sandy sites (these at 7-10 m). Sampling was repeated 64 times in 4 sets of 5-6 days each month. September and November samples were affected by the cyanobacterium Trichodesmium. September samples were not prefiltered and standard deviations between duplicate chlorophyll samples were much higher than other months. November samples were filtered through a 10 µm mesh to remove Trichodesmium - particlate matter data therefore was Percent cover and abundances of individual taxa were assessed with 4 x 50 transects over both channel reefs. Rapid ecological assessments (REAs, 48 swims of 10-15 mins) were used for comparison of the macrobenthos and physical parameters on reef (25 REAs) and sand (23 REAs). Percent total cover of alcyoniid and other soft corals, hard corals, turf and macro algae, sand and unconsolidated rubble were estimated. Inventories of genera of soft corals, gorgonians, sponges, tunicates and zoanthids (growth forms and phyla) were complied and abundances estimated using a ranked scale (0=absent, 1=1 or few colonies, 2=uncommon, 3=moderately common, 4=common, 5=dominant). The standing crop of soft corals was assesed by measuring the projected areas and colony volumes of individuals in each of the 6 most common soft coral genera. Soft coral biomass per m2 was estimated by collecting 15 specimens each of the 2 dominant soft coral species (Sinularia flexibilis and S. capitalis) after measuring their projected areas and height. These were then dried to constant weight ashed and then the ash-free weight determined (the relationship between the AFDW and colony area was linear in both taxa).Concentrations of phytoplankton pigments and suspended particulate nutrients were measured (in µg 1-1). Net removal of chlorophyll (as a marker for phytoplankton), particulate organic carbon (for determining energy gain), and particulate phosphorus and nitrogen were estimated.
To investigate the rates of in situ depletion of natural suspended particulate matter (containing living and non-living particles) by reef communities dominated by zooxanthellate alcyoniid soft corals.
Soft coral genera: Alcyonium, Anthelia, Cladiella, Dendronephthya, Dicotella, Efflatounaria, Ellisella, Isis hippuris, Junceella, Lobophyton, Melathaea, Nephthea, Paralemnalia, Parerythropodium, Plexauridae, Sarcophyton, Scleronephthya, Sinularia, Xenia.The most common soft coral taxa (in order of percent cover) were: Sinularia flexibilis S. capitalis, Sinularia spp. Sarcophyton spp, Nephthea spp, Lobophyton spp.Few other cryptic filter feeders were found and total cover of epibenthic sponges, bivalves and tunicates amounted to

本研究于佩洛鲁斯海峡（Pelorus Channel）与幻视海峡（Fantome Channel）的南端开展，该区域位于棕榈群（Palms Group）内两座相邻岛屿之间，此处珊瑚礁宽度为50至150米，观测点位覆盖沙质底质（海峡中部区域分布更为广泛）。

于6米水深处布设海流计，在3至4天的观测周期内以每10分钟1次的频率采集数据，单台设备平均获取120组观测值。采用石膏块法测量相对流速：每台海流计下方布设2块石膏块，同时在每条珊瑚礁上垂直于流向的方向布设10块石膏块，留置24小时（对应2个潮汐周期）。

分别在珊瑚礁上游5至8米水深、下游相同水深以及沙质底质点位（水深7至10米）采集水样。每月开展4组采样，每组持续5至6天，全年共重复采样64次。9月与11月的水样受蓝藻束毛藻（Trichodesmium）影响：9月水样未进行预过滤，重复叶绿素样品的标准差显著高于其他月份；11月水样通过10 µm孔径的滤膜过滤以去除束毛藻，因此颗粒物数据（原文此处未完成）。

通过在两条海峡珊瑚礁上布设4条50米样带，对各分类群的盖度与丰度进行评估。采用快速生态评估法（Rapid Ecological Assessments, REAs，共开展48次时长10至15分钟的水下勘查）对比珊瑚礁（25次REAs）与沙质底质（23次REAs）的大型底栖生物群落与物理参数。对共附生软珊瑚（alcyoniid）及其他软珊瑚、石珊瑚、藻席、大型藻类、沙质沉积物与未固结碎石的总盖度进行估算。

对软珊瑚、柳珊瑚、海绵、被囊动物以及群体海葵的属级类群（包括生长型与门类）进行编目，并采用分级量表估算其丰度：0=未检出，1=1个或少量群体，2=少见，3=中等常见，4=常见，5=优势种。针对6种最常见的软珊瑚属的个体，通过测量其投影面积与群体体积，评估软珊瑚的现存量。

通过采集2种优势软珊瑚物种（细指软珊瑚*Sinularia flexibilis*与*S. capitalis*）的各15份标本，先测量其投影面积与高度，再将标本烘干至恒重并灰化，测定其无灰干重（ash-free dry weight, AFDW），结果显示两种类群的无灰干重与群体面积均呈线性相关关系，据此估算单位面积软珊瑚生物量。测定浮游植物色素与悬浮颗粒营养盐的浓度（单位：µg·L⁻¹），并估算叶绿素（作为浮游植物标志物）、颗粒有机碳（用于表征能量获取）以及颗粒态磷与氮的净去除速率。

本研究旨在探究以虫黄藻共生共附生软珊瑚（zooxanthellate alcyoniid soft corals）为优势类群的珊瑚礁群落，对天然悬浮颗粒物（包含活体与非活体颗粒）的原位消耗速率。

软珊瑚属类群包括：海鸡冠珊瑚属*Alcyonium*、短指软珊瑚属*Anthelia*、克拉达软珊瑚属*Cladiella*、丛枝软珊瑚属*Dendronephthya*、二列软珊瑚属*Dicotella*、埃弗拉软珊瑚属*Efflatounaria*、鞭柳珊瑚属*Ellisella*、海柏*Isis hippuris*、节柳珊瑚属*Junceella*、叶软珊瑚属*Lobophyton*、美软珊瑚属*Melathaea*、软指珊瑚属*Nephthea*、副莱姆纳软珊瑚属*Paralemnalia*、副红珊瑚属*Parerythropodium*、丛柳珊瑚科*Plexauridae*、肉芝软珊瑚属*Sarcophyton*、硬指软珊瑚属*Scleronephthya*、指形软珊瑚属*Sinularia*、叉指软珊瑚属*Xenia*。

按盖度从高到低排序，最常见的软珊瑚类群依次为：细指软珊瑚*Sinularia flexibilis*、*S. capitalis*、指形软珊瑚未定种*Sinularia* spp.、肉芝软珊瑚未定种*Sarcophyton* spp.、软指珊瑚未定种*Nephthea* spp.以及叶软珊瑚未定种*Lobophyton* spp.。

仅发现少量隐匿性滤食性生物，底栖海绵、双壳类与被囊动物的总盖度为（原文未完成）。