Spatial patterns in shallow-water crinoid communities in the central and northern Great Barrier Reef

Shallow-water crinoid communities of the Central Great Barrier Reef were investigated. 1114 crinoid specimens were collected from 46 sites (24 sites on 12 reefs, 2 sites per reef, and 22 sites at Davies Reef). 43 comatuloid crinoid species from 21 genera and 6 families were identified. 1689 symbionts from the 1114 crinoids were assigned to 46 taxa from 5 invertebrate classes (see separate record).Site locations were classified as nearshore (Green Island), mid-shelf reefs (Davies, Flora, John Brewer, Lodestone, Marx, Rib, Startle), and outer-shelf reefs (Michaelmas Cay, Noggin, Potter, Ribbon No.7, Wardle). Reefs were categorised as either previously infested by Acanthaster planci allowing or as unaffected reefs.Habitat features recorded were: substrate composition, surface complexity, current strength, amount of benthic sediment, and slope angle. R= reef front (windward), B=back reef (leeward), S=sides either northern or southern (flank aspects of the outer slope), L=lagoon (inside).Living posture (Cryptic = less than 20% of the arms visible; Protected = at least the central disc of the animal hidden Free-sitting = centro-dorsal disc visible but animal protected from at least one side; Exposed = animal visible from all directions, generally perched on top of the substrate); minimum and maximum arm length (to nearest cm); and colour were recorded for each specimen. Crinoid nocturnicity was noted.Species abundance and species richness were recorded and Cramer values applied. To provide ecological information on crinoid communities of the Great Barrier Reef.First large-scale study of the structure and composition of crinoid communities on the central Great Barrier Reef. Crinoid species identified: Amphimetra laevipinna, Antedonid sp., Capillaster multiradiatus, Cenometra bella, Clarkcomanthus albinotus, Clarkcomanthus littoralis, Clarkcomanthus luteofuscum, Comanthina schlegeli, Comanthus alternans, Comanthus gisleni, Comanthus parvicirrus, Comanthus wahlbergi, Comaster brevicirrus, Comaster gracilis, Comaster multifidus, Comaster pulcher, Comatella maculate, Comatella nigra, Comatella sp., Comatella stelligera, Comatula pectinata, Comatula purpurea, Decametra laevipinna, Decametra sp.a, Dorometra nana, Euantedon polytes, Himerometra bartschi, Himerometra magnipinna, Himerometra robustipinna, Iconometra intermedia, Liparometra articulate, Oligometra serripinna, Oxycomanthus benetti, Oxycomanthus comanthipinna, Oxycomanthus exilis, Oxycomanthus mirus, Oxycomanthus perplexum, Petasometra clarae, Stephanometra indica, Stephanometra oxyacantha, Stephanometra spicata, Stephanometra spinipinna, Tropiometra afra.

本研究对大堡礁中部的浅水海百合（crinoid）群落展开了系统性调查。总计从46个采样点采集到1114份海百合标本：其中12座礁体各设置2个采样点，合计24个点位，另有22个采样点位于戴维斯礁（Davies Reef）。经形态鉴定，共发现隶属于6科21属的43种羽星类海百合（comatuloid crinoid）；从上述1114份海百合标本中，共分离得到1689个共生生物，它们隶属于5个无脊椎动物纲下的46个类群（详见独立记录）。采样点位置被划分为三类：近岸海域（绿岛（Green Island））、陆架中部礁体（涵盖戴维斯礁、弗洛拉礁、约翰·布鲁尔礁、磁石礁、马克思礁、里布礁、斯塔特尔礁）以及陆架外缘礁体（涵盖迈克尔马斯礁、诺金礁、波特礁、7号丝带礁、沃德尔礁）。礁体被划分为两类：此前曾受长棘海星（Acanthaster planci）侵扰的礁体，以及未受其侵扰的礁体。本次调查记录的栖息地特征包括：底质组成、表面复杂度、水流强度、底栖沉积物含量以及坡角。采样位点按以下规则标记：R代表礁前（迎风侧，reef front (windward)），B代表礁后（背风侧，back reef (leeward)），S代表南北侧翼（外坡的侧翼区域，sides either northern or southern (flank aspects of the outer slope)），L代表潟湖（内部区域，lagoon (inside)）。每一份标本均记录了其栖息姿态：隐蔽型（Cryptic）——腕部暴露比例低于20%；保护型（Protected）——动物至少中央盘体被遮蔽；自由栖居型（Free-sitting）——背中央盘可见，但动物至少一侧受遮蔽；暴露型（Exposed）——动物可被全方位观测，通常栖息于底质表面上方；同时记录了腕部最小与最大长度（精确至厘米级）以及体色。此外，还记录了海百合的夜行性特征。本研究统计了物种丰度与物种丰富度，并采用克莱默值（Cramer values）进行分析，旨在为大堡礁海百合群落提供生态学相关基础数据。本研究是首个针对大堡礁中部海百合群落结构与组成的大规模系统性调查。已鉴定的海百合物种包括：光羽双羽海百合（Amphimetra laevipinna）、Antedonid sp.（海羊齿未定种）、多辐毛细海百合（Capillaster multiradiatus）、美丽美海百合（Cenometra bella）、白克拉克海百合（Clarkcomanthus albinotus）、近岸克拉克海百合（Clarkcomanthus littoralis）、黄褐克拉克海百合（Clarkcomanthus luteofuscum）、许氏枝海百合（Comanthina schlegeli）、交替海百合（Comanthus alternans）、吉氏海百合（Comanthus gisleni）、细腕海百合（Comanthus parvicirrus）、瓦氏海百合（Comanthus wahlbergi）、短腕羽海百合（Comaster brevicirrus）、细羽海百合（Comaster gracilis）、多裂羽海百合（Comaster multifidus）、美丽羽海百合（Comaster pulcher）、斑羽星（Comatella maculata）、黑羽星（Comatella nigra）、Comatella sp.（羽星未定种）、星状羽星（Comatella stelligera）、梳状羽星（Comatula pectinata）、紫色羽星（Comatula purpurea）、光羽十腕海百合（Decametra laevipinna）、Decametra sp.a（十腕海百合未定种a）、多罗美特拉海百合（Dorometra nana）、多棘真海羊齿（Euantedon polytes）、巴氏美羽海百合（Himerometra bartschi）、大鳍美羽海百合（Himerometra magnipinna）、粗鳍美羽海百合（Himerometra robustipinna）、中间图标海百合（Iconometra intermedia）、关节脂海百合（Liparometra articulate）、梳齿寡海百合（Oligometra serripinna）、贝氏尖羽海百合（Oxycomanthus benetti）、枝海百合尖羽海百合（Oxycomanthus comanthipinna）、细弱尖羽海百合（Oxycomanthus exilis）、奇异尖羽海百合（Oxycomanthus mirus）、困惑尖羽海百合（Oxycomanthus perplexum）、克拉拉柔海百合（Petasometra clarae）、印度冠海百合（Stephanometra indica）、尖棘冠海百合（Stephanometra oxyacantha）、穗状冠海百合（Stephanometra spicata）、刺鳍冠海百合（Stephanometra spinipinna）、黑热带海百合（Tropiometra afra）。