Mixotrophy in soft corals of the Great Barrier Reef

Primary production, respiration and bathymetric distribution were investigated in the 10 most common zooxanthellate soft corals on mid-shelf reefs of the Great Barrier Reef (Davies and nearby reefs). Oxygen flux of corals collected from 5-20 m was measured at 6m depth over 24 hours using data-logger respirometers.The photosynthetic and respiratory rates of 10 zooxanthellate and 2 azooxanthellate soft coral genera were determined. Colonies were collected from depths of 5, 10 and 20 m and measured at 6 m depth - only colonies which appeared to have recovered from handling were used in respirometric measurements.Irradiance and oxygen flux rates of the 10 zooxanthellate taxa were measured. The degree of contraction or expansion of each soft coral was recorded every 3 hours during the day and once or twice at night for every 24 h respirometry run.Transects (25 m x 0.5m, perpendicular to the slope) were surveyed at 5 m depth intervals from 5-30 m on windward, leeward, northern and southern flanks (note not all went to 30 m deep); mean density of all common soft coral taxa were recorded, and photosynthetically active radiation (PAR) was measured.
To assess the contribution of phototrophy to the carbon requirements of the most common taxa inhabiting the upper 20 m on the central Great Barrier Reef.To examine the effect of depth and degree of colony contraction on rates of phototrophy.
Samples of specimens were collected for taxonomic identification: these are kept in the Northern Territory Museum, Darwin.Soft corals: Family Alcyoniidae (Lobophytum spp., Sarcophyton spp., Sinularia 7 spp.); Family Asterospiculariidae (Asterospicularia sp.); Family Briareidae (Briareum stechii); Family Nephtheidae (Capnella lacertiliensis, Dedronephthya 2 spp., Nephthya sp., Paralemnalia clavata, Paralemnalia digitiformis, Scleronephthya sp.); Family Xeniidae (Efflatounaria sp., Xenia spp.).Reefs:

本研究针对大堡礁陆架中部礁区（戴维斯礁及邻近礁群）中10种最常见的虫黄藻共生软珊瑚（zooxanthellate soft corals），开展了初级生产力、呼吸作用及水深分布特征的调查。采集自5-20米水深的珊瑚样本，于6米水深环境中利用数据记录式呼吸仪开展了为期24小时的氧气通量测定。本研究同时测定了10种虫黄藻共生及2种无虫黄藻共生（azooxanthellate）软珊瑚属的光合速率与呼吸速率。珊瑚群落采集自5、10及20米水深，于6米水深环境中开展测定；仅选取经人工处理后恢复状态良好的群落用于呼吸计量实验。测定了这10种虫黄藻共生软珊瑚类群的光照强度与氧气通量速率。在每一轮24小时的呼吸计量实验中，日间每3小时记录一次软珊瑚的收缩或伸展程度，夜间则每1-2次记录一次。沿礁体的向风、背风、北、南四个侧翼，以5米水深为间隔，于5-30米水深范围内布设25米×0.5米（垂直于礁坡）的样带开展调查（注：并非所有样带均延伸至30米水深）；记录所有常见软珊瑚类群的平均密度，并测定了光合有效辐射（photosynthetically active radiation, PAR）。
本研究的核心目标包括：评估光养作用对栖息于大堡礁中部20米以浅水域的常见类群的碳需求贡献；探究水深与珊瑚群落收缩程度对光养速率的影响。
用于分类鉴定的标本样本保存于达尔文市北领地博物馆（Northern Territory Museum）。
软珊瑚类群如下：软柳珊瑚科（Alcyoniidae）：裂皮软珊瑚属（Lobophytum spp.）、肉芝软珊瑚属（Sarcophyton spp.）、Sinularia属7个物种；星针软珊瑚科（Asterospiculariidae）：星针软珊瑚属（Asterospicularia sp.）；碧珊瑚科（Briareidae）：Briareum stechii；穗珊瑚科（Nephtheidae）：Capnella lacertiliensis、Dedronephthya属2个物种、Nephthya sp.、Paralemnalia clavata、Paralemnalia digitiformis、Scleronephthya sp.；丛枝软珊瑚科（Xeniidae）：Efflatounaria sp.、Xenia spp.。
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