Distribution of Vitamin B12 in waters of the central Great Barrier Reef

A highly sensitive and selective method was used to estimate concentrations of cyanocobalamin (Vitamin B12) in sea water along a transect of reefs across the central portion of the Great Barrier Reef. Water samples were collected from a depth of 0.5 m along each transect (moving from reef front to reef back) at Pandora, Rib and Myrmidon Reefs. Samples were also collected from Palm Passage at a depth of 10m. Analyses were based on clinical techniques of radioimmunoassay, combining the RIA method with preconcentration of Vitamin B12 by displacement liquid chromatography on C18 SEP-PAK columns. Analyses of the column eluate by radioassay proved sensitive to B12 at femtomolar concentrations (50-2400 pg B12/L seawater). The concentrations calculated from the radioassay translated directly into units of pg B12/L and ng folate/L seawater as a consequence of the concentration procedure. Concentrations above calibration range (2400 pg B 12; 24.0 ng folate) were determined by extrapolation. To determine changes in Vitamin B12 concentrations of sea water along a transect of reefs across the central portion of the Great Barrier Reef.

本研究采用高灵敏高选择性的分析方法，对大堡礁（Great Barrier Reef）中部区域礁体断面海域的海水中氰钴胺（cyanocobalamin，维生素B12）浓度进行了测定。研究人员在潘多拉礁（Pandora Reef）、里布礁（Rib Reef）与迈尔米登礁（Myrmidon Reef）沿每条礁体断面（从礁前至礁后方向）采集了0.5米深度处的海水样品；同时在棕榈水道（Palm Passage）10米深度处采集了额外的海水样品。本次分析基于临床放射免疫分析（radioimmunoassay）技术，将RIA法与通过C18 SEP-PAK柱的置换液相色谱法对维生素B12进行预富集的步骤相结合。经放射检测对柱洗脱液的分析结果表明，该方法可检测飞摩尔浓度（femtomolar）范围的维生素B12，检测线性范围为50~2400 pg B12/L海水。由于预富集步骤的存在，通过放射检测得到的浓度可直接换算为pg B12/L与ng 叶酸（folate）/L海水单位。对于超出校准范围（2400 pg B12；24.0 ng 叶酸/L）的样品浓度，采用外推法进行定量。本研究旨在探明大堡礁中部区域礁体断面海域海水的维生素B12浓度变化特征。