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，对大堡礁中部海域礁带断面处海水中的氰钴胺（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）和迈尔米登礁（Myrmidon Reef）沿每条礁带（从礁前至礁后方向）于0.5米水深处采集海水样本；同时在棕榈水道（Palm Passage）10米水深处采集了海水样本。分析采用临床放射免疫分析技术，将放射免疫分析法（RIA）与通过C18 SEP-PAK柱置换液相色谱法对维生素B12进行预富集的步骤相结合。通过放射分析法对柱洗脱液进行检测，结果显示该方法对飞摩尔级浓度的维生素B12具有良好灵敏度，检测范围为50~2400 pg B12/L海水。经富集步骤后，通过放射分析计算得到的浓度可直接换算为pg B12/L和ng 叶酸（folate）/L海水单位。超出校准范围（2400 pg B12；24.0 ng 叶酸）的浓度结果通过外推法得到。
本研究旨在测定大堡礁中部礁带断面处海水的维生素B12浓度变化情况。