Water quality measurements from the river plumes in the central Great Barrier Reef, associated with Cyclone Sadie (1994)

On the 4th February, 1994, water samples were collected from 10 stations along an offshore transect between the Brook Islands and the Mulgrave River. Cyclone Sadie caused a large rain depression over most of the north Queensland catchment area and sampling took place two days after the main flood peak had occurred. Samples were collected hourly, while the research vessel was steaming. Surface samples were collected at six stations, using a bucket. At a further four stations, samples were collected at four depths using a series of three Niskin bottles spaced over a depth profile for subsurface samples and a bucket to collect the surface samples. In situ temperatures were recorded using digital reversing thermometers attached to the Niskin bottles.Samples were analysed for chlorophyll, suspended solids, dissolved inorganic and organic nutrients and salinity.Water transparency was measured using a secchi disk and the presence of Trichodesmium spp. noted visually. Additional data collected at each station were cloud cover, wind speed, wind direction, tide and acoustic depth. This research was undertaken to examine changes in water quality in a flood plume resulting from increased river runoff into the Great Barrier Reef lagoon.

1994年2月4日，研究人员在布鲁克群岛（Brook Islands）与马尔格雷夫河（Mulgrave River）之间的近海断面上的10个站位采集了水样。气旋萨迪（Cyclone Sadie）在昆士兰州北部大部分集水区引发了强降雨低压系统，本次采样在主洪峰过境两天后开展。科考船航行期间，每小时采集一次水样。其中6个站位采用采水桶采集表层水样；剩余4个站位则分层采集水样：底层水样通过沿深度剖面布设的3个尼斯金采水器（Niskin bottles）在四个深度层级采集，表层水样仍采用采水桶采集。附着于尼斯金采水器的数字倒置温度计可记录原位水温。研究人员对采集的水样开展了叶绿素、悬浮固体、溶解态无机与有机营养盐以及盐度的检测分析。采用塞氏盘（Secchi disk）测定水体透明度，并通过目视记录束毛藻属（Trichodesmium spp.）的存在情况。各站位同步采集的辅助数据包括云量、风速、风向、潮汐以及声学测深数据。本研究旨在探究河流径流量增加后，注入大堡礁泻湖（Great Barrier Reef lagoon）的洪水羽流所引发的水质变化。