Diffusion culture experiments using natural phytoplankton from the Great Barrier Reef

Seventeen experiments were carried out between April 1983 and June 1985 to measure in situ growth rates of phytoplankton communities and constituent species in mid- to outer-shelf waters of the central Great Barrier Reef. Growth rates of identifiable phytoplankton taxa, composite groups of phytoplankton (eg microflagellates) and size classes were calculated from changes in cell numbers or chlorophyll concentration occurring while size-fractionated natural phytoplankton assemblages were incubated in situ within diffusion chambers.

Growth experiments were carried out either in the lagoons of, or most commonly, in waters immediately adjacent to three reefs in the central GBR province, Myrmidon Reef, Rib Reef and Davies Reef. Myrmidon Reef was selected to typify conditions found on the outer shelf and in oceanic waters of the western Coral Sea. Located on a protrusion extending seaward from the continental shelfbreak, the sheltered northern side of Myrmidon Reef is exposed to oceanic waters in the southward flowing East Australian Current. Davies Reef and Rib Reef have mid- shelf locations and are surrounded by waters typifying the reef matrix and outer GBR lagoon. Sites at or near reefs for individual experiments were selected to enable safe deployment of diffusion chambers at depths corresponding to desired light penetration depths.

Water samples for dissolved nutrient, chlorophyll, phaeophytin, temperature and salinity analyses were collected daily from incubation depths at the mooring sites.
At most deep water stations underwater light profiles were measured to determine irradiance levels at the depths of incubation.

The purpose of these experiments was to measure in situ growth rates of phytoplankton communities and constituent species in mid- to outer-shelf waters of the central Great Barrier Reef.

本研究于1983年4月至1985年6月间共计开展17项实验，旨在原位测定大堡礁（Great Barrier Reef）中部中陆架至外陆架水域的浮游植物群落及其组成物种的原位生长速率。实验通过将经粒径分级的天然浮游植物群落置于扩散室（diffusion chamber）内原位培养，根据细胞数量或叶绿素浓度的变化，计算可识别浮游植物类群、浮游植物复合类群（如微型鞭毛藻（microflagellates））以及不同粒径级别的生长速率。

实验点位分为两类，要么设于大堡礁中部海域三个礁体的泻湖内，最常见的则是紧邻这三个礁体的周边水域，这三个礁体分别为迈尔密敦礁（Myrmidon Reef）、里布礁（Rib Reef）与戴维斯礁（Davies Reef）。其中迈尔密敦礁被选为代表外陆架及西珊瑚海大洋水域环境的典型礁体：该礁体位于从大陆架断裂带向海延伸的隆起处，其受庇护的北侧海域会受到向南流动的东澳洋流（East Australian Current）输送的大洋水影响。戴维斯礁与里布礁地处中陆架区域，周边水域兼具礁体基质与大堡礁外缘泻湖的典型水文特征。各项实验的采样点位均选在礁体附近或礁体周边，以便将扩散室安全部署于目标光照穿透深度对应的水深处。

每日从锚泊站点的培养水深处采集水样，用于溶解态营养盐、叶绿素、脱镁叶绿素、温度及盐度分析。在多数深水站位，研究人员还会测定水下光剖面，以确定培养水深处的辐照度水平。

本系列实验的核心目的为原位测定大堡礁中部中陆架至外陆架水域的浮游植物群落及其组成物种的原位生长速率。