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.1983年4月至1985年6月间，本研究共开展17项实验，旨在测定大堡礁(Great Barrier Reef)中部中陆架至外陆架水域中浮游植物(phytoplankton)群落及其组成物种的原位生长速率。可识别浮游植物类群、浮游植物复合类群（例如微型鞭毛虫(microflagellates)）以及粒径分级组的生长速率，可通过分级粒径的天然浮游植物集合体在扩散培养舱(diffusion chambers)内原位培养期间的细胞数量或叶绿素(chlorophyll)浓度变化计算得到。生长实验可选择在礁体潟湖内开展，最常见的布设方案则为在大堡礁中部区域的三座毗邻礁体周边近岸水域进行；这三座礁分别为迈密登礁(Myrmidon Reef)、里布礁(Rib Reef)与戴维斯礁(Davies Reef)。迈密登礁被选为代表西珊瑚海(Coral Sea)外陆架及大洋水域的典型研究位点。该礁坐落于从陆架坡折(continental shelfbreak)向海延伸的凸起地形之上，其受庇护的北侧直面向南流动的东澳洋流(East Australian Current)所携带的大洋水域。戴维斯礁与里布礁地处中陆架区域，周边水域为典型的礁体基质及大堡礁外潟湖水域。各项实验的礁体周边或附近采样位点均经过精心挑选，以确保扩散培养舱可安全布设于目标光穿透深度的水域中。每日从锚泊站位的培养深度采集水样，用于溶解态营养盐、叶绿素(chlorophyll)、脱镁叶绿素(phaeophytin)、温度及盐度分析。在多数深水采样站位，科研人员会测定水下光剖面，以确定培养深度处的辐照度水平。本系列实验的核心目的，是测定大堡礁(Great Barrier Reef)中部中陆架至外陆架水域中浮游植物(phytoplankton)群落及其组成物种的原位生长速率。