Microphytobenthos community production at Great Palm Island, Great Barrier Reef

Production of the microphytobenthos community on a nearshore coral reef in Cannon Bay, Great Palm Island was measured over 7 trips between February 1996 and February 1997. Benthic microalgal production was measured in 4-chamber data logging respirometers placed to avoid Calianassa spp. mounds. The water within each chamber was flushed for 4 minutes every 26 minutes. Oxygen concentration within the chambers, in situ irradiance (PAR) and water temperature were recorded simultaneously at 1 minute intervals over at least 24 hours.The effect of nutrients excreted by holothurians on productivity was measured during experiments run in December 1996 (2) and February 1997 (3). Two 4 chamber respirometers were deployed for each experiment, for a period of 24 hours. An individual Holothuria atra (wet weight 140 to 220 g) was enclosed in a cartridge filter housing attached to 4 of the 8 chambers. The water (containing ammonium excreted by the holothurian) was injected into the attached chamber during each flushing. For 4 of the experiments, duplicate water samples for ammonium analyses were taken from all chambers on 2-3 occasions, 5 minutes after a flushing interval ended.To estimate microalgal biomass in sediments, 3 replicate samples of the upper 5 mm of sediment were collected under each chamber after completion of each respirometer deployment and the chlorophyll a concentration determined. This research was undertaken to:1. investigate seasonal variation in net and gross microphytobenthos community production on a near-shore reef in the Great Barrier Reef 2. investigate the influence of light and temperature on production3. test whether the presence of holothurians is beneficial to in situ benthic microalgal production due to increased availability of nutrients

1996年2月至1997年2月期间，通过7次考察测定了大棕榈岛Cannon湾近岸珊瑚礁上底栖微藻群落的生产力。底栖微藻生产力的测量采用4室数据记录呼吸仪（respirometers），放置时避开招潮蟹属（Calianassa spp.）丘堆。每个呼吸仪室内的水体每26分钟冲洗4分钟。

室内的氧气浓度、原位辐照度（PAR）和水温每1分钟同时记录一次，持续至少24小时。

1996年12月（2次）和1997年2月（3次）开展的实验中，测定了海参排泄营养物质对生产力的影响。每次实验部署两台4室呼吸仪，持续24小时。将单只绿刺参（Holothuria atra，湿重140-220克）置于筒式过滤器外壳中，并连接至8个室中的4个。每次冲洗时，含海参排泄铵的水体被注入相连室内。在4次实验中，冲洗间隔结束5分钟后，从所有室采集重复水样进行铵分析，共进行2-3次。

为估算沉积物中的微藻生物量，每次呼吸仪部署完成后，从各室下方采集上层5毫米沉积物的3个重复样本，并测定叶绿素a浓度。

本研究旨在：1. 探究大堡礁近岸珊瑚礁底栖微藻群落净生产力与总生产力的季节变化；2. 探究光照和温度对生产力的影响；3. 验证海参排泄的营养物质是否通过增加养分可利用性，对原位底栖微藻生产力产生有益作用。