Copepod egg production in Exmouth Gulf, Western Australia

Ten stations were sampled in Exmouth Gulf (7 on the eastern side and 3 on the western). At each station water temperature and salinity were measured at 1m depth intervals and secchi depth recorded. Values for Chlorophyll a, particulate carbon and nitrogen were determined. Egg production rates by 4 of the dominant copepod species were measured by bottle incubations (Acartia fossae, Parvocalanus crassirostris) and the egg-ratio technique (Oithona attenuata and Oithona simplex). Egg production data was used to calculate adult females grazing rates of the total particulate carbon each day.Plankton abundance and biomass did not differ greatly within the gulf; however, highest values of chlorophyll a, particulate carbon and nitrogen, and copepod egg production rates occurred in the south-east of the gulf. Though egg production rates were low and apparently severely food-limited, resuspension of bottom sediments or export of material from adjacent salt flats may fuel production in shallow inshore areas of the gulf. P. crassirostris appeared to be omnivorous and 0. attenuata primarily herbivorous, but the trophic resources used by 0. simplex and A. fossae could not be identified. From the egg production data, it was calculated that adult females of the four dominant copepod species graze 12% of the total particulate carbon each day. This research was undertaken to: 1. Investigate plankton community structure and abundance in Exmouth Gulf2. Estimate egg production rates by the dominant copepod species in relation to their potential trophic resources and to the hydrography of the area.

在埃克斯茅斯湾（Exmouth Gulf）设置了10个采样站点（东侧7个，西侧3个）。每个站点以1米深度间隔测量水温与盐度，并记录塞氏深度（Secchi depth）。同时测定了叶绿素a（Chlorophyll a）、颗粒碳及颗粒氮的浓度值。针对4种优势桡足类物种（copepod species），采用瓶培养法（Acartia fossae、Parvocalanus crassirostris）与卵比率技术（Oithona attenuata、Oithona simplex）测定其产卵率。产卵数据被用于计算成年雌性桡足类每日对总颗粒碳的摄食率。湾内浮游生物的丰度与生物量无显著差异；但叶绿素a、颗粒碳氮含量及桡足类产卵率的最高值均出现在湾东南部。尽管产卵率较低且明显受食物限制，底部沉积物的再悬浮或邻近盐滩的物质输出可能为湾内浅近岸区域的生产提供能量来源。Parvocalanus crassirostris表现为杂食性，Oithona attenuata主要为植食性，而Oithona simplex与Acartia fossae所利用的营养资源尚无法确定。基于产卵数据计算得出，这4种优势桡足类的成年雌性每日摄食总颗粒碳的12%。本研究旨在：1. 调查埃克斯茅斯湾浮游生物群落结构与丰度；2. 评估优势桡足类物种的产卵率与其潜在营养资源及区域水文特征的关系。