Phytoplankton abundance can be affected both by physicochemical factors such as nutrients, temperature or light availability (bottom-up control), and by the abundance of predators (top-down control). Phytoplankton research in the Arabian Gulf has so far focussed on bottom-up control of the phytoplankton community, this study was the first to include top-down control as well. High abundances of the three diatom genera Chaetoceros, Guinardia and Bacteriastrum were observed locally during summer. Other important phytoplankton genera observed in this study included the cyanobacteria Trichodesmium and Nostoc, the diatom Leptocylindrus, and the dinoflagellate Prorocentrum. Whereas Trichodesmium was characteristic for the main body of the Arabian Gulf, from Khafji to Dhahran, Nostoc, Leptocylindrus and Prorocentrum characterized the phytoplankton community in the southern waters, the Gulf of Salwa and Half Moon Bay. This is a high salinity environment that is separated from the main body of the Arabian Gulf by a shallow sill. Here, we observed a seasonal change in the phytoplankton community, with a dominance of Nostoc and Leptocylindrus during summer, followed by a dominance of Prorocentrum during winter. Chaetoceros and Bacteriastrum showed significant correlation with the abundance of copepod Oithona brevicornis and the ghost shrimp Belzebub hanseni. Nostoc, Leptocylindrus and Prorocentrum all showed significant correlation with salinity and the concentration of total suspended solids.

浮游植物丰度既受物理化学因素的影响，如营养物质、温度或光照（自下而上控制），也受捕食者丰度（自上而下控制）的影响。迄今为止，阿拉伯湾的浮游植物研究主要集中在浮游植物群落的自下而上控制，这项研究也是第一个包括自上而下控制的研究。夏季在当地观察到高丰度的三个硅藻属Chaetoceros、Guinardia和Bacteriastrum。在这项研究中观察到的其他重要浮游植物属包括蓝藻Trichodesmium和Nostoc、硅藻Leptocylindrus和甲藻Prorocentrum 。. 而红海束毛是为阿拉伯海湾的主体特征，从海夫吉到达兰，发菜，丹麦细和原甲藻浮游植物群落特征南部海域，萨尔瓦湾和半月湾。这是一个高盐度环境，与阿拉伯湾主体之间有一道浅窗台。在这里，我们观察到浮游植物群落的季节性变化，夏季以Nostoc和Leptocylindrus 为主，冬季以Prorocentrum 为主。角角藻和细菌与桡足类Oithona brevicornis和鬼虾Belzebub hanseni的丰度显着相关。Nostoc、Leptocylindrus和Prorocentrum都与盐度和总悬浮固体浓度显着相关。