Phytoplankton, zooplankton and ichthyoplankton abundance, distribution and diversity investigation in the Iranian waters of the Oman Sea

This study was carried out in the North of Oman Sea in parts of Iranian waters during pre-monsoon and post monsoon seasons between 2007 and 2009. Number of 10 transects were chosen from coastal to maximum 50 meter depth. Cruise was done with Fredous ship and Rosette bottle multi watersampler was used for sampling. A phytoplankton community in the North of Oman Sea included in 204 species and divided in six taxonomic divisions: Bacillariophyceae (89 species), Dinophyceae (105species), Cyanophyceae (6species), Dicthyochophyceae (2species), Euglenaphyceae and silicoflagellate each (1species) respectively. Density decreased in most transects from inshore toward offshore waters and maximum density was in surface layear.Significant differences between each transects were found. Dinophyceae and Bacillariophyceae were dominant in pre-monsoon and post-monsoon respectively throughout two years. Important genuses of diatoms are Rhizosolenia, Chaetoceros, Pleurosigma, Coscinodiscus, Gyrosigma, Nitzscha, Navicula, and Leptocylindrus. And also there were Dinophyceae like: Scrippsiella, Pyrophacus, Gymnodinium, Pyrodinium, Prorocentrum, Cochlodinium, and Noctiluca. Phytoplankton density in the post-monsoon were recorded higher than pre-monsoon, furthermore phytoplankton density in 2009 was more than 2007. Cochlodinium polykrikoides density increased in 2009 especially in the pre-monsoon then dropped to post-monsoon season. Zooplankton population in this study is characterized by 8 phylum, 8 classes, 15 orders, 35 families and 78 genuses. Copepoda was the most abundant group of zooplankton and included in 4 orders of Cyclopoida, Calanoida, Poecilostomatoid and Harpacticoida. The static result showed significance among different transects layers and lines. In this study, 31 ichthyoplankton families with different density and distribution were recorded. In the pre-monsoon eight families was identified and Scainidaea family had the highest density and also in postmonsoon 6 families was classified in which scainidae was dominant family. In pre-monsoon 2009, we found 8 families that Pomacentridae family had higher density; Hemiramophidae was in the second position and followed by Clupeidae. In post-monsoon season density and diversity were increased and 23 families were recorded. Myctophidae family was the most abundant. The highest frequency there was other important families like Engraulidae, Synodontidae, Scainidae, and Leiognathidae in this period. Result of this study indicated that the monsoon was important and effect on abundance, distribution and species composition of plankton