Diurnal variation of phytoplankton community in the coastal waters of South Andaman Island with special emphasis on bloom forming species

1383-1397Species composition, abundance and distribution of phytoplankton dynamics were studied from the coastal waters of South Andaman Islands during December 2015 to February 2016. Physico-chemical parameters and phytoplankton species composition were observed during the study. Environmental parameters such as surface water temperature - 33ºC (r=0.96; pppp-1) were recorded. A total of 82 species under 50 genera of phytoplanktons were recorded belonging to Bacillariophyceae, Dinophyceae, Cyanophyceae and Silicoflagellate groups. Diatoms were represented by 68 species belonging to 40 genera, Dinoflagellates were represented by 12 species belonging to 8 genera, and 1 species belonging to a genera Cyanophyceae and Silicoflagellate were observed. Among the diatoms, Coscinodiscus centralis, Rhizosolenia alata, R. imbricata, Bacteriastrum furcatum, Leptocylindrus danicus, Odentella sinensis, Pleurosigma sp., Skeletonema costatum and Thalassionema nitzschioides and among the dinoflagellates, Ceratium furca, Prorocentrum micans, P. divergens and Pyrophacus sp. were the most prevalent diatoms and dinoflagellates encountered in the samples. The population density fluctuated between in the range of 53-63034 cells.mL-1. The highest population density was recorded in January at (St.1) Chatham bay due to the blooming of diatom R. imbricata (63000 cells.mL-1), were observed. Moreover, increase in water temperature and salinity was also found to be an influencing co-factor that had contributed to the algal bloom

Flat elbow crab spotted

During a routine field survey, two specimens were collected from the landing of the bottom set gillnet operated at a water depth of 6-7 m on a rocky substratum at Chepala Kancheru, Visakhapatnam on 15th November 2018. The specimen was identified as Flat Elbow Crab, Aethra edentata Edmondson, 1951. The length and width of the carapace varied from 52 mm to 54 mm and 62 mm to 65 mm respectively. The length of the abdomen ranged from 22 mm to 25 mm. The species is characterized by transversely oval-shaped carapace