Hydrobiological and Bio-Optical Characterization of a Red Tide Occurredin Meda Creek, Porbandar, India

Abstract

Red tides are becoming more common in aquatic ecosystems, particularly the coastal habitats which are highly influenced by climatic and anthropogenic activities. We provide the first report of a red tide event in Meda creek, west coast of India. Light and scanning electron microscopy were used to identify the bloom forming organism, while physicochemical, biological and biooptical parameters were determined to characterize the aquatic body of the Meda Creek. The dominant bloom forming organisms were observed as unarmored, spherical, dorsoventrally compressed flagellate with truncated apex, notched and rounded hypocone, displaced premedian cingulum and extending sulcus. The length wise size of the cell varied from 20 to 30.83μM, whereas, the width varied from 14 to 27.5μM. The organisms was identified as Gymnodinium sp. High Performance Liquid Chromatography (HPLC) and spectral profile of the bloom indicatedeleven major peaks corresponding to that of 19-but-fucoxanthin (52.75%), astaxanthin (9.62%), fucoxanthin (8.81%), Mgdv (6.45%), prasinoxanthin (3.35%), chlorophyll C2 (3.22%), neoxanthin (3.12%), antheraxanthin (3.14%), diadinoxanthin (2.63%) and diatoxanthin (1.38%). Chlorophyll a concentration in the bloom sample was 38.8μg/L. Water temperature, salinity, NH3-N, NO2-N, NO3-N, PO4-Pwere higher during the bloom period than the non-blooming ones, while metals including Fe, Zn, Cr, Mn and Co were lower. No death of aquatic biota was observed. We propose that eutrophication along with the warm and saline conditions provided enabling conditions for occurrence the bloom. Also, most of the pigments expressed have antioxidant role and might be purposeful for the survival of the organism in the extreme condition of temperature and salinity recorded. Proper management and monitoring measures might help mitigate further occurrences of this bloom in the light changing climate and increasing anthropogenic impacts.