SEAWEED EXTRACT AS AN ORGANIC MEDIUM FOR THE GROWTH AND MAINTENANCE OF MARINE MICROALGAL SPECIES
The effect of drifted seaweed extract on the growth of marine microalgae viz., Chlorella marina and Nannochloropsis oculata was studied. Drifted seaweeds constitute 70% of brown seaweeds. The drifted brown seaweeds (Sargassum wightii, S. oligocystum, Padina tetrastromatica, Stoechospernum marginatum and S. vulgare), green algae (Caulerpa toxifolia and Caulerpa racemosa), red seaweeds (Gracilaria edulis and Kappaphucus alvarezi), and seagrass (Halodule, Cymodaceae and Zostrea sp.) were collected from the coastal region of Thoothukudi, Gulf of Mannar, southeast coast of India. Seaweed extract was prepared and the growth of the microalgal species in seawater with seaweed extract was compared with Conway medium. Aqueous seaweed extract was prepared according to Cho et al (1999) with minor modifications. The chemical composition of the drifted seaweed powdered sample is shown in Table1.
Two culture treatments were tested: seawater with Conway medium, seawater with seaweed extract at different concentrations such as 1.5, 3 and 5ml of extract for 100 ml of seawater and seawater without nutrient enrichment. The culture media was inoculated with respective algal cells as initial concentration from stock culture.Cell density of all treatments with triplicates and control were measured at alternative day using hemocytometer.
The results of the study indicated that higher densities of 13.20n×106 were observed in Chlorella marina on 9th day of culture period at 1.5ml seaweed extract (Fig.1). Similarly, the growth and cell density of Nannochloropsis oculata (15.37 n×106) was almost similar to that of walne's medium (16.71n×106) on 11th and 9th day of culture period respectively (Fig.2). However, the cultures maintained using seawater without nutrients did not show any growth. Thus, it could be concluded that seaweed extract could be used as an alternate source of organic medium for the growth and maintenance of marine microalgae in hatcheries of aquaculture industry.
