Characterization and Eco-Physiology of Fish Killing Chattonella Species in Malaysian and Singapore Coastal Waters

Rohmanan, Nurrul Hadzriena (2023) Characterization and Eco-Physiology of Fish Killing Chattonella Species in Malaysian and Singapore Coastal Waters. Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

The occurrence of C. antiqua and C. subsalsa have been reported globally and reflects a wide environmental adaptation of this red tide flagellate. This raphidophyte species was reported with morphological variation due to lacks of rigid cell and this character made morphological species identification challenging. Chattonella cell was isolated using the single cell isolation technique and the establishment of the clonal cultures was essential for the physiology, taxonomic and genetic studies. All Chattonella was viewed under light inverted microscope (Olympus CKX53) and the cells was observed with the presence of variable cell shape, two flagella, a clear nucleus at the center and a variable arrangement of chloroplast with an oval or peanut-like shape. C. subsalsa from Singapore was observed with the presence of tubular invagination located at the posterior end of Chattonella cells. For C. subsalsa, the average cell length and width was 49.69 ± 4.28 μm, and 26.76 ± 2.22 m, respectively while the average cell length for C. antiqua was 63.61 ± 17 m, and the average cell width was 32.66 ± 10 m. In clarifying the mechanism of harmful algae bloom of Chattonella from Malaysian coastal water and Singapore, Chattonella spp. from different localities were examined in laboratory eco-physiologically. The cultured strains of Chattonella spp. were acclimatized at different experimental condition to prevent shock. All Chattonella cells could grow well in temperatures of 20, 25 and 30C and showed a good adaptation at 50–230 μmol photons m-2 s-1 with variation on the optimum light irradiance. For salinity experiment, different salinity media for f/2 medium were made by adding salt and altering with deionized water and to get an appropriate salinity. All Chattonella cells exhibited the euryhaline character and could grow in salinity range from 15–33 PSU. No cells were found alive in 10 PSU except for C. antiqua from Bachok with only a slow growth rate reported. The optimal condition will lead to the onset of harmful algae bloom where the species with higher physiological tolerance and adaptive strategy will predominate the rest species. However, a drastic change to a lower or higher environmental parameters other than the favorable one will kill the vegetative cell eventually. Meanwhile, most vegetative cell of Chattonella was observed with a spiral and rugged movement in conducive conditions whereas showed a slow movement when being subjected to any unfavorable conditions. These eco physiological features of C. antiqua and C. subsalsa from tropical region would be an advantage to bloom during favorable condition and this finding could be a reference for future HABs monitoring especially hot spots areas for aquaculture activities. Keywords: Chattonella spp; Harmful Algae Blooms; Temperature; Salinity; Light irradiance; f/2 medium; Tropical Region; Malaysia; Singapore