Author: Maxine Allayne Darlene  Mowe, Ph.D. Lecturer (National University of Singapore)

Description:
Cyanobacterial blooms (C-HABs) are a global problem for water resources in view of their potential to bloom and produce toxins. Most studies have focused on cyanobacterial bloom and toxin production in temperate regions with fewer carried out in the tropics. Thus, the main focus of this research was to elucidate the autecology of dominant toxin-producing tropical cyanobacterial bloom species in Singapore. Species of Microcystis (M. ichthyoblabe, M. flos-aquae, M. aeruginosa and M. viridis) were isolated from Singapore’s reservoirs, with some found to produce microcystins (MC-RR and MC-LR). Laboratory-based temperature, nutrient and light experiments were conducted on these species and overall findings revealed that high nutrient concentrations increased M. ichthyoblabe and M. flos-aquae growth, while low phosphorus concentrations increased toxin cell quotas of both species. Temperature increases from 27°C–36°C did not increase the growth of most Microcystis species, while toxin cell quotas in most isolates increased significantly at a higher temperature (33°C) compared to those at ambient temperature (27°C). Low light intensity resulted in high growth rates for M. ichthyoblabe while high light intensity resulted in high growth rates of M. aeruginosa, while high light intensity increased M. ichthyoblabe and M. flos-aquae toxin cell quotas. Overall, these findings indicated that Microcystis toxin production may increase with impending climate warming while high nutrient concentrations are necessary for C-HAB proliferation with light intensity playing a smaller role in the tropics. These broader lessons can be applied to the management of future C-HABs in the region.

Category: Scientific Program Abstract > Special Session > SS43 Physiological and Environmental Drivers of HAB Formation and Toxicity