The urban lake, Lake Hugh Muntz on the Gold Coast, has experienced blooms of cyanobacteria in recent years. One of the key species is Chrysosporum ovalisporum which produces the toxins, cylindrospermopsin, and deoxycylindrospermopsin (CYN and deoxy-CYN respectively). Lake Hugh Muntz is freshwater in the surface waters with a deeper higher salinity layer below a halocline. It has been proposed to manage the blooms with mixing of the lake waters, thereby increasing salinity in the surface waters to suppress growth. However, the effect of salinity on growth and toxin production is unclear. Additionally, the seasonal effects of temperature on growth rates are unknown. Therefore, the aim of these experiments was to investigate how a range of salinities and temperatures affected growth rates and toxin levels of two strains of C. ovalisporum isolated from Lake Hugh Muntz (LHC01 and LHC02). This study found that both strains grew well in a wide range of salinities, and at 85% seawater growth was reduced. Maximum growth occurred at temperatures in the range of 28°C and 32°C, with lower growth below this range. Toxin analyses indicated that the two strains had differing toxin cell quotas, and that seawater levels also affected toxin cell quotas. In summary, this study suggests that the management strategy of artificial mixing of the water column to increase the surface salinity may not be an effective management option. The temperature range tolerated by these strains indicated that, while warmer waters would be preferred, populations can be sustained year-round in Lake Hugh Muntz. It was also demonstrated that this species and its strains can vary their CYN production in response to changing environmental conditions.