There are concerns that human impacts on freshwater systems – particularly temperature increases linked to climate change and nutrient enrichment caused by run-off and pollution – are encouraging the spread of blue-green algae (cyanobacteria) capable of generating toxic blooms that threaten human and animal health. One such case is the recent spread of Cylindrospermopsis raciborskii, a nitrogen-fixing cyanobacterium, through temperate lakes around the world. Although it’s known that this species can tolerate high temperatures and competes strongly for phosphorus, little work has been done to clarify how C. raciborskii is affected by interacting environmental factors. American researchers maintained communities of C. raciborskii mixed with ten other phytoplankton species (including diatoms, green algae, cryptophytes and cyanobacteria native to temperate lakes) in 500 ml glass flasks for 51 days. There were four treatments, namely high and low temperature (30 & 25 oC) crossed with high and low phosphorus concentration (25 & 1 µmol / litre). (The lower temperature corresponds to the peak summer temperatures in medium-sized temperate lakes, and the higher temperature may be reached in these lakes later this century as a result of global warming). Every three days samples were taken and the densities of the various species determined by cell counts. The phosphorus concentration significantly affected the composition of the phytoplankton community, with C. raciborskii dominating under low-phosphorus conditions and green algae dominating under high-phosphorus conditions. However, there was no detectable effect of temperature on the final abundance of C. raciborskii. These findings were a surprise, given the attention that temperature has received in explaining the spread of C. raciborskii, and they also show that some species of blue-green algae compete best at low levels of limiting resources such as phosphorus. Although increases in peak summer temperature are unlikely to have a large effect on invasions by C. raciborskii, it’s possible that the length of time when temperatures are above 15–17 oC (below which C. raciborskii can’t grow) may be more important.
Reference: Ryan, C.N. et al. 2017. The effects of phosphorus and temperatureon the competitive success of an invasive cyanobacterium. Aquatic Ecology 51, 463–472. https://www.researchgate.net/publication/317098689_The_effects_of_phosphorus_and_temperature_on_the_competitive_success_of_an_invasive_cyanobacterium
Freshwater Research News 
MujoH
July 5, 2018
Interesting findings, can different concentrations of phosphorous affect other species from genus Cylindrospermopsis?