Sulfolipid profiles of Microcystis aeruginosa and cyanobacterial blooms as an indicator of P availability

While phosphorus (P) scarcity can limit primary productivity in lakes, its oversupply can lead to the formation of cyanobacteria-dominated algal blooms. P availability influences bloom dynamics and can be seasonally limiting, even in eutrophic lakes. Marine phytoplankton alter their lipid profile by increasing sulfolipids when P is limiting. We asked whether Microcystis spp. respond in a similar manner. The ratio of sulfoquinovosyl diaclyglycerol (SQDG) to phosphatidylglycerol (PG) was used to examine lipid remodeling. In batch cultures of M. aeruginosa, the SQDG:PG ratio increased from ~0.9 to ~3.3 with decreasing initial P concentration. In P-limited Lake Erie mesocosms, SQDG:PG increased in controls from ~6 to ~11 after 48 hr, while P-addition decreased the ratio from ~6 to ~3. In non-P-limited mesocosms, the ratio was unchanged after 48 hr and P-addition treatments had no effect. In Lake Erie in situ measurements, SQDG:PG showed an inverse correlation with total dissolved P. There was no correlation with either soluble reactive P or N:P ratio. This study demonstrates that Microcystis remodels its lipid profile in response to P scarcity, providing a potential short-term, time-integrating marker of nutrient history for cyanobacterial populations during fresh water blooms.