Lipid bound phosphorus in the seston of Lake Erie and its tributaries and its use as an indicator of algal P-limitation

Concentrations of lipid-phosphorus (LP) in aquatic ecosystems can be influenced by algal biomass and the nutritional state of microbial communities, potentially serving a useful indicator of P-limitation. We examined the effectiveness of LP as a bioindicator by examining concentrations of LP and environmental factors controlling its abundance across Lake Erie and its tributaries. LP concentrations were correlated with chlorophyll a (Chl a ) and total suspended solids, total P, and particulate carbon (PC), nitrogen, and P (PP) in both river and lake waters, while dissolved nutrients were only related to lake LP concentrations. Tributary LP was generally higher than in-lake values, and stoichiometric relationships between PC, PP, and LP indicated that Chl a was correlated with tributary LP. Chl a, bacterial production, and LP concentrations decreased significantly across nutrient gradients going from the west to east across the lake. Consistent relationships between lake particulate C:P ratios and Chl a : LP ratios were found across seasons, and higher values of both in August suggested algal P-limitation during this period. To further explore environmental controls on LP, we compared the relative influence of temperature, phytoplankton taxonomy, and water chemistry on lake LP concentrations. Though LP was correlated with well-known factors associated with cyanobacterial abundance in the lake (temperature and ammonium), particulate biomass and algal P-limitation seemed to be the most important correlates of LP concentration, suggesting that Chl a :LP ratios could provide a metric of P-limitation in aquatic ecosystems.