Seasonal variability in baseline delta N-15 and usage as a nutrient indicator in Lake Poyang, China

Seasonal variation in nitrogen isotope ratios (N-15) of four baseline candidates belonging to the planktonic and benthic food webs of Lake Poyang, China, was investigated. These baseline candidates were particulate organic matter (POM), sediment organic matter (SOM), a filterer mussel (Corbicula flumine), and a grazer snail (Bellamya aeruginosa). N-15 values of POM and SOM varied significantly among the sampling seasons, while no significant seasonal variation was observed among the N-15 values of the mussels and snails sampled in different seasons. POM N-15 was correlated with lake water PO4-P, while SOM N-15 was correlated with NO3-N. Mussel N-15 and lake water TN, NO3-N, and PO4-P were significantly correlated as were snail N-15 and TN, TP, and NO3-N. SOM and snails were better bioindicators of the water column nutrient concentration of Lake Poyang. The significant correlations between mussel N-15 and POM, as well as between snail N-15 and SOM, indicated the potential use of these baselines in trophic evaluations in planktonic and benthic food webs in this water-level fluctuating lake