Seasonal variability in baseline δ15N and usage as a nutrient indicator in Lake Poyang, China

Abstract

Seasonal variation in nitrogen isotope ratios (δ15N) 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). δ15N values of POM and SOM varied significantly among the sampling seasons, while no significant seasonal variation was observed among the δ15N values of the mussels and snails sampled in different seasons. POM δ15N was correlated with lake water PO4-P, while SOM δ15N was correlated with NO3-N. Mussel δ15N and lake water TN, NO3-N, and PO4-P were significantly correlated as were snail δ15N 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 δ15N and POM, as well as between snail δ15N and SOM, indicated the potential use of these baselines in trophic evaluations in planktonic and benthic food webs in this water-level fluctuating lake.