Stable carbon and nitrogen isotope ratios as tools to evaluate the nature of particulate organic matter in the Venice lagoon

摘要: Abstract Complex environments, such as transitional waters, are characterized by several sources of particulate organic matter (POM). The analyses stable isotopes, δ 13 C and 15 N, usually used to discriminate between allochthonous autochthonous POM. This study aimed characterize the nature POM through isotopic analysis for first time in Venice lagoon. Water samples were seasonally collected during 2011 2012 at 28 stations monitoring program accomplishment objectives Framework Directive (WFD, Directive, 2000/60/CE ). Dissolved nutrient concentrations, chlorophyll a , total suspended solids determined was C, N C/N molar ratio. results showed mixed (autochthonous allochthonous) all lagoon stations. Nevertheless, autumn, enriched significantly depleted suggested major influence terrestrial contribution, probably due increase freshwater inputs land runoff. Differently, summer period sewage discharges biological processes well primary production microbial degradation prevailed, giving strong seasonal values (up 18.2‰). PCA evidenced spatial distinction load among polyhaline, euhaline not confined areas, identified WFD accomplishment. Through application multiple mixing model (IsoSource) means two variables five different sources, prevalence (82%) over estimated