Source, biogeochemical cycling, and fluorescence characteristics of dissolved organic matter in an agro–urban estuary

• Published in: Limnology and oceanography 2011-01, Vol.56 (1), p.243-256
• Main Authors: Fellman, Jason B., Petrone, Kevin C., Grierson, Pauline F.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; Marine; Marine and continental quaternary; Sea water ecosystems; Surficial geology; Synecology
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.2011.56.1.0243

Seasonal measurements of dissolved organic matter (DOM) fluorescence characteristics were combined with weekly to bi-weekly measurements of carbon (C), nitrogen (N), and phosphorus (P) (including particulate, dissolved organic and inorganic forms) and chlorophyll to determine how riverine inputs and autochthonous production influence DOM and nutrient dynamics in the Swan-Canning estuary, Western Australia. Estuarine concentrations of C, N, and P were influenced by multiple factors, including the seasonal riverine flux of DOM, N, and P, the regeneration of mainly inorganic N and P from benthic anoxia, and the delivery of DOM and nutrients from urban drains. Parallel factor analysis of excitation-emission matrices identified eight fluorescence components that were used to fingerprint three distinct sources of estuarine DOM: (1) riverine DOM derived mainly from vascular plant material, (2) autochthonous DOM recently produced within the estuary (indicated by tryptophan-like fluorescence), and (3) autochthonous DOM originating from within the lower estuary or coastal marine environment enriched in marine humic-like and tyrosine-like fluorescence. Overall, fluorescence DOM characteristics shifted from humic-like in the upper and mid-estuary to protein-like in the lower estuary, which likely reflects the increased contribution of autochthonous relative to terrigenous DOM closer to the estuary mouth. Our findings show that DOM composition varies with season and estuary position as riverine DOM inputs, mainly from terrestrial plant material, are supplemented by autochthonous DOM contributions associated with discrete inputs of inorganic nutrients.