Extent of Dissolved Organic Matter Lability and Prevalence of Priming Effect in Connecticut River: Implication of Precipitation Event, Seasonality, and Land Cover

Abstract:

Biological and photochemical lability of dissolved organic matter (DOM) in inland waters determine how much DOM can be removed during transport and provide insight on how terrestrial ecosystems are connected to coastal ecosystems. The two removal processes are also indirectly linked as one process can serve as a priming mechanism for the other, boosting the amount of the DOM that can be removed in the following process (i.e. photo-priming for biological removal and bio-priming for photochemical removal). This study focuses on these two topics of lability and priming in inland waters and presents the results of biological lability and photochemical lability experiments conducted on samples collected from the Connecticut River from June, 2015 to August, 2016 (n= 401 and n=310). The samples for the experiments were collected from 42 sites that cover the gradient of stream order, latitude, and land cover of the watershed, and roughly a third of the samples were collected during storm events. A subset of samples were also tested for photo-priming and bio-priming effect on biological lability and photochemical lability, respectively, where the samples used for the initial lability experiments were tested for lability by the alternate removal process (i.e. samples that had been tested for photochemical lability were further tested for biological lability and vice versa). The preliminary analyses of the data show: 1. Both biological photochemical lability show wide ranges of values ranging from 0% to 80%; 2. Photo-priming by UV light exposure (30 days) is more prevalent than previously thought and 80% of the tested samples showed greater biological DOM loss after the UV-treatment (not including the loss through photochemical process).; 3. Biological-priming can also make more DOM susceptible to photochemical removal and 57% of the tested samples showed greater photochemical loss after the biological priming treatment (not including the loss through biological process). More in-depth analyses including the effect of precipitation events, the importance of watershed land cover, and the use of optical data for inferring lability will be presented during the conference, with a special focus on how increasing storm intensity and drought conditions may affect the lability of DOM in inland waters.