Related Subjects

Carbon loss and optical property changes during long-term photochemical and biological degradation of estuarine dissolved organic matter

Author(s): Moran MA, Sheldon WM, Zepp RG


Terrestrially derived dissolved organic matter (DOM) impacts the optical properties of coastal seawater and affects carbon cycling on a global scale. We studied sequential long-term photochemical and biological degradation of estuarine dissolved organic matter from the Satilla River, an estuary in the southeastern United States that is dominated by vascular plant-derived organic matter. During photodegradation, dissolved organic carbon (DOC) loss (amounting to 31% of the initial DOC) was much less extensive than colored dissolved organic matter (CDOM) or fluorescent dissolved organic matter (FDOM) loss (50% and 56% of the initial CDOM and FDOM), and analysis of kinetics suggested a reservoir of DOC that was resistant to photodegradation. In contrast, CDOM photodegradation closely followed first-order kinetics over two half-lives with no indication of a nondegradable component. FDOM loss was slightly biased toward fluorophores considered representative of terrestrial humic substances. Additional changes in optical properties included increases in spectral slope and shifts in fluorescence excitation/emission maxima that were generally consistent with previous observations from field studies of photobleached DOM. Biological degradation of photobleached DOM was more rapid than that of unbleached material, and this net positive effect was evident even for extensively photodegraded material. Bacterial degradation caused shifts in the opposite direction from photochemical degradation for both spectral slope and excitation/emission maxima and thus dampened but did not eliminate changes in optical properties caused by photobleaching.

Similar Articles

Estimating global "blue carbon" emissions from conversion and degradation of vegetated coastal ecosystems

Author(s): Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al.

Major role of marine vegetation on the oceanic carbon cycle

Author(s): Duarte CM, Middelburg JJ, Caraco N

Seagrass community metabolism: Assessing the carbon sink capacity of seagrass meadows

Author(s): Duarte CM, Marbà N, Gacia E, Fourqurean JW, Beggins J, et al.

Seagrass sediments as a global carbon sink: Isotopic constraints

Author(s): Kennedy H, Beggins J, Duarte CM, Fourqurean JW, Holmer M, et al.

Distribution of Terrestrially Derived Dissolved Organic Matter on the Southeastern U

Author(s): Moran MA, Pomeroy LR, Sheppard ES, Atkinson LP, Hodson RE

Fluorescence spectroscopy and multi-way techniques

Author(s): Murphy KR, Stedmon CA, Graeber D, Bro R

Limnol Oceanography 50: 686-697

Author(s): Stedmon CA, Markager S  (2005a) Resolving the variability in dissolved organic matter fluorescence in a temperate estuary and its catchment using PARAFAC analysis

Limnol Oceanography 50: 1415-1426

Author(s): Stedmon CA, Markager S (2005b) Tracing the production and degradation of autochthonous fractions of dissolved organic matter by fluorescence analysis