Tidal marshes as a source of optically and chemically distinctive colored dissolved organic matter in the Chesapeake Bay

Abstract

The role of tidal marshes as a source of dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) for adjacent estuarine waters was studied in the Rhode River subestuary of the Chesapeake Bay. Water in a tidal creek draining brackish, high-elevation marshes was sampled every hour during several semidiurnal tidal cycles in order to examine the tidal exchange of dissolved organic matter (DOM). Water leaving the marsh during ebbing tide was consistently enriched in DOC compared to water entering the marsh during flooding tide. There was a net DOC export from the marsh to the estuary during seasons of both low and high marsh plant biomass. Optical analysis demonstrated that, in addition to contributing to the carbon budgets, the marsh had a strong influence on the estuary's CDOM dynamics. Marsh-exported CDOM had optical properties that were consistently and markedly different from those of CDOM in the adjacent estuary. Specifically, marsh CDOM had: (1) considerably stronger absorption, (2) larger DOC-specific absorption, (3) lower exponential spectral slope, (4) larger fluorescence signal, (5) lower fluorescence per unit absorbance, and (6) higher fluorescence at wavelengths .400 nm. These optical characteristics are indicative of relatively complex, high-molecular-weight, aromatic-rich DOM, and this was confirmed by results of molecular-weight-distribution analysis. Our findings illustrate the importance of tidal marshes as sources of optically and chemically distinctive dissolved organic compounds, and their influence on CDOM dynamics, DOC budgets, and, thus, photochemical and biogeochemical processes, in adjacent estuarine ecosystems.

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

“…In addition, refractory DOM is also thought to be produced through biological processes or photochemical reactions (Mopper and Kieber, 2002;Ogawa et al, 2001). Photochemistry may be especially important in Chesapeake Bay DOM cycling as a significant amount of allochthonous DOM from tidal marshes undergoes photochemical oxidation (Tzortziou et al, 2008(Tzortziou et al, , 2007 and, thus, may be an important source of labile DOM in the main stem of the bay. Therefore, following a few other models of DOM cycling (Anderson and Williams, 1999;Pahlow et al, 2008), we included a refractory DOM pool.…”

“…The major allochthonous source of DOM is the Susquehanna river (Fisher et al, 1998). Smaller rivers (sub-estuaries), atmospheric deposition (Seitzinger and Sanders, 1999), wetland discharge (Tzortziou et al, 2008), and terrestrial runoff and leaching (Berman and Bronk, 2003) also add significant amounts of DOM to the estuary. Internal sources of DOM include benthic fluxes (Burdige and Zheng, 1998), extracellular release by phytoplankton, grazer-mediated release and excretion, release via cell lysis (both viral and bacterial), solubilization of particles, and bacterial transformation and release (Carlson, 2002).…”

Microbially-Mediated Transformations of Estuarine Dissolved Organic Matter

“…As riverine DOM is transported toward the ocean, its quantity and composition is often altered (Cole et al, 2007) by a variety of chemical, biological and physical processes (Tzortziou et al, 2008), making estuaries hot spots of DOM cycling. Significant gradients exist in the composition of DOM in estuaries (Sleighter and Hatcher, 2008;Medeiros et al, 2015c;Seidel et al, 2015).…”

Characteristics and sources of chromophoric dissolved organic matter in lakes of the Yungui Plateau, China, differing in trophic state and altitude

“…Both the trophic state and altitude of a lake can be expected to have a fundamental effect on dissolved organic carbon (DOC) concentration and composition (Williamson et al 1999;Sobek et al 2007;Webster et al 2008). Eutrophication by increased terrestrial nutrient input will significantly increase the CDOM concentration by increasing algal blooms (Tzortziou et al 2008;Zhang et al 2009). Altitude affects CDOM in three ways: (1) high altitude inhibits human activity and, thus, decreases anthropogenic CDOM input; (2) UV-B radiation increases with altitude, which leads to higher increases in the photochemical degradation rate of CDOM, which further lowers the equilibrium CDOM concentration and alters CDOM composition; (3) the natural export of CDOM from terrestrial to aquatic ecosystems will decrease as terrestrial productivity and the size of the catchment area decreases with increasing altitude (Jansson et al 2008).…”