Abstract
Tidal wetlands are a significant source of dissolved organic matter (DOM) to coastal ecosystems, which impacts nutrient cycling, light exposure, carbon dynamics, phytoplankton activity, microbial growth, and ecosystem productivity. There is a wide variety of research on the properties and sources of DOM; however, little is known about the characteristics and degradation of DOM specifically sourced from tidal wetland plants. By conducting microbial and combined UV exposure and microbial incubation experiments of leachates from fresh and senescent plants in Chesapeake Bay wetlands, it was demonstrated that senescent material leached more dissolved organic carbon (DOC) than fresh material (77.9 ± 54.3 vs 21.6 ± 11.8 mg DOC L−1, respectively). Degradation followed an exponential decay pattern, and the senescent material averaged 50.5 ± 9.45% biodegradable DOC (%BDOC), or the loss of DOC due to microbial degradation. In comparison, the fresh material averaged a greater %BDOC (72.6 ± 19.2%). Percent remaining of absorbance (83.3 ± 26.7% for fresh, 90.1 ± 10.8% for senescent) was greater than percent remaining DOC, indicating that colored DOM is less bioavailable than non-colored material. Concentrations of DOC leached, %BDOC, and SUVA280 varied between species, indicating that the species composition of the marsh likely impacts the quantity and quality of exported DOC. Comparing the UV + microbial to the microbial only incubations did not reveal any clear effects on %BDOC but UV exposure enhanced loss of absorbance during subsequent dark incubation. These results demonstrate the impacts of senescence on the quality and concentration of DOM leached from tidal wetland plants, and that microbes combined with UV impact the degradation of this DOM differently from microbes alone.
Highlights
Tidal wetlands are a significant source of dissolved organic matter (DOM) to coastal ecosystems, consistently exporting dissolved organic carbon (DOC) through tidal flushing during
The DOC consumed during microbial-only incubations is commonly referred to as percent biodegradable DOC or %BDOC
By the end of the incubation, the fresh material averaged 72.6 ± 19.2% BDOC which is significantly greater than the %BDOC of senescent material which averaged 50.5 ± 9.45% (p = 0.0320)
Summary
Tidal wetlands are a significant source of dissolved organic matter (DOM) to coastal ecosystems, consistently exporting dissolved organic carbon (DOC) through tidal flushing duringCommunicated by Carolyn A. Tidal wetlands are a significant source of dissolved organic matter (DOM) to coastal ecosystems, consistently exporting dissolved organic carbon (DOC) through tidal flushing during. Tidal wetlands are an important component of biogeochemical cycles and estuarine metabolism in coastal ecosystems (Hansell and Carlson 2015). DOM, here operationally defined as a mixture of soluble organic compounds that can pass through a 0.2 μm pore size filter, is constituted primarily of dissolved organic carbon (DOC), and dissolved organic nitrogen and phosphorus (Hansell and Carlson 2015). The dynamics of DOM, impact C, N, and P cycling, phytoplankton activity, microbial growth, and ecosystem productivity (Tzortziou et al 2007; 2008; 2011; Fellman et al 2010; Hansell and Carlson 2015; Logozzo et al 2021). It is important to understand the sources of DOM, how DOM moves through ecosystems, and how DOM is transformed in aquatic environments
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