More Like this

1. Photodegradation disproportionately impacts biodegradation of semi‐labile DOM in streams

   https://doi.org/10.1002/lno.11244  

   Bowen, Jennifer C. ; Kaplan, Louis A. ; Cory, Rose M. ( July 2019 , Limnology and Oceanography)

   Exposure of dissolved organic matter (DOM) to sunlight can increase or decrease the fraction that is biodegradable (BDOM), but conceptual models fail to explain this dichotomy. We investigated the effect of sunlight exposure on BDOM, addressing three knowledge gaps: (1) how fractions of DOM overlap in their susceptibility to degradation by sunlight and microbes, (2) how the net effect of sunlight on BDOM changes with photon dose, and (3) how rates of DOM photodegradation and biodegradation compare in a stream. Stream waters were exposed to sunlight, and then fed through bioreactors designed to separate labile and semi‐labile pools within BDOM. The net effects of photodegradation on DOM biodegradability, while generally positive, represented the balance between photochemical production and removal of BDOM that was mediated by photon dose. By using sunlight exposure times representative of sunlight exposures in a headwater stream and bioreactors colonized with natural communities and scaled to whole‐stream dynamics, we were able to relate our laboratory findings to the stream. The impact of sunlight exposure on rates of DOM biodegradation in streams was calculated using rates of light absorption by chromophoric DOM, apparent quantum yields for photomineralization and photochemical alteration of BDOM, and mass transfer coefficients for labile and semi‐labile DOM. Rates of photochemical alteration of labile DOM were an order of magnitude lower than rates of biodegradation of labile DOM, but for semi‐labile DOM, these rates were similar, suggesting that sunlight plays a substantial role in the fate of semi‐labile DOM in streams.

    

   more » « less
2. Cascading influence of inorganic nitrogen sources on DOM production, composition, lability and microbial community structure in the open ocean: Nitrogen Source Effects on Marine DOM and Microbes

   https://doi.org/10.1111/1462-2920.13825  

   Goldberg, S. J. ; Nelson, C. E. ; Viviani, D. A. ; Shulse, C. N. ; Church, M. J. ( September 2017 , Environmental Microbiology)
3. Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream

   https://doi.org/10.3390/w13202919  

   Lu, Yuehan ; Shang, Peng ; Chen, Shuo ; Du, Yingxun ; Bonizzoni, Marco ; Ward, Amelia K. ( October 2021 , Water)

   Streams in the southeastern United States Coastal Plains serve as an essential source of energy and nutrients for important estuarine ecosystems, and dissolved organic matter (DOM) exported from these streams can have profound impacts on the biogeochemical and ecological functions of fluvial networks. Here, we examined hydrological and temperature controls of DOM during low-flow periods from a forested stream located within the Coastal Plain physiographic region of Alabama, USA. We analyzed DOM via combining dissolved organic carbon (DOC) analysis, fluorescence excitation–emission matrix combined with parallel factor analysis (EEM-PARAFAC), and microbial degradation experiments. Four fluorescence components were identified: terrestrial humic-like DOM, microbial humic-like DOM, tyrosine-like DOM, and tryptophan-like DOM. Humic-like DOM accounted for ~70% of total fluorescence, and biodegradation experiments showed that it was less bioreactive than protein-like DOM that accounted for ~30% of total fluorescence. This observation indicates fluorescent DOM (FDOM) was controlled primarily by soil inputs and not substantially influenced by instream production and processing, suggesting that the bulk of FDOM in these streams is transported to downstream environments with limited in situ modification. Linear regression and redundancy analysis models identified that the seasonal variations in DOM were dictated primarily by hydrology and temperature. Overall, high discharge and shallow flow paths led to the enrichment of less-degraded DOM with higher percentages of microbial humic-like and tyrosine-like compounds, whereas high temperatures favored the accumulation of high-aromaticity, high-molecular-weight, terrestrial, humic-like compounds in stream water. The flux of DOC and four fluorescence components was driven primarily by water discharge. Thus, the instantaneous exports of both refractory humic-like DOM and reactive protein-like DOM were higher in wetter seasons (winter and spring). As high temperatures and severe precipitation are projected to become more prominent in the southeastern U.S. due to climate change, our findings have important implications for future changes in the amount, source, and composition of DOM in Coastal Plain streams and the associated impacts on downstream carbon and nutrient supplies and water quality. 

   more » « less
4. Molecular level characterization of DOM along a freshwater-to-estuarine coastal gradient in the Florida Everglades

   https://doi.org/10.1007/s00027-022-00887-y  

   Leyva, Dennys ; Jaffé, Rudolf ; Courson, Jessica ; Kominoski, John S. ; Tariq, Muhammad Usman ; Saeed, Fahad ; Fernandez-Lima, Francisco ( October 2022 , Aquatic Sciences)
5. Correspondence between DOM molecules and microbial community in a subtropical coastal estuary on a spatiotemporal scale

   https://doi.org/10.1016/j.envint.2021.106558  

   Chen, Qi ; Chen, Feng ; Gonsior, Michael ; Li, Yunyun ; Wang, Yu ; He, Chen ; Cai, Ruanhong ; Xu, Jinxin ; Wang, Yimeng ; Xu, Dapeng ; et al ( September 2021 , Environment International)