Details:

Journal Title:
Frontiers in Marine Science
Personal Author:
Lu, Kaijun ; Liu, Zhanfei
Lu, Kaijun ; Liu, Zhanfei Less -
NOAA Program & Office:
NOS (National Ocean Service) ; OAR (Oceanic and Atmospheric Research) ; Sea Grant
NOS (National Ocean Service) ; OAR (Oceanic and Atmospheric Research) ; Sea Grant Less -
Sea Grant Program:
TAMU (Texas Sea Grant)
Description:
Riverine dissolved organic matter (DOM) is a major source of reduced carbon exported from land to marine environments, and the inflow of riverine organic matter greatly affects biogeochemical cycling in estuaries and bays. Thus, any change in DOM composition, such as changes caused by flood waters as a result of storms and hurricanes, can subsequently affect estuarine environments. To investigate the impact of high flow events on riverine DOM, multidimensional molecular level information on DOM from four South Texas Rivers (Aransas, Lavaca, Mission, and Nueces Rivers) was acquired using high-resolution Ion Mobility Quadrupole Time of Flight Liquid Chromatography Mass Spectrometry (IM Q-TOF LCMS). Base-flow samples were collected in May, July, and October of 2016, June of 2017, and March of 2018, while high-flow samples were collected in September of 2017, as well as June and September of 2018. Based on the molecular formulas assigned from IM Q-TOF LCMS, the H/C ratio decreased during high-flow events (1.52 to 1.51 in ESI+ and 1.19 to 1.07 in ESI−), while the O/C ratio increased (0.31 to 0.33 in ESI−). Furthermore, DOM shifted from a protein-like and lipid-like dominated community at base flow conditions, to a lignin, tannin and condensed aromatic structure dominated community during high flow events, based on MS and tandem MS data. These changes in high-flow riverine DOM indicate an increase of terrestrial signal, which is likely a result of mobilization of terrestrial organic matter from the watersheds by flooding. The mobilized DOM, though refractory at high-flow conditions in rivers, could be reactive in coastal regions when conditions change, and thus could potentially fuel microbial activities downstream. In addition, about 3.76–21.8% of DOM molecules contain structural isomers among different flow conditions. This low number of isomer percentages suggests that DOM, as the products of various enzymatic biochemical reactions, is constrained in the number of isomers. Taken together, results from our study provide insights into structural changes of riverine DOM in response to extreme climate events in subtropical regions and have implications in understanding biogeochemical changes in estuaries under a changing climate.
Keywords:
[+]
riverine dissolved organic matter, hurricane harvey, high flow, liquid chromatography massspectrometry, South Texas, structural isomers
Source:
Frontiers in Marine Science, 6, 18
DOI:
https://doi.org/10.3389/fmars.2019.00673
Document Type:
Journal Article
Funding:
Grant no. NA15NOS4780185 ; Grant no. NA14OAR4170102
Grant no. NA15NOS4780185 ; Grant no. NA14OAR4170102 Less -
Rights Information:
CC BY
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:2916fe9f8f30e7ee560dc05a22ad1c8e62155b7428b3137d1fdc49de3900a0d1
Download URL:
https://repository.library.noaa.gov/view/noaa/28851/noaa_28851_DS1.pdf
File Type:

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