| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | October 29, 2018 |
| Latest Amendment Date: | October 29, 2018 |
| Award Number: | 1902131 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Henrietta Edmonds
hedmonds@nsf.gov (703)292-7427 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | November 1, 2018 |
| End Date: | October 31, 2021 (Estimated) |
| Total Intended Award Amount: | $127,146.00 |
| Total Awarded Amount to Date: | $127,146.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
310 E CAMPUS RD RM 409 ATHENS GA US 30602-1589 (706)542-5939 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Athens GA US 30602-5016 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Chemical Oceanography |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
This project will examine changes in dissolved organic matter (DOM) composition and microbial decay processes in a marsh-dominated estuary that occur in response to the passage of hurricanes and tropical storms. The investigators will focus on the estuary around Sapelo Island off Georgia, which is the site of the Georgia Coastal Ecosystem Long Term Ecological Research (GCE-LTER) program. After decades escaping major storms, the estuary was hit by Hurricane Matthew in October 2016 and by Hurricane Irma in September 2017, and it is likely to be influenced by heavy rainfall from the passage of Hurricane Michael around October 11-12th, 2018. Although pulses in river discharge can deliver fresh, easily consumed organic matter to the estuary, the effects of DOM delivery during hurricanes on microbial processes are not well constrained. This is important because microbial processing of DOM can influence air-sea fluxes of carbon dioxide and other biogeochemical processes. This project will promote education by supporting a graduate student. Findings from this research will be disseminated in the Schoolyard Program that is organized every summer by the NSF-funded Georgia Coastal Ecosystem LTER. The program immerses science and math K-12 teachers from across the State of Georgia in hands-on research activities and discussions on coastal processes. All data generated as part of this project will be made publicly available.
A detailed year-long investigation of DOM composition based on optical measurements and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) data in 2015-2016 captured the effects of Hurricane Matthew, which resulted in a significant input of dissolved organic carbon (DOC) and change in DOM composition in the estuary. Sampling in 2017 captured a similar effect shortly after the passage of Hurricane Irma. DOC consumption by microbes was found to be strongly tied to DOM composition. The investigators propose to collect additional samples in the estuary in mid-October 2018, when Hurricane Michael is expected to impact the region because of heavy rainfall inland. They will also quantify biologically labile DOM via microbial dark incubations. They will compare DOM composition and lability between background samples not influenced by hurricanes and samples from the 3 hurricanes that will have been captured by the combined studies. While the two earlier hurricanes caused large storm surges in the estuary, Hurricane Michael is expected to cause heavy rainfall but smaller storm surge. The occurrence of three major hurricanes in three consecutive years is highly unusual for this estuary, and together with the fortuitous fact that two detailed programs to investigate DOM dynamics were in place, provides an excellent opportunity to quantify the impact of hurricanes on organic carbon delivery and processing in a marsh-dominated estuary.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Intellectual Merit: This award supported the investigation of changes in dissolved organic matter (DOM) composition and microbial degradation that occur in a marsh-dominated estuary in response to the passage of hurricanes and tropical storms. These extreme events often result in large fluxes of dissolved organic carbon (DOC) to estuaries. Precipitation associated with tropical storms may be increasing in the southeastern U.S. Thus, understanding how extreme events impact DOM dynamics in these complex coastal ecosystems is key to understand their potential impact on carbon cycling and CO2 air-sea exchange. After decades escaping major storms, the Altamaha River and Estuary off Georgia (U.S.A.) was hit by multiple hurricanes in consecutive years (Matthew in 2016, Irma in 2017 and Dorian in 2019), providing an opportunity to investigate their impacts on DOM dynamics in coastal systems. In this project, we investigated the DOM composition at the estuary over multiple years capturing the passage of hurricanes which resulted in significant storm surges, as well as high precipitation events and seasonal variations in river discharge. Our results showed that river discharge is the primary driver of changes in DOM composition in the system at seasonal scales, with the terrigenous character of the DOM increasing approximately linearly with river flow for discharges higher than ~150 m3 s-1. During low discharge conditions, the signature of marsh-derived compounds becomes more important. The passage of hurricanes resulted in large increases in DOC content and biodegradation rates throughout the estuary. Traditional measures of terrigenous DOM, such as those obtained from optical analyses, indicate that the terrigenous content in the estuary is linearly related to freshwater content, and that the signatures are similar after extreme events and during peak river flow. Analyses at the molecular level revealed significant differences, however, with a large increase of highly aromatic compounds after extreme events exceeding what would be expected by freshwater content alone, likely associated with remobilization of DOM stored in adjacent forested wetlands. Although biodegradation rates increase after the passage of hurricanes, the terrigenous material added during those extreme events does not appear to be particularly labile and may thus be exported to the coastal ocean. Additional studies are needed to characterize the components of the added DOM that may be responsible for the increased biomineralization observed after extreme events, since they likely play a key role controlling carbon exchange with the atmosphere.
Broader Impacts: This project supported the training of two female graduate students in organic geochemistry. Findings supported by this study were described in five scientific articles and were presented at various international scientific conferences and invited seminars. Observations have been made publicly available at BCO-DMO (https://www.bco-dmo.org/project/472758, BCO-DMO 472758) and at the Georgia Coastal Ecosystems LTER data portal (https://gce‐lter.marsci.uga.edu; ORG-GCET-1904).
Last Modified: 03/29/2022
Modified by: Patricia M Medeiros
Addendum # 1
Observations are also publicly available at https://www.bco-dmo.org/project/876719.
Added: 07/11/2022
Submitted by: Patricia M Medeiros
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