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Abstract The interconnected estuarine complex of the Altamaha River and adjacent sounds located in Georgia (USA) functions as a hotspot for organic matter transformation as it is transported to the Atlantic Ocean. Here, we investigated how dissolved organic matter (DOM) composition changes both spatially and seasonally along the estuary and how it influences bacterial processing. Surface samples were collected during high tide at fifteen stations throughout the estuary in April, July, October 2017, and January 2018. Bulk, optical, and molecular analyses were conducted on samples before and after dark incubations to assess DOM sources and transformation patterns in the system. The dominant driver of change in DOM composition was found to be the terrigenous‐marine gradient in organic matter sources. Six distinct clusters were identified based on the terrigenous signature of the DOM pool, explaining 45% of the variance in DOM composition in the system. Bacterial consumption of dissolved organic carbon (DOC) was strongly influenced by DOM composition, with increased degradation rates for DOM with a larger terrigenous character. However, changes in optical properties suggested that less aromatic DOM that co‐varied with the terrigenous material was preferentially degraded. The passage of Hurricane Irma in September 2017 resulted in a 27% ± 7% increase in DOC content, likely due to inundation associated with storm surge and increased local precipitation, and DOC biodegradation was 17% ± 8% higher than during summer. These effects lasted for at least one month after the storm, revealing that hurricanes can have a large impact on DOM composition and cycling in coastal systems.
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Microbial transformation of virus-induced dissolved organic matter from picocyanobacteria: coupling of bacterial diversity and DOM chemodiversity
Abstract Picocyanobacteria make up half of the ocean’s primary production, and they are subjected to frequent viral infection. Viral lysis of picocyanobacteria is a major driving force converting biologically fixed carbon into dissolved organic carbon (DOC). Viral-induced dissolved organic matter (vDOM) released from picocyanobacteria provides complex organic matter to bacterioplankton in the marine ecosystem. In order to understand how picocyanobacterial vDOM are transformed by bacteria and the impact of this process on bacterial community structure, viral lysate of picocyanobacteria was incubated with coastal seawater for 90 days. The transformation of vDOM was analyzed by ultrahigh-resolution mass spectrometry and the shift of bacterial populations analyzed using high-throughput sequencing technology. Addition of picocyanobacterial vDOM introduced abundant nitrogen components into the coastal water, which were largely degraded during the 90 days’ incubation period. However, some DOM signatures were accumulated and the total assigned formulae number increased over time. In contrast to the control (no addition of vDOM), bacterial community enriched with vDOM changed markedly with increased biodiversity indices. The network analysis showed that key bacterial species formed complex relationship with vDOM components, suggesting the potential correspondence between bacterial populations and DOM molecules. We demonstrate that coastal bacterioplankton are able to quickly utilize and transform lysis products of picocyanobacteria, meanwhile, bacterial community varies with changing chemodiverisity of DOM. vDOM released from picocyanobacteria generated a complex labile DOM pool, which was converted to a rather stable DOM pool after microbial processing in the time frame of days to weeks.
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- Award ID(s):
- 1829888
- PAR ID:
- 10485664
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- The ISME Journal
- Volume:
- 13
- Issue:
- 10
- ISSN:
- 1751-7362
- Format(s):
- Medium: X Size: p. 2551-2565
- Size(s):
- p. 2551-2565
- Sponsoring Org:
- National Science Foundation
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