Free-Living and Particle-Associated Bacterioplankton in Large Rivers of the Mississippi River Basin Demonstrate Biogeographic Patterns

ABSTRACTThe different drainage basins of large rivers such as the Mississippi River represent interesting systems in which to study patterns in freshwater microbial biogeography. Spatial variability in bacterioplankton communities in six major rivers (the Upper Mississippi, Missouri, Illinois, Ohio, Tennessee, and Arkansas) of the Mississippi River Basin was characterized using Ion Torrent 16S rRNA amplicon sequencing. When all systems were combined, particle-associated (>3 μm) bacterial assemblages were found to be different from free-living bacterioplankton in terms of overall community structure, partly because of differences in the proportional abundance of sequences affiliated with major bacterial lineages (Alphaproteobacteria,Cyanobacteria, andPlanctomycetes). Both particle-associated and free-living communities ordinated by river system, a pattern that was apparent even after rare sequences or those affiliated withCyanobacteriawere removed from the analyses. Ordination of samples by river system correlated with environmental characteristics of each river, such as nutrient status and turbidity. Communities in the Upper Mississippi and the Missouri and in the Ohio and the Tennessee, pairs of rivers that join each other, contained similar taxa in terms of presence-absence data but differed in the proportional abundance of major lineages. The most common sequence types detected in particle-associated communities were picocyanobacteria in theSynechococcus/Prochlorococcus/Cyanobium(Syn/Pro) clade, while free-living communities also contained a high proportion of LD12 (SAR11/Pelagibacter)-likeAlphaproteobacteria. This research shows that while different tributaries of large river systems such as the Mississippi River harbor distinct bacterioplankton communities, there is also microhabitat variation such as that between free-living and particle-associated assemblages.

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Adapting to Climate Change in the Upper Mississippi River Basin: Exploring Stakeholder Perspectives on River System Management and Flood Risk Reduction

Environmental Health Insights ◽

10.1177/1178630220984153 ◽

2020 ◽

Vol 14 ◽

pp. 117863022098415

Author(s):

Tamsen Reed ◽

Lisa Reyes Mason ◽

Christine C. Ekenga

Keyword(s):

River Basin ◽

Mississippi River ◽

Flood Risk ◽

River System ◽

System Management ◽

Mississippi River Basin ◽

Upper Mississippi River ◽

River Flooding ◽

Stakeholder Perspectives ◽

Upper Mississippi River Basin

In the Midwestern United States (US), river flooding is a climate change-related hazard that poses a significant threat to health, well-being and economic stability. The 2019 Midwest floods led to major flooding at every monitoring site along the Mississippi River, set record water levels at 42 sites, and resulted in an estimated $6.2 billion in infrastructure damage and recovery costs. Although the risks associated with increasing flooding in the Midwestern US have been well recognized, less is known about the adaptation challenges and opportunities in the region, particularly in the Upper Mississippi River Basin. This exploratory study examined stakeholder perspectives on river system management, flood risk reduction, and adaptation planning in the Upper Mississippi River Basin. We conducted in-depth interviews with flood management stakeholders between August and October 2019. Interview data were analyzed using thematic analysis. Five themes emerged from the interviews: (1) River flooding in the Midwestern US is a different experience than US coastal flooding; (2) River flooding in the Midwestern US is a regional experience that requires a regional response; (3) Local actors face constrained resources for flood risk protection and recovery; (4) Differentiated responsibility across levels of governments makes recovery and response difficult to navigate; and (5) Competing stakeholder goals challenge cooperative flood hazard management. Overall, these results suggest that locally focused adaptation efforts, while perhaps appropriate for coastal communities or more urban contexts, are suboptimal strategies for communities in the flood-prone river basins of the Midwestern US. Instead, structures and support for regional collaboration should be considered and pursued.

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