Publications by authors named "J Michael Beman"

35 Publications

Biogeochemistry and hydrography shape microbial community assembly and activity in the eastern tropical North Pacific Ocean oxygen minimum zone.

Environ Microbiol 2021 06 13;23(6):2765-2781. Epub 2020 Sep 13.

Life and Environmental Sciences, University of California, Merced, CA, USA.

Oceanic oxygen minimum zones (OMZs) play a pivotal role in biogeochemical cycles due to extensive microbial activity. How OMZ microbial communities assemble and respond to environmental variation is therefore essential to understanding OMZ functioning and ocean biogeochemistry. Sampling along depth profiles at five stations in the eastern tropical North Pacific Ocean (ETNP), we captured systematic variations in dissolved oxygen (DO) and associated variables (nitrite, chlorophyll, and ammonium) with depth and between stations. We quantitatively analysed relationships between oceanographic gradients and microbial community assembly and activity based on paired 16S rDNA and 16S rRNA sequencing. Overall microbial community composition and diversity were strongly related to regional variations in density, DO, and other variables (regression and redundancy analysis r  = 0.68-0.82), displaying predictable patterns with depth and between stations. Although similar factors influenced the active community, diversity was substantially lower within the OMZ. We also identified multiple active microbiological networks that tracked specific gradients or features - particularly subsurface ammonium and nitrite maxima. Our findings indicate that overall microbial community assembly is consistently shaped by hydrography and biogeochemistry, while active segments of the community form discrete networks inhabiting distinct portions of the water column, and that both are tightly tuned to environmental conditions in the ETNP.
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http://dx.doi.org/10.1111/1462-2920.15215DOI Listing
June 2021

Climatic, physical, and biogeochemical changes drive rapid oxygen loss and recovery in a marine ecosystem.

Sci Rep 2019 11 6;9(1):16114. Epub 2019 Nov 6.

Life and Environmental Sciences, University of California Merced, Merced, CA, 95343, USA.

Dissolved oxygen (DO) concentrations shape the biogeochemistry and ecological structure of aquatic ecosystems; as a result, understanding how and why DO varies in space and time is of fundamental importance. Using high-resolution, in situ DO time-series collected over the course of a year in a novel marine ecosystem (Jellyfish Lake, Palau), we show that DO declined throughout the marine lake and subsequently recovered in the upper water column. These shifts were accompanied by variations in water temperature and were correlated to changes in wind, precipitation, and especially sea surface height that occurred during the 2015-2016 El Niño-Southern Oscillation event. Multiple approaches used to calculate rates of community respiration, net community production, and gross primary production from DO changes showed that DO consumption and production did not accelerate nor collapse; instead, their variance increased during lake deoxygenation and recovery, and then stabilized. Spatial and temporal variations in rates were significantly related to climatic variability and changes in DO, and causality testing indicated that these relationships were both correlative and causative. Our data indicate that climatic, physical, and biogeochemical properties and processes collectively regulated DO, producing linked feedbacks that drove DO decline and recovery.
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http://dx.doi.org/10.1038/s41598-019-52430-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834605PMC
November 2019

Microbes and macro-invertebrates show parallel β-diversity but contrasting α-diversity patterns in a marine natural experiment.

Proc Biol Sci 2019 10 9;286(1912):20190999. Epub 2019 Oct 9.

Life and Environmental Sciences, University of California Merced, Merced, CA, USA.

Documenting ecological patterns across spatially, temporally and taxonomically diverse ecological communities is necessary for a general understanding of the processes shaping biodiversity. A major gap in our understanding remains the comparison of diversity patterns across a broad spectrum of evolutionarily and functionally diverse organisms, particularly in the marine realm. Here, we aim to narrow this gap by comparing the diversity patterns of free-living microbes and macro-invertebrates across a natural experiment provided by the marine lakes of Palau: geographically discrete and environmentally heterogeneous bodies of seawater with comparable geological and climatic history, and a similar regional species pool. We find contrasting patterns of α-diversity but remarkably similar patterns of β-diversity between microbial and macro-invertebrate communities among lakes. Pairwise dissimilarities in community composition among lakes are positively correlated between microbes and macro-invertebrates, and influenced to a similar degree by marked gradients in oxygen concentration and salinity. Our findings indicate that a shared spatio-temporal and environmental context may result in parallel patterns of β-diversity in microbes and macro-invertebrates, in spite of key trait differences between these organisms. This raises the possibility that parallel processes also influence transitions among regional biota across the tree of life, at least in the marine realm.
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http://dx.doi.org/10.1098/rspb.2019.0999DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790787PMC
October 2019
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