Environmental drivers of microbial dynamics 

We couple comparative microbial phylogenetic analysis with geochemical analysis to characterize the spatial and temporal variability in microbial community structure (abundance, diversity and taxonomy) at the microbe-mineral interface. Comparative phylogenetic analysis has the potential to provide significant insight into the environmental drivers of naturally occurring genomic variability and distribution of microbial genes and potential biochemical mechanisms.

PROJECT THEMES:
Linking benthic microbial dynamics to diel redox varriation

In shallow coastal ecosystems, excess primary productivity and respiration of pelagic phototrophic organisms generate striking diel variations in dissolved oxygen concentrations, leading to substantial vertical migration of redox transition zones in the sediment. However, the relationship between microbial community dynamics and the establishment of these geochemical gradients, especially over a diel time frame, remains poorly constrained.  We examine the biogeochemical drivers of diel redox dynamics by integrating comprehensive geochemical, taxonomic, functional gene abundance, and thermodynamic datasets from sediment cores.  Current work is focused within He'eia Fishpond.

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Spatial and temporal dynamics of microbial community structure

Hawaiian ahupuaʻa - areas of land spanning from ridge to reef - present a unique biogeographical opportunity to assess microbial biodiversity patterns across geological, hydrological, and chemical landscapes. Little is known about the microbial biodiversity of fishponds (loko iʻa), taro patches (loʻi kalo) and Hawaii’s groundwater aquifer ecosystems, and the extent to which microbial community dynamics vary during climate forcing remains unknown. Our current work includes field sites across the pae ʻāina and features a high-resolution sample archive from across a network of 14 stations within the Heʻeia Coastal Ocean Observing System across a continuum of climatic events, ranging from neutral baseline to El Niño influenced conditions, spanning 52 weeks (July 2014 – July 2015).

Integrated within a larger framework of addressing water sustainability in Hawaiʻi (UHM EPSCOR proposal ʻIke Wai 2015), we investigate microbial community structure along flow paths of the Pearl Harbor and Hualālai aquifer systems. These data will provide important evidence on subsurface water quality, terrestrial subsurface biogeography, microbial dispersal, selection, and ecological habitat partitioning in the subsurface. By better understanding temporal and spatial changes in subsurface microbial community structure, we will attempt to develop our capability to use microbes as tracers to determine terrestrial subsurface fluid connectivity and flow direction by integrating geochemical and hydrological models with biological data. 

Effects of microbes on plant nutrition

Plant-associated microbes, both above- (e.g., endophytic) and below-ground (e.g., root-associated), can play an important role in modulating plant growth and health through both mutualistic and pathogenic interactions. We are interested in the role of microbial communities in supplying nitrogen, phosphorus and cations to host plants, potentially permitting the vigorous growth of plants in nutrient-limited soils, and feeding back on local soil chemistry. This work stems from strong ethnographic and anecdotal evidence that suggest place-specific adaptations of Hawaiian cropping systems may have inadvertently cultivated and capitalized on microbial communities to enhance agricultural production. We are currently working at loʻi kalo across Oahu (Kakoʻo Ōiwi, Papahana Kuaola, Hoʻokuaʻāina, Kanwai) and in the dryland field systems of South Kona and Kohala, Hawaii island.

Research Interests:

Environmental drivers of microbial dynamics

Microbial impact on biogeochemical cycles

Relationships between thermodynamic and kinetic metabolic processes

Study Sites: