Microbial impact on biogeochemical cycling

The data resulting from our comparative phylogenetic analyses provide a strong phylogenetic framework to assess the role of microbes in these ecosystems by suggesting distributions of potential metabolic processes. Using a combination of field sampling, experimental approaches to directly quantify rates of processes and genomics, we  undertake a fundamental investigation of the microbially driven geochemical processes that mediate biogeochemical cycling. Our research primarily focuses on the role of heterotrophic anaerobic processes (such as sulfur and iron reduction) in regulating nutrient flux and heterotrophic productivity.

Nutrient cycling in fishponds
Metabolic rate reactions

In coastal systems, organic carbon loads tend to be high due to terrigenous and anthropogenic inputs. Oxidation of carbon is driven by diverse populations of microbes utilizing a wide variety of electron acceptors such as sulfate (as it is the most abundant electron acceptor in the ocean) or iron (as it makes up a significant portion of our sediment). Sulfate reduction and iron reduction are dominant heterotrophic pathways in the sediment and are likely to be tightly coupled processes. The spatial distribution of redox reactive iron and sulfur species influences nutrient cycling within coastal sediments and can account for up to 50% of the yearly primary production in overlying waters. We focus on identifying the chemical reactions that are microbially mediated within the sediment of the Heʻeia loko iʻa, the kinetics of these processes, and the extent to which these microbes influence the cycling of nutrients for algal growth. 

Microbial agricultural managment
Loʻi Kalo

Dramatic changes in land use over the last century have seriously impacted the health and sustainability of indigenous ahupuaʻa resources. Many traditional agroecosystems face challenges including congested irrigation systems, invasive plants, and inadequate aeration and pollution. Consequently, anoxic conditions are prevalent, promoting microbial processes that can remove nutrients from the watershed and or influence the mobilization of pollutants (such as arsenic) that can easily accumulate in crops such as kalo. Because management techniques have the potential to alter soil geochemistry and bioavailability of compounds and nutrients, restoring our ahupuaʻa resources requires an understanding of the extent and mechanism to which benthic microbes influence the cycling of elements, especially the toxic species like arsenic, in Hawaiʻi’s soils.

Sulfur cycling in hydrothermal vents
Middle Valley Hydrothermal vents

We evaluate the effect of key variables on the rates of sulfate reduction within hydrothermal vent chimneys in the context of bacterial and archaeal diversity, total biomass, the abundance of functional genes related to sulfate reduction, and in situ geochemistry. This research presents an opportunity to better understand the key variables that influence the rates of microbial sulfate reduction in hydrothermal environments and provides a framework for modeling sulfate reduction in mid-ocean ridge systems

PROJECT THEMES:
Research Interests:
Study Sites:

Environmental drivers of microbial dynamics

Microbial impact on biogeochemical cycles

Relationships between thermodynamic and kinetic metabolic processes

Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Laieikawai Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana Frank Kiana FrankHawaii Microbes Microbiology Labhuiofrank PBRC PBRC PBRC PBRC PBRC PBRC PBRC