Research

Research Background

My research involves assessing how ecosystem functions are affected by environmental changes and microbial diversity. With a focus on aquatic environments, I have looked at systems on all sides of the Pacific (fresh and marine) and have gained a strong foundation in Earth and Environmental Science, Marine Science/Oceanography, Limnology, and Ecology. I have increased my contacts and study locations by working with a wide range of people and agencies all over the world. Finally, much of my work has involved undergraduate researchers who I mentored and taught skills that they have used to obtain employment and/or attend graduate school.

Southern California Coastal Monitoring

At Scripps Institution of Oceanography, I contributed to the Southern California Coastal Ocean Observing System (SCCOOS) by looking at temporal variability of the microbial community using flow cytometry and sequence analysis. I used a combination of network analysis, machine learning, and other methods to assess how changes in the microbial community and/or subsets of the microbial community vary with different environmental parameters and ecosystem functioning.

https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/1462-2920.15548

I was also lucky enough to be in the midst of a multi-year time-series when a large and uncharacteristic harmful algal bloom occurred. I contextualized the HAB results using our time-series and existing time-series of algae, oxygen, and physical parameters.

https://online.ucpress.edu/elementa/article/doi/10.1525/elementa.2021.00088/191404

I also used causality testing to model how biogenic volatile organic compounds affect and are affected by different phytoplankton species and environmental parameters like temperature, current, and tidal height using the Scripps Pier time-series.

https://www.sciencedirect.com/science/article/abs/pii/S030442032030150X

Finally, I helped to initiate and process data from the Scripps Ecological Observatory. This involved operating and maintaining equipment that samples the microbial community and many different dissolved gases at a very high frequency so that high resolution relationships between populations of microbes, ecosystem functioning, environmental variables, and potentially biogenic gases can be assessed.

Marine Lakes of Palau

I spent a total of 4 field seasons in Palau where I:

Used marine lakes as natural mesocosms to represent miniature oceans to assess the controls on ecosystem functioning and the creation of redox gradients. The functions I assessed were primary production, community respiration, and net community production (measured via bottle-based incubations) as these processes produce and consume oxygen and set the stage for other redox reactions. The controls were explored through reciprocal transplants (to manipulate light and temperature) and additions (to manipulate nutrients and labile carbon).

https://www.frontiersin.org/articles/10.3389/fmars.2017.00012/full

https://online.ucpress.edu/elementa/article/12/1/00007/203890

Measured oxygen and environmental variables using miniDOT (PME) sensors that I deployed in a marine lake (Ongeim'l Tketau) for more than a year during the 2015/2016 El Niño and recovery. I used the data to calculate primary production, community respiration, and net community production over this time period as I watched the chemocline shoal and re-deepen. Throughout this process the jellyfish population died off and then began to reestablish. I was able to see how environmental forcing affected the physical structure of the lake and microbial processes during shoaling, but how bottom-up effects (i.e., primary production and community respiration) helped to reestablish the "original" water column structure during re-deepening. This was a unique opportunity to assess how microbes bioengineer the environment while potentially affecting economically important organisms (i.e., the jellyfish that tourists swim with in Ongeim'l Tketau).

https://www.nature.com/articles/s41598-019-52430-z

Monterey Bay, CA

I have spent a significant amount of time in Monterey Bay, CA where I measured community respiration both inside and outside the kelp forest over time. I connected the rates I measured to changes in the microbial community and upwelling using network analysis (a population modelling tool).

https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/1758-2229.12635

Pacific Ocean Transects

In 2011 I was one of a select group of researchers to be given access to data collected by oceanic wave gliders (ocean drones) that traversed the Pacific Ocean (starting in San Francisco, CA and ending in Japan and Australia). I used these data to calculate community respiration and related it to coincident measurements of chlorophyll, temperature, and turbidity.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0099821

Eastern Tropical North Pacific

I participated in two research cruises in the Eastern Tropical North Pacific (one of which I served as co-chief scientist for) in which we assessed how active members of the microbial community contributed to community respiration and nitrogen cycling at a range of oxygen concentrations inside and outside the oxygen minimum zone found there. We also manipulated oxygen concentrations by bubbling in N2 or O2 gas to assess how environmental perturbations affected microbial activities and vice versa.

https://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.15215

https://www.nature.com/articles/s41467-021-27381-7

More to come...

High Elevation Lakes of the Sierra Nevada

In the high elevation lakes of the Sierra Nevada I have assisted with 1) collection and analysis of aquatic microorganisms, 2) measuring respiration and methane production, and 3) quantification of nitrogen cycling genes.

Rocky Intertidal of Northern California

I have also collaborated with researchers in the rocky intertidal by sampling and counting invertebrate species. The California coast experienced massive invertebrate die-offs in 2013 and 2014 and I assisted with tracking the disappearance and return of species to intertidal habitats in Northern California.

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