April 7, 2025
Congratulations to Emily Speciale who successfully defended her MSc thesis entitled ‘The molecular physiology of mixotrophic phytoplankton under iron-limited upwelling conditions’. Emily investigated how the gene expression of mixotrophs in the Califormia Current System respond to varying iron states. Emily will continue in the Marchetti Lab as a PhD candidate.
June 28, 2024
Johnson successfully defended his Ph.D dissertation titled ‘Phytoplankton molecular physiology associated with upwelling dynamics through field and laboratory studies’. He used a combination of physiological and molecular approaches to examine how phytoplankton respond to upwelling cycles under varying iron states. He also performed laboratory experiments to examine how diatom isolates from the California Current System are influenced by the Upwelling Conveyor Belt Cycle. Johnson will continue in our lab as a bioinformatic specialist.
April 18, 2024
Meredith successfully defended her Ph.D dissertation titled ‘The Influence of Phytoplankton Productivity and Molecular Physiology on Biogeochemical Dynamics of Two Contrasting Ocean Environments’. Meredith examined primary productivity dynamics as part of the NASA EXPORTS program field campaigns in the North Pacific and North Atlantic. She used a combination of physiological and molecular methods to elucidate how phytoplankton respond to their environment and influence the export of carbon from the surface ocean. She also conducted laboratory studies on Bathycoccus, an important picoeukaryote from the North Pacific. Meredith will be starting a post-doc at the University of East Anglia this summer.
March 22,2024
Congratulations to Prisca Lim who defended their M.Sc. thesis titled ‘Drivers of marine phytoplankton diversity and connectivity in the Galápagos Archipelago spanning an ENSO cycle’. Prisca analyzed DNA sequences from our Galápagos cruises from 2014 – 2022 spanning the El Niño in 2015/16 and the La Niña event from 2020-2022. Phytoplankton composition and size structure are highly dependent on the environmental conditions across the region which exhibit both high spatial and temporal variability. Publication soon to follow.
February 27, 2024
Former PhD student Carly Moreno has led a study just published in mSystems examining how diatom natural assemblages respond to changes in environmental conditions in waters adjacent to the Western Antarctic Peninsula using metatranscriptomic approaches. She also opportunistically examined a bloom of the centric diatom Actinocyclus in coastal waters.
February 24, 2024
Ph.D student Johnson Lin is the lead author on a study recently published in Limnology and Oceanography where we examined how diatoms respond to upwelling when under various iron states at narrow and wide shelf regions in the California Current System.
September 28, 2023
Former undergraduate student Emily Pierce led a publication on comparing different methods for identification of diatoms in dynamic coastal communities. In this study, Emily compared 18s rRNA gene analysis with FlowCam imaging and light microscopy. Her findings show some consistencies, although cross-method comparisons should proceed with caution.
Comparison of advanced methodologies for diatom identification within dynamic coastal communities
September 16, 2022
Our first paper contribution to the NASA EXPORTS program was recently published in Elementa: Science of the Anthropocene. In this study, Ph.D. candidate Meredith Meyer provides our findings on trends in new and regenerated production during the North Pacific EXPORTS field campaign. Meredith and coauthors show that the majority of net primary production (NPP) is performed by small cells growing on regenerated sources of nitrogen. Yet, any variations in NPP are primary driven by changes in nitrate-based new production.
May 18, 2022
Our second publication investigating the protistan communities in the Galápagos Archipelago was published recently in Frontiers in Marine Sciences. Former post-doc Se Hyeon jang led this effort to examine how environmental conditions influence marine protists with an emphasis on the micrograzer communities. We also report observation from a red tide bloom in Elizabeth Bay, Isabela Island. A bloom of the dinoflagellate Scripsiella lachrymosa was being actively grazed by another dinoflagellate, Polykrikos kofoidii.
Protistan communities within the Galápagos Archipelago with an emphasis on micrograzers
Dec. 19, 2021
Our new publication led by former graduate student Erika Neave was recently published in Environmental Microbiology. This publication is the first highlighting my groups research in the Galápagos Archipelago where we participated on annual research cruises that spanned the 2015/16 El Niño event. In this study, we found that the composition of the marine protist community was significantly influenced by deep water masses. This suggests that the ocean currents are a major source of plankton seed populations to the surface waters in the Galápagos and thus substantially influences plankton composition when these currents change as a result of El Niño-Southern Oscillation (ENSO) events.
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