Date of Award

2025

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Specialization

Biological Oceanography

Department

Oceanography

First Advisor

Tatiana A. Rynearson

Abstract

DNA metabarcoding has been widely adopted due to its power in investigating the composition of protistan communities, accurately identifying even small and cryptic taxa. However, the compositional nature of DNA metabarcoding results, and the distortion of natural abundances due to variation of the often-used 18S rRNA gene copy number over several orders of magnitude, renders these results semi-quantitative at best, limiting the application of DNA metabarcoding to ecological study. Here, we constructed mock communities from uni-algal cultures of taxonomically diverse phytoplankton and conducted metabarcoding using multiple primer sets and both DNA and cDNA as PCR templates. For each culture, chlorophyll a concentrations, cellular carbon, biovolume, and cell counts were also measured to investigate relationships between biomass and metabarcoding sequence abundance. The strongest regression relationship found was between relative abundance of 18S V4 reads and cellular carbon (R2 = 0.57). Otherwise, regression relationships between relative or absolute abundance and biomass were weak to moderate across gene regions and nucleic acids. Regression relationships did improve for functional groups, specifically diatoms and haptophytes. Regression relationships for absolute abundance and select measures of biomass were strong for these groups (R2 > 0.7), suggesting that metabarcoding results represent biomass quite well for some groups of phytoplankton, while more work is needed for other groups, including dinoflagellates.

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Available for download on Wednesday, May 27, 2026

Included in

Oceanography Commons

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