Seasonal Patterns in Protist Diversity Across Depths in the Santa Barbara Channel

Paul G Matson, Bowling Green State University, Department of Biological Sciences, Bowling Green, CA, United States; University of California Santa Barbara, Marine Science Institute, Santa Barbara, CA, United States, Dylan Catlett, University of California, Santa Barbara, Santa Barbara, CA, United States, Craig A Carlson, University of California Santa Barbara, Marine Science Institute/Department of Ecology, Evolution and Marine Biology, Santa Barbara, CA, United States, Thomas S Lankiewicz, University of California, Santa Barbara, United States, David Siegel, University of California Santa Barbara, Santa Barbara, United States, Emma Wear, University of California Santa Barbara, Santa Barbara, CA, United States; University of Montana, Flathead Lake Biological Station, Polson, MT, United States and Debora Iglesias-Rodriguez, University of California, Santa Barbara, Ecology, Evolution, and Marine Biology, Santa Barbara, United States
Abstract:
Biodiversity plays an important role in the structure and function of ecosystems. For marine microbes, taxonomic identification has long been challenging due to limited morphological characteristics and poor performance of laboratory cultures. Advances in high-throughput sequencing technologies have facilitated a major expansion in our ability to generate datasets to assess diversity within marine microbial plankton. Protists represent a diverse group of marine planktonic microbes, serving a multitude of roles within ecological and biogeochemical processes. Here we present data from amplicon sequencing of the V9 hypervariable region of the 18S rRNA gene of protists in monthly samples collected from the Santa Barbara Channel (SBC), CA, USA from 2011 to 2014. Data from these samples, collected both at the surface along a 40 km cross-channel transect as well as a 300-m depth-stratified vertical profile at the center of the transect, indicate seasonal patterns in alpha-diversity in amplicon assemblages that attenuate with increased depths. While diatoms and dinoflagellates remain conspicuous in surface assemblages across all seasons, shifts in relative abundances occur within these groups (e.g., pennate- versus centric-diatoms) and in others (e.g., mamiellophytes increasing in winter). Across depths, surface assemblages characterized by diatoms, dinoflagellates (Dinophyceae), and prymnesiophytes transition to assemblages dominated by radiolarians (Polycystinea and Acantherea), dinoflagellates (Dinophyceae and Syndiniales), parasitic alveolates (Apicomplexa), and euglenozoa (Diplonemea) at depths ≥150m. These results not only provide insight into planktonic protist diversity across space and time within the SBC, but also establish a valuable baseline for future biodiversity assessments in the region for detecting impacts of changing ocean climate on marine microbial assemblages.
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