Temporal and Spatial Diversity of Cryptophytes in San Diego Coastal Waters

Cryptophytes are unicellular protists that are ubiquitous in both marine and freshwater environments, occasionally forming blooms. They play an important role in primary production and trophic transfer of energy, both as a food source for grazers and as grazers themselves. Here we present findings on the temporal and spatial abundance and molecular diversity of cryptophytes off the Scripps Institution of Oceanography Pier in San Diego, CA and in the San Diego Bay. Flow cytometry revealed large changes in cell density within and between years 2015-2017 at the SIO pier. Based on 18S rDNA amplicon sequencing and amplicon sequence variant (ASV) analysis for 2016, approximately 22 ASVs are present. The Teleaulax-Plagioselmis-Geminigera clade dominated genetic data, likely responsible for increases and decreases in cell density. One heterotrophic cryptophyte ASV was detected, but some other cryptophytes may be mixotrophic as demonstrated by others. Comparing cryptophyte diversity off the SIO pier with that of the San Diego Bay yields two bay-specific clades (Chroomonas, Falcomonas) and two SIO pier-specific clades (Hemiselmis, Hemiarma). These ASVs could serve as marker microbes for tracking water parcels through a tidal cycle in a semi-closed system like the San Diego Bay.