Fall 2019

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)


Moss Landing Marine Laboratories


Meiofauna are abundant and diverse infaunal organisms between 50-1000μm that are specially adapted to live in the interstitial spaces between sedimentary particles. Despite their ubiquity, they remain an understudied component of benthic systems. Modern DNA metabarcoding tools allow for the total sequencing of mixed communities from a single sample. Samples of meiofauna (n = 148) were collected at 10 sandy beaches along the coast of California during summer 2017 to characterize meiofauna community structure based on (1) latitude, (2) location north or south of Point Conception (a known biogeographic break), (3) tidal height and (4) sediment grain size and mineralogy. Meiofauna were found to form distinct communities within each domain (north/central/south California) and at each site. Southern sites had larger and more diverse meiofauna communities than northern sites, suggesting a rough fit to a latitudinal diversity gradient. Broad oceanographic conditions, particularly temperature and salinity, appear to impact meiofauna across larger scales. No significant distributional break was seen in the area surrounding Point Conception, although small changes to the proportions of major phyla were observed for Point Conception and San Francisco Bay. Within the tidal range, meiofauna richness generally decreased with increasing tidal height although patterns were not uniform across sites. Meiofauna responded significantly to both sedimentologic and mineralogical properties. Richness declined with increasing mean grain size, and the most distinct communities correlated most strongly with the presence of potassium feldspars. This study is the broadest examination of meiofauna within California, and these results form a necessary foundation for future comparison studies using meiofauna as an ecological monitoring group.