Geographic characterization of meiofaunal communities along the California coast and potential abiotic drivers

For my thesis research, I study community composition in meiofauna —all the little critters that live in between grains of sand— and how those communities are influenced by different environmental factors. You may think you’ve never heard of them, but Tardigrades (or water bears) are representative members of this group and they’ve definitely made the jump into popular science.

That being said, when you create a group of organisms based on size (roughly 50um-1mm), it means they can have vast differences in their biology, ecology, and life history. There isn’t much commonality to tie them together. Of the 36 living phyla of animals, approximately 26 are included in the meiofauna.

As you can imagine, you have to know a lot about many different obscure groups to be able to study them well. Add to this that they are microscopic, and you can begin to focus in on (see what I did there) the challenges facing researchers. It has been suggested that the effort required to assigning 10% of nematodes to known species is 120-fold the effort required to successfully assign all vertebrate morphospecies within a tropical rainforest (Lawton et al. 1998). 

The research goals and hypothesis of my thesis play on the idea of scale, analyzing pattern in meiofauna communities from the very broad (the total length of California) to the very narrow (the mineral composition of the sand the meiofauna live in). I’ve included my specific questions below:

  1. Do we see a change in meiofaunal communities with latitude consistent with the Latitudinal Diversity Gradient?

  2. Does meiofaunal community structure change with respect to known biogeographical faunal breaks such as Point Conception?

  3. Does meiofaunal community composition change with respect to tidal height?

  4. How do meiofaunal communities change along a continuum of sediment characteristics (ie. grain size and mineral composition)?

I use molecular techniques to try to avoid some of these traditional problems (although it creates new problems). Specifically, I use a process known as metabarcoding to identify individual species in a sample. Metabarcoding relies on the premise that our DNA is a like a fingerprint. It’s unique to us, or in this case, unique to a specific group. By targeting a specific gene (or region of a gene) I expect all meiofauna to have, I can distinguish them from other organisms.

My methods involve taking a sample of sand and extracting all the DNA from it using a kit. Then, I target the 18S gene (and sometimes CO1) and sequence all the DNA with that gene in the sample. When you run it against a reference database, you theoretically end up with a list of all the species in your sample.

Meiofauna are important for many reasons. They form the base of the sandy-beach food web, which supports many species. The sandy beach also links the terrestrial and offshore habitats. They have also been suggested as good indicators for studying ecosystem health. Communities change as a result of natural and anthropogenic (human-driven) stressors such as pollution, beach modification, trampling, warming, increases in pH, and others.

(I would like to thank the following funding sources for supporting my work: KQED-CSUMB Science Communication Scholarship, James Nybbaken Memorial Scholarship, Xiphias Martin Scholarship, Meyers Oceanographic & Marine Biology Trust, COAST Graduate Student Research Award, and Simpkins Family Marine Science Scholarship.)