Pervasive Plastics: A New Challenge for Sand Crabs
Sandy beaches cover ~ 75% of the world’s shorelines, 60-90% of the shorelines of Southern California counties and are fundamental to most coastal economies and cultures. The sand crab (Emerita analoga) is found intertidally upon almost every Californian sandy beach, and so an excellent potential sentinel of ecosystem change across shorelines in a wide geographic area. Given the rise of plastic pollution across our seas and coasts over recent decades, there is a high likelihood plastics are entering marine food webs and impacting coastal ecosystem. We have recently demonstrated microplastics (particles or fibers<5mm) are now common across our beach sands and experimentally demonstrated E. analoga ingest microplastics under controlled laboratory condition. Most disturbingly, we have now confirmed background levels of microplastics within the bodies of adult E. analoga from beaches across southern California. We sampled sand crabs populations from San Diego to Northern San Francisco county beaches to test for the presence of microplastics. The ubiquity of this contamination makes ascertaining the effects upon sand crabs and their associated food webs difficult as there appears to be no areas free from plastic exposure and contamination.
I will test the particles and fibers to determine their chemical makeup in one of two ways. 1 using polarizing light and a compound microscope or 2 using an FTIR spectroscopy microscope. The later requires more funding, therefore method one will be employed over the next few weeks. During a test of the FTIR spectroscopy machine we found polypropylene, polyester, synthetic cellulose and cotton fibers as well as polypropylene, polyethylene and a mix of tiling glue/cement particles.
I am examining the fresh water sediment that is housing the re-introduction of the California Red Legged frog in the Santa Monica Mountains. As of this week I have found particles and fibers in the sediment samples. Amphibians breathe through their skin leaving them highly vulnerable to the pollutants in their environment.
I have also received a grant from the WRPI/USDA to examine our local watersheds in Ventura county and quantify the amount of particle pollutants above and below human pollution sources. I am testing Calleguas creek, Ventura river, Santa Clara river and the Perkins Estuary. These water ways lead directly to the ocean at critical habitat locations for endangered shore birds such as the California Least Tern and the Western Snowy Plover.