Low pH effects on early development and toxin transporter activity in sea urchins (Strongylocentrotus Purpuratus, Tripneustes gratilla, Echinometra mathaei)

This study explores both the direct effects of ocean acidification on early embryology and the indirect effects of a low pH environment on the embryos ability to expel toxins through membrane-bound transporters. This work was done on three different species of sea urchins, Strongylocentrotus Purpuratus, Tripneustes gratilla, and Echinometra mathaei, each collected at a different location (Monterey, CA, Hawaii, and Washington Island, respectively). Cell counts in individuals were performed to assess impact on early development. Surface membrane toxin transporters (mrp, pgp) were blocked, and accumulation of a toxin proxy, calcein-am, was noted by measuring the fluorescent levels as calcein-am hydrolyzed into fluorescent calcein in the embryo. The results indicate negative effects of low pH on early development of Echinometra, while the toxin transporters in all three species appear to work more effectively at low pH. There is some evidence that specific types of transporters may work more effectively until a threshold pH, below where the transporter no longer functions as well. In general, Echinometra had less transporter activity than Tripneustes.