| Summary: | Single page poster The oceans serve as an important carbon sink, but rising amounts of dissolved carbon are reducing their pH. Projections anticipate a decrease in mean surface pH from 8.07 to 7.67 by 2100, and some regions are already experiencing pH fluctuations with lows below 7.15 units. Studies have demonstrated Strongylocentrotus purpuratus urchins to be evolving in response to acidifying conditions, but successful spawning amongst this species may be inhibited by more acidic seawater. To determine the effect of reduced pH on fertilization success, we simulated spawning by mixing collected gametes in seawater solutions of decreasing pH and assessed eggs for fertilization using a compound microscope. We found that mean percent fertilization decreased significantly from pH 8.06 (M=98%, SD=1.81) to pH 7.00 (M=84%, SD=12.33) seawater; t(8)=-2.52, p=.026. Natural pH fluctuations combined with ocean acidification could bring pH levels below 7.00 in the near future, possibly inhibiting the success of S. purpuratus reproduction. The resultant decline in urchin populations would have negative consequences for the Pacific kelp forests in which this species lives and could disrupt these fragile ecosystems.
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