Geographically Opposing Responses of Sea Urchin Recruitment to Changes in Ocean Climate

Sea urchins are voracious herbivores that influence the ecological structure and function of nearshore ecosystems throughout the world. Urchin population growth rates may be particularly sensitive to climate change because adult reproduction and larval development can vary greatly with food availability and temperature, and the transport of their larvae, which spend months feeding in the plankton, are affected by changes in ocean currents. Yet how climate alters sea urchin populations in space and time by modifying larval recruitment and year-class strength remains untested. Using an unprecedented spatially replicated 27-year dataset we illustrate how ocean temperature and climate oscillations differentially affect larval recruitment of the purple sea urchin (Strongylocentrotus purpuratus) and give rise to geographic asynchrony between northern California (positive) vs southern California (negative). Importantly, we found a strong correlation between larval recruitment and regional year class strength suggesting that recruitment variation plays an important role in controlling population dynamics. These results are the first to show that climatic fluctuations shape broad-scale patterns of sea urchin larval recruitment and are likely to control dynamics of both populations and marine ecosystems that vary over the geographical range of their distribution.