Meeting Abstract
Anthropogenic CO2-induced ocean acidification (OA) poses a threat to marine calcifying organisms. Early life-history stages may be especially vulnerable given their small size and relatively poor homeostatic capacities. In previous work we found significant effects on larval growth, but no significant genetic variation for resilience to near-future levels of OA, within a population of sea urchins (Arbacia punctulata). Here we tested for a difference in larval response to OA using latitudinally separated populations of A. punctulata from Woods Hole, MA and Charleston, SC. We fertilized eggs and reared larvae to the 4-arm stage (before food was needed) at two CO2 levels (1x and 2.5x current) and at each of the two populations’ collection temperatures (14 and 24°C), using a factorial design that treated fertilization and rearing conditions separately, producing a total of 16 treatments. Larval growth after 3 d (@ 24°C) and 6 d (@ 14°C) was quantified by recording 11 landmarks in three dimensions to measure 6 skeletal elements and several aspects of body size. Increased CO2 during larval rearing had a significant and negative effect on skeletal measures in both populations but no significant effect on measures of body size. Larvae from the southern population were significantly larger in skeletal and body measurements. However, we found no significant interaction between population and CO2 or between temperature and CO2 in their effects on larval growth. Our findings suggest that A. punctulata does not show evidence of variation in resilience to acidification either within or between populations. A lack of genetic variation will make it more difficult for populations or species to rapidly evolve in response to future changes in ocean acidity.
