Laboratory experiments suggest that calcifying developmental stages of marine invertebrates may be the most ocean acidification (OA)-sensitive life-history stage and represent a life-history bottleneck. To better extrapolate laboratory findings to future OA conditions, developmental responses in sea urchin embryos/larvae were compared under ecologically relevant
in situ
exposures on vent-elevated
p
CO
2
and ambient
p
CO
2
coral reefs in Papua New Guinea.
Echinometra
embryos/larvae were reared in meshed chambers moored in arrays on either venting reefs or adjacent non-vent reefs. After 24 and 48 h, larval development and morphology were quantified. Compared with controls (mean pH
(T)
= 7.89–7.92), larvae developing in elevated
p
CO
2
vent conditions (pH
(T)
= 7.50–7.72) displayed a significant reduction in size and increased abnormality, with a significant correlation of seawater pH with both larval size and larval asymmetry across all experiments. Reciprocal transplants (embryos from vent adults transplanted to control conditions, and
vice versa
) were also undertaken to identify if adult acclimatization can translate resilience to offspring (i.e. transgenerational processes). Embryos originating from vent adults were, however, no more tolerant to reduced pH. Sea temperature and chlorophyll-
a
concentrations (i.e. larval nutrition) did not contribute to difference in larval size, but abnormality was correlated with chlorophyll levels. This study is the first to examine the response of marine larvae to OA scenarios in the natural environment where, importantly, we found that stunted and abnormal development observed
in situ
are consistent with laboratory observations reported in sea urchins, in both the direction and magnitude of the response.
Direct and latent effects of ocean acidification on the transition of a sea urchin from planktonic larva to benthic juvenile