Larval and Post-Larval Stages of Pacific Oyster (Crassostrea gigas) Are Resistant to Elevated CO2

Abstract

The average pH of surface oceans has decreased by 0.1 unit since industrialization and is expected to decrease by another 0.3–0.7 units before the year 2300 due to the absorption of anthropogenic CO2. This human-caused pH change is posing serious threats and challenges to the Pacific oyster (Crassostrea gigas), especially to their larval stages. Our knowledge of the effect of reduced pH on C. gigas larvae presently relies presumptively on four short-term (<4 days) survival and growth studies. Using multiple physiological measurements and life stages, the effects of long-term (40 days) exposure to pH 8.1, 7.7 and 7.4 on larval shell growth, metamorphosis, respiration and filtration rates at the time of metamorphosis, along with the juvenile shell growth and structure of the C. gigas, were examined in this study. The mean survival and growth rates were not affected by pH. The metabolic, feeding and metamorphosis rates of pediveliger larvae were similar, between pH 8.1 and 7.7. The pediveligers at pH 7.4 showed reduced weight-specific metabolic and filtration rates, yet were able to sustain a more rapid post-settlement growth rate. However, no evidence suggested that low pH treatments resulted in alterations to the shell ultrastructures (SEM images) or elemental compositions (i.e., Mg/Ca and Sr/Ca ratios). Thus, larval and post-larval forms of the C. gigas in the Yellow Sea are probably resistant to elevated CO2 and decreased near-future pH scenarios. The pre-adapted ability to resist a wide range of decreased pH may provide C. gigas with the necessary tolerance to withstand rapid pH changes over the coming century.

Ocean acidification stress index for shellfish (OASIS): Linking Pacific oyster larval survival and exposure to variable carbonate chemistry regimes

“…The overall survival-to-settlement competency size in this study fell below commercial hatchery targets (30-60%; A Barton, personal communication;Breese and Malouf, 1975) for all cohorts, but was within the range of other published studies for oyster larvae (Talmage and Gobler, 2012;Eierman and Hare, 2013;Ko et al, 2013). To our knowledge, however, laboratory studies that have measured long-term larval survival under acidification have not captured embryological exposure to acidified conditions, only the exposure of larvae at least 24 hours old (Talmage and Gobler, 2010;Ko et al, 2013Ko et al, , 2014, potentially underestimating deleterious effects.…”

“…The overall survival-to-settlement competency size in this study fell below commercial hatchery targets (30-60%; A Barton, personal communication;Breese and Malouf, 1975) for all cohorts, but was within the range of other published studies for oyster larvae (Talmage and Gobler, 2012;Eierman and Hare, 2013;Ko et al, 2013). To our knowledge, however, laboratory studies that have measured long-term larval survival under acidification have not captured embryological exposure to acidified conditions, only the exposure of larvae at least 24 hours old (Talmage and Gobler, 2010;Ko et al, 2013Ko et al, , 2014, potentially underestimating deleterious effects. While our results generally show better survival for larvae raised in buffered water, differences in survival are complicated to assess statistically given the limited number of replicates due to logistical constraints, including limited laboratory space that prevented the installation of more culture chambers, lack of feasibility of sampling efforts, and the prioritization of repetition of the experiment (i.e., more cohorts) over increased sample replication.…”

Identification of molecular and physiological responses to chronic environmental challenge in an invasive species: the Pacific oyster, Crassostrea gigas

“…), although this may vary with different populations (Ginger et al. ). However, oysters of the genus Crassostrea are generally found in intertidal to low subtidal levels in estuaries and lagoons, environments where conditions can change dramatically.…”

“…Previous investigations have reported C. gigas as sensitive to both elevated temperatures and lowered pH with significant mortalities predicted (Kurihara et al 2007;Be-niash et al 2010;Lannig et al 2010;Gazeau et al 2011;Tomanek et al 2011;Dineshram et al 2012;Barros et al 2013), although this may vary with different populations (Ginger et al 2013). However, oysters of the genus Crassostrea are generally found in intertidal to low subtidal levels in estuaries and lagoons, environments where conditions can change dramatically.…”

Comparison of larval development in domesticated and naturalized stocks of the Pacific oyster Crassostrea gigas exposed to high pCO2 conditions

“…Miller et al 2009, Talmage & Gobler 2011, Frieder et al 2017. Among these, however, many initiated ex perimental exposure likely after PDI development (~16 hpf;Miller et al 2009, Talmage & Gobler 2009, Thiyagarajan & Ginger 2012, Ko et al 2013, Gobler & Talmage 2014, Clark & Gobler 2016, provided potentially inadequate microalgal diets (mentioned previously), and based their estimates of size and developmental progression on a limited number of remaining individuals (Talmage & Gobler 2009, Gobler & Talmage 2014, all of which can skew results and weaken conclusions with regards to treatment effects. Additionally, few studies have exa mined larval performance over multiple cohorts in the same analysis.…”