Effects of crushed mussel, Perna canaliculus, shell enrichment on seawater carbonate buffering and development of conspecific larvae exposed to near-future ocean acidification

Perna canaliculus is an aquaculture species vulnerable to ocean acidification (OA). Returning shell waste to the sea after commercial processing has potential to provide localized buffering to OA. We investigated whether seawater enrichment with crushed shell buffers carbonate chemistry and improves P. canaliculus larval performance under current (400 mu atm) and future (1,100 mu atm) PCO2 conditions. Fertilized eggs from two parent pools were reared for 42 hr in seawater previously enriched with shell or non-enriched. Aragonite saturation state (omega(A)) decreased in high PCO2 seawater (omega(A) 1.26, compared to 2.54 under present-day conditions). This was partially mitigated by shell enrichment (omega(A) 1.44). In high PCO2 ethylenediaminetetraacetic acid (EDTA)-treated seawater, shell enrichment resulted in minor increases in the proportion of larvae developing into normal veligers (no shell = 3.7 +/- 3.0%, shell = 9.6 +/- 4.7%; mean +/- SD). Larvae failed to develop normally in the absence of EDTA, with the exception of ambient PCO2 seawater enriched with shell, which yielded a pool-dependent mean 2.3-17.8% normal veligers, possibly reflecting other properties of crushed shell including metal uptake. Non-buffering effects of crushed shell, parental pool, and inclusion of a chelator (EDTA) in seawater appeared to have a greater influence upon larval performance than buffering per se, warranting further investigation.

Automated summary

The addition of crushed shells in high PCO2 seawater partially mitigated the negative effects on P. canaliculus larvae. Other factors such as non-buffering effects of crushed shell, parental pool, and inclusion of a chelator (EDTA) in seawater seemed to have a bigger impact on larval performance than buffering itself, indicating the need for further investigation.