Balancing essential and non-essential metal bioavailability during hatchery rearing of Greenshell mussel (Perna canaliculus) larvae

The use of ethylenediaminetetraacetic acid (EDTA) during bivalve hatchery production is thought to improve larval yields due to the reduced exposure to toxic metals (such as Cu); however, few studies have focused on the bioavailability of metals during the rearing process. GreenshellTM mussels (Perna canaliculus) were reared for 48 h with and without EDTA (12 ?M) exposure and larvae were subsequently raised to 21 days post-fertilisation with and without EDTA exposure. Survival, shell length, algal ingestion rate, swimming activity, total metal concentration in water, bioavailable metal concentrations and larval metal accumulation were monitored for the 21 day period. Larval fitness (specifically D-yields) was improved on day 2 in the EDTA treatment, whereas an overall negative effect of EDTA treatment on fitness was observed on day 10 and 21. During the first 48 h, increased survival in the EDTA treatment is believed to be due to the reduction of bioavailable Zn concentrations in the rearing seawater. No other metal (essential or non-essential) displayed a consistent trend when comparing metal bioavailability to any of the fitness parameters measured throughout the experiment. Though the measured metal bioavailability was not clearly linked to fitness, the uptake of Al, P, Cr, Fe, Co, Ni, Zn, As, Cd, and Hg by P. canaliculus was reduced during the first 48 h, suggesting that the biological regulation of these elements is just as important as the bioavailability. Overall, treatment of the rearing seawater with 12 ?M EDTA is effective for improving GreenshellTM mussel larval yields by decreasing metal bioavailability during the first two days of development but has minimal benefit between day 2 and 21.

Automated summary

The use of 12 μM EDTA in rearing seawater improves GreenshellTM mussel larval yields by reducing metal bioavailability during the first 48 hours, but has minimal benefit on larval fitness between day 2 and 21. The biological regulation of elements such as Al, P, Cr, Fe, Co, Ni, Zn, As, Cd, and Hg in the rearing process is just as important as metal bioavailability for larval development.