Effects of clam size, food type, sediment characteristic, and seawater carbonate chemistry on grazing capacity of Venus clam Cyclina sinensis (Gmelin, 1791)

摘要

Aquaculture in saline-alkaline water has a major problem:microalgal blooming causes the pH of water to increase dramatically,thereby causing damage to the reared organisms.To solve this problem,we set out to find a candidate filter-feeding bivalve species suitable for saline-alkaline water to graze on microalgae and to control the pH.In the current study,we investigated the effect of carbonate alkalinity (CA,2.5,10.0,and 20.0 meq/L) and pH (8.0,8.5,and 9.0) on the grazing capacity (GC) of the clam Cyclina sinensis.Additionally,the effect of clam size (small,medium,and large) and microalgae species (Nannochloropsis oculata,Chaetoceros müelleri,and Isochrysis galbana),and the effect of bottom sediment characteristic (mud,sandy mud,and muddy sand) and thickness (3 and 6 cm) were analyzed as well.The results show that the GC on L galbana was the highest and small size had the maximum GC/W (W:wet weight including body and shells).No significant differences were observed between sediment type and thickness.Regarding CA and pH,a significant decrease in GC by the pH or by their interaction was found.The GC ofC.sinensis was not greatly reduced in the treatments ofpH＜8.5 and CA＜20.0,and also not affected by bottom sediment type,indicating that this clam is capable to manage microalgal concentrations and might be a candidate species for pH reduction in saline-alkaline water ponds.