A Laboratory Study of the Effect of Phytoplankton Concentration, Water Flow and Their Interaction on the Growth of the Sandy Shore Suspension Feeding Clam Gafrarium tumidum

The effects of water flow rate and phytoplankton concentration on the growth of the sandy shoreclam Gafrarium tumidum was investigated in a laboratory flume study using a 3 × 3 factorial design. After 60days, shell length, shell weight and tissue dry weight increased significantly with phytoplankton concentration.For the effect of flow rate, growth was faster when flow rate increased from low to medium level; furtherincreases in flow rate, however, either did not sustain faster growth or resulted in a reduction in growth. Thecondition index (CI) of a standard-sized clam was significantly higher at low flow rate than at medium and highflow rates and was negatively correlated with phytoplankton concentration. The uncoupled growth of shell andtissue in response to flow rate and phytoplankton concentration may be adaptations to low food environments,so that energy can either be stored to sustain life or reserved for gametogenesis during the reproductive period.