Size effects of suspended particles on gill damage in green-lipped mussel Perna viridis

The green-lipped mussels Perna viridis were exposed to <500 μm suspended solids (SS) with concentrations of 0 (control), 250, 500, 750 and 1000 mg/L for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significantly higher damages to the cilia on the frontal surface of the gill filaments than that on the abfrontal surface in both demibranchs. Percent ciliary depletion varied with SS concentrations and time. No sign of recovery of the gill filaments was observed after the mussels were transferred to clean seawater. In a second experiment, mussels were exposed to SS with size range from <63, >125-<250 and >250-<500 μm at 600 mg/L, together with a control (0 mg/L) for 14 days, followed by transferring to clean, filtered seawater for 28 days. Results of scanning microscopy showed significant ciliary damages in both the ascending and descending lamellae under the three particle size groups as compared with the control. Percent depletion of frontal cilia was most serious for the >250-<500 μm size group and least for the <63 μm size group. However, percent depletion of abfrontal cilia was most serious for the >125-<250 μm size group and least for the <63 μm size group. No recovery of ciliary damages was observed. The effects of particle size of suspended sediments on the morphological damages of gill filaments in the green-lipped mussels were discussed.