BODY SIZE AND CLEARANCE RATES IN THE MANGROVE BIVALVE Geloina erosa (SOLANDER 1786): EFFECTS OF TURBIDITY DEPLETION OVER TIME

This study examined clearance rates of the mangrove bivalve Geloina erosa (Solander 1786), focusing on the effects of body size (small vs. large) and exposure time (2, 4, 6 hours). Fresh G. erosa were purchased from Dumaguete Public Market (Philippines), acclimatized for 48 hours, and tested in aerated 5-L setups with 500 g of oven-dried mangrove silt suspended in 4 L of filtered seawater. A total of 9 individuals per size class was placed in each setup. The remaining suspended solids were measured using pre-weighed Whatman filters dried at 60-80°C, and rates were calculated as (dried residue weight - initial filter weight) / seawater volume (g L⁻¹ h⁻¹). Mean rates were low: small size (0.00347 at 2 h, 0.00172 at 4 h, 0.00117 at 6 h g L⁻¹ h⁻¹); large size (0.00339, 0.00167, 0.00113 g L⁻¹ h⁻¹, respectively). Rates declined significantly over time in both size classes (ANOVA: F=231-2031, p0.05). Findings support those of Argente et al. (2014), who found that G. erosa filtration is turbidity-dependent, with body size irrelevant in this long-lived species (Argente et al., 2014), unlike in faster-growing bivalves. Recommendations include testing at varying silt levels to test thresholds and modifying setups to mitigate low rates.