The effect of the abundance of venus clams (Gafrarium tumidum Röding, 1798) on sediment accretion in the sandy intertidal of Pari Island

Bivalves may play an ecological role as ecosystem engineers by changing sediment physical structure. As a filter/suspension feeder, they can produce biodeposits, and their burrowing activities can stir sediment. In this study, we investigated whether the abundance of Venus clam ( Gafrarium tumidum Röding, 1798) influences sediment accretion in the sandy intertidal area of Pari Island, Indonesia. We created 18 plots consisting of nine defaunated and nine non-defaunated treatment plots. On each plot, 111-559 clams were deployed, and four pieces of one-inch PVC were planted randomly to see sediment elevation. Sediment accretion was measured by sediment elevation. Observations were carried out for seven months. At the end of the observations, clam abundances were 0-64 ind/m 2 in the defaunated plots and 0-47 ind/m 2 in the non-defaunated plots. The average sediment accretion in the defaunated plots was 0.98-3.3 cm, while in the non-defaunated plots was 1.95-4.43 cm. This study showed that the clam had no significant effect (p-value > 0.05) on sediment accretion in both plots as its abundance was insufficient to alter sediment. The sediment accretion occurred not caused by clam but by others such as sipuncula and physical oceanography factors in the research location.