The interactions between physical, chemical and biological processes influencing lagoonal and coastal bottoms are poorly understood, despite their ecological and economic importance in relation to aquaculture, and particularly shellfish farming. In such systems, it is known that the biota may play an important role in determining the erosion potential of intertidal and subtidal sediments. An increase in erosion rate may result from bioturbation due to burrowing organisms, particularly bivalves, associated with physical disturbance due to tidal currents. Within this framework, a laboratory benthic annular flume system (AFS) was deployed to evaluate the relationship between sediment stability of a subtidal mudflat and density of the infaunal Manila clam, Ruditapes philippinarum, under the influence of different current velocities. There was a significant correlation between mean erosion rate and current velocities in all treatments with clams (P < 0.001). There was also a significant correlation between mean erosion rate and R. philippinarum density (P < 0.001), reflecting bioturbation enhanced sediment erosion. The effects of clam density on sediment erodibility were more marked at the lower current velocities. In the control, the critical erosion velocity (Ūcrit) was about 32 cm s-1. With increasing R. philippinarum density, Ūcrit decreased down to the minimum value of about 20 cm s-1 at a density of 206 clams m-2. Our study led to the conclusion that the burrowing activity of R. philippinarum reduces sediment stability, particularly at relatively low current velocities (25 cm s-1) and at densities below those found in the clam cultivation areas.
Impact of the infaunal Manila clam, Ruditapes philippinarum, on sediment stability.
SGRO, Lucia Angelica;MISTRI, Michele;
2005
Abstract
The interactions between physical, chemical and biological processes influencing lagoonal and coastal bottoms are poorly understood, despite their ecological and economic importance in relation to aquaculture, and particularly shellfish farming. In such systems, it is known that the biota may play an important role in determining the erosion potential of intertidal and subtidal sediments. An increase in erosion rate may result from bioturbation due to burrowing organisms, particularly bivalves, associated with physical disturbance due to tidal currents. Within this framework, a laboratory benthic annular flume system (AFS) was deployed to evaluate the relationship between sediment stability of a subtidal mudflat and density of the infaunal Manila clam, Ruditapes philippinarum, under the influence of different current velocities. There was a significant correlation between mean erosion rate and current velocities in all treatments with clams (P < 0.001). There was also a significant correlation between mean erosion rate and R. philippinarum density (P < 0.001), reflecting bioturbation enhanced sediment erosion. The effects of clam density on sediment erodibility were more marked at the lower current velocities. In the control, the critical erosion velocity (Ūcrit) was about 32 cm s-1. With increasing R. philippinarum density, Ūcrit decreased down to the minimum value of about 20 cm s-1 at a density of 206 clams m-2. Our study led to the conclusion that the burrowing activity of R. philippinarum reduces sediment stability, particularly at relatively low current velocities (25 cm s-1) and at densities below those found in the clam cultivation areas.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
