Impact of the infaunal Manila clam, Ruditapes philippinarum, on sediment stability

Abstract

The aim of this study was to examine the impact of bioturbation by the Manila clam, Ruditapes philippinarum, on sediment stability. 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 clam 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 erodability were more marked at the lower current velocities. In the control, the critical erosion velocity ( " U crit ) was about 32 cm s )1 . With increasing R. philippinarum density, " U crit decreased down to the minimum value of about 20 cm s )1 at a density of 206 clams m )2 . This study demonstrated 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 within the Sacca di Goro lagoon.

Effects of different aquaculture methods for introduced bivalves (Hyriopsis cumingii) on seston removal and phosphorus balance at the water–sediment interface

“…In the benthic treatments, the feces and pseudofeces were buried at the sediment surface, whereas they were excreted into water in the suspended treatments, which could also explain why the concentrations of water TP and PP in the suspended treatments were significantly higher than those of the benthic treatments in our experiment (Figure 4). In addition, Nizzoli et al (2011) believe that suspended mussels, as the high sediment OM content below the mussel ropes, could stimulate heterotrophic microbial metabolism and mineralization of organic N and P. Many studies on bivalve effects showed that they can also affect nutrient cycling by many other mechanisms, such as assimilation and absorption, bioturbation of sediments through bivalve movements, oxygen depletion and others (Newell 2004;Sgro et al 2005). Vaughn and Hakenkamp (2001) posit that if bivalve biodiversity is declining and populations release more nutrients than they absorb, bivalves may serve as a nutrient source, whereas they may serve as a nutrient sink while a population is growing or if biomass is being lost from the ecosystem by export or permanent burial.…”

“…Furthermore, bivalve respiration activity and decomposition of feces and pseudofeces deplete sediment oxygen content, thereby stimulating anoxic conditions in the sediments and P release by redox-sensitive iron dynamics (Bartoli et al 2001;Nizzoli et al 2005). For the suspended aquaculture method, suspending bivalves in the water may release less P by weakening the bioturbation of sediments (Widdows et al 1998;Sgro et al 2005). Improving bivalve contact with water may improve filtration efficiency.…”

Density-dependent biodiversity effects on physical habitat modification by freshwater bivalves

“…Burrowing variables.-Burrowing activity of marine bivalves influences erosion (Sgro et al 2005), and exposed bivalve shells increase near-bed turbulence and promote erosion in marine systems (Widdows et al 2002). Because freshwater mussel species vary in burrowing activity and depth (Allen and Vaughn 2009), we wanted to see if mussel effects on gravel erosion were partly due to burrowing behavior.…”

“…Because freshwater mussels vary in burrowing behavior (Allen and Vaughn 2009), and because burrowing activity by bivalves in marine systems promotes erosion (Sgro et al 2005), we hypothesized that burrowing behavior by mussels might be a plausible mechanism to explain mussel effects on gravel erosion. Although our multiple regression models using burrowing variables only explained 13% of the variation in gravel erosion, our analysis lends some support to this hypothesis.…”

Short-term dynamics of sedimentary organic matter in a littoral area of the North Adriatic Sea (Italy): Evidence from234Th and7Be

“…Bioturbation and deep mixed layer depths were recorded in this study, where sedimentary material had high C/N thus indicating the refractory nature of organic material. Sediment disturbance due to activities of bivalves cannot be dismissed in this study considering that burrowing marine bivalves alter sediment loading, deposition, and stability patterns [23,24], and Dauwe et al [19] evidenced that the deep-living subsurface-deposit feeding bivalve Thyasira sp. is known to affect sediment chemistry and the fate of organic matter distribution in the sediment.…”