Modeling Bedload Transport of Juvenile Bivalves: Predicted Changes in Distribution and Scale of Postlarval Dispersal

Abstract

The potential consequences of bedload transport of postlarvae for patterns of distribution of marine invertebrates were explored by developing a bedload transport model for juvenile bivalves in a small estuary in New Jersey, USA. A simple numerical model of tidal current hydrodynamics was developed based on field measurements of shear stresses near the bottom. Burrowing behavior of bivalves was incorporated into the model of bedload transport by using estimates of entrainment rates of Gemma gemma and Mya arenaria in a laboratory flume, and jump lengths of the bivalves were estimated by methods previously developed for noncohesive particles. Based on the flood domination and strong gradient of shear stresses in the Navesink estuary, our model predicted that juvenile bivalves would accumulate in the center of the estuary, traveling up to several kilometers over 30 days. Field distributions of juvenile bivalves were consistent with the model predictions for other species of bivalves but not for G. gemma, for which field distributions of both <500-and >500-μm individuals were concentrated in the eastern end of the estuary. Differences between the bedload model and G. gemma distributions suggest that spatial variation in burrowing behavior or biological interactions are playing an important role in maintaining distribution patterns of this species in spite of high levels of bedload transport. This modeling approach is applicable to other juvenile benthic invertebrates that disperse as bedload and is a useful model against which to compare field observations of rates of transport and patterns of distribution and abundance.

Effect of salinity and substrate grain size on larval settlement of the asari clam (Manila clam, Ruditapes philippinarum)

“…In the field, the larval settlement may be lower in sites where the sediments are 0.063-0.125 mm in size. Larvae that settled on 0.063-0.125-mm sediment in the field might be more susceptible to hydrodynamic erosion (Hunt et al, 2009;Toba et al, 2011), because they typically lie on the top of the sediment. These suggestions require further confirmation by field investigation.…”

Multispecies Mortality Patterns of Commercial Bivalves in Relation to Estuarine Salinity Fluctuation

“…These forces affect the estuarine circulation and hence, the renovation or residence time of the water and its physicochemical properties (Summer and Belaineh 2005;Kimmel et al 2009). The fluctuations in environmental conditions which are characteristic of estuaries have an enormous impact on many different biogeochemical processes in the waters and sediments (Alber 2002;Kimmerer 2002a, b;Azevedo et al 2008;Boyer et al 2010) and on the biology of the species living there fully or partially (Powell et al 2002;Anger et al 2008;Hunt et al 2009). In many cases, the species affected are those that support important fisheries in and around the estuaries.…”

Post-settlement dispersal: the neglected link in maintenance of soft-sediment biodiversity

“…These models must include interactions between nearbed hydrodynamics, sediment transport and species-specific behaviours, which will regulate modes and rates of dispersal. See [12,36] for a starting point for such an approach.…”