Transport
of juvenile clams: effects of species and sediment grain size
H.L. Hunt-2004
Journal of
Experimental Marine Biology and Ecology, 312(2): 271-284
Abstract:
Erosion
and transport of juvenile benthic invertebrates, including bivalves, have
the potential to alter patterns of distribution and abundance during the
early post-settlement period. However, the factors influencing rates of
postlarval dispersal are not well understood. Both hydrodynamics and
behaviour (e.g. burrowing) are likely to play a role in determining patterns
of transport of juvenile bivalves. To determine the relationship between
sediment transport and bivalve dispersal, experiments were conducted in a
racetrack flume to examine the effect of grain size, flow, and clam size on
rates of erosion of two species of juvenile clams (Mya arenaria and Mercenaria
mercenaria). Results of the experiments were compared to predictions of
erosion thresholds based on the physical characteristics of the sediment and
clams. Erosion of Mercenaria was greater than Mya, the
opposite of predictions based on Mercenaria's greater density,
indicating the importance of burrowing behaviour. In most cases, erosion
also was greater in the finer sand, in contrast to the predicted similarity
of erosion thresholds of the two sediments. However, clam erosion did
increase with increasing shear velocity and decrease with clam size, as
expected. The results of this study indicate that both hydrodynamics and
behaviour play roles in the transport of these two species of juvenile
bivalves and that their vulnerability to passive erosion cannot be predicted
solely from knowledge of sediment transport.
(Institute
of Marine and Coastal Sciences, Rutgers University, 71 Dudley Rd., New
Brunswick, NJ 08901, USA, e-mail: hhunt@unbsj.ca)