A METHOD FOR THE MEASUREMENT OF BEDLOAD SEDIMENT TRANSPORT AND PASSIVE FAUNAL TRANSPORT ON INTERTIDAL SANDFLATS

A simple and inexpensive sampler to measure bedload sediment transport in shallow subtidal or intertidal areas is described. The cylindrical sub-sediment trap with an aspect ratio of 20 (height:diameter) is an improvement over conventional bedload samplers which are difficult to use in shallow areas or fail to collect the biological material associated with bedload. Traps deployed on a low-energy intertidal sandflat for six months provided daily estimates of bedload transport (quartz grains: 0.001-40 kg m-1 d-1), passive infaunal transport (e.g., the bivalve Mya arenaria, max: 800 ind m-1 d-1), and organic detrital flux (e.g., macrophyte fragments, max: 400 g dry wt m-1 d-1). Bedload rates estimated with traps were compared predictions from a numerical bedload model to evaluate the trap's collection and retention efficiency. A significant linear regression between observed (trap) and predicted (model) rates (r2 = 0.65, p < 0.001, n = 97) indicated that the traps were useful for the measurement of high- and low-frequency variability in bedload transport. Potential applications of the traps in benthic oceanography include recruitment and recolonization studies.