Particle transport through a narrow tidal inlet due to tidal forcing and implications for larval transport

For estuarine-dependent species, especially those that spawn offshore and whose larvae must reach estuarine nursery areas, advective transport through tidal inlets may be a major factor influencing recruitment variability. We examined the role of tidal forcing on particle transport through a narrow, microtidal inlet along the Texas coast by using a three-dimensional hydrodynamic and particle transport model. Although tidal forcing is relatively small in the study area, tidal currents through the inlet effectively transport passive particles a distance of about 15 km landward of the inlet. The majority of the particles that enter the inlet are transported to regions that are not suitable for larval settlement. There is limited tidal dispersion of the particles into the bays due to shoreline geometry and bathymetry. Most of the particles that enter the inlet are expelled offshore in the ebb tidal jet resulting in estuarine-shelf exchange of particles. When acting alone, tidal forcing is not effective at retaining particles in a suitable estuarine habitat, suggesting that other physical or biological mechanisms are required to maintain larvae in an estuarine habitat or that there is substantial along-shelf transport of larvae.