Rate of Tube Building and Sediment Particle Size Selection during Tube Construction by the Tanaid Crustacean, Leptochelia dubia

Abstract

In estuaries, organic coatings play an important role in the aggregation of mineral particles. Particles acquire adhesive surfaces through the activities of bacteria and microalgae in the sediment and water column. Eventually, they may become incorporated into larger aggregates and structures, such as tubes, constructed by infaunal benthic animals. Where these structures are large enough, and the adhesive bonds between particles strong enough, individual particles may remain in place at bed shear stresses otherwise strong enough to cause sediment transport. This study examined the aggregation of particles during tube building by the ubiquitous tanaid crustaceanLeptochelia dubia. Particle size selection and rates of tube building were determined as functions of animal size, temperature, and the presence or absence of bacteria and microalgae. These data were used to model seasonal patterns of sediment binding by a population ofL. dubia in Yaquina Bay, Oregon, taking into account seasonal changes in sizes and abundance of animals. Rates of tube building (mass of sediment per day) increased with animal size, but temperature had no effect. The model indicated that the field population ofL. dubia bound sediment into tubes at a gross rate of 350 g m−2 d−1, averaged over a 2-yr period. Seasonally, gross rates of tube building were predicted to range from 70 g m−2 d−1 (during late winter-early spring) to 600 g m−2 d−1 (during autumn). When constructing tubes from sterile sediments, small animals selected silt-sized particles while large animals discriminated against these particles. The presence of microbes in sediments tended to reduce particle selectivity.