RATE OF TUBE BUILDING AND SEDIMENT PARTICLE-SIZE SELECTION DURING TUBE CONSTRUCTION BY THE TANAID CRUSTACEAN, LEPTOCHELIA-DUBIA

In estuaries, organic coatings play an important role in the aggregati on of mineral particles. Particles acquire adhesive surfaces through t he activities of bacteria and microalgae in the sediment and water col umn. Eventually, they may become incorporated into larger aggregates a nd structures, such as tubes, constructed by infaunal benthic animals. Where these structures are large enough, and the adhesive bonds betwe en particles strong enough, individual particles may remain in place a t bed shear stresses otherwise strong enough to cause sediment transpo rt. This study examined the aggregation of particles during tube build ing by the ubiquitous tanaid crustacean Leptochelia dubia. Particle si ze selection and rates of tube building were determined as functions o f animal size, temperature, and the presence or absence of bacteria an d microalgae. These data were used to model seasonal patterns of sedim ent binding by a population of L. dubia in Yaquina Bay, Oregon, taking into account seasonal changes in sizes and abundance of animals. Rate s of tube building (mass of sediment per day) increased with animal si ze, but temperature had no effect. The model indicated that the field population of L. dubia bound sediment into tubes at a gross rate of 35 0 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 parti cles. The presence of microbes in sediments tended to reduce particle selectivity.