Effects of sediment transport on deposit feeding: Scaling arguments1

At least five dimensionless variables are needed for dimensional analysis of an individual surface‐deposit feeder using particles containing microbial food both locally produced (by in situ growth) and advected (via sediment transport). From scaling arguments which provide the relationships among these variables, it is apparent that food availability is determined primarily by the ratios of geophysical sediment transport rate into the particle pool from which the animal feeds to its ingestion rate, and of particle residence time in the feeding pool to the microbial doubling time. Increasing sediment transport can either increase or decrease local food availability. Transport patterns beneath waves have dramatic effects: wave mixing makes available to the animal particles which otherwise would be literally out of reach. Specialization on advected particles and reliance on microbial gardening are favored under different environmental conditions, specified in terms of dimensionless ratios. The scaling model also places previous models of deposit feeding in an environmental context. It contrasts with an alternative, nutrient spiraling approach in having a basis in natural selection for its optimization arguments.