Dispersal of marine meiofauna. Areview and conceptual model explaining passive transport and active emergence with implications for recruitment

Abstract

A number of recent studies have shown that water-column processes exert an important influence on meiofaunal recruitment and colonization of new areas. T h ~ s paper reviews those studies which have investigated the water-column occurrence of meiofauna and the subsequent settlement process. Two distinct patterns exist for recruitment via water-column pathways: active entry of meiofauna into the water and passive erosion of meiofauna from the sediments. A conceptual model is proposed in which 4 factors interact to determine whether active vs passive mechanisms are most important for a given community: taxonomic con~position, hydrodynamics, aboveground structure, and disturbance. For the melofauna of areas which are hydrodynamically benign and dominated by actice swimmers (e. g, seagrass beds), water-column recruitment should involve substrate cholce through active swimming. In areas which are free of aboveground structure and more rigorous hydrodynami-cally (e. g. tidal flats, beaches) passive recruitment processes dominate and are modified by behaviors which may influence transport and settlement. In all habitats, structure probably acts to enhance active emergence to some extent while disturbance events may lead to increased suspension and possibly actlve emergence Future directions are discussed with an emphasis on the need for the development and standardization of new methodologies which can be used in a variety of habitats.