Benthic faunal response to a high energy gradient

Macrofauna and meiofauna were quantitatively sampled along 3 transects through high energy surf zones to nearshore waters.While 1 transect included some gravel patches, the other 2 exhibited increasingly finer sand and more silt and clay fraction with distance beyond the breaker zone.Meiofaunal abundance and biomass increased beyond the breakers and then decreased again further offshore.Macrofaunal abundance and diversity increased offshore; biomass increased offshore in one case while it reached a peak a little way beyond the breakers in the other.Numerical classification revealed 3 macrofaunal assemblages.The first occupied the surf zone or inner turbulent zone and included species characteristic of the sublittoral fringe of intertidal sandy beaches.The third assemblage occupied the outer turbulent zone; it started well beyond the break point and was marked by a rapid increase in biomass and diversity.The second assemblage represents a transition zone between these 2. It had no unique species but included reduced numbers of some species typical of both inner and outer turbulent zones.This transition zone, just outside the breakers, marks the region where wave energy reaching the bottom rapidly declines from its peak at the break point.A zonation scheme for the intertidal and subtidal macrofauna of high energy sandy coasts is proposed and implications of this are discussed.