The effects of meiofauna on settling macrofauna: meiofauna may structure macrofaunal communities.

When macrofaunal larvae and juveniles recruit into the benthos, they are in the same size catagory as the meiofauna. These small size classes have been consistently ignored in macrofaunal studies despite the increasingly accepted idea that communities are structured not only by interactions between adults, but also by interactions which occurred when the animals were young and in the meiofaunal size catagory. I have tested the effects of turbellarians and other meiofauna on settling macrofaunal larvae and young juveniles in a one-week field experiment. Increased densities of both turbellarians and other meiofauna (tested separately) significantly reduced densities of juvenile spionids and deposit feeders. Syllid abundances increased in high density turbellarian treatments. Nereid polychaete, other predatory polychaete, and bivalve densities showed no significant differences among treatments. By both altering densities and acting selectively on various groups of macrofaunal juveniles, meiofauna may significantly affect the structure of macrofaunal communities.