Experimental Analysis of Structural versus Trophic Importance of Seagrass Beds. I. Effects of Macrofaunal and Meiofaunal Invertebrates

Manipulative experiments using patches of artificial seagrass were set up at two temperature Australian locations in order to identify whether invertebrates were principally attracted to the structural features of seagrass habitats or to high levels of associated food production. Faunal responses to different treatments were largely consistent at the two sites. Number of species, abundance, biomass and productivity of invertebrates were all overwhelmingly influenced by the addition of surface debris to treatments, whereas the presence of artificial seagrass leaves produced little response. Total invertebrate numbers were negatively affected by the presence of buried seagrass material, and nematodes were negatively affected by reduction in quantity of fine organic particles amongst sediment. Invertebrate communities were therefore inferred to be primarily structured by food availability, particularly food in the form of seagrass debris for epifauna and fine organic particles for infaunal nematodes, and to show little direct dependence on structural characteristics of seagrass beds.