EXPERIMENTAL STUDIES OF PREDATION ON METAZOANS INHABITING SPARTINA-ALTERNIFLORA STEMS

The short-term effects of invertebrate, Palaemonetes pugio Holthuis, a nd vertebrate predators, Fundulus heteroclitus Baird and Girard, on Sp artina alterniflora Loisel resident metazoan assemblages were investig ated experimentally in June 1993 and July 1994. Live or standing-dead S. alterniflora stems were transplanted into defaunated sand within ex perimental buckets in which treatment densities of P. pugio and F. het eroclitus were varied. Harpacticoid copepods were the only stem-associ ated faunal group affected by both shrimp and fish. The presence of P. pugio for one full tidal cycle (24 h) resulted in a significant 62% r eduction in the numbers of copepod nauplii on live stems. Varying shri mp densities did not influence appreciably the effect on nauplii numbe rs. F. heteroclitus consumed almost 50% of the juvenile and adult harp acticoid copepods on standing-dead stems over 3 days. Stem architectur al and faunal distributional differences between live and standing-dea d stems resulted in approximate to 50% of the fauna on live stems resi ding on interior surfaces inaccessible to predators. The fauna residen t on salt marsh vegetation represents a previously unconsidered resour ce for macroepibenthic predators foraging in intertidal marshes.