Created pools and food availability for fishes in a restored salt marsh

Trophic support functions for fishes are a key goal of salt marsh restoration. Food availability in restored sites may be enhanced by creation of shallow pools, which are important sources of prey items in tidal wetlands. Young restored salt marshes are typically sparsely vegetated and are subject to rapidly changing geomorphology. Scouring and sedimentation create and fill shallow depressions, producing a shifting mosaic of tidal pools. In a large (8-ha) southern California experimental restoration site, we created shallow pools and assessed their development of foods for fishes. Created pools quickly developed abundant invertebrate prey, with densities exceeding those found in older, naturally formed pools (P < 0.0001). Opportunistic mobile and disturbance-associated taxa (calanoid copepods, nematodes, Polydora complex, and Trichocorixa reticulata) accounted for higher invertebrate densities in created pools. We repeated experiments in spring, summer, and fall and found seasonal variability in trophic development. We also applied bottom-up (nitrogen addition) and top-down (fish exclusion) treatments to pools. Some measures of algal biomass were increased by nitrogen fertilization (P = 0.001-0.06), but there were no upward-cascading effects on invertebrate composition or abundance. Fish abundance in the site varied seasonally, but there were no compelling effects of fish exclusion treatments on algal or invertebrate abundance. Incorporating shallow depressions into salt marsh restoration projects is a potential tool to jumpstart fish-support functions.