Macro-Restoration of Tidal Wetlands: A Whole Estuary Approach

Abstract

A large-scale wetland restoration case-study is discussed in response to fish losses in an open cycle, cooling water system at a generating facility located on Delaware Bay, USA. Stable isotope analyses of vegetation, resident and marine transient finfishes in marshes and open waters of the estuary are described, along with biochemical condition of individuals as it relates to habitat quality, and secondary production. Population dynamics of spot (Leiostomus xanthurus), a “target species” impacted by the generating facility was used to compare fish losses at the intake with new production of this species in the restored marshes. A “whole estuary” (or seascape) approach to restoration was adopted, one that integrates the concepts of donor control, linkages between tidal salt marshes, the marsh-estuary-coastal continuum and the recruitment success of marine transients. We emphasize that individual wetlands do not function in isolation; rather they are spatially explicit and functionally connected habitat mosaics incorporating ecological processes driven by organism behavior. Linkages among habitats that affect the growth and survival of earlier life stages therefore tend to be underplayed in restoration planning; but few species are confined to a single habitat; e.g., tidal salt marshes. In contrast, the findings of our seascape focused study demonstrated consistent and predictable animal density or productivity ‘hotspots’ in relation to spatial position within the seascape. Both ontogenetic habitat shifts, the use of transitory and temporary habitats, and the concept of the estuarine seascape are discussed in the context of restoring not just habitats, but also estuarine-coastal “connectivity”.