Assessment of out-of-kind mitigation success of an artificial reef deployed in Delaware Bay, USA

Abstract

An out-of-kind, off-site mitigation reef was constructed in 1989 to replace an oligohaline tidal marsh and subtidal mudflat of the upper Delaware Estuary that had been filled in 1985 to create the Wilmington Harbor South Dredged Material Disposal Area. Habitat loss consisted of 57.4 ha of subtidal, soft-bottom habitat. The mitigation reef (0.651 ha of surface area) consisted of 16 prefabricated concrete reef structures, arranged in four clusters of four units each, near Brown's Shoal in Delaware Bay. We estimated benthic secondary production of the two sites using published production: biomass ratios (P:B) as a tool for conducting comparisons of benthic epifaunal communities. Results indicate that the artificial reef provides enhanced benthic secondary production per unit area (2000-12 000 kcal yr-1) over the lost habitat (177 kcal yr-1), but that total production (3 and 77 million kcal yr-1) does not equal what has been lost (100 million kcal/yr). The construction of this reef, while not completely effective in its intended mitigation, provides a benchmark by which to design and judge future mitigation efforts. © 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.