Assessing the viability of pre-industrial sediment prior to remediation using primary producer (Zostera marina and Spartina alterniflora) growth and survival

Abstract

Boat Harbour, Nova Scotia, Canada, has served as a polishing pond for treated pulp and paper effluent since 1967. In 2020, the effluent flow ceased, and the site will be remediated. The focus of the remediation is the removal of a layer of contaminated sediment, shown to contain high levels of metals and dioxins and furans. Our primary objective was to test whether the underlying pre-industrial sediment could support growth and survival of estuarine plants. A large-diameter (15 cm) corer was used to extract cores from underneath the contaminated layer. These cores were inserted into a reference estuary, along with cores of reference estuarine sediment. Four 3 × 3 subtidal plots were used to test transplants of the estuarine plant Zostera marina, and five 1 × 9 marsh edge plots were used to test Spartina alterniflora. No significant differences in plant growth or survival were observed between Boat Harbour and reference sediment after 2 months. Postexperiment analysis of contaminants (metals and polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs)) in both types of sediment and plant tissues showed similarly low levels of contaminants. Findings indicate that pre-industrial sediment in the harbor should be able to support plant growth after removal of overlying contaminated sediment.