Short-term response of a downstream marine system to opening a tidal-river causeway

Abstract

The spill gates of the causeway on the Petitcodiac River in New Brunswick, Canada, were permanently opened in April 2010. We examined the short-term effect this had on downstream intertidal mudflats of the upper Bay of Fundy. Specifically, a before-after-control-impact design was used to determine if the causeway opening affected the invertebrate community (crustaceans, polychaetes, and molluscs), abiotic sediment conditions (sediment water content, mean particle size, penetrability, and aRPD depth), or resource availability (sediment chlorophyll a concentration, and organic matter content) of 5 intertidal mudflats (2 impacted sites, 3 reference sites) up to 5 months post-opening. We detected no biologically or statistically meaningful differences between impacted and reference sites for any of the measured variables. This suggests that opening the causeway did not have an impact on these intertidal mudflats, at least within half a year of the opening. We speculate that this is likely a result of the macrotidal nature of the Bay of Fundy, that overwhelmed any changes to hydrodynamics and sedimentation which occurred after the opening of the causeway.