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Effects of impoundment and water-level fluctuations on macrophyte and macroinvertebrate communities of a dammed tidal river
Richardson, S.M.; Hanson, J.M.; Locke, A. (2002). Effects of impoundment and water-level fluctuations on macrophyte and macroinvertebrate communities of a dammed tidal river. Aquat. Ecol. 36(4): 493-510
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588, more
Peer reviewed article  

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Keyword
    Fresh water

Authors  Top 
  • Richardson, S.M.
  • Hanson, J.M., correspondent
  • Locke, A.

Abstract
    A freshwater headpond was created in 1968 when a causeway was built across a tidal portion of the Petitcodiac River, New Brunswick, Canada. In the 32-year history of this tidal barrier, there have been numerous water-level drawdowns to manage risk of flooding (relatively minor and of short duration) and to permit passage of anadromous fishes past the dam structure (often of several weeks duration). Following five years of routine management to prevent flooding, there were three major water-level drawdowns that fully exposed the littoral zone to air for varying lengths of time during the spring of 1997 (7 days), 1998 (19 days), and 1999 (55 days). The 1998 and 1999 drawdowns resulted in significant decreases in biomass of macrophytes and benthic macroinvertebrates in the littoral and sublittoral zones, compared to 1997. The largest decrease occurred between 1997 and 1998 when populations of most species were largely eliminated. The remaining species were those resilient to prolonged exposure to the atmosphere. The only macrophyte to increase in biomass over the three years was Polygonum lapathifolium, which formed impenetrable mats in 1999. Hexagenia limbata in the sublittoral zone was the only benthic invertebrate species to increase in biomass. The age distribution of the eastern floater (Pyganodon cataracta) population suggested that a major drawdown accompanied by salt-water intrusion had eliminated the entire freshwater community in 1988. The goals of allowing passage of anadromous fishes past the dam structure and the development of a stable, artificial, freshwater-lake community appear to be incompatible.

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