Fish Assemblage and Ecosystem Metabolism Responses to Reconnection of the Bird's Point-New Madrid Floodway during the 2011 Mississippi River Flood

Abstract

Understanding the ecological function of developed large rivers remains elusive because these systems have long been altered for multiple uses. In particular, floodplains of large rivers, such as the Mississippi River, have been contained behind extensive levees. A historic flood occurred in the lower Mississippi River system during spring of 2011, prompting the US Army Corps of Engineers to activate the Bird's Point-New Madrid floodway, a 55 000-ha, agriculturally dominated, leveed area. Water entered the floodway at flows >1 m s−1 through two crevasses created in the upper portion of the levee and exited through a crevasse at the lower end. During the month, the floodway was inundated; we quantified discharge, water chemistry, primary production and fish production in the floodway and the adjacent river. Water entering the floodway was retained <1.3 d, and nutrient concentrations were not elevated in the floodway beyond those in the river, despite expected contributions from a legacy of fertilization. Primary production equaled respiration in the floodway, while the adjacent river was heterotrophic. Gizzard shad and freshwater drum were more abundant in the floodway than the river, while channel catfish were more abundant in the river. Growth rates of young native fishes, normalized for temperature, were the same in the floodway and the river, with the exception of gizzard shad, which grew faster in the floodway. Fish community structure, especially in the lower floodway, was temporally and spatially dynamic. Even though it has been heavily modified for agriculture, the floodway provided benefits, albeit limited, to the Mississippi River. With multifunctional management and strategic planning, systems such as these may provide substantial services such as flood abatement, nutrient transformation and fish production in the Mississippi River basin and potentially reduce nutrient loading downstream in areas such as the Gulf of Mexico. Copyright © 2015 John Wiley & Sons, Ltd.

Document Type

Article

DOI

https://doi.org/10.1002/rra.2932

Keywords

2011 Mississippi River Flood, ecosystem metabolism, fish community, fish growth rates

Publication Date

6-1-2016

Journal Title

River Research and Applications

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