Behind the berms: comparing water quality and zooplankton communities between coves of varying connection to Harlan County Reservoir, Nebraska

Abstract

Mason BE, Koupal KD, Wuellner MR, Kreitman JW. 2023. Behind the berms: comparing water quality and zooplankton communities between coves of varying connection to Harlan Country Reservoir, Nebraska. Lake Reserv Manage. 39:327–339.

Coves are an important feature of reservoirs throughout the United States. Over time, sediment deposition and lateral drift can form a berm in the cove mouth that can restrict or eliminate exchange of surface water between the main reservoir and the coves. Little attention has been given to water quality and the zooplankton communities within these coves that provide unique habitats. This study compared several water quality parameters and the zooplankton communities between disconnected coves, connected coves, and the main reservoir of Harlan County Reservoir, Nebraska. Temperature, dissolved oxygen, pH, dissolved nitrates, and dissolved phosphates were similar between both cove types and the main reservoir. Parameters indicating water clarity and productivity were significantly different among the 3 habitats; disconnected coves had the highest turbidity and chlorophyll a (Chl-a) readings, while the main reservoir had the lowest. Similarly, Secchi depth was also lowest within disconnected coves and highest within the main reservoir. Zooplankton densities were highest in disconnected coves compared to connected coves or the main reservoir. Zooplankton communities in disconnected coves were largely dominated by rotifers, Ostracoda, Cyclopoida, Bosmina, Leptodora, and Ceriodaphnia, while the main reservoir had higher densities of Harpacticoida, Calanoida, and Daphnia. Interestingly, zooplankton communities were largely similar between connected coves and the main reservoir, indicating an influence of surface water exchange in these coves. As reservoirs in the United States continue to age, cove isolation is likely to become more common. Results from this study can help predict the potential changes that may occur as coves become disconnected.

Keywords:

• Coves
• irrigation reservoir
• water quality
• zooplankton

Acknowledgments

We thank the personnel with the Kearney office of the Nebraska Game and Parks Commission and the US Army Corps of Engineers office at Harlan County Reservoir who assisted with the planning and execution of this project. Additional appreciation is extended to Tony Long, William Frisch, Sam Wallick, Garrett Rowles, Thyme Cooke, Luke Rogers, Amanda Medaries, William Schriener, Christine Ruskamp, Jessica Davis, Sean Farrier, Brett Miller, and Charles Mordhorst for their assistance with field sampling and laboratory processing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Federal Aid in Sport Fish Restoration [F-160-R-16].