The food web has not moved a mussel: no evidence of quagga mussel effects on plankton communities, endangered Razorback Sucker (Xyrauchen texanus) abundance after 15 years of monitoring in Lake Mead, Nevada-Arizona, USA

Authors: Elizabeth Renner, Michael Schwemm

Year: 2021

Abstract

Quagga mussels are an aquatic invasive species known to cause cascading ecosystem effects on freshwater ecosystems. We sought to characterize variation in Lake Mead’s limnological characteristics and plankton communities over time and by basin using long-term sampling data gathered by the US Bureau of Reclamation. We examined relationships between quagga mussel veliger biomass, plankton community composition, and endangered Razorback Sucker abundance at multiple spatial (sampling station, basin) and temporal (month, year) scales. We failed to detect significant shifts in phytoplankton or zooplankton community composition or biomass in response to increases in quagga mussel veliger biomass. Veliger biomass was not correlated with Razorback Sucker abundance, but reservoir water level was associated with Razorback Sucker abundance. Ongoing drought and declines in water availability in the Colorado River Basin may be hindering Razorback Sucker recovery efforts in Lake Mead.