Food depletion regulates the demography of invasive dreissenid mussels in a stratified lake

Alexander Y Karatayev,Lyubov E Burlakova,Vadim A Karatayev,Knut Mehler,Mark D Clapsadl,Mark D Rowe

doi:10.1002/lno.10924

Abstract

AbstractLake stratification produces sharp gradients in temperature and pelagic resources which have cascading effects on the traits of aquatic populations, including invasive species and their ecosystem impacts. We study the consequences of such common environmental gradients on the demography of quagga mussels, one of the world's most aggressive invasive species. Coupling a series of in situ experiments with a biophysical model of the pelagic community, we quantify mussel growth and recruitment in littoral vs. profundal benthic habitats of eastern Lake Erie. We found that both severe food depletion and cold temperatures in the hypolimnion during summer stratification cause mussels to grow twice as slowly and currently inhibit recruitment in profundal compared to littoral habitats. Together with the high biomass and large mean mussel size found in long‐term monitoring surveys in the profundal habitats, our results imply that mussels successfully colonizing profundal habitats have relatively long lifespans with low growth rates, and therefore lower productivity, compared to mussels in shallow areas. Consequently, the bulk of dreissenid biomass in Lake Erie and other Great Lakes found in the vast but resource‐poor profundal habitats may have very limited impacts on epilimnetic communities compared to mussels in littoral areas. By contrast, mussels in profundal habitats strongly reduce food availability to hypolimnetic communities throughout the year. Thus, our results explain how the ecosystem impacts of sessile freshwater invaders are likely to vary among habitats and lakes depending on the relative size of profundal populations and the extent of stratification.

Highlights

Lake stratification produces sharp gradients in temperature and pelagic resources which have cascading effects on the traits of aquatic populations, including invasive species and their ecosystem impacts
Because substrata were different at the shallow and deep sites, cages were suspended at about 70 cm above the bottom surface with floats to avoid siltation. Given that both food and temperatures differ strongly between littoral and profundal habitats, in 2016 we examined growth and recruitment along a depth gradient at profundal sites in order to determine the influence of each driver on mussel demography
The bulk of dreissenid biomass found in profundal habitats of deep lakes or lake basins may have very limited ecological impacts on epilimnetic resources, compared to shallower warmer areas where mussels have high growth and production and higher ecosystem impacts through their feeding and filtering activities

Summary

Introduction

Lake stratification produces sharp gradients in temperature and pelagic resources which have cascading effects on the traits of aquatic populations, including invasive species and their ecosystem impacts. In lakes with strong stratification during productive summer seasons, species are distributed along environmental gradients from the warm, well-mixed littoral zone, where the surface mixedlayer intersects the bottom, to the deep and cold profundal zone (located below the compensation depth where insufficient light penetrates to support photosynthesis), where bottom habitats and hypolimnetic waters are isolated by the thermocline from the surface waters for much of the growing season Benthic invertebrates in these ecosystems face large depth-dependent gradients in food resources and temperature that strongly affect their reproduction, growth, and productivity (Brinkhurst 1974; Wetzel 1983; Jonasson 2004).

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