Benthic invaders control the phosphorus cycle in the world’s largest freshwater ecosystem

Abstract

The productivity of aquatic ecosystems depends on the supply of limiting nutrients. The invasion of the Laurentian Great Lakes, the world’s largest freshwater ecosystem, by dreissenid (zebra and quagga) mussels has dramatically altered the ecology of these lakes. A key open question is how dreissenids affect the cycling of phosphorus (P), the nutrient that limits productivity in the Great Lakes. We show that a single species, the quagga mussel, is now the primary regulator of P cycling in the lower four Great Lakes. By virtue of their enormous biomass, quagga mussels sequester large quantities of P in their tissues and dramatically intensify benthic P exchanges. Mass balance analysis reveals a previously unrecognized sensitivity of the Great Lakes ecosystem, where P availability is now regulated by the dynamics of mussel populations while the role of the external inputs of phosphorus is suppressed. Our results show that a single invasive species can have dramatic consequences for geochemical cycles even in the world’s largest aquatic ecosystems. The ongoing spread of dreissenids across a multitude of lakes in North America and Europe is likely to affect carbon and nutrient cycling in these systems for many decades, with important implications for water quality management.

Management of the Phosphorus–Cladophora Dynamic at a Site on Lake Ontario Using a Multi-Module Bioavailable P Model

“…Considerable attention has also been directed to mussel P cycling in the Great Lakes nearshore, where it has been posited that mussel SRP excretion could sustain nuisance algal growth drawing only upon the PP reserves of offshore waters. The nearshore case differs significantly from that addressed in a whole lake context by Li et al [70] as the water residence time is must shorter in coastal environments (days to weeks) and the proximity to point source and riverine discharges is much greater [29]. Early work in conceptualizing a dreissenid-driven nearshore phosphorus shunt [71] and publication of the first in situ measurements of mussel SRP excretion [72] helped motivate field studies interpreted to suggest that mussel cycling was the dominant P source fueling nuisance growth of the alga [73,74].…”

“…As the distribution of quagga mussels proceeded lakeward to include colonization of profundal habitat, several modeling studies investigated the impact of mussels in regulating phytoplankton and phosphorus dynamics in the offshore waters of the Great Lakes, e.g., the vertical distribution of phytoplankton [62,64], nearshore-offshore transport of phosphorus [31] and the impact of phosphorus loads on lakewide production [19]. Most recently, Li et al [70] employed a mass balance approach in demonstrating the capacity of mussels to retard the response of whole lake phosphorus levels to changes in external load, here at a time scale of years to decades.…”

Microplastics in Invasive Freshwater Mussels (Dreissena sp.): Spatiotemporal Variation and Occurrence With Chemical Contaminants

“…Dreissenid mussels are ecosystem engineers of considerable abundance and ecological importance in the Great Lakes and other freshwater ecosystems (Li et al, 2021). Quantifying their interactions with microplastics is critical for understanding the dynamics of plastic pollution.…”

“…For example, Dreissena sp. are widespread invasive species which change food webs, water clarity, biogeochemistry, and invertebrate biomass (Karatayev et al, 2002;Li et al, 2021). Microplastic concentrations in the Great Lakes are similar to or higher than levels in oceans (Eriksen et al, 2013), and dreissenids ingest microplastics in the laboratory (Magni et al, 2018;Pedersen et al, 2020).…”

Coastal silicon cycling amplified by oyster aquaculture

“…Filter-feeders play an important role in regulating the biogeochemistry, and thus ecology of aquatic ecosystems (Newell 1988, Li et al 2021. Suspensionfeeding bivalves alter biogeochemical cycles by consuming particulate nutrients from the water column, excreting dissolved nutrients, and providing habitat for biofilms on their shells (Galtsoff 1964, Sma & Baggaley 1976, Prins et al 1997, Welsh & Castadelli 2004, Svenningsen et al 2012.…”