Influence of invasive quagga mussels, phosphorus loads, and climate on spatial and temporal patterns of productivity in Lake Michigan: A biophysical modeling study

Abstract

We applied a three‐dimensional biophysical model to Lake Michigan for the years 2000, 2005, and 2010 to consider the mechanisms controlling spatial and temporal patterns of phytoplankton abundance (chlorophyll a) and lake‐wide productivity. Model skill was assessed by comparison to satellite‐derived Chl a and field‐measured water quality variables. We evaluated model sensitivity to scenarios of varying mussel filter feeding intensity, tributary phosphorus loads, and warm vs. cool winter‐spring climate scenarios. During the winter‐spring phytoplankton bloom, spatial patterns of Chl a were controlled by variables that influenced surface mixed layer depth: deep mixing reduced net phytoplankton growth through light limitation and by exposing the full water column to mussel filter feeding. Onset of summer and winter stratification promoted higher surface Chl a initially by increasing mean light exposure and by separating the euphotic zone from mussels. During the summer stratified period, areas of relatively high Chl a were associated with coastal plumes influenced by tributary‐derived nutrients and coastal upwelling‐downwelling. While mussels influenced spatial and temporal distribution of Chl a, lake‐wide, annual mean primary production was more sensitive to phosphorus and warm/cool meteorology scenarios than to mussel filter feeding scenarios. Although Chl a and primary production declined over the quagga mussel invasion, our results suggest that increased nutrient loads would increase lake‐wide productivity even in the presence of mussels; however, altered spatial and temporal patterns of productivity caused by mussel filter feeding would likely persist.

Spatially heterogeneous trends in nearshore and offshore chlorophyll a concentrations in lakes Michigan and Huron (1998–2013)

“…Similar to the findings of Warner and Lesht (2015) and Rowe et al (2017), the mechanism underlying this increase in the range of chlorophyll concentrations varied by season. Similar to the findings of Warner and Lesht (2015) and Rowe et al (2017), the mechanism underlying this increase in the range of chlorophyll concentrations varied by season.…”

“…Nutrient abatement programmes intended to limit excessive anthropogenic nutrient loading to aquatic systems from both point-and non-point-sources have generally proven effective and have resulted in improved water quality as indicated by reduced nutrient concentrations and algal biomass (Guildford and Hecky, 2000;Smith, 2006). Rowe et al 2017) the spatial details of an ecosystem's response to reductions in nutrient loading can be difficult to predict and thus complicate efforts to verify the success of nutrient reduction programmes by monitoring. Rowe et al 2017) the spatial details of an ecosystem's response to reductions in nutrient loading can be difficult to predict and thus complicate efforts to verify the success of nutrient reduction programmes by monitoring.…”

“…Additionally, as ice cover has been correlated to chlorophyll concentrations(Warner and Lesht 2015), decreases in ice cover in the Great Lakes(Wang et al 2012) may have contributed to increased internal loading during the spring months, particularly in nearshore locations. Additionally, as chlorophyll concentrations are responsive to precipitation and tributary loading(Warner and Lesht, 2015;Rowe et al 2017), nearshore locations may be supplemented by nutrients from tributaries and increased run-off from elevated precipitation throughout the Great Lakes (McBean and Motiee 2008). Nutrients in nearshore locations may remain sequestered in the benthos, which remains mixed during the summer stratification.…”

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

“…To illustrate how vertical mixing, stratification, and mussel grazing influence the dynamics of food availability to mussels at littoral vs. profundal habitats in 2015 and to estimate the relative food availability throughout the water column in 2016, we ran simulations using a 1‐dimensional (vertical column) version of the biophysical model described by Rowe et al (). Rowe et al ( a ) showed that 1‐dimensional biophysical model simulations can reproduce seasonal patterns of phytoplankton abundance observed in the Great Lakes, including the spring bloom during the late isothermal and early stratification periods, the deep chlorophyll maximum during stratification, and secondary maxima in surface and bottom chlorophyll associated with fall turnover.…”

A Hybrid Lagrangian-Eulerian Particle Model for Ecosystem Simulation

“…[1980] and Nicklisch et al [2007]. Also, the light attenuation functions are adjusted to 434 Rowe et al (2017). 435…”