A re-evaluation of the empirical relationships connecting dissolved oxygen and phosphorus loading af

Abstract Lake Simcoe has had many stressors in the past decades. High total phosphorus (TP) loads into the lake led to end-of-summer volume-weighted hypolimnetic dissolved oxygen (MVWHDO) levels that were lethal to coldwater fish species. Additionally, dreissenid mussels became established in the lake around 1996, and may have affected nutrient cycling and phytoplankton abundance. Using data averaged over two time periods following dreissenid mussel establishment, we re-evaluated empirical relationships connecting TP loading rate and MVWHDO concentration that were developed with pre-dreissenid data. Oxygen depletion rate predicted chlorophyll (Chla) well within the range of other Ontario lakes. Measured Chla corresponded well with Chla predicted from lake TP concentration except at the shallowest station, indicating that the lake may becoming more spatially heterogeneous. Interestingly though, the Chla:TP temporal trend increased post-dreissenids when it is often observed to decrease (e.g., Great Lakes). Measured lake TP concentration was better predicted by TP loads when averaged over the ice-free season compared with the spring. The final model predicted MVWHDO directly from TP load very closely except for the 2002–2006 time period when the end-of-summer date was September 15 rather than September 30, suggesting that the date when MVWHDO is determined should be continuously re-evaluated. Additionally, trend analyses on each variable from 1980 to 2008 did not identify any changes that coincided with dreissenid establishment. Given that this model appears to be sound for the post-dreissenid period, an estimated TP load of 44 tonnes/yr was predicted that would yield the current MVWHDO target level of 7 mg/L.

[1]  Shiao Y Wang,et al.  Filtration dynamics of the zebra mussel, Dreissena polymorpha , 1996 .

[2]  K. H. Nicholls,et al.  A Limnological Basis For A Lake Simcoe Phosphorus Loading Objective , 1997 .

[3]  K. Nicholls,et al.  Recent Changes in Lake Erie (North Shore) Phytoplankton: Cumulative Impacts of Phosphorus Loading Reductions and the Zebra Mussel Introduction , 1993 .

[4]  David O. Evans.  Effects of hypoxia on scope-for-activity and power capacity of lake trout (Salvelinus namaycush) , 2007 .

[5]  David R. Barton,et al.  Effects of water movement on the distribution of invasive dreissenid mussels in Lake Simcoe, Ontario , 2011 .

[6]  J. Rasmussen,et al.  Impact of zebra mussel (Dreissena polymorpha) on phosphorus cycling and chlorophyll in lakes , 1995 .

[7]  A. Mazumder.  Phosphorus–Chlorophyll Relationships under Contrasting Herbivory and Thermal Stratification: Predictions and Patterns , 1994 .

[8]  Y. Allen,et al.  Historical land use, phosphorus loading, and loss of fish habitat in Lake Simcoe, Canada , 1996 .

[9]  K. Nicholls,et al.  Reduced chlorophyll to phosphorus ratios in nearshore Great Lakes waters coincide with the establishment of dreissenid mussels , 1999 .

[10]  M. Charlton.  Hypolimnion Oxygen Consumption in Lakes: Discussion of Productivity and Morphometry Effects , 1980 .

[11]  Anders Grimvall,et al.  Performance of partial Mann–Kendall tests for trend detection in the presence of covariates , 2002 .

[12]  David O. Evans,et al.  Invasion of zebra mussel, Dreissena polymorpha, in Lake Simcoe , 2011 .

[13]  T. Ozersky,et al.  Submerged aquatic vegetation in Cook's Bay, Lake Simcoe: Assessment of changes in response to increased water transparency , 2011 .

[14]  Joelle D. Young,et al.  Changes in the thermal stability of Lake Simcoe from 1980 to 2008 , 2011 .

[15]  William D. Taylor,et al.  The nearshore phosphorus shunt: a consequence of ecosystem engineering by dreissenids in the Laurentian Great Lakes , 2004 .

[16]  Donald O. Whittemore,et al.  Non-parametric trend analysis of water quality data of rivers in Kansas , 1993 .

[17]  P. Dillon,et al.  Long-term phosphorus budgets and an examination of a steady-state mass balance model for central Ontario lakes , 1996 .

[18]  L. Lin,et al.  A concordance correlation coefficient to evaluate reproducibility. , 1989, Biometrics.

[19]  P. Dillon,et al.  Lakeshore Capacity Study: Part I—Test of Effects of Shoreline Development on the Trophic Status of Lakes , 1994 .

[20]  M. Futter,et al.  A Review of the Components, Coefficients and Technical Assumptions of Ontario's Lakeshore Capacity Model , 2006 .

[21]  A. Paterson,et al.  Long-term trends in zooplankton of Dorset, Ontario, lakes: the probable interactive effects of changes in pH, total phosphorus, dissolved organic carbon, and predators , 2008 .

[22]  Jennifer G. Winter,et al.  Phosphorus Inputs to Lake Simcoe from 1990 to 2003: Declines in Tributary Loads and Observations on Lake Water Quality , 2007 .

[23]  C. Tudorancea,et al.  Species-level and community-level data analyses reveal spatial differences and temporal change in the crustacean zooplankton of a large Canadian lake (Lake Simcoe, Ontario) , 2001 .