Selecting parameters

Factors that affect the relationships between total phosphorus (TP) and chlorophyll a (Chl a) and between total nitrogen (TN) and Chl a can be specified with sliders shown on the left.

• Lake depth - Lake depth influences the average amount of inorganic sediment observed in a lake, where inorganic sediment concentrations in shallow lakes tends to be greater than in deep lakes. Observations with lake depth near the selected lake depth are shown in green in the plotted TP data.

• Dissolved organic carbon (DOC) - DOC is an indicator of the amount allochthonous organic material in the lake. For the TN-Chl a model, DOC provides a means of estimating the dissolved organic nitrogen contribution to TN. Observations with DOC near the selected DOC concentration are shown in green in the plotted TN data.

• Level III Ecoregion - Ecoregions were defined by Omernik (2014) to identify regions of the United States in which ecosystems were thought to be similar. For these models, ecoregions provide a useful way to characterize differences in the amount of phosphorus (P) that is bound to inorganic sediment and differences in the relationship between dissolved organic carbon (DOC) and dissolved organic nitrogen. Observations collected in the selected ecoregion are shown in blue in the plotted data.

The last two sliders allow the user to specify the targeted Chl a concentration and the certainty level associated with the resulting model predictions of TP and TN.

Plots for phosphorus show relationships between chlorophyll (Chl a) and total phosphorus (TP) (left plot). The gray line indicates the relationship between chlorophyll and total phosphorus if all phosphorus is bound within phytoplankton. The blue line shows the ambient relationship that takes into account phosphorus bound to inorganic sediment. The right plot shows the relationship between non-phytoplankton turbidity (Turb_np), a measure of inorganic suspended sediment, and TP. The line shows average amount of phosphorus associated with each unit of non-phytoplankton turbidity for the selected ecoregion. NLA samples collected from the selected ecoregion are highlighted in blue, and samples collected from lakes with similar depths to that specified for the lake of interest are highlighted in green.

Plots for nitrogen show relationships between Chl a and the difference between total nitrogen (TN) and dissolved inorganic nitrogen (DIN). The gray line indicates the relationship between chlorophyll and nitrogen if all nitrogen is bound within phytoplankton. The blue line shows the ambient relationship that takes into account dissolved organic nitrogen. The right plot shows the observed values of DOC and TN - DIN. The solid line shows the estimated relationship between these two parameters for the selected ecoregion. NLA samples collected from the selected ecoregion are highlighted in blue, and samples collected from lakes with similar DOC concentrations to that specified for the lake of interest are highlighted in green.