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Laurentian Great Lakes phytoplankton and their water quality characteristics, including a diatom-based model for paleoreconstruction of phosphorus.

Reavie ED, Heathcote AJ, Shaw Chraïbi VL - PLoS ONE (2014)

Bottom Line: Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP.We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core.The diatom-based transfer function can be used in lake management when retrospective data are needed for tracking long-term degradation, remediation and trajectories.

View Article: PubMed Central - PubMed

Affiliation: Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, Minnesota, United States of America.

ABSTRACT
Recent shifts in water quality and food web characteristics driven by anthropogenic impacts on the Laurentian Great Lakes warranted an examination of pelagic primary producers as tracers of environmental change. The distributions of the 263 common phytoplankton taxa were related to water quality variables to determine taxon-specific responses that may be useful in indicator models. A detailed checklist of taxa and their environmental optima are provided. Multivariate analyses indicated a strong relationship between total phosphorus (TP) and patterns in the diatom assemblages across the Great Lakes. Of the 118 common diatom taxa, 90 (76%) had a directional response along the TP gradient. We further evaluated a diatom-based transfer function for TP based on the weighted-average abundance of taxa, assuming unimodal distributions along the TP gradient. The r(2) between observed and inferred TP in the training dataset was 0.79. Substantial spatial and environmental autocorrelation within the training set of samples justified the need for further model validation. A randomization procedure indicated that the actual transfer function consistently performed better than functions based on reshuffled environmental data. Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP. We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core. Passive, multivariate analysis of the fossil samples against the training set indicated that phosphorus was a strong determinant of historical diatom assemblages, verifying that the transfer function was suited to reconstruct past TP in Lake Superior. Collectively, these results showed that phytoplankton coefficients for water quality can be robust indicators of Great Lakes pelagic condition. The diatom-based transfer function can be used in lake management when retrospective data are needed for tracking long-term degradation, remediation and trajectories.

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Histograms show percentage of variation in data explained by four water quality gradients.Total height indicates the total variation explained while gray height indicates the unique fraction of variance captured by that variable.
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pone-0104705-g004: Histograms show percentage of variation in data explained by four water quality gradients.Total height indicates the total variation explained while gray height indicates the unique fraction of variance captured by that variable.

Mentions: Figure 4 illustrates variance partitioning of the diatom relative density data by selected environmental variables. The total and unique effects of TP were 6.8% and 4.8% respectively (Table 3), a 29% reduction in explained variance. Based on relative biovolumes the total and unique effects were 9.1% and 6.0%, indicating a closer linkage between TP and diatom biovolumes than densities. That the unique TP effect is lower than total is due to redundancies, such as correlation to variables like chlorophyll a and turbidity (Figure 1). While it is difficult to confirm the relative importance of these variance partitioning values, the unique variance explained by TP surpasses that observed for TP training sets developed in Europe [46] and Minnesota [47], [48]; 3.9% and 2.5% respectively, as presented by Juggins et al. [22]. Of the selected variables, TP independently explained the most variation in the assemblage data, in contrast to alkalinity and chloride which had more than 70% reduction from total to uniquely explained variance. NOx explained the least variation but was minimally confounded by other variables. For TP to be confounded with other correlated variables is not surprising, but these results suggest that changes in the diatom assemblages across the Great Lakes are meaningfully related to TP.


Laurentian Great Lakes phytoplankton and their water quality characteristics, including a diatom-based model for paleoreconstruction of phosphorus.

Reavie ED, Heathcote AJ, Shaw Chraïbi VL - PLoS ONE (2014)

Histograms show percentage of variation in data explained by four water quality gradients.Total height indicates the total variation explained while gray height indicates the unique fraction of variance captured by that variable.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126776&req=5

pone-0104705-g004: Histograms show percentage of variation in data explained by four water quality gradients.Total height indicates the total variation explained while gray height indicates the unique fraction of variance captured by that variable.
Mentions: Figure 4 illustrates variance partitioning of the diatom relative density data by selected environmental variables. The total and unique effects of TP were 6.8% and 4.8% respectively (Table 3), a 29% reduction in explained variance. Based on relative biovolumes the total and unique effects were 9.1% and 6.0%, indicating a closer linkage between TP and diatom biovolumes than densities. That the unique TP effect is lower than total is due to redundancies, such as correlation to variables like chlorophyll a and turbidity (Figure 1). While it is difficult to confirm the relative importance of these variance partitioning values, the unique variance explained by TP surpasses that observed for TP training sets developed in Europe [46] and Minnesota [47], [48]; 3.9% and 2.5% respectively, as presented by Juggins et al. [22]. Of the selected variables, TP independently explained the most variation in the assemblage data, in contrast to alkalinity and chloride which had more than 70% reduction from total to uniquely explained variance. NOx explained the least variation but was minimally confounded by other variables. For TP to be confounded with other correlated variables is not surprising, but these results suggest that changes in the diatom assemblages across the Great Lakes are meaningfully related to TP.

Bottom Line: Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP.We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core.The diatom-based transfer function can be used in lake management when retrospective data are needed for tracking long-term degradation, remediation and trajectories.

View Article: PubMed Central - PubMed

Affiliation: Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, Minnesota, United States of America.

ABSTRACT
Recent shifts in water quality and food web characteristics driven by anthropogenic impacts on the Laurentian Great Lakes warranted an examination of pelagic primary producers as tracers of environmental change. The distributions of the 263 common phytoplankton taxa were related to water quality variables to determine taxon-specific responses that may be useful in indicator models. A detailed checklist of taxa and their environmental optima are provided. Multivariate analyses indicated a strong relationship between total phosphorus (TP) and patterns in the diatom assemblages across the Great Lakes. Of the 118 common diatom taxa, 90 (76%) had a directional response along the TP gradient. We further evaluated a diatom-based transfer function for TP based on the weighted-average abundance of taxa, assuming unimodal distributions along the TP gradient. The r(2) between observed and inferred TP in the training dataset was 0.79. Substantial spatial and environmental autocorrelation within the training set of samples justified the need for further model validation. A randomization procedure indicated that the actual transfer function consistently performed better than functions based on reshuffled environmental data. Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP. We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core. Passive, multivariate analysis of the fossil samples against the training set indicated that phosphorus was a strong determinant of historical diatom assemblages, verifying that the transfer function was suited to reconstruct past TP in Lake Superior. Collectively, these results showed that phytoplankton coefficients for water quality can be robust indicators of Great Lakes pelagic condition. The diatom-based transfer function can be used in lake management when retrospective data are needed for tracking long-term degradation, remediation and trajectories.

Show MeSH
Related in: MedlinePlus