Using change-point analysis and weighted averaging approaches to explore the relationships between common benthic diatoms and in-stream environmental variables in mid-atlantic highlands streams,USA |
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Authors: | Christine L Weilhoefer Yangdong Pan |
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Institution: | (1) Environmental Science and Resources, Portland State University, Portland, OR 97207, USA;(2) Present address: Pacific Coastal Ecology Branch, Western Ecology Division, US EPA, 2111 S.E. Marine Science Dr., Newport, OR 97365, USA |
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Abstract: | Diatoms are increasingly being used in the bioassessment of aquatic systems. However, autecological information for many common
taxa is incomplete. We explored the potential of classification (CT) and regression tree (RT) approaches to identify the hierarchical
interaction among water quality variables in predicting the relative abundance of ten common stream diatom taxa in the Mid-Atlantic
Highlands ecoregion. RT analysis was also used to identify environmental change points corresponding to major shifts in species
abundances. We also used traditional weighted-averaging approaches (WA) to model taxon pH and total phosphorus (TP) optima.
RT and WA approaches provided different, yet complementary, information on the complex relationships between common stream
diatoms and environmental variables. Both RT and CT highlighted the interaction of stream acidity (pH, acid neutralizing capacity
(ANC)), and TP in structuring the stream diatom assemblage. For the RT of taxa, where pH was an important predictor, higher
pH predicted higher relative abundances. In contrast, higher TP predicted lower relative abundances for some diatom taxa (e.g.,
Achnanthidium minutissimum (Kütz.) Czarnecki), while predicting higher relative abundances for other taxa (e.g., Planothidium lanceolatum (Bréb.) Round & Bukht., Gomphonema parvulum (Kütz.) Kütz.). The environmental change point for pH derived from RT analysis was lower than WA optima for all species.
We suggest that RT change point analysis can be used to complement traditional WA optima approaches, especially when diatom
taxa’s abundances are affected by interactive environmental factors, to provide more refined information on stream diatom
environmental preferences.
Handling editor: L. Naselli-Flores |
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Keywords: | Change point analysis Classification and regression trees Diatom pH Total phosphorus Weighted-average |
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