Water-chemistry transfer functions for epiphytic diatoms in standing freshwaters and a comparison with models based on littoral sediment assemblages (Flanders, Belgium) |
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| Authors: | Luc Denys |
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| Institution: | (1) Research Institute for Nature and Forest (INBO), Kliniekstraat 25, Brussels, B-1070, Belgium;(2) Biology Department, PLP, University of Antwerpen, Universiteitsplein 1, Wilrijk, B-2610, Belgium |
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| Abstract: | Quantitative inference models for water-chemistry variables are derived from epiphytic diatom assemblages in 186 lentic and
mostly shallow freshwaters in lower Belgium (Flanders). When the complete pH range is considered (pH 3.4–9.3), robust transfer
functions are obtained for median pH (jack-knifed r
2 = 0.88, RMSEP = 0.38 pH units or 6.4% of the observed range) and dissolved inorganic carbon concentration (jack-knifed r
2 = 0.86, RMSEP = 0.194 log10 mg DIC l−1 or 10.2% of the observed range) by means of weighted-averaging partial least squares regression (WA-PLS). For these variables,
the calibration models are as reliable as those based on sedimentary diatom assemblages. Inferences of pH may be improved
by combining estimates from epiphytic and sediment assemblages. In circumneutral and alkaline conditions, WA-PLS calibration
of maximum or median total phosphorus is possible (log-transformed; jack-knifed r
2 = 0.64 or 0.66 and RMSEP = 14% or 12.3% of the observed range, respectively). It makes little difference if taxa showing
no response to TP are taken into consideration or not. These models considerably expand the prospects of using historical
herbarium materials to hindcast environmental conditions and also allow more accurate interpretation of current compositional
changes in epiphytic communities. Compared to littoral sediment assemblages, fewer water-column variables can be inferred
reliably from epiphyton. This probably results from differences between the effective gradients in both habitats, together
with lower in situ species diversity and less effective spatial integration (i.e. lower recruitment of phytoplankton) in the
epiphyton. A comparison of the HOF response-model types and WA-optima of diatom taxa for epiphytic and sediment assemblages
shows that the relationship to individual variables, and in particular to those related to trophic status, may differ with
habitat. Thus, the combination of samples from both habitat types in the same calibration model is not recommended.
Electronic Supplementary Material Supplementary material is available and is accessible for authorised users in the online version of this article at |
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| Keywords: | Bacillariophyceae Phytobenthos Shallow waters Water quality Microhabitat Herbarium macrophytes |
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