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Reconstructing epilimnetic total phosphorus using diatoms: statistical and ecological constraints

Lookup NU author(s): Professor Steve Juggins

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Abstract

Diatoms respond rapidly to eutrophication and diatom-based models for inferring total phosphorus (TP) have found wide application in palaeolimnology, especially in tracking trajectories of past and recent nutrient enrichment and in establishing pre-disturbance targets for restoration. Using new analysis of existing training sets and sediment-cores we examine the statistical and ecological constraints of diatom-inferred TP (DI-TP) models. Although the models show an apparently strong relationship between measured and inferred TP in the training sets, even under cross-validation, the models display three fundamental weaknesses, namely (1) the relationship between TP and diatom relative abundance is heavily confounded with secondary variables such as alkalinity and lake depth, (2) the models contain many taxa that are not significantly related to TP, and (3) comparison between different models shows poor or no spatial replicability. At some sites the sediment-core diatom assemblage change tracks the TP gradient in the training sets and DI-TP reconstructions are consistent with monitored TP data and known catchment histories for the recent past. At others diatom species turnover is apparently related to variables other than TP, and DI-TP fails to even reproduce plausible trends. Pre-disturbance DI-TP values are also questionable at most sites. We argue that these problems pervade many DI-TP models, particularly those where violations of the basic assumptions of the transfer function approach are ignored.


Publication metadata

Author(s): Juggins S, Anderson NJ, Ramstack Hobbs JM, Heathcote AJ

Publication type: Article

Publication status: Published

Journal: Journal of Paleolimnology

Year: 2013

Volume: 49

Issue: 3

Pages: 373-390

Print publication date: 15/02/2013

ISSN (print): 0921-2728

ISSN (electronic): 1573-0417

Publisher: Springer

URL: http://dx.doi.org/10.1007/s10933-013-9678-x

DOI: 10.1007/s10933-013-9678-x


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