Validation of a diatom–phosphorus calibration set for Sweden

Abstract

1. A weighted averaging (WA) regression and calibration model for diatoms and total phosphorus (TP) was developed from a dataset of 45 surface‐sediment samples from Swedish lakes. Jack‐knifed error statistics were comparable with those for similar diatom–TP datasets: r2jack=0.47, root mean squared error of prediction (RMSEP)=0.24 log10μg TP L–1 and mean bias=–0.002 log10 μg TP L–1 for the simple WA model; r2jack=0.36, RMSEP=0.27 log10 μg TP L–1 and mean bias=0.017 log10 μg TP L–1 for WA with tolerance downweighting. 2. The model was used to estimate TP concentrations for the Ekoln basin of Lake Mälaren using a 210Pb‐dated sediment core record. Highly eutrophic conditions developed in the basin in the 1960s as a result of nutrient inputs from cultivated land and the city of Uppsala. A reduction in the supply of phosphorus from sewage outlets in the late 1960s resulted in less eutrophic conditions. 3. The model results indicated levels of 50–60 μg TP L–1 prior to 1900. The rapid eutrophication of the lake basin after the 1950s and the subsequent recovery were evident from the diatom data. 4. Diatom‐inferred TP (DI–TP) values were validated by comparison with monitored data for the period 1966–95. The diatom model tended to underestimate TP at high levels (> 80 μg L–1) but overestimate at lower concentrations. 5. A good agreement was observed between the trends in TP concentration and the DI–TP concentration and the timing of the maximum was well reflected by the diatom‐based reconstruction. A significant correlation (r2=0.69, P < 0.01) was found between DI–TP and measured TP at this site.

Tracing pollution and recovery using sediments in an urban estuary, northern Baltic Sea: are we far from ecological reference conditions?

“…Rapid recovery from pollution after the reduction of external loading has also been recorded for some lakes (e.g. Schiendler 1974, Bradshaw & Anderson 2001.…”

Phytate as a novel phosphorus-specific paleo-indicator in aquatic sediments

“…In the absence of a phosphorus-specific paleoindicator, historical rates of phosphorus loading are usually inferred from changes in diatom assemblages and quantitative diatom-total phosphorus transfer functions (Anderson 1997;Bennion et al 2004;Bradshaw and Anderson 2001;Hall et al 1997). However, diatom-based inference models rely on calibration against large modern data sets of surfacesediment diatoms and associated water chemistry, which typically involve >50 sites and are therefore time consuming and laborious to collect.…”

The use of diatom records to establish reference conditions for UK lakes subject to eutrophication

“…Numerous diatom-P transfer functions have been developed for European lakes (e.g. Wunsam and Schmidt 1995;Bennion et al 1996a;Lotter et al 1998;Bradshaw and Anderson 2001;Kauppila et al 2002;Chen et al 2008), several of which were combined in the EU project EDDI ("European Diatom Database") (Battarbee et al 2001b). The approach is able to provide estimates of baseline (reference) TP concentrations in lakes and, when coupled with dating of sediment cores, the timing, rates and possible causes of enrichment at a particular site (e.g.…”