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A comparison of diatom phosphorus transfer functions and export coefficient models as tools for reconstructing lake nutrient histories (2005)

BENNION, HELEN ; JOHNES, PENNY ; FERRIER, ROBERT ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 50 (2005), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. We compared the baseline phosphorus (P) concentrations inferred by diatom-P transfer functions and export coefficient models at 62 lakes in Great Britain to assess whether the techniques produce similar estimates of historical nutrient status.2. There was a strong linear relationship between the two sets of values over the whole total P (TP) gradient (2–200 μg TP L−1). However, a systematic bias was observed with the diatom model producing the higher values in 46 lakes (of which values differed by more than 10 μg TP L−1 in 21). The export coefficient model gave the higher values in 10 lakes (of which the values differed by more than 10 μg TP L−1 in only 4).3. The difference between baseline and present-day TP concentrations was calculated to compare the extent of eutrophication inferred by the two sets of model output. There was generally poor agreement between the amounts of change estimated by the two approaches. The discrepancy in both the baseline values and the degree of change inferred by the models was greatest in the shallow and more productive sites.4. Both approaches were applied to two lakes in the English Lake District where long-term P data exist, to assess how well the models track measured P concentrations since approximately 1850. There was good agreement between the pre-enrichment TP concentrations generated by the models. The diatom model paralleled the steeper rise in maximum soluble reactive P (SRP) more closely than the gradual increase in annual mean TP in both lakes. The export coefficient model produced a closer fit to observed annual mean TP concentrations for both sites, tracking the changes in total external nutrient loading.5. A combined approach is recommended, with the diatom model employed to reflect the nature and timing of the in-lake response to changes in nutrient loading, and the export coefficient model used to establish the origins and extent of changes in the external load and to assess potential reduction in loading under different management scenarios.6. However, caution must be exercised when applying these models to shallow lakes where the export coefficient model TP estimate will not include internal P loading from lake sediments and where the diatom TP inferences may over-estimate TP concentrations because of the high abundance of benthic taxa, many of which are poor indicators of trophic state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01428.x

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2

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The validation of diatom-phosphorus transfer functions: an example from Mondsee, Austria (1995)

BENNION, HELEN ; WUNSAM, SYBILLE ; SCHMIDT, ROLAND

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 34 (1995), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. A diatom-phosphorus weighted averaging (WA) transfer function, derived from a training set of currently oligotrophic to mesotrophic European Alpine lakes, was applied to a high-resolution sediment core with annual laminae from Mondsee, an Austrian pre-alpine lake, in order to reconstruct the eurrophication history of the lake.2. The water chemistry records of total phosphorus (TP) available for Mondsee were compared with the diatom-inferred TP from the model for the period 1975–93. The trend in TP values as inferred by the model paralleled the monitored trend in TP values closely, with matching peaks in 1979/80, a decrease in values from the early 1980s, a second smaller peak in 1986/7, and a further reduction in concentrations in the last 6 years.3. However, there was a clear mismatch between the actual timing of the major TP peak, with the water chemistry records reporting its occurrence in 1979, and the diatom model indicating a small peak in 1980 and the highest concentrations in 1982. This can be attributed to the uncertainty of the sediment chronology for this section of the core, and possibly to the inconsistency between the core resolution and the resolution of the diatom model.4. In terms of the actual concentrations of TP inferred by the model, they compared reasonably well with the measured data, although the model tends to underestimate for the lower core section owing largely to poor diatom assemblage analogues. In the upper part of the core, the diatom-inferred TP values were in extremely close agreement with the monitored chemical data.5. This validation study indicates that diatom-phosphorus transfer functions are robust and are able reliably to infer past-TP concentrations from fossil diatom assemblages in sediment cores. Despite the natural intra- and interannual variability in diatom assemblages and epilimnetic water chemistry, the technique can provide accurate estimates of TP with an annual resolution. The model can be applied to selected sites with suitable sediment records to reconstruct lake TP histories, thus providing a pragmatic management tool for addressing lake eutrophication problems.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00887.x

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3

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A 250 year comparison of historical, macrofossil and pollen records of aquatic plants in a shallow lake (2005)

DAVIDSON, THOMAS A. ; SAYER, CARL D. ; BENNION, HELEN ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 50 (2005), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Sedimentary remains of aquatic plants, both vegetative (turions, leaves, spines) and reproductive (fruits, seeds, pollen), may provide a record of temporal changes in the submerged vegetation of lakes. An independent assessment of the degree to which these remains reflect past floristic change is, however, rarely possible.2. By exploiting an extensive series of historical plant records for a small shallow lake we compare plant macrofossil (three cores) and pollen (one core) profiles with the documented sequence of submerged vegetation change since c. 1750 AD. The data set is based on 146 site visits with 658 observations including 42 taxa classified as aquatic, spanning 250 years.3. Approximately 40% of the historically recorded aquatic taxa were represented by macro-remains. In general macrofossils underestimated past species diversity, with pondweeds (three of eight historically recorded Potamogeton species were found) particularly poorly represented. Nonetheless, several taxa not reported from historical surveys (e.g. Myriophyllum alterniflorum and Characeae) were present in the sediment record.4. The pollen record revealed taxa which left no macro-remains (e.g. Littorella uniflora), and the macrofossil record provided improved taxonomic resolution for some taxa (e.g. Potamogeton) and a more reliable record of persistence, appearance and loss of others (e.g. Myriophyllum spp. and Nymphaeaceae).5. Detrended correspondence analysis indicated that changes in the community composition evidenced by the palaeolimnological and historical records were synchronous and of a similar magnitude. Both records pointed to a major change at around 1800, with the historical record suggesting a more abrupt change than the sedimentary data. There was good agreement on a subsequent change c. 1930.6. The palaeolimnological data did not provide a complete inventory of historically recorded species. Nevertheless, these results suggest that combined macrofossil and pollen records provide a reliable indication of temporal change in the dominant components of the submerged and floating-leaved aquatic vegetation of shallow lakes. As such palaeolimnology may provide a useful tool for establishing community dynamics and successions of plants over decadal to centennial timescales.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01414.x

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Temporal and geographical variation in lake trophic status in the English Lake District: evidence from (sub)fossil diatoms and aquatic macrophytes (2000)

Bennion, Helen ; Monteith, Donald ; Appleby, Peter

Oxford, UK : Blackwell Science Ltd

Freshwater biology 45 (2000), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. A sediment core (representing 250–300 years) was taken from each of three lakes of conservation interest and contrasting trophic status in the English Lake District: Wastwater, Bassenthwaite Lake and Esthwaite Water. Lithostratigraphic analyses, radiometric dating and analysis of fossil diatoms were carried out.  2. Transfer functions, based on the diatoms, were used to reconstruct total phosphorus (TP) and, thus, eutrophication at the study lakes. In Wastwater, changes in lake pH were also reconstructed.  3. The lakes were also classified according to their present macrophyte flora, the latter being compared with previous records.  4. The fossil diatoms of Wastwater were continuously dominated by taxa typical of oligotrophic, circumneutral waters, indicating that the lake has not been enriched or acidified in the last 250 years. The aquatic macrophyte flora has probably remained unchanged since before the Industrial Revolution.  5. The diatom assemblages of both Bassenthwaite Lake and Esthwaite Water began to change in the mid-1800s. Further change occurred from the 1960s, at the onset of a recent period of eutrophication. These two lakes have experienced continued nutrient enrichment throughout the 1970s, 80s and 90s, largely associated with increasing phosphorus inputs from sewage effluent. There is no evidence of any recovery in response to recent reductions in external nutrient loads.  6. Only in Esthwaite Water has the change in aquatic macrophytes been pronounced.  7. Palaeolimnological reconstruction is useful in determining background conditions and natural variation in lake ecosystems.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00626.x

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5

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Tracing lake trophic history with a chironomid–total phosphorus inference model (2001)

Brooks, Stephen J. ; Bennion, Helen ; Birks, H. John B.

Oxford UK : Blackwell Science Ltd

Freshwater biology 46 (2001), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. In the absence of historical water chemistry data, predictive biological indicator groups preserved in lake sediments can be employed to reconstruct the history of lake eutrophication. Diatoms are well established in this role, but to augment diatom-based inferences of nutrient status we investigate the potential use of chironomid midges (Insecta: Chironomidae).2. Canonical correspondence analysis (CCA) of modern chironomid assemblages in surface sediments from 44 lakes in the English Midlands and Wales, U.K., shows that five environmental variables (total phosphorus (TP), bottom dissolved oxygen, maximum lake depth, Secchi depth and surface water temperature) make a statistically significant (P 〈 0.05) contribution to explaining the variance in the chironomid data, of which TP makes the largest contribution (29%).3. The relationship is used to develop a series of weighted averaging (WA) and partial least squares (PLS), (WA-PLS) models to infer log10TP. The models are evaluated by leave-one-out (jack-knifing) cross-validation. The simplest minimal adequate model is provided by WA with unweighted inverse deshrinking of root mean square error of prediction (RMSEPjack=0.34 and r2jack=0.60).4. Using this model, the trophic history of Betton Pool, Shropshire, U.K., is reconstructed from the mid-19th century to the present day and the results from the chironomid-TP model are compared with inferences from a diatom-TP model (Bennion, Juggins & Anderson, 1996). Both reconstructions suggest that there was a gradual rise in TP since 1850 AD until about 1974, followed by a more pronounced and rapid increase that has continued until the present. Inferred TP values from the WA chironomid inference model agree with diatom-inferred values.5. The study demonstrates that fossil chironomid assemblages can be used to investigate quantitatively the trophic history of lakes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00684.x

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6

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A diatom-phosphorus transfer function for shallow, eutrophic ponds in southeast England (1994)

Bennion, Helen

Springer

Hydrobiologia 275-276 (1994), S. 391-410

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ISSN: 1573-5117

Keywords: diatoms ; phosphorus ; palaeolimnology ; transfer function ; United Kingdom ; shallow

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Shallow ponds in southeast England are often eutrophic with high phosphorus concentrations. The aim of this study was to develop a diatom-phosphorus ‘transfer function’ to enable past phosphorus levels in such waters to be inferred from the sediment record. A water chemistry survey of 123 randomly chosen, shallow, artificial ponds in southeast England was carried out. Principal components analysis (PCA) revealed that phosphorus was an important environmental variable. A subset of 31 sites was selected along a total phosphorus (TP) gradient (winter TP range 7–1123 µg 1-1), in order to explore the relationship between the surface-sediment diatom assemblages and the contemporary water chemistry using canonical correspondence analysis (CCA). Annual mean TP was the most significant variable in explaining the variance in the diatom species data. Weighted averaging (WA) regression and calibration techniques were used to generate a transfer function, enabling annual mean TP (range 25–646 µg 1-1) to be inferred from the diatom species TP optima of 102 common taxa in the dataset (r 2 = 0.79; RMSE = 0.161; RMSE(boot) = 0.279; n = 30). The model was applied to fossil diatom assemblages in a sediment core from Marsworth Reservoir, Hertfordshire, a Site of Special Scientific Interest (SSSI), with currently high TP levels of 476 µg 1-1, to reconstruct past epilimnetic annual mean TP concentrations. The study shows that artificial, shallow waters can be suitable for palaeolimnological research and that it is possible to reliably infer lake water TP using the WA technique, across a large range of phosphorus concentrations. This method has the potential to provide limnologists, conservationists and water quality managers with an estimate of pre-enrichment phosphorus concentrations and an indication of the onset and development of eutrophication at a site. This information is essential for lake management strategies and restoration programmes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00026729

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