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The impacts of changing nutrient load and climate on a deep, eutrophic, monomictic lake

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posted on 2019-03-11, 12:16 authored by Alan D. Radbourne, J. Alex Elliott, Stephen C. Maberly, David RyvesDavid Ryves, Nicholas John AndersonNicholas John Anderson
1. Nutrient availability and climate have substantial effects on the structure and function of lakes. Predicted changes to climate (particularly temperature) over the 21st century are expected to adjust physical lake functions, changing thermal and nutrient use processes. Both increasing anthropogenic nutrient inputs and net reductions following remediation will also drive ecological change. Therefore, there is an increasing necessity to disentangle the effects of nutrient and temperature change on lakes to understand how they might act in additive and antagonistic ways. 2. This study quantified internal and external nutrient loads at Rostherne Mere, UK, a deep (zmax = 30 m), monomictic eutrophic lake (average annual TP >100 μg L-1) that has a long, stable period of stratification (~8.5 months). A lake biophysical model (PROTECH) was used to assess the effect of changes in these loads and climate change on lake productivity in a factorial modelling experiment. 3. During the summer, phosphorus released from the sediment is largely restricted to the hypolimnion and phytoplankton production is supported by the external load. On overturn, phosphorus at depth is distributed throughout the water column with the elevated concentration persisting to support algal productivity in the following spring. 4. Consequently, the model showed that internal nutrient loading was the main driver of current and future changes in the concentration of phosphorus (responsible for up to 86% P reduction), phytoplankton chlorophyll a and cyanobacterial blooms. However, although the external phosphorus load had a relatively small influence on annual mean phosphorus concentration, it had a statistically significant effect on chlorophyll a concentration, because it supported algal production during summer stratification. 5. Climate had minimal direct impact, but a substantial indirect impact by altering the timing, depth and length of lake stratification (~14 days longer by 2100), and therefore altered nutrient cycling and phosphorus availability. 6. In summary, the recovery trajectory at Rostherne Mere is limited by the annual internal SRP load replenishment that realistically is unlikely to change greatly on a shorter time-scale. Therefore, the external SRP load has the potential to play an important role as it can be managed further, yet is complicated by the indirect impact of climate changing stratification and flushing patterns.

Funding

This study was supported by the Natural Environment Research Council (NERC) [grant number NE/L002493/1] and ADR acknowledges the support of the research studentship award from Central England NERC Training Alliance (CENTA).

History

Department

  • Geography and Environment

Published in

Freshwater Biology

Volume

64

Issue

6

Pages

1169 - 1182

Citation

RADBOURNE, A.D. ... et al, 2019. The impacts of changing nutrient load and climate on a deep, eutrophic, monomictic lake. Freshwater Biology, 64(6), pp. 1169-1182.

Publisher

Wiley

Version

  • VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

2019-02-11

Publication date

2019-03-22

Notes

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

ISSN

0046-5070

Language

  • en

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