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Inferring past zooplanktivorous fish and macrophyte density in a shallow lake: application of a new regression tree model

Inferring past zooplanktivorous fish and macrophyte density in a shallow lake: application of a new regression tree model
Inferring past zooplanktivorous fish and macrophyte density in a shallow lake: application of a new regression tree model
1. Eutrophication has a profound effect on the biological structure and function of shallow lakes, altering the composition and abundance of submerged macrophyte and fish
assemblages. Relatively little is known, however, about decadal to centennial-scale change in these important aspects of shallow lake ecology.

2. Established palaeolimnological inference models are limited to reconstructing a single variable. As macrophyte and zooplanktivorous fish abundance exert dual and interacting controls on cladoceran assemblages a single variable inference model may contain significant error.

To obviate this problem, we applied a new cladoceran-based multivariate regression tree (MRT) model to cladoceran subfossil assemblages from dated cores from a small shallow lake (Felbrigg Lake, U.K.) to assess long-term change in fish and submerged acrophyte abundance. Plant macrofossil, chironomid and mollusc subfossil assemblages were also analysed to track changes in biological structure and function and to evaluate the inferences of the MRT model.

3. Over the 200+ year period covered by the sediment cores, there was good agreement in the timing and nature of ecological change reflected by the plant macrofossil, mollusc, chironomid and cladoceran data. The sediment sequence was divided into three dated zones: c. 1797–1890, c. 1890–1954 and c. 1954–present. Prior to 1890 plant-associated mollusc, cladoceran and chironomid assemblages indicated a species-rich macrophyte community; a scenario confirmed by the plant macrofossil data. From c. 1890 to 1954 macrophyte-associated species of all three invertebrate groups remained abundant but the proportion of pelagic cladocerans rose. Post-1954 mollusc and chironomid assemblages changed to sediment associated detrital feeders and the proportion of pelagic cladoceran
taxa increased further.

4. The cladoceran-based MRT model indicated a long period of stability, c. 1790–1927,characterised by abundant submerged macrophytes and zooplanktivorous fish. From
c. 1927 to 1980, the MRT model inferred a decline in zooplanktivorous fish density (ZF) but relative stability in August macrophyte abundance. From 1980 to 2000, an increase in zooplanktivorous fish was inferred tallying well with available data on the fish population (since the 1970s), which indicated extirpation of perch in the 1970s and a subsequent increase in the rudd population. The model inferred little change in August macrophyte abundance until post-c. 1980 at which point it indicated a decline.

The surface sediment assemblage was placed in MRT group A, where submerged plants are absent or very rare in late summer in good agreement with current conditions at the site.

5. The MRT model, applied here for the first time, appears to have successfully tracked changes in macrophyte abundance and ZF over the last 200 years at Felbrigg Lake.

The inferences agreed with historical observations on the fish community and the supporting palaeolimnological data. Given that multiple structuring forces shape most biological communities, the application of a model capable of allowing for this represents a significant advance in palaeolimnology.
chironomids, cladocera, fish, macrophytes, mollusca, regression tree, shallow lakes
0046-5070
584-599
Davidson, T. A.
e993cf89-8fc4-41d1-8dea-7f3d3856fac2
Sayer, C. D.
257776cf-63e2-4072-8119-dbfc208c3f27
Langdon, P. G.
95b97671-f9fe-4884-aca6-9aa3cd1a6d7f
Burgess, A.
710be038-bfea-4ab6-a912-e0005a897446
Jackson, M.
f73553de-6f67-41c2-9f3d-613b61a00d80
Davidson, T. A.
e993cf89-8fc4-41d1-8dea-7f3d3856fac2
Sayer, C. D.
257776cf-63e2-4072-8119-dbfc208c3f27
Langdon, P. G.
95b97671-f9fe-4884-aca6-9aa3cd1a6d7f
Burgess, A.
710be038-bfea-4ab6-a912-e0005a897446
Jackson, M.
f73553de-6f67-41c2-9f3d-613b61a00d80

Davidson, T. A., Sayer, C. D., Langdon, P. G., Burgess, A. and Jackson, M. (2010) Inferring past zooplanktivorous fish and macrophyte density in a shallow lake: application of a new regression tree model. Freshwater Biology, 55 (3), 584-599. (doi:10.1111/j.1365-2427.2009.02391.x).

Record type: Article

Abstract

1. Eutrophication has a profound effect on the biological structure and function of shallow lakes, altering the composition and abundance of submerged macrophyte and fish
assemblages. Relatively little is known, however, about decadal to centennial-scale change in these important aspects of shallow lake ecology.

2. Established palaeolimnological inference models are limited to reconstructing a single variable. As macrophyte and zooplanktivorous fish abundance exert dual and interacting controls on cladoceran assemblages a single variable inference model may contain significant error.

To obviate this problem, we applied a new cladoceran-based multivariate regression tree (MRT) model to cladoceran subfossil assemblages from dated cores from a small shallow lake (Felbrigg Lake, U.K.) to assess long-term change in fish and submerged acrophyte abundance. Plant macrofossil, chironomid and mollusc subfossil assemblages were also analysed to track changes in biological structure and function and to evaluate the inferences of the MRT model.

3. Over the 200+ year period covered by the sediment cores, there was good agreement in the timing and nature of ecological change reflected by the plant macrofossil, mollusc, chironomid and cladoceran data. The sediment sequence was divided into three dated zones: c. 1797–1890, c. 1890–1954 and c. 1954–present. Prior to 1890 plant-associated mollusc, cladoceran and chironomid assemblages indicated a species-rich macrophyte community; a scenario confirmed by the plant macrofossil data. From c. 1890 to 1954 macrophyte-associated species of all three invertebrate groups remained abundant but the proportion of pelagic cladocerans rose. Post-1954 mollusc and chironomid assemblages changed to sediment associated detrital feeders and the proportion of pelagic cladoceran
taxa increased further.

4. The cladoceran-based MRT model indicated a long period of stability, c. 1790–1927,characterised by abundant submerged macrophytes and zooplanktivorous fish. From
c. 1927 to 1980, the MRT model inferred a decline in zooplanktivorous fish density (ZF) but relative stability in August macrophyte abundance. From 1980 to 2000, an increase in zooplanktivorous fish was inferred tallying well with available data on the fish population (since the 1970s), which indicated extirpation of perch in the 1970s and a subsequent increase in the rudd population. The model inferred little change in August macrophyte abundance until post-c. 1980 at which point it indicated a decline.

The surface sediment assemblage was placed in MRT group A, where submerged plants are absent or very rare in late summer in good agreement with current conditions at the site.

5. The MRT model, applied here for the first time, appears to have successfully tracked changes in macrophyte abundance and ZF over the last 200 years at Felbrigg Lake.

The inferences agreed with historical observations on the fish community and the supporting palaeolimnological data. Given that multiple structuring forces shape most biological communities, the application of a model capable of allowing for this represents a significant advance in palaeolimnology.

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More information

Published date: March 2010
Keywords: chironomids, cladocera, fish, macrophytes, mollusca, regression tree, shallow lakes

Identifiers

Local EPrints ID: 80502
URI: http://eprints.soton.ac.uk/id/eprint/80502
ISSN: 0046-5070
PURE UUID: b0835fca-e70b-40e2-99fc-59c7030a0d6d
ORCID for P. G. Langdon: ORCID iD orcid.org/0000-0003-2724-2643

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Date deposited: 24 Mar 2010
Last modified: 14 Mar 2024 02:41

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Contributors

Author: T. A. Davidson
Author: C. D. Sayer
Author: P. G. Langdon ORCID iD
Author: A. Burgess
Author: M. Jackson

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