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Assessment of Biological Indicators of Lake Health in Waikato Shallow Lakes - a Pilot Study 2006/07

TR 2008/18
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Report: TR 2008/18

Authors: Keri Neilson, Kevin Collier and Mark Hamer

Abstract

The development of monitoring methods and indicators of lake ecosystem health is essential in providing cost-effective methods to assess changes within and around the lakes of the Waikato region.  The aim of the current project is to assess a number of biotic and functional variables as potential indicators of lake health.  We evaluated the use of LakeSPI, zooplankton and invertebrate community analyses, and decomposition rates in ten shallow lakes of varying type (peat, riverine and dune) within the Waikato region.  Sampling was carried out in December 2006, January 2007 and March 2007. Results obtained were compared to the results of water quality sampling and to a predetermined relative condition based on existing knowledge of each lake.  Zooplankton communities were analysed to produce a rotifer inferred Trophic Level Index (TLI) for each lake.  These values were similar to the TLI values calculated from the water quality results.  The relative condition of lakes based on the rotifer inferred TLI values was similar to that expected for peat and riverine lakes, but not for dune lakes.  The LakeSPI technique can only be used to produce an index in lakes that are vegetated, and therefore can not be used to detect small changes in shallow devegetated lakes.  However the technique detected an apparent deterioration in one of the dune lakes in the current study.  Three sampling techniques were used for collecting lake macroinvertebrate samples – net sweeps, artificial substrates and ponar grabs.  Results of cluster analyses suggest that samples collected with the ponar grab may be the most meaningful for assessing lake health.  Analysis of decomposition rates of birchwood sticks provided encouraging results and further testing of this technique is suggested.  Recommendations are made for a second year of sampling to further assess indicators and sampling techniques in a greater number of lakes.  

Assessment of Biological Indicators of Lake Health in Waikato Shallow Lakes - a Pilot Study 2006/07 [PDF, 227 KB]

Contents
  Acknowledgement  iii
  Abstract  viii
1 Introduction  1
2  Methods  2
2.1 Study sites  2
2.2  Water quality  3
2.2.1  Water sampling 3
2.3  Zooplankton  3
2.4  Submerged macrophytes  3
2.5  Decomposition rates  3
2.6  Invertebrates  4
2.6.1  Sample collection and processing  4
2.6.2  Data analysis  4
3  Results 5
3.1  Water quality 5
3.2  Zooplankton  6
3.3  Submerged macrophytes 7
3.4  Decomposition rates  8
3.5  Invertebrates 9
4  Conclusions and recommendations  13
  References  16
  Appendix 1  18
  Water quality monitoring methodology and sampling  18