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Zooplankton monitoring for TLI and lake health assessment of the Waikato lakes: 2015-2016

Report: TR 2016/24

Author: Ian C Duggan (Environmental Research Institute, School of Science, Faculty of Science and Engineering, The University of Waikato).

About this report

Zooplankton were examined from nine regularly sampled Waikato Regional Council lakes in 2015 and early 2016, to explore trends in rotifer inferred TLI assessments through time, as well as changes in the proportions of native versus non-native zooplankton, and crustacean versus rotifers as part of developing ecosystem health indicators for lakes. Additionally, seven lakes were examined less intensively (usually single samples) from lakes less frequently, or not previously, sampled. Lakes can be ranked in the following order from highest (poor ecosystem health) to lowest (good ecosystem health) rotifer inferred TLI (RTLI) values: 2 out of 16 lakes were classified as hypertrophic, 6 lakes were classified as supertrophic, 6 lakes were classified as eutrophic, 1 lake was classified as mesotrophic and 1 lake was classified as oligotrophic. Clear-cut patterns in crustacean or rotifer dominance were not evident for most lakes. However, Lake Waahi was heavily crustacean dominated in the current study, primarily due to high proportions of the Australian copepod Boeckella symmetrica and North American cladoceran Daphnia galeata. Overall, the effects that non-native zooplankton species are having on New Zealand lake ecosystems are not well appreciated. However, changes in zooplankton species composition have been noted following invasions. Further work is required to determine these broader ecosystem-level effects.

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Zooplankton monitoring for TLI and lake health assessment of the Waikato lakes: 2015-2016
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Acknowledgement i
Executive summary v
Introduction 1
Methods 2
Results and Discussion 2
Trends in the proprtions of non-native species 4
Proportions of crustacean versus rotifer species abundances 5
References 10