River and stream water quality and ecology - Greater Wellington ...

5. Periphyton – state and trends 57
5.1 State 57
5.1.1 Approach to analysis 57
5.1.2 Periphyton cover 58
5.1.3 Periphyton biomass 60
5.1.4 Periphyton classes and relationship with landcover 60
5.1.5 Relationships between periphyton growth and environmental
variables 62
5.1.6 Macrophytes 65
5.2 Temporal trends 66
5.2.1 Approach to analysis 66
5.2.2 Results 67
5.3 Synthesis 73
6. Macroinvertebrates – state and trends 75
6.1 State 75
6.1.1 Approach to analysis 75
6.1.2 Macroinvertebrate metrics 77
6.1.3 Relationships between MCI, landcover and environmental
variables 79
6.2 Temporal trends 81
6.2.1 Approach to analysis 81
6.2.2 Results 82
6.3 Synthesis 86
7. Fish – state and trends 89
7.1 State 89
7.1.1 Approach to analysis 89
7.1.2 Results 91
7.2 Temporal trends 98
7.2.1 Approach to analysis 98
7.2.2 Results 98
7.3 Synthesis 98
8. Discussion 100
8.1 Regional overview 100
8.1.1 State 100
8.1.2 Temporal trends 102
8.2 National context 103
8.2.1 Water quality 103
8.2.2 Ecological health 105
8.3 Key issues affecting river and stream health 105
8.3.1 Nutrient enrichment 105
8.3.2 Poor clarity and sedimentation 107
8.3.3 Toxicity 109
8.3.4 Microbiological contamination 111
8.3.5 Habitat degradation 112
8.4 Downstream receiving environments 114
8.5 Monitoring limitations and knowledge gaps 115
9. Conclusions 117