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Macroinvertebrate Monitoring

 

Different stream macroinvertebrates show different responses to changes in their environment such as water quality or low flows and different species show different tolerances to pollution. Macroinvertebrates are good indicators of local conditions because they tend to stay in one place and are affected by the environmental conditions over an extended period of time, unlike water quality results, which tend to be spot measurements, i.e. that exact point in time. Also stream macroinvertebrates are the best indicator of the life supporting capacity of a stream or river, as they are usually near the middle of the food web and an important component of stream ecosystems.

This report summarises the results from the February/March 2006 round of macroinvertebrate monitoring carried out at four Waiarohia Stream sites, the 19 River Water Quality Monitoring Network sites, four Otarao catchment sites and six rivers both upstream and downstream of different resource consent activities throughout Northland.

The monitoring was carried out following the standard protocols developed by the NZ Macroinvertebrate working group in 2001; ‘Protocols for sampling macroinvertebrates in Wadeable streams' (Stark et al. 20011). Four standard biotic indices were calculated to assess water quality and biological health at the sites;

  1. Species richness
  2. Macroinvertebrate Community Index (MCI)
  3. Semi Quantitative Macroinvertebrate Community Index (SQMCI)
  4. The percentage of Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) taxa (%EPT taxa)

Photo of staff carrying out macroinvertebrate monitoring.Staff carrying out macroinvertebrate monitoring.

For more information on sampling methods and biotic indices check out the detailed macroinvertebrate monitoring report for 2006 on the Regional Council website.

Biotic indices results

The table below shows the four biotic index scores for all sites monitored in 2006. MCI, SQMCI and %EPT taxa have been colour coded to show the range in water quality or degradation at each site. For example, red indicates poor water quality and a severely degraded site, through orange and yellow which indicate moderate water quality, to green which indicates good water quality or a stream still in a relatively ‘pristine' state (very little impact from humans).

Waiarohia sites

Site description Species richness MCI SQMCI %EPT taxa
Rust Ave Bridge 18 79 4.45 16.7
Russell Road Bridge North 17 85 4.64 23.5
Kamo tributary 14 70 2.82 14.3
Whau Valley Road 19 86 4.16 26.3

RWQMN sites

Site description Species richness MCI SQMCI %EPT taxa
Awanui @ Waihue channel 18 77 4.11 22.2
Awanui @ FNDC water take 17 92 4.52 47.1
Victoria @ Thompsons Bridge 18 78 3.99 22.2
Waipapa @ Forest Ranger 29 125 6.04 55.2
Waitangi @ Waimate North 24 108 5.83 45.8
Waitangi @ Watea 16 69 3.89 6.3
Whakapara @ Cableway 11 80 4.35 36.4
Mangahahuru @ Apotu Road 10 78 3.47 20
Mangahahuru @ Main Road 22 86 5.08 31.8
Wairua @ Purua 11 66 3.99 0
Mangere @ Knights Road 23 80 4.36 13.0
Mangakahia @ Titoki 11 89 4.10 27.3
Opouteke @ Suspension Bridge 14 77 2.68 35.7
Mangakahia @ Twin bridges 16 78 3.14 12.5
Punakitere @ Taheke Recorder 19 98 4.49 47.4
Waiotu @ SH1 15 80 3.98 33.3
Kaihu @ gorge 20 79 4.04 20.0
Waipoua @ SH12 Rest area 20 136 8.11 65.0
Manganui @ Permanent station 13 80 4.22 7.7

Otarao catchment sites

Site description Species richness MCI SQMCI %EPT taxa
Otarao near Mangakahia River 11 70 4.14 0
Ruahuia at Viaduct 20 133 7.39 60
Otarao at Norvil Road 10 78 4.18 0
Otarao above Mangakahia Road 15 83 4.36 13.3

Resource consent sites

Site description Species richness MCI SQMCI %EPT taxa
Dam B downstream 17 89 3.69 29.4
Dam B upstream 31 123 5.11 54.8
Dam C downstream 15 89 3.83 20
Dam C upstream 13 128 7.23 53.8
Oxidation pond A downstream 12 71 3.06 0
Oxidation pond A upstream 8 57 3.82 0
Meat works downstream 10 69 4.28 10
Meat works upstream 8 80 4.00 25
Oxidation pond B downstream 22 98 4.54 40.9
Oxidation pond B upstream 18 101 6.66 50.0
Quarry downstream 22 112 6.65 36.4
Quarry upstream 15 100 4.07 33.3

Interpretation of MCI & SQMCI (Boothroyd & Stark 2000[2])

Interpretation MCI score SQMCI score
Clean water >120 >6.0
Doubtful quality or possible mild pollution 100-119 5.0-5.99
Probable moderate pollution 80-99 4.0-4.99
Probable severe pollution <80 <4.0

Colour codes for %EPT taxa

>60% EPT taxa
40 – 59.9% EPT taxa
20 – 39.9 % EPT taxa
Less than 20% EPT taxa

1 Stark, J.D.; Boothroyd, I.K.G.; Harding, J.S.; Maxted, J.R. and Scarsbrook, M.R. (2001). Protocols for sampling macroinvertebrates in wadeable streams. New Zealand Macroinvertebrate Working group Report No. 1. Prepared for the Ministry for the Environment. Sustainable Management Fund Project No. 5103, 57p.