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Macroinvertebrate Monitoring

 

Different stream macroinvertebrates (aquatic animals such as insects, worms and snails) 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 chain and an important component of stream ecosystems.

This section summarises the results from the February/March 2008 round of macroinvertebrate monitoring, undertaken at four Waiarohia Stream sites, 32 RWQMN sites, and five rivers both upstream and downstream of consented activities in Northland.

The monitoring was carried out following the standard protocol 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:

· Species richness;

· Macroinvertebrate Community Index (MCI);

· Semi Quantitative Macroinvertebrate Community Index (SQMCI); and

· The percentage of Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) taxa (%EPT taxa).

Photo: Macroinvertebrate sampling in the Waipoua River

Biotic Indices Results

The table below shows the four biotic index scores for all sites monitored in 2008. 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, orange and yellow indicate moderate water quality and green 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 24 79.2 3.03 20.8
Russell Road Bridge North 28 91.4 4.08 32.1
Kamo tributary 7 60 3.89 0.0
Whau Valley Road 23 91.3 3.73 30.4

RWQMN Sites

Site description Species richness MCI SQMCI %EPT taxa
Waipoua @ SH12 Rest area 29 135.2 8.21 72.4
Opouteke @ Suspension Bridge 20 88 3.55 35
Mangakahia @ Twin bridges 19 88.4 3.1 36.8
Waipapa @ Forest Ranger 29 126.2 6.49 55.2
Kaihu @ gorge 24 86.7 2.73 29.2
Mangahahuru @ Main Road 28 100.7 6.05 35.7
Waimamaku @ SH12 24 106.7 3.56 50
Victoria @ Thompsons Bridge 26 118.5 6.28 50
Waipapa @ Kerikeri 8 97.5 4.99 25
Kerikeri @ Stone Store 20 84 3.28 30
Mangamuka @ Iwitaua Road 20 101 6.6 50
Waitangi @ Waimate North 29 93.8 5.07 31.0
Waitangi @ Watea 17 80 3.67 11.8
Whakapara @ Cableway 22 79 4.02 22.7
Waipao @ Draffin Road 15 98.7 4.2 53.3
Mangakahia @ Titoki 18 86.3 4.25 33.3
Ngunguru @ Waipoka Road 2 90 4.5 0
Kaeo @ Dip Road 7 122.9 6.04 42.9
Punakitere @ Taheke Recorder 24 93.3 4.57 45.8
Oruru @ Bowling club 11 83.6 4.16 27.3
Waiotu @ SH1 11 86 3.54 45.5
Awanui @ FNDC water take 20 95 4.09 45
Mangahahuru @ Apotu Road 13 76.7 3.77 30.8
Waiharakeke @ Foot Bridge 6 104 4.01 50
Paparoa @ Foot Bridge 11 89.1 4.55 9.1
Hakaru @ U/S of SH1 19 72.6 4.17 21.1
Wairua @ Purua 13 80 4.47 15.4
Utakura @ Horeke Road 8 92.5 4.18 25
Awanui @ Waihue channel 5 105 4.16 40
Mangere @ Knights Road 22 72.4 4.22 9.1
Ruakaka @ Flyger Road 22 102.7 4.97 40.9
Manganui @ Permanent station 13 83.1 4.17 15.4

Resource Consent Sites

Site description Species richness MCI SQMCI %EPT taxa
Dam downstream 15 68 3.14 13.3
Dam upstream 20 123 7.15 50
Oxidation pond A downstream 18 71.8 3.45 5.6
Oxidation pond A upstream 10 84.4 3.93 10
Meat works downstream 12 86.7 4.21 16.7
Meat works upstream 6 104.0 4.01 50
Oxidation pond B downstream 17 107.1 3.58 52.9
Oxidation pond B upstream 17 103.5 5.89 52.9
Quarry downstream 14 108.6 4.73 35.7
Quarry upstream 11 90.9 3.77 18.2

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

Macroinvertebrate Results Summary

Waiarohia Stream Sites

As for 2007, the results from 2008 indicate that three of the Waiarohia Stream sites; at Rust Ave Bridge, at the Northern Russell Road Bridge and Whau Valley Road, have macroinvertebrate communities associated with moderate to degraded water quality. The results for the small tributary that flows from Kamo into Waiarohia Stream indicate a macroinvertebrate index score indicative of a severely degraded stream with poor water quality.

River Water Quality Monitoring Network Sites

Based on MCI and SQMCI values, macroinvertebrate results for 2008 indicated clean water at four RWQMN sites; Waipoua River at SH12 rest area, Waipapa River in Puketi Forest, Victoria River at Thompsons Bridge, and Mangamuka River at Iwiatua Road Bridge. This is consistent with the water quality results for these sites. The MCI results also indicated clean water for the Kaeo River at Dip Road however caution should be taken with low diversity communities such as this.

Macroinvertebrate results for 2008 indicate that the following sites are severely impacted and/or have poor water quality:

· Hakaru River upstream of SH1

· Mangahahuru River at Apotu Road

· Mangere River at Knights Road

· Whakapara River at Slipway

Trend analysis on 22 of the 32 RWQMN sites sampled shows that stream health is increasing in the Waipoua River based on MCI and SQMCI results. However, four sites - Waiarohia Stream at Whau Valley Road, Punakitere River at Taheke Recorder, Opouteke River at Suspension Bridge and Waiotu River at SH1 Bridge - appear to have decreasing stream health.

Resource Consent Sites

In 2008, macroinvertebrate communities upstream and downstream of the discharges of two oxidation ponds, one dam, one quarry and one meatworks were sampled.

The results show a difference in macroinvertebrate communities upstream and downstream of the two oxidation ponds. The macroinvertebrate index scores downstream of both discharges indicated poorer water quality and more degradation when compared to the upstream samples. However, some of this difference could be attributed to changes in surrounding land use. Results for the dam site also indicated poorer stream health downstream of the discharge when compared to upstream.

Macroinvertebrate results for the meatworks and quarry consent sites indicate that these discharges are having a limited impact on water quality and stream health.


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.