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)

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