Annual report 2006-2007 - Taranaki Regional Council

taxa was found at site F, slightly above the historical median (Table 3). This richness was
only slightly less than the number of taxa recorded at the nearest upstream site (E) (Figure
2). Three ‘highly sensitive’ taxa were present (indicative of good water quality conditions),
one of which was abundant (Deleatidium mayfly), along with five ‘moderately sensitive’ taxa
(Coloburiscus and Austroclima mayflies, elmid beetles, Archichauliodes dobsonfly and
Aphrophila cranefly); and four ‘tolerant’ taxa (very abundant Aoteapsyche caddisfly, and
abundant orthoclad, Maoridiamesa and Austrosimulium midges). These characteristic taxa
were similar to community compositions at upstream sites and there were very few
significant differences within individual taxon abundances between the adjacent sites E and
F as emphasised by the similar SQMCIS scores (Table 2).
MCI value
Number of taxa and MCI values in the Kahouri Stream u/s of Stratford
CC pow er station (KHI000457)
140
120
100
80
60
40
20
0
Jan-88
Jan-89
Jan-90
Jan-91
Jan-92
Jan-93
Jan-94
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
Jan-04
Jan-05
Jan-06
Jan-07
MCI value M edian M CI to date
No. of taxa M edian no. of taxa to date
Figure 8 Number of taxa and MCI values in the Kahouri Stream at site F (KHI000457)
Similar to the communities of upstream sites, the community at site F had a moderately high
proportion of ‘sensitive’ taxa (62% of total richness), which was reflected in the MCI score of
96 units, similar to the long term median score (Table 3). The MCI score was slightly (but not
significantly) lower than that recorded at site E upstream, reflective of the loss of two ‘highly
sensitive’ taxa in the community at this site upstream of the Stratford Power Station.
Small differences in community composition between adjacent sites E and F were illustrated
by the small difference in SQMCIs scores which were within 0.5 unit. The score at site F (5.5
units) was significantly higher than the median score recorded by the eight most recent
surveys at this site (Table 2). The MCI and SQMCIs both indicated that there was no real
downstream deterioration of macroinvertebrate communities in the reach of the Kahouri
Stream between site E and F, which is often demonstrated in catchments due to non-point
sources of nutrients (TRC, 1999). This was demonstrated by the median SQMCIs (Figure 3)
which decreased in a downstream direction. This may reflect the generally intact and good
quality riparian vegetation in the Kahouri Stream which may limit effects during summer
low flow conditions.
Site G: Kahouri Stream (KHI000465)
This partially shaded site located downstream of the Stratford Power Station discharges was
about 1 km downstream of site F, and downstream of discharges from the power station. A
community richness of 22 taxa found at this site was very similar to the historical median
(Table 3). Two ‘highly sensitive’ taxa were recorded, reflecting good water quality
conditions, and one of these taxa was abundant (Deleatidium mayfly). The community was
also characterised by eight ‘moderately sensitive’ taxa (Coloburiscus and Austroclima
11
70
60
50
40
30
20
10
0
No. of taxa