22 7.3.2 Water Physiochemistry Spot water quality measurements were taken at each site at the time of the surveys using a handheld YSI meter. Spot measurements were undertaken during summer, within a particularly hot, dry period of weather. General water quality across the sites was excellent, with measured parameters representative of good ecosystem functionality (Table 5). Water temperatures had a range of 17.9 °C - 18.5 °C across all sites is considered to be fairly high and may be stressful for some invertebrates such as stoneflies (Biggs et. al., 2002). A heatwave was passing over New Zealand with daily high temperatures reaching the high twenties and into the thirties at the time of sampling. Dissolved oxygen levels at all sites were very good, with all sites above the 20th percentile (90%) and sites T-Stream East and WKP-2 above the 80th percentile (Australian and New Zealand Governments, 2018). pH at all sites was near neutral, ranging from 7.57 – 7.95. These values are good for stream life (Biggs et al., 2002). Conductivity levels ranged from 117.5 to 126.4 µS/cm and were indicative of a low level of nutrient enrichment (Biggs et al., 2002). Table 5: Measured water physiochemistry results at freshwater survey sites, January and February 2019. T-Stream West T-Stream East WKP-3 WKP-2 Temp (°C) 18.5 18.5 18.4 17.9 DO (mg/L) 9.8 10.04 9.92 10.30 DO % Sat 104.7 107.1 105.6 108.9 pH 7.95 7.57 7.61 7.79 Conductivity (µS/cm) 118.5 117.5 126.0 126.4 7.3.3 Periphyton Total Periphyton mean cover ranged from 55% at site T-Stream West, to 87% at site WKP-2. periphyton cover group ‘thin/mat film’, or diatoms, was the dominant group at sites T-Stream West, T-Stream East and WKP-2, with an average coverage range of 43% to 56% across the three sites. ‘Medium mat’ was the dominant group at site WKP-3 with 35% cover. The group ‘thick mat’ was only present at site WKP-3, with an average cover of 0.6%. Filamentous algae was rare across the sites. Short filamentous algae was recorded in low coverage at sites TSteam West, WKP-3 and WKP-2. Long filamentous algae was only present at site WKP-2 where it had an average coverage of 23%. Mean periphyton cover for diatoms / cyanobacteria (>3 cm thick) was well below the aesthetic/recreation (1 November – 30 April) guideline value of a maximum streambed cover of 60%, with less than 1% coverage at site WKP-3 only. The mean filamentous periphyton (>2 cm long) cover was below the 30% guideline for aesthetics/recreation and trout habitat and angling, with 23% coverage at site WK-2 (Biggs 2000). Periphyton communities were representative of healthy communities and good water quality. Communities were dominated by diatoms from the phyla Bacillariophyceae, with 16 species identified across all sites. Blue-green algae, or cyanobacteria, were recorded in lower abundance across all sites with seven species identified. Species from the phylas desminds (Zygnemophyceae), golden-brown algae (Cryptophyceae), red algae (Rhodophyta) and flagellates were also recorded at some sites.
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