River and stream water quality and ecology - Greater Wellington ...

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Variable Explanation/relevance Nutrients - Nitrogen - Phosphorus River and stream water quality and ecology in the Wellington region: State and trends Vital elements for aquatic plant and algal growth – may be limiting factors in plant growth when in short supply but in sufficient quantities they may also promote unsightly algal blooms and nuisance plant growth. Dissolved inorganic nutrient concentrations (ammoniacal nitrogen, nitrite-nitrate nitrogen and dissolved reactive phosphorus) are most relevant for predicting the potential for nuisance plant growth as they are the principal forms available to plants (ie, soluble). Total nutrient concentrations are also relevant in surface waters, because particulate matter can settle out in quiescent areas and become biologically available to plants via mineralisation. Nitrate, in sufficient concentrations, is harmful to livestock and humans, and toxic to aquatic life. Ammoniacal nitrogen comprises ammonium (NH4+) and unionised ammonia (NH3). Ammonia is rarely found in any significant amounts in natural waters and its presence most commonly indicates the presence of domestic, agricultural or industrial effluent. Ammonia is very soluble in water and can be toxic to aquatic life, especially fish. Toxicity is a function of both temperature and pH, with toxicity increasing with increasing water temperature and alkalinity. E. coli Indicator of pollution with faecal matter, useful for determining the suitability of waters for contact recreation and stock drinking – presence in water may indicate the presence of harmful pathogens that can cause eye, ear, nose and throat infections, skin diseases, and gastrointestinal disorders – a number of parasites and pathogens can also be transmitted by contaminated water to livestock and affect their health. E. coli is the most specific indicator of faecal contamination and is nearly always found in high numbers in the gut of humans and warm blooded animals. E. coli is the preferred microbiological indicator for faecal contamination and health effects in fresh waters. Heavy metals Natural elements of which some (eg, copper and zinc) are essential for metabolism. Can be toxic to aquatic life at higher concentrations and tend to bioaccumulate. Toxicity can vary depending on many factors, including water temperature, pH and hardness. Periphyton Periphyton is the slimy material attached to the surfaces of rocks and other bottom substrate in rivers and streams. It comprises algae, diatoms, bacteria, and fungi and plays a key role in aquatic food webs because it is the main source of food for benthic invertebrates, which in turn are an important food source for fish. Excessive periphyton growths may block intake screens for water supply, and reduce the aesthetic, recreational and ecosystem values of rivers and streams. Macroinvertebrates Macroinvertebrates are organisms that lack a backbone and are larger than 250 microns in size. Four major groups of macroinvertebrates exist: insects such as mayflies, caddisflies and dragonflies; molluscs such as snails and mussels; crustaceans such as freshwater shrimps and amphipods; and oligochaetes, aquatic worm species that live in muddy streambeds. Different macroinvertebrate species have different tolerances to environmental factors such as dissolved oxygen, nutrients and fine sediment, such that the presence or absence of different species in an environment may indicate changes in water quality. Macroinvertebrates indicate long-term water quality conditions compared with spot physico-chemical samples which only represent water quality at time of sampling. WGN_DOCS-#1100598-V3 PAGE 133 OF 160
River and stream water quality and ecology in the Wellington region: State and trends Water quality Variables measured/analysed at each RSoE site are presented in Table A3.2. As far as practicable, individual RSoE monitoring sites are sampled at the same time of the month (and usually at the same time of the day) throughout the year 36 , and where possible all sites on a river or stream are sampled on the same day. Water samples are collected in mid stream (where possible), typically in run-type habitat from a representative reach of stream. Samples requiring laboratory analysis are placed in chillibins with ice and couriered overnight to RJ Hill Laboratories in Hamilton. Field meters are calibrated on the morning of the day of sampling. Table A3.2: Current field and analytical water quality methods and detection limits Variable Method Detection limit Water temperature Field Meter – generally YSI 550A and YSI 556 meters 0.01 ºC Dissolved oxygen Field Meter – generally YSI 550A and YSI 556 meters 0.01 mg/L Visual clarity Black disc (20 mm disc if clarity 1.5 m) 0.01 m pH Field Meter – generally YSI 550A and YSI 556 meters 0.01 units Conductivity Field Meter – generally YSI 550A and YSI 556 meters 0.1 uS/cm Turbidity Analysis using a Hach 2100N, Turbidity meter. APHA 2130 B 21 st ed. 2005 0.05 NTU Total suspended solids Gravimetric. APHA 2540 D 21 st ed. 2005 2 mg/L Total organic carbon Ammoniacal nitrogen Nitrite Catalytic oxidation, IR detection, for Total C. Acidification, purging for Total Inorganic C. TOC = TC – TIC. APHA5310 B 21st ed. 2005 Filtered sample. Phenol/hyperclorite colorimetry. Discrete Analyser. (NH4-N = NH4+-N + NH3-N) APHA 4500-NH3 F (modified from manual analysis) 21st ed. 2005 Automated Azo dye colorimetry, Flow injection analyser. APHA 4500- NO3 - I (proposed) 21st ed. 2005 0.5 mg/L 0.001 mg/L 0.002 mg/L Nitrate Calculation: (Nitrate-N + Nitrite-N) – Nitrite-N 0.002 mg/L Nitrate + nitrite nitrogen Total oxidised nitrogen. Automated cadmium reduction, Flow injection analyser. APHA 4500-NO3 - I (Proposed) 21st ed. 2005 0.002 mg/L Total Kjeldahl nitrogen Kjeldahl digestion, phenol/hyperclorite colorimetry (Discrete Analysis). APHA 4500-N Org C. (modified) 4500-NH3 F (modified) 21st ed. 2005 0.1 mg/L Total nitrogen Calculation: TKN + Nitrate-N +Nitrite-N 0.1 mg/L Total phosphorus Dissolved reactive phosphorus Total Phosphorus digestion, ascorbic acid colorimetry. Discrete Analyser. APHA 4500-P E (modified from manual analysis) 21st ed. 2005 Filtered sample. Molybdenum blue colorimetry. Discrete Analyser. APHA 4500-P E (modified from manual analysis) 21st ed. 2005 0.004 mg/L 0.004 mg/L Faecal coliforms APHA 21st ed. Method 9222D 1 cfu/100mL E. coli APHA 21st ed. Method 9222G 1 cfu/100mL Dissolved copper Filtered sample, ICP-MS, trace level. APHA 3125 B 21 st ed. 2005 0.0005 mg/L Dissolved lead Filtered sample, ICP-MS, trace level. APHA 3125 B 21 st ed. 2005 0.0001 mg/L Dissolved zinc Filtered sample, ICP-MS, trace level. APHA 3125 B 21 st ed. 2005 0.0010 mg/L 36 Some variation has occurred as a result of changes in sampling rounds/personnel. PAGE 134 OF 160 WGN_DOCS-#1100598-V3
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River and stream water quality and
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DISCLAIMER This report has been pre
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observed trends were unclear. The p
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5. Periphyton - state and trends 57
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Figure 2.1: RSoE monitoring sites a
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2.4.2 Biological variables River an
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4.2 Temporal trends River and strea
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TN (mg/L) Temperature ( 0 c) Shade
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Chlorophyll a (mg/m 2 ) 90 80 70 60
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25th percentile summer time flow m
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RS06 Shade RS11 Habitat RS35 RS49 R
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