Land use influences stream nitrate uptake in the Lake Taupo catchment

Abstract

We quantified nitrate (NO 3 ( ) uptake during summer for 11 streams draining into oligotrophic Lake Taupo. Nitrate uptake lengths (S w ) ranged from 258 to 12035 m, uptake velocities (V f ) ranged from 0.2 to 6.8 m/day and removal efficiencies (P r ) ranged from 1% to 59%. Nitrate uptake velocities and areal uptake rates were, respectively, 9-and 26-fold higher for streams in pasture and pine forest land use than in native vegetation. However, average NO 3 ( export from these streams was also 8-fold higher. Our results suggested that NO 3 ( uptake velocity (V f ) was highest in streams with higher dissolved phosphorus (P) concentrations and flow velocities, and smaller benthic substrate size, which were characteristic of catchments dominated by pasture and pine forest land use. Uptake (as removal efficiency, P r ) accounted for an average 16% of the stream NO 3 ( export to Lake Taupo. However, since most uptake is assimilatory, removal from the water column is likely to only represent temporary sequestration of NO 3( and a conversion of inorganic to organic and/or particulate N.

Water quality in New Zealand’s planted forests: a review

“…Hence a minimum concentration of 80% of saturated concentration is required by the Resource Management Act (1991). In most studies, concentrations of DO in mature forests were above this concentration (Collier and Bowman 2003;Collier and Halliday 2000;Matheson et al 2011;Pruden et al 1990). An exception of 72% was recorded in a forested Northland stream by Baillie et al (2005), which the authors attributed to the warmer thermal regimes in this region.…”

“…A preliminary study by Fish (1968) found very low levels of Cu (often below detection (Collier and Bowman 2003;Cooper et al 1987;Fahey and Stansfield 2006;Friberg et al 1997;Harding and Winterbourn 1995;Macaskill et al 1997;Matheson et al 2011;Parkyn et al 2006;Thompson et al 2009;Thompson and Townsend 2004b;Townsend et al 1997;Young et al 2005). The wider range of NO 3 -N/ NO x -N concentrations compared with TN is influenced by studies that measured that measured concentrations of NO 3 -N at the high end of the range and either did not measure TN or measured TN at a lower sampling intensity than NO 3 -N. Death et al 2003;Friberg and Winterbourn 1997;Harding and Winterbourn 1995;Parkyn et al 2006;Quinn et al 1997;Quinn et al 2004;Shearer and Young 2011;Stark and Maxted 2007;Townsend et al 1997.…”

“…Invertebrate communities were characterised by high abundances of more pollution tolerant taxa such as Chironomidae, (Fahey and Stansfield 2006;Friberg et al 1997;Macaskill et al 1997;Matheson et al 2011;Parkyn et al 2006;Thompson and Townsend 2004b;Townsend et al 1997;Young et al 2005). The anomaly of a wider range of NO 3 -N/NO x -N concentrations than TN concentrations in planted forest streams ( Figure 4a) was influenced by Fahey & Stansfield's (2006) Hawke's Bay study and probably due to the lower sampling intensity of TN, capturing a smaller range of concentrations compared with NO 3 -N (sample size for NO 3 -N and TN, 62-64 and 3-4 respectively).…”

Riparian management: A restoration tool for New Zealand streams

“…); (iii) periphytic biofilms can reduce summer stream nitrate loads up to 59%, particularly in shallower, faster‐flowing streams with higher water column P availability (Matheson et al . ); and (iv) vegetated drains have some capacity for nutrient retention (Nguyen & Sukias ). However, in streams with high nutrient concentrations, in‐stream plants may not be able to reduce nutrient loads (O'Brien et al .…”

“…Bankside experimental systems demonstrated declines in instream nutrient uptake by periphyton with increased levels of shading (Quinn et al 1997;Matheson et al 2012) and provided confirmation of the summer-time nutrient uptake potential of watercress (Sukias & McKergow 2010). In situ short-term nutrient addition experiments have shown the following: (i) low-nutrient uptake rates in low-nutrient tussock streams (Simon et al 2005); (ii) nutrient uptake is correlated with periphyton chlorophyll a (Niyogi et al 2004); (iii) periphytic biofilms can reduce summer stream nitrate loads up to 59%, particularly in shallower, faster-flowing streams with higher water column P availability (Matheson et al 2011); and (iv) vegetated drains have some capacity for nutrient retention (Nguyen & Sukias 2002). However, in streams with high nutrient concentrations, in-stream plants may not be McColl (1978), Smith (1992), Hicks (1992), Williamson et al (1996), Davies-Colley (1997) (Tables S1-S3) able to reduce nutrient loads (O'Brien et al 2014).…”