Comparative assessment of N₂O emissions from a New Zealand hypereutrophic lake against an oligotrophic reservoir

Figures & data

Table 1. Summary of the monitoring from Lake Horowhenua (LH, n = 66) and the Turitea water reservoir (TR, n = 53), data represent min value – max value (average in parenthesis).

Site	Water T (°C)	Cond (µS/cm)	DO (mg/L)	pH	Chla (mg/L)	TSS (g/L)	N-NO2^− (µg/L)	N-NO3^− (µg/L)	P-PO4^3− (µg/L)	N2O (µg/L)
LH – 5 m	6.0–32.0 (17.8)	148–409 (238)	0.94–21.2 (9.96)	6.2–9.5 (7.7)	0.01–10.1 (0.76)*	0.01–2.58 (0.20)	1.20–99.3 (22.9)	1.66–3432 (862)	2.14–435 (83.3)	0.21–13.3 (1.18)
LH – 15 m	6.10–31.4 (17.3)	162–943 (240)	0.26–15.5 (9.28)	6.2–9.2 (7.6)	0.01–5.47 (0.42)*	0.01–2.24 (0.12)	1.99–98.4 (23.4)	0.78–3420 (1028)	5.28–1515 (104)	0.29–10.0 (1.13)
TR – 5 m	9.0–20.9 (14.2)	75.2–174 (88.3)	7.76–11.63 (10.0)	6.1–9.9 (8.1)	0.0–0.02 (0.00)	0.00–0.21 (0.01)	1.15–10.3 (3.34)	0.18–343 (155)	0.33–246 (17.2)	0.00–2.04 (0.61)
TR – 5 m`	8.60–21.0 (14.0)	75.7–95.2 (86.0)	7.95–11.8 (10.1)	6.6–9.8 (10.1)	0.0–0.01 (0.00)	0.00–0.04 (0.01)	0.00–6.85 (2.79)	0.00–294 (130)	0.42–164 (14.4)	0.00–1.53 (0.56)

For each site, the sampling location had no statistical impact on any of the parameters recorded (p-value > 0.05, two-tails t-test, α = 0.05).

*Median value of 0.028 and 0.025 mg-Chla/L for LH – 5 m and LH – 15 m, respectively.

Table 2. N₂O Fluxes (mg·m⁻²·d⁻¹) reported from studies focusing on greenhouse gases emissions from lakes and reservoirs and acknowledging a relation between emissions and the presence of primary producers.

Ecosystem	N2O			References
	Min	Max	Mean
Lakes (Oligo – Eutrophic)	0.32	0.74	n.s.	Mengis 1997
Hypereutrophic lake	−6.36	50.4	1.38	Wang et al. 2006
Eutrophic reservoir	0.20	2.24	1.14	Deemer et al. 2011
Lakes – high N deposition	0.00	10.6	1.66	McCrackin and Elser 2011
Lakes – low N deposition	0.00	1.66	0.16
Lakes and reservoirs	−0.35	9.06	0.23	DelSontro et al. 2018
Eutrophic lake	0.01	1.93	0.17	Miao et al. (2020)
Reservoir	−0.02	1.51	0.15*	This study
Hypereutrophic lake	−0.05	6.93	0.30*	This study

*Median.

Figure 1. Seasonal distribution of N₂O dissolved concentration (µg·L⁻¹) at Lake Horowhenua (left) and the Turitea reservoir (right).

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