Ammonia, anhydrous

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline available

Principles of method if other than guideline:

Zostera marina L. plants were subjected to water ammonium and nitrate concentrations of 9:3, 25:25, 2550, 25:125, 75:75 and 12525 pM, respectively. We used 2 sediment types, mud and sand, and 2 (growing season) temperatures, 15 and 20°C. The ammonium: nitrate treatment of 2550 pM was applied at 15°C only. The ammonium:nitrate treatment of 9:3 pM was applied at 17°C and on mud only. Sampling was conducted after 2 and 5 wk. The 9:3 treatment was sampled after 3 and 6 wk.

Culture experiment. Zostera marina plants were collected and rinsed in the harbour-canal of Goes (SW Netherlands, 51" 32' N, 3" 50' E, 12 October 1992). The plants for the arnrn0nium:nitrate 9:3 FM treatment were collected in the Wadden Sea (Eems and Terschelling, 53" 22'N, 5" 13'E, 11 August 1993). The plants were transported (at 8 °C, corresponding to the temperature in Goese Sas) to the laboratory, and maintained overnight at 4°C. The following day, pairs of plants were placed in 75 mL jars filled with coarse sand or mud originating from dune sand or from a Z. marina habitat in Zandkreek, respectively (both in the Netherlands). A thin layer of sand was put over the mud to counter nutrient exchange with the overlying water. Twenty jars per container were placed in 18 containers filled with synthetic sea water (25.4% S, Wimex, of Wiegandt GmbH, Krefeld, Germany), and maintained under an 8 h dark:16 h light cycle corresponding to growing season conditions; light intensity just below the water is surface averaged 90 µE m-1 S-1. The containers were placed in random sequence in a temperature controlled (15°C) water bath. For technical details of the set-up, see Roelofs et al. (1984). The plants were allowed to acclimate for 3 wk. Macroalgae were removed, with caution taken not to damage the plants, from the second week onwards (in situ, water dynamics would have im.peded macroalgal growth). On 5 November 1992 (9:3 treatment: 27 August 1993), the treatments started: NaN03 and NH,Cl enriched synthetic sea water was pumped through the containers. In making the stock solutions, it was calculated that the 25.4 permille S synthetic sea water (Wimex, 3 batches tested) already contamed 10 pM ammonium and 25 pM nitrate on average Sea salts of Reef Crystals (Aquarium Systems, Sarrbourg, France, 3 batches) were also tested, and appeared to contain even more ammonium and/or nitrate on average, which was also the case with Rila sea salts, tested by Rohrmann et a1 (1992) Also, the variation was larger in Reef Crystals sea salt than in Wimex sea salt. The ammonium nitrate 9:3 µM treatment was applied using a self-prepared saltmix, derived from uncontaminated 'pro analysis´ salts. Regrettably, it was too expensive and time-consuming to prepare this mix for all treatments. Each container was replenished once a day from its own stock container The containers for the 20°C treatment were thermostatically heated Water In the containers was gently aerated to ensure complete mixing.

GLP compliance:

no

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

other: Zostera marina

Details on test organisms:

See method description above

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

6 wk

Test temperature:

15, 17 and 20°C

Salinity:

25.4 permille

Nominal and measured concentrations:

9, 25, 75 and 125 µM

Details on test conditions:

See method description above.

Reference substance (positive control):

no

Duration:

6 wk

Dose descriptor:

NOEC

Effect conc.:

9 µmol/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth, number of shoots, necrosis

Reported statistics and error estimates:

Analysis of variance was used in this split-plot experiment (sediment type being a subplot factor, the containers being the experimental unit), whereby N-treatment, temperature and their interaction were tested with the following error-term: N-treat-ment X temperature X replicate + N-treatment X replicate + temperature X replicate, and sediment type and the interactions of sediment type with the other parameters were tested against the residual error (Steel & Torrie 1980, Freund & Littell 1985). For comparison of means, Tukey's test was used. The ANOVA and Tukey's test were carried out uslng the Statistical Analysis System, procedure GLM (SAS 1989).

Validity criteria fulfilled:

not applicable

Conclusions:

The NOEC for Zostera marina is 9µM (= 153 µg/L) when exposed via the water phase. 25 µM resulted in significant necrosis.

Executive summary:

The NOEC for Zostera marina is 9µM (= 153 µg/L) when exposed via the water phase. 25 µM resulted in significant necrosis.

Description of key information

The NOEC for Zostera marina is 9 µM (= 153 µg/L) when exposed via the water phase. 25 µM resulted in significant necrosis.

Key value for chemical safety assessment

EC10 or NOEC for marine water plants:

153 µg/L

Additional information

The NOEC for Zostera marina is 9 µM (= 153 µg/L) when exposed via the water phase. 25 µM resulted in significant necrosis.