COMPARATIVE STUDY ON NITROGEN UPTAKE KINETICS FOR SIX NATIVE ORNAMENTAL VASCULAR AQUATIC PLANTS

Abstract

Evaluating aquatic vascular plants for their nutrient remediation potential in aquaculture waters as biofilters has been found promising in past studies. The ongoing research on new species of plants proved to be equally encouraging. This study evaluated ammonia and nitrate uptake kinetics in six species of native, aquatic vascular plants: Acorus calamus, Decodon verticillatus, Eriophorum angustifolium, Kosteletzkya virginica, Scirpus cyperinus, and Solidago sempervirens. Uptake kinetics was evaluated using the multiple-flask and the perturbation methods and analyzed according to the Michaelis-Menten enzyme kinetics model. The results from ammonia uptake are as follows: K. virginica was found to have the highest rate of uptake (Vₘₐₓ= 2.50µmol*gfw⁻¹ *hr⁻¹), indicating that this species would be the best candidate for areas here pulses of ammonia occur; S. sempervirens (Vₘₐₓ= 1.00µmol*gfw⁻¹ *hr⁻¹), E. angustifolium 0.97µmol*gfw⁻¹*hr⁻¹), A. calamus (Vₘₐₓ0.80µmol*gfw⁻¹*hr⁻¹), and D. verticillatus (Vₘₐₓ= 0.56µmol*gfw⁻¹*hr⁻¹), were found to have a lower rate of uptake, indicating that these species would be good candidates for remediation of areas with continuous deposition of moderate concentrations ammonia. D. verticillatus (Kₘ=10.40) had the highest affinity for ammonia, followed by A. calamus (Kₘ=10.30), S. sempervirens (Kₘ=-17.00), E. angustifolium (Kₘ=47.20), and K. virginica (Kₘ=115.00). S. cyperinus did not exhibit ammonia uptake, but does use nitrate as an nitrogen source. The results for nitrate uptake indicated S. cyperinus with the highest rate of uptake (Vₘₐₓ=0.16µmol*gfw⁻¹*hr⁻¹) and the second highest affinity (Kₘ=49.20). E. ngustifolium (Vₘₐₓ= 0.09µmol*gfw⁻¹*hr⁻¹) had the second highest rate of nitrate uptake, followed by A. calamus (Vₘₐₓ= 0.06µmol*gfw⁻¹*hr⁻¹). However, A. calamus had the highest affinity for nitrate (Kₘ=25.9), where as E. angustifolium had the lowest affinity (Kₘ=250.30). D. verticillatus, K. virginica, and S. sempervirens showed evidence of nitrate uptake, but no saturation. Therefore, for these three species, Michaelis-Menten kinetics did not apply. From the results of this study, all six species that were evaluated are potential remediators for the cleanup of aquaculture waters.