Title: Nutrient Dynamics in Four Macrophyte Species in a Flood Wetland along the Little Ruaha River in Iringa Municipality, Tanzania

Author: Francis M.M. Chale

Faculty of Science and Technology, Teofilo Kisanji University, P.O. Box 1104, Mbeya, United Republic of Tanzania.

*Correspondence: francischale@gmail.com

Abstract

Studies were carried out on nutrient dynamics in a flood wetland in a tropical environment. The studies involved wetland water quality characteristics, nutrient accumulations in four macrophyte species and in the sediments. The plant species studied included: Polygonum senegalense, Ludwigia stolonifera, Typha domingensis and Cyperus dives. Standard methods were used for water quality characterization, and for the plants, nutrient levels were determined in the various plant organs. Dried and milled below-ground and above-ground plant organs were digested with a strong oxidizing agent, after which total nitrogen and total phosphorus determined. Sediment sample treatments and analyses were as described for the plant materials. The water had pH 6.45. Ammonium nitrogen and soluble reactive phosphorus concentrations were 0.20 mg l-1 and 0.18 mg l-1, respectively. Total nitrogen and phosphorus in the water were 0.99 mg l-1 and 0.33 mg l-1, respectively. L. stolonifera accumulated 10.89 mg g-1 nitrogen and 5.92 mg g-1 phosphorus, which were the highest for the four plant species. C. dives accumulated a mean of 6.81 mg g-1 nitrogen and 2.72 mg g-1 phosphorus. P. senegalense plants had averages of 6.55 mg g-1 and 2.49 mg g-1, nitrogen and phosphorus, respectively. T. domingensis accumulated the least amounts of the nutrients, being 2.04 mg g-1 nitrogen and 0.60 mg g-1 phosphorus. The above-ground plant components had on average higher nutrient levels than the below-ground plant components. L. stolonifera can be classified as a hyperaccumulator for the two nutrients and could be used in wastewater treatment. T. domingensis seems to be the least suited in water treatment.

Keywords: Flood wetland, Nutrient dynamics, Polygonum senegalense, Ludwigia stolonifera, Cyperus dives, Typha domingensis