Identification of Macrophyte Indicator Species to Evaluate the Water Quality in Wetland

Abstract

Present study conducted to assess the SP?ti?! yeri?tion of mecrophvte distribution 2nd water quality parameters of a rehabilitated and non-rehabilitated areas of the Diyawannawa wetland with the aim of identifying suitable macrophyte indicator species for water quality monitonng. Sites A, B and C were located in non-rehabilitated area and the sites D, E and F were located in rehabilitated areas in Diyawannawa wetland. The sampling was conducted from April to October 2016. At each site, water pH, temperature, conductivity, sa!inity, total dissolved solids (TDS), dissolved oxygen concentration (DO), biological oxygen demand (BOD5), chemical oxygen demand (COD), depth, visibility, total nitrate (TN), chlorophyli a (Chl a) and total phosphorus (TP) concentration were measured and the percentage cover of macrophytes were recorded. The correlation of percentage cover of macrophyte species to the water quality parameters were assessed using Pemson's correlation analysis. Principal component Analysis (PCA) based on the percentage cover of macrophyte species was performed to identify the characteristic species at each site. M[NITAB 14 software was used for statistical analysis ofdata. The percentage cover of Hydril/a verticil/ata, Pistia straiiotes and Cypreus iria did not show significant spatial variations among rehabilitated and non-rehabilitated areas. Significantly high percentage cover of Nymphaea ampla (64%) and Annona glabra (l I %) were recorded in site A in non-rehabilitated area. Eichhornia crassipes (22%) showed significantly high percentage cover in site B in non- rehabilitated area and site E in rehabilitated area. Cryptocoryne wendtii recorded significantly high percentage cover In sites A (10%) and E (7%), The highest mean percentage cover of Salvinia ;nolesta (30%) were recorded in site E. The spatial variation of physico chemical parameters Indicated significantly high DO in sites E (10.61 mg/l) and F (10.28 mg/l). Significantly high Chl a concentrations were recorded from sites B, E and F. In addition, site F recorded significantly high BOD5 (6.56 mg/l), TN (0.04 mg/l) and COD (454.8 mg/l). There was no significant spatial variation of TP among sampling sites. S. molesta and E. crassipes showed positive correlations with Chl a and TP and N. rubra showed a positive correlation with TN. H. verticillata and P. stratiotes did not show significant correlations with water quality parameters. According to PCA, considering PC scores I to 3, site A in the non-rehabilitated area was characterized by N. ampla and C. wendtii, site B by E. crassipes and P. stratiotes and site C by A. glabra. In rehabilitated area, site D was characterized by C. iria and Ceratophyllum demersum, site E by S. molesta and site F by N, rubra. The PCA based on water quality parameters grouped the sites E and F together and were characterized by high TN and Chl a concentrations. The results of the present study indicated that there is significant spatial variation of percentage macrophyte cover in relation to water quality parameters. Further, this study identified S. molesia and Eichhornia crassipes and N. rubr.a as suitable indicator of Chl a and TP and TN in wetland health monitoring studies.