A remote sensing approach for assessing the invasion of Najas marina in Madu Ganga Estuary, Sri Lanka

Supuni Dhameera Gangani Thennakoon Mudal Silva, Dahanayakage Don Gihan Lakmal Dahanayaka, Mudiyanselage Jayantha Sisirakumara Wijeyaratne


The present study was carried out to determine the distribution of Najas marina, an invasive floral species in the Ramsar site of Madu Ganga Estuary in Sri Lanka using ASTER satellite data. Cloud free ASTER imageries of Madu Ganga Estuary with 15 m resolution were atmospherically corrected using the FLAASH in ENVI software. The NDVI was calculated and unsupervised classification was applied for the study site for each image and the distribution maps of N. marina were developed from 2007 to 2014. Methodology was validated using in situ data, which were collected in 2014 with monthly intervals parallel to ASTER overpass. The derived distribution maps indicated that N. marina was distributed in about 31% of the estuary in April 2014. The highest densities were mostly found in bay areas and peripheral areas. Maps developed for December 2007, December 2009 and December 2013 indicated that there is a temporal variation in the distribution of N. marina over the years. The overall distribution of N. marina has decreased from December 2007 to December 2009 and increased from December 2009 to April 2014. Low water levels and stagnation of water appears to be conducive for the variation of this species. These factors should be taken into consideration when managing the invasion of N. marina in this economically and ecologically important estuary.


Najadaceae, Invasive species, Ramsar wetland, Submerged macrophytes.

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Amarathunga A.A.D., Sureshkumar N., Weerasekara K.A.W.S., Wickramaarachchi W.D.N., Azmy S.A.M. (2010). Study the effect of salinity and nutrients for the growth of Najas marina and its impact to aquatic biodiversity in Madu Ganga Ramsar wetland in Sri Lanka. Proc. 15th International Forestry and Environment Symposium.November26-27, 2010. Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka. pp: 155-163.

Armstrong R. (1993). Remote sensing of submerged vegetation canopies for biomass estimation. International Journal of Remote Sensing, 14(3): 621-627.

Bambaradeniya C.N.B. (2002). The status and implications of invasive alien species in Sri Lanka. Zoos Print Journal, 17(11): 930-935.

Bambaradeniya C.N.B., Ekanayake S.P., Kekulandala L.D.C.B., Fernando R.H.S.S., Samarawickrama V.A.P., Priyadharshana T.G.M. (2002). An assessment of the status of biodiversity in the Madu Ganga Mangrove estuary. IUCN, Sri Lanka.

Cao J.J., Wang Y., Zhu Z.L. (2012). Growth response of the submerged macrophytes Myriophyllum spicatum to sediment nutrient levels and water-level fluctuations. Aquatic Biology, 17: 295-303.

Cooleya T., Andersona G.P., Felde G.W., Hoke M.L., Ratkowskia A.J., Chetwynd J.H., Gardner J.A., Adler-Golden S.M., Matthew M.W., Berk A., Bernstein L.S., Acharya P.K., Milled D., Lewise P. (2002). FLAASH, a MODTRAN4-based atmospheric correction algorithm, its application and validation, IGARSS 2002. IEEE International, 3: 1414-1418.

Dahanayaka D.D.G.L., Tonooka H., Wijeyaratne M.J.S., Minato A., Ozawa S. (2011). Change detection in the channel segment of Negombo Estuary, Sri Lanka using time series satellite data and its possible impacts on estuarine productivity, 9th AFAF, The Asian Fisheries Society. pp: 156-157.

Dahanayaka D.D.G.L., Tonooka H., Wijeyaratne M.J.S., Minato A., Ozawa S. 2012. Monitoring land use changes and their impacts on the productivity of Negombo Estuary, Sri Lanka using time series satellite data. Asian Fisheries Science, 25: 197-212.

Dahanayaka D.D.G.L., Tonooka H., Wijeyaratne M.J.S., Minato A., Ozawa S. (2013). Two decadal trends of surface chlorophyll-a concentrations in tropical lagoon environments in Sri Lanka using satellite and in-situ data. Asian Journal of Geoinformatics, 13(3): 15-25.

Dahanayaka D.D.G.L., Tonooka H., Wijeyaratne M.J.S., Minato A., Ozawa S. (2015). Comparison of three chlorophyll-a estimation approaches using ASTER data acquired over Sri Lankan coastal water bodies. Malaysian Journal of Remote Sensing and GIS, 4(1): 21-29.

Heege T., Fischer J. (2004). Mapping of water constituents in lake constance using multispectral airborne scanner data and a physically based processing scheme. Canadian Journal of Remote Sensing, 30(1): 77-86.

IUCN and CEA (2006). National wetland directory of Sri Lanka. The World Conservation Union, Central Environmental Authority and International Water Management Institute, Colombo, Sri Lanka.

Joshi C., Leeuw J., Skidmore A.K., Andel J., Lekhak H.D., Duren I.C. (2005). Remote Sensing and GIS for mapping and management of invasive shrub Chromolaena odorata in Nepal. Proc. of 8thAGILE Conference on Geographic Information Science, Estoril, Potugal. pp: 71-80.

Kishino M., Tanaka A., Ishizaka J. (2005). Retrieval of Chlorophyll a, suspended solids, and colored dissolved organic matter in Tokyo Bay using ASTER data. Remote Sensing of Environment, 99: 66-74.

Kumudinie O.M.C., Wijeyaratne M.J.S. (2005). Feasibility of controlling accidentally introduced invasive species Chitalaornata in Sri Lanka. Verhandlungen des International ennVerein Limnologie, 29: 1025-1027.

Lyzenga D.R. (1978). Passive remote sensing techniques for mapping water depth and bottom features. Applied Optics, 17(3): 379-383.

Mahalingam J.B., Kumar A. (2014). Evaluation of vegetation cover in Chamarajanagar district using NDVI technique. Research Directions, 2(3):1-5.

McCormick C.M. (1999). Mapping exotic vegetation in the Everglades from large-scale aerial photographs. Photogrammetric Engineering and Remote Sensing, 65(2): 179-184.

Mumby P.J., Green E.P., Edwards A.J., Clark C.D. (1997). Measurement of sea grass standing crop using satellite and digital airborne remote sensing. Marine Ecology Progress Series, 159(6): 51-60.

Narumalani S. (2008). Mapping and modeling of invasive species using Remote Sensing and GIS. www.pnclink.org/pnc2008/english/abs/04-Keynote _1330.pdf.

Nas B., Karabork H., Ekercin S., Berktay A. (2009). Mapping chlorophyll-a through in-situ measurements and Terra ASTER satellite data. Environmental Monitoring and Assessment, 157(1-4): 375-382.

Polley H.W., Johnson, H.B., Mayeux H.S. (1997). Leaf physiology, production, water use, and nitrogen dynamics of the grassland invader Acacia smallii at elevated CO2 concentrations. Tree Physiology, 17: 89-96.

Sakuno Y., Matsunaga T. (2002). Feasibility study for the estimation of primary production using ASTER TIR data in coastal environments. Proceedings of Japanese Conference on Remote Sensing, 32: 49-50.

Sakuno Y., Kunii H. (2013). Estimation of growth area of aquatic macrophytes expanding spontaneously in Lake Shinji using ASTER data. International Journal of Geoscience, 4: 1-5.

USGS (2011). NDVI: The foundation for remote sensing phenology. United States Geological Survey. phenology.cr.usgs.gov/ndvi_foundation.php.

Sangakkara S.M.A.I., Wijeyaratne M.J.S. (2015). Community structures of zooplankton and trophic status of some inland reservoirs in the low country intermediate zone of Sri Lanka. Sri Lanka Journal of Aquatic Science, 20(2): 59-74.

Silva T.M.S.D.G., Wijeyaratne M.J.S. (2015). Factors affecting the invasion of Najas marina, Linnaeus 1753 (Family Najadaceae) in the Ramsar Wetland of Madu Ganga Estuary. Proceeding of the 20th Annual Session of Sri Lanka. Sri Lanka Association for Fisheries and Aquatic Resources.

Zhang X. (1998). On the estimation of biomass of submerged vegetation using Landsat thematic mapper (TM) imagery: a case study of the Honghu Lake, PR China. International Journal of Remote Sensing, 19(1): 11-20.


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