Biomass assessment of floating aquatic plant <em>Eichhornia crassipes</em> - a study in Batticaloa Lagoon, Sri Lanka using sentinel 2A satellite images

Abstract

Batticaloa Lagoon is one of the estuaries in the country which is frequently affected by floating aquatic plants; mainly Eichhornia crassipes. The present study aimed to develop a relationship between field measured and satellite derived biomass that can satisfactorily estimate the spatial distribution of green and dry biomass of the floating aquatic plants in Batticaloa Lagoon. Cloud free six Sentinel-2A images were acquired for the period of March 2017 to February 2018. Real time field measurements of biomass of floating aquatic plants were obtained in 12 locations in two weeks interval. A buffer zone of 3 km was created around the lagoon to obtain Land Use/Land Cover (LULC) distribution to study the influence of surrounding LULC on floating aquatic plants. A number of band ratios and indices were developed using Sentinel-2A images to establish relationships with the field estimated biomass. The LULC analysis revealed that paddy was the abundant land use in the study area and the cultivation was highly seasonal which impacts the distribution of floating aquatic plants in dry and wet seasons. Among 21 tested band ratios and indices, normalized difference red edge index (NDREI, r 2 =0.78) and band ratio B8/B (r 2 =0.67) for the green biomass and band ratio B3/B4 (r 2 =0.73) and NDREI-Narrow (r 2 =0.61) for the dry biomass in dry and wet season showed strong positive correlation with field biomass. The temporal distribution of the estimated biomass also confirmed the potential of Sentinel-2A images to be used as a source of data for monitoring of floating aquatic plants in the lagoon due to high spatial and spectral resolution of NIR and Red edge bands. These estimated biomass maps can be used to identify the locations which are affected by aquatic plants in order to take proper control measures.

Growth of water hyacinth biomass and its impact on the floristic composition of aquatic plants in a wetland ecosystem of the Brahmaputra floodplain of Assam, India

“…The target sample was separated and washed properly in the field to remove debris materials. After properly cleaning the samples, it weighed to obtain the average fresh weight biomass or the amount of green biomass (GM) of each quadrant’s individual stem of water hyacinth ( Delina, Dayawansa & Silva, 2019 ; Madsen & Madsen, 1993 ). The value of average biomass per individual was multiplied by the total number of plants of the particular quadrant to obtain the total biomass.…”

Vegetation indices for Pontederia crassipes Pellegrini & Horn and multitemporal distribution in the Hydroituango reservoir•

“…Our results confirm the important influence of the amount of precipitation on the effectiveness of controls for P. crassipes and highlight the need for differentiated control strategies during the dry and the rainy seasons. It is important to highlight that the positive influence of precipitation on P. crassipes expansion can be compounded when there are crops near or in the flood plain of a water body, leading to increases in water hyacinth cover also during the dry season [33]. Therefore, evaluating the spatial relation between P. crassipes expansion areas and the different land uses around those areas will shed light on additional management strategies at basin level.…”