Sudip Manna

Estimating aboveground biomass in Avicennia marina plantation in Indian Sundarbans using high-resolution satellite data

Abstract Mangroves are active carbon sequesters playing a crucial role in coastal ecosystems. In the present study, aboveground biomass (AGB) was estimated in a 5-year-old Avicennia marina plantation (approximate area ≈ 190     ha ) of Indian Sundarbans using high-resolution satellite data in order to assess its carbon sequestration potential. The reflectance values of each band of LISS IV satellite data and the vegetation indices, viz., normalized difference vegetation index (NDVI), optimized soil adjusted vegetation index (OSAVI), and transformed difference vegetation index (TDVI), derived from the satellite data, were correlated with the AGB. OSAVI showed the strongest positive linear relationship with the AGB and hence carbon content of the stand. OSAVI was found to predict the AGB to a great extent ( r 2 = 0.72 ) as it is known to nullify the background soil reflectance effect added to vegetation reflectance. The total AGB of the entire plantation was estimated to be 236 metric tons having a carbon stock of 54.9 metric tons, sequestered within a time span of 5 years. Integration of this technique for monitoring and management of young mangrove plantations will give time and cost effective results.

A comparison of CO2 dynamics and air-water fluxes in a river-dominated estuary and a mangrove-dominated marine estuary

The fugacity of CO2 [fCO2 (water)] and air-water CO2 flux were compared between a river-dominated anthropogenically disturbed open estuary, the Hugli and a comparatively pristine mangrove dominated semi-closed marine estuary, the Matla on the east coast of India. Annual mean salinity of the Hugli Estuary (≈ 7.1) was much less compared to the Matla Estuary (≈ 20.0). All the stations of the Hugli Estuary were highly supersaturated with CO2 (annual mean ~ 2200 µatm) whereas, the Matla was marginally oversaturated (annual mean ~ 530 µatm). During the post-monsoon season, the outer station of the Matla Estuary was under saturated with respect to CO2 and acted as a sink. The annual mean CO2 emission from the Hugli Estuary (32.4 mol C m-2 yr-1) was 14 times higher than the Matla Estuary (2.3 mol C m-2 yr-1). CO2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river-dominated estuary.

Assessment of the spatio-temporal distribution of soil properties in East Kolkata wetland ecosystem (A Ramsar site: 1208)

The present investigation was made to characterize spatial and temporal variations in soil properties and to evaluate possible differences that could be dependent on the tannery effluent discharges, municipal sewage discharges, vegetation cover, soil settlement rate, crop rotation, etc. Soil total organic matter (TOM), cations like, Sodium (Na), Ammonium (NH4), Potassium (K), Calcium (Ca) and Magnesium (Mg) contents in the bank soils and bottom sediments were recorded from seven different characteristic sites in East Kolkata wetland ecosystem, a Ramsar site (Ramsar site No. 1208). The profile maps were constructed by geostatistical methods to describe the spatial distribution as well as temporal variations of all the factors to identify the influences of composite wastewaters. The work was initiated to identify causes and consequences of the waste dumping in the concerned region for the past hundred years and thereby to suggest necessary precautionary measures to prevent further loss of soil quality.

Estimation of Air-Sea CO 2 Exchange and Decadal Change of Surface Water f CO 2 in a Shallow Continental Shelf Using in Situ and Remote Sensing Data During Winter

The air-sea CO2 exchange (fCO2) was estimated in the outer estuary to offshore transition zone of the northern Bay of Bengal using in situ measurements and remote sensing data obtained from moderate resolution imaging spectroradiometer (MODIS) and advanced very high resolution radiometer (AVHRR). The in situ measurements were done during winter months (December, January and February) of the year 2011–12. Sea surface CO2 fugacity (fCO2), sea surface temperature (SST) and chlorophyll-a were measured in situ to develop an empirical relationship with fCO2 but only the SST showed a significant correlation (r 2 = 0.55, n = 64, p < 0.05). This relationship was used to assess fCO2 (water) and its temporal change in decadal scale from the year 2002–2003 to 2011–2012 of the winter months using remotely sensed SST data. The study area acted as a mild sink for atmospheric CO2 at the mean rate of −28 µmol m−2 h−1 (MODIS derived) to −40 µmol m−2 h−1 (AVHRR derived). An overall winter-to-winter increasing trend of fCO2 was observed in the last decade which is accompanied by a similar decrease in the chlorophyll-a concentrations.

Implementing a Spatial Model to Derive Potential Fishing Zones in the Northern Bay of Bengal Lying Adjacent to West Bengal Coast, India

Potential fishing zones (PFZ’s) are those regions where the fishes aggregate due to an abundance of food and they are demarcated by tracing those regions in the ocean, where a sharp sea surface temperature (SST) gradient along with optimal chlorophyll (Chl) concentration co-exists at a given time. In this regard, Indian National Centre for Ocean Information Services (INCOIS) disseminates the daily PFZ forecasts in Bay of Bengal and Arabian Sea to aid the fishermen community. The present study is an endeavor to develop a local spatial model derived Potential Fishing Zone (PFZ) in the northern Bay of Bengal (nBoB) lying adjacent to the West Bengal coast. Satellite derived SST and chlorophyll data obtained for two consecutive winter seasons of 2010–11 and 2011–12 were used to generate line density (LD) raster. Shapefiles of INCOIS predicted PFZs were overlaid on these LD raster to extract the corresponding pixel values. Histogram ranges of the extracted pixels were fixed and same values lying in the LD raster of both SST and chlorophyll other than INCOIS PFZs were detected by a spatial model in ERDAS. The PFZs thus derived were validated against the ground fish catch data and it was observed that good fish catch was seen in the model derived additional PFZs also. The catch per unit effort (CPUE) values was found to be very close to that of the CPUE value of PFZ advisories of INCOIS. However, the CPUE in the non PFZ areas were significantly lower than the former two categories.