Sufia Zaman

RISING WATER SALINITY: A THREAT TO MANGROVES OF INDIAN SUNDARBANS

Abstract Mangroves constitute an important ecosystem because of their global extent and high productivity. These plants thrive in the intertidal zones of the tropics and subtropics that are characterized by regular tidal inundation and fluctuating salinity. Mangrove species are well adapted, both morphologically and physiologically, to survive under saline conditions, but in hypersaline environment their growth is reduced. The present chapter is a critical analysis on the impact of salinity on the growth of a common mangrove species (Hertiera fomes). The analysis has been carried out in the framework of Indian Sundarbans, which has contrasting salinity profiles in different segments owing to barrage discharge and siltation phenomena. Analysis of the decadal profile of salinity indicates a gradual lowering in the western Indian Sundarbans due to Farrakka barrage discharge and run-off from catchments. The central sector, however, exhibits a contrasting picture of increment of aquatic salinity through time, mainly due to disconnection of the Bidyadhari River with the Ganga–Bhagrirathi–Hooghly River system (in the western part). This has made the Matla River in the central Indian Sundarbans hypersaline in nature (that used to get water from the Bidyadhari River) finally leading to an insecure ecological condition for the growth and survival of mangroves. The possible remedial measures to combat the situation have also been listed considering the ecological framework of the study zone.

Decadal Variation of Nutrient Level in Two Major Estuaries in Indian Sundarbans

The impact of the nutrient level on the water quality in the Hooghly and Matla estuarine complex in Indian Sundarbans was assessed for three decades (1984-2014). Nitrate, phosphate and silicate were used as indicators of nutrient related water quality in the estuarine water. Our first order analysis reflects significant spatio-temporal variations of selected nutrients with relatively higher values in the Hooghly estuary (in the western Indian Sundarbans) compared to the Matla estuary (in the central Indian Sundarbans). Significant variations were observed in dissolved nitrate, phosphate and silicate concentrations between stations and years (p < 0.01). Such pronounced variations may be attributed to the location of highly industrialized and urbanized city of Kolkata, Howrah and Haldia port-cum-industrial complex adjacent to the Hooghly estuary. The sudden rise of selected nutrients during premonsoon, 2009 (irrespective of sampling stations) is directly related to AILA, a super-cyclone that occurred in the lower Gangetic delta during 22nd 25th May, 2009.

Study of the Microbial Health in and Around the Lower Stretch ofHooghly Estuary

We investigated microbial load and few common hydrological parameters in the Hooghly Estuarine stretch of the Maritime State of West Bengal (India). The study site is located in the Lower Gangetic Delta and is the western part of the famous mangroves ecosystems of Indian Sundarbans. We observed significant spatial variations of all hydrological parameters (except surface water temperature) which are mainly due to the proximity of the stations to the Bay of Bengal. Significant spatial variations were also observed in the Total Bacterial Count (TBC), Fecal Coliform (FC) count, Total Coliform (TC) count, E. coli count, Streptococcus sp. count, which can be related to the type and magnitude of anthropogenic activities operating in and around the selected stations. A long term monitoring is required to understand the spatio-temporal variations of hydrological parameters and microbial load in the Lower Gangetic Delta as it sustains a unique genetic diversity in the Indian subcontinent

Signal of Climate Change through Decadal Variation of Aquatic pH in Indian Sundarbans

Repeat hydrographic and time series data for 30 years in the western Indian Sundarbans exhibit direct evidence for acidification of estuarine water. The long-term trend in surface water pH is interpreted as signal of climate change and its possible causes are briefly outlined in this first-order analysis. The significant spatio-temporal variation of surface water pH can be attributed to factors like seawater intrusion into the estuary from Bay of Bengal, sewage discharge (from point and nonpoint sources) and photosynthetic activity by the mangrove vegetation that exhibit variable biomass and area around the selected stations. The sudden rise of surface water pH during 2009 in all the stations is a direct consequence of sea water intrusion during AILA, a super cyclone that hit Sundarbans on 25th May, 2009. The significant negative correlation of mangrove vegetation pool (assessed from AwiFS data for June 2010) with percentage of pH fall (r = - 0.6978; p <0.01) strongly supports the positive influence of mangrove photosynthetic activity in shifting the equilibrium towards alkalinity.

Status of Heavy Metal in the Lower Gangetic Delta: Implication of Acidification on Compartmentation

Increased atmospheric carbon dioxide concentrations are causing greater dissolution of carbon dioxide into the estuarine water, which is the key factor behind today’s ongoing ocean acidification and subsequent compartmentation of heavy metals in the system. We conducted a long term survey on temporal variation of pH and its impact on heavy metals in the Matla estuary, situated in the central part of Indian Sundarbans. The present study indicates the key role of acidification (major driver) in the exchange of heavy metals from sediment compartment to the overlying aquatic phase. The lowering of pH favours the process of dissolution of selected heavy metals (Zn, Cu and Pb) and promotes the transference of metallic compounds from the sediment to the aquatic phase.

ANTIBACTERIAL ACTIVITY OF MARSILEA QUADRIFOLIA: A FLORAL SPECIES

Investigation was undertaken to evaluate antibacterial activity of the aquatic fern named as Marsilea quadrifolia against various gram positive and gram negative multi drug resistant bacteria through disc diffusion assay. The ethyl acetate extract of this plant is more effective in terms of antibacterial activity than water extract which indicates that ethyl acetate solvent extracted the active components from the plant parts in a more efficient way compared to water extract.

Get Nutrition and Cool the Earth

The present paper is an attempt to assess the carbon and nitrogen percentages in the Above Ground Biomass (AGB) of wheatgrass (Triticaum aestivum) collected from the organic garden of Techno India University, West Bengal after a period of 14 days from the date of sowing seeds on 4 March, 2017. The carbon percentage ranges between 30.99% to 31.92% (mean value = 31.51 ± 0.404). The nitrogen percentage is significantly less compared to carbon value (1.26% 1.31%; mean value = 1.292± 0.016). The stored carbon and nitrogen levels in the seedlings suggest the species as a potential sink of green house gases.

Impact of Aquatic Salinity on Mangrove Seedlings: A Case Study on Heritiera fomes (Common Name: Sundari)

Mangroves are the characteristic littoral plant formation of tropical and subtropical sheltered coastlines [1]. Being on the land sea interface, they are always associated with and subjected to saline seawater. However saline condition is not a prerequisite for their development, rather mangroves choose saline condition to avoid the competition with the more vigorous terrestrial plants. Based on the physiological studies, Bowman [2] and Davis [3] concluded that mangroves are not salt lovers, rather salt tolerants. But excessive saline conditions retard seed germination, impede growth and development of mangroves. Indian Sundarbans, the famous mangrove chunk of the tropics is gradually losing Heritiera fomes (commonly known as Sundari) owing to increase of salinity in the central sector of the delta complex around the Matla River. Reports of alteration of growth in mangroves due to difference in salinity between western and central sectors of Indian Sundarbans are available [4]. However no study has yet been carried on the effect of salinity fluctuation on the photosynthetic pigments and carotenoid level of mangroves under culture conditions from this part of the Indian sub-continent. The effects of salinity on mangroves have been studied in relation to antioxidative enzymes [5,6], leaf structure, rates of transpiration, stomatal conductance and rates of photosynthesis [7,8] and changes in chloroplast structure and function [5,9]. Reported that Na+/H+ antiport catalyzed exchange of Na+ for H+ across the vacuolar membrane of the cells of Bruguiera sexangula offered tolerance to ionic stress imposed by NaCl and this mechanism was important for cellular salinity adjustments. Also, the mechanism of acclimation to salt in mangroves was suggested to be linked to the changes in the vacuolar size in B. sexangula [10]. Further, one of the biochemical mechanisms by which mangroves counter the high osmolarity of salt was accumulation of compatible solutes [5].

How Bruguiera gymnorhizza seedlings respond to climate change induced salinity rise

A study was undertaken during August 2017 to evaluate the effect of salinity on chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid and proline contents of hydroponically grown seedlings of Bruguiera gymnorhizza. The primary aim was to observe its tolerance to changing salinity. The selected seedlings were exposed to fi ve different salinity levels (2,5,10,15 and 20psu) for a period of 30 days and observations were done at a regular interval of 7,14,21 and 30 days respectively. The concentrations of chlorophyll exhibited signifi cant positive correlations with salinity (p<0.01). The chlorophyll a:b ratio in the plant varied between 2.39 to 3.71 throughout the period of investigation. The salinity fl uctuation did not affect the carotenoid level and proline content in the leaves of the species as evidenced from the insignifi cant r values. The results show that Bruguiera gymnorhizza of Indian Sundarbans region can tolerate and adapt to high saline condition as witnessed in the central sector of the deltaic complex around the Matla River. Research Article How Bruguiera gymnorhizza seedlings respond to climate change induced salinity rise? Prosenjit Pramanick1, Subrata Trivedi2, Sufi a Zaman1 and Abhijit Mitra3* 1Department of Oceanography, Techno India University West Bengal, Salt Lake Campus, Kolkata 700091, India 2Department of Biology, Faculty of Science, University of Tabuk, Ministry of Higher Education, Kingdom of Saudi Arabia 3Department of Marine Science, University of Calcutta, 35 B.C. Road, Kolkata 700019, India *Address for Correspondence: Abhijit Mitra, Department of Marine Science, University of Calcutta, 35 B.C. Road, Kolkata 700019, India, Email: abhijit_mitra@hotmail.com Submitted: 15 September 2017 Approved: 20 September 2017 Published: 22 September 2017 Copyright:

Mangrove Health Card: A Case Study on Indian Sundarbans

Relative abundance and Shannon-Weiner species diversity index of true mangrove species were estimated in 10 sampling stations of Indian Sundarbans during 2013. The mangrove patches in the selected stations were categorized into a 4-point scale depending on the values of Shannon-Weiner species diversity index. The health of the mangrove forest as per our constructed 4-point scale was found to be regulated primarily by anthropogenic factors, although in station like Sagar South, the natural erosion may be the key player in determining the mangrove floral diversity.