Decomposers of the Marine and Estuarine Ecosystems

Abstract

Decomposers are widely distributed in the salty blue soup of the planet Earth and occupy a key position in an ecological food chain/web. They are considered as ‘cleaners’ of the ecosystem as they are capable of degrading complex organic matter in to simpler forms. The vast volume of saltwater may be the reason behind the presence of wide variety and large number of decomposers in the marine and estuarine ecosystems.

Appendices

Annexure 7A: Study on the Quality of Edible Oyster in Indian Sundarbans with Respect to Coliform Load

7.1.1 1. Introduction

The Indian Sundarbans is one of the most biologically productive, taxonomically diverse, mangrove-dominated ecosystems of the tropics (Mitra et al. 1992), which has been declared as a World Heritage Site in 1987 by UNESCO. The deltaic lobe is a unique genetic reservoir sustaining a wide spectrum of commercially important finfish and shellfish. In recent times, thrust has been given on the culture of edible oyster, Saccostrea cucullata, as alternative livelihood scheme for the local people (Mitra and Banerjee 2005) It is therefore extremely important to evaluate the quality of meat of these commercially important bivalve species in terms of coliform load. Necessity of such work arises mainly due to discharge of anthropogenic wastes in coastal areas due to which the zone becomes vulnerable in terms of microbial load (Glasoe and Aimee 2004). The microbes from the ambient media often get accumulated in shellfish because of their filter-feeding activity. Under favourable condition, a single large oyster may filter up to 5 l of water per hour. Such a species is thus an effective filter device of particles that enter in the estuarine environment through urban, industrial and municipal wastes (Pommepuy 1996). Considering this property of oyster, some directives have been given in connection to marketing of live bivalves. An EC Directive (91/492/EEC) has defined the health conditions for production and marketing of live bivalves. All Member States are required to classify their harvesting areas into one of three categories according to the level of faecal indicators present in shellfish samples. Shellfish from Category A can be placed directly on the market. They must meet a standard of no more than 230 Escherichia coli per 100 g shellfish flesh (or 300 FC/100 g) as well as other standard for specific pathogens (such as Salmonella), chemicals and algal biotoxins. Shellfish from category B must be purified before marketing, and shellfish from category C must be placed again in clear water for 2 months prior to marketing (Pommepuy 1996) Although such types of classification do not exist in Indian coastal and estuarine shellfish culture area, but a survey was conducted in three sampling stations of Indian Sundarbans during April, 2007 to assess the health of aquatic subsystem and edible oyster in terms of microbial load.

7.1.2 2. Materials and Methods

The present investigation was carried out during the month of April, 2007 at three different stations, namely, Namkhana, Frasergaunje and Sajnekhali. The sampling stations were selected considering the magnitude of anthropogenic pressure. Station 1 (Namkhana) is situated in the western sector of the Sundarbans, which is not only an important fish landing station but also receives the wastewater from Kolkata and nearby Haldia port–cum–industrial complex. Station 2 (Frasergaunje) is also an official fish landing station of the state of West Bengal, but in addition to this activity, the water of this station receives the discharge of several hotels and tourism units located at Bakkhali station. Station 3 (Sajnekhali) is situated in the eastern sector of Indian Sundarbans, which is noted for its wilderness. Anthropogenic stress is minimum in this sampling station owing to presence of mangrove forest. Water samples were collected using water sampler and the sediment samples were collected with the help of the Petersen grab. The water and sediment samples for microbial analysis were immediately transferred into the sterile bottles, and central portions of the sediment samples were aseptically taken and put into sterile polythene bags and transported to the laboratory under ice for bacteriological examinations. Oyster samples were collected from the intertidal zone of the selected sampling stations for carrying out microbial load analysis in terms of total coliform and faecal coliform.

For bacterial analysis, the oyster samples were accurately weighed and blended with 0.1 % peptone buffer and 3 % NaCl diluent for 1 min and finally inoculated taking different dilutions. The incubation was done at 37 °C for 24 h, and the result was expressed from MPN index per gram basis. For bacteriological analysis of water and sediment samples, the standard method as stated APHA 20th Edition, 2001 was followed.

7.1.3 3. Results and Discussion

The station-wise order of microbial contamination in the study area is Namkhana > Frasergaunje > Sajnekhali. This spatial variation may be attributed to the degree of anthropogenic stress. Namkhana and Frasergaunje, being the fish landing sites, are constantly exposed to wastes of complex nature. In addition to decomposed fish products, these sampling stations are also contaminated with zinc, copper and lead released from antifouling paints required for conditioning fishing vessels and trawlers. Sajnekhali, on the other hand, is a wildlife sanctuary with minimum environmental stress. The area sustains unique mangrove vegetation, which acts as agents of bioremediation. The mode of activities and degree of anthropogenic stress have been reflected through microbial load

The result indicates an alarming situation with respect to coliform load in the shellfish tissues sampled from Namkhana and Frasergaunje. Hence, not only depuration but also a proper feasibility report is needed to initiate oyster culture in these areas. Oyster being an edible product needs continuous monitoring with respect to coliform load to overcome the barrier of consumer acceptability, which may otherwise pose an adverse effect on the human health (consumers).

Today, shellfish industry has gained considerable momentum, and different types of molluscs are widely available in the markets (Fig. 7A.1).

Fig. 7A.1

Availability of different aquacultural products in the local market for internal consumption

Marketing of oyster or any aquacultural products (both for internal consumption and export) is a function of purity of the cultured species. Under such circumstances, results of the present work may serve as baseline information for initiating oyster industry in the maritime state of West Bengal (Tables 7A.1, 7A.2, 7A.3, 7A.4, 7A.5 and 7A.6).

Table 7A.1 Total coliform load (five test tube method) in water samples collected from the sampling stations during April 2007

Table 7A.2 Total coliform load (three test tube method) in sediment samples collected from the sampling stations during April 2007

Table 7A.3 Total coliform load (three test tube method) in edible oyster samples collected from the sampling stations during April 2007

Table 7A.4 Total faecal coliform load (five test tube method) in water samples collected from the sampling stations during April 2007

Table 7A.5 Total faecal coliform load (three test tube method) in sediment samples collected from the sampling stations during April 2007

Table 7A.6 Total faecal coliform load (three test tube method) in edible oyster samples collected from the sampling stations during April 2007

Annexure 7B: Study of the Microbial Health in and Around the Lower Stretch of Hooghly Estuary

7.2.1 1. Introduction

Microorganisms such as bacteria, fungi, actinomycetes, etc., are widely distributed in the water and sediment of marine and brackish water environments. They have far reaching effects on the biological as well as the geochemical systems. They also play an important role in the decompositions of organic matter, dissolution of inorganic insoluble salts and regeneration of nutrients. The activities of the total heterotrophic bacteria and the relative abundance reflect the hydrographic structure or the nature and nutrient concentrations in the aquatic environment (Oppenheimer and Wood 1962).

The overloading of nutrients and organic load also provides a favourable environment for the growth and survival of a wide spectrum of microbial strains. The high population densities and activities often common in the coastal areas result in pollution and release of contaminated wastewater. Pathogenic microorganisms such as bacteria and viruses, abundant in human wastes, are often discharged into natural waters with little or no treatment. Survival of microbes in waters depends on many parameters such as biological (interaction with other bacteria) and physical factors (temperature). Numerous studies have been carried out in coastal areas over long periods of time, demonstrating the various abiotic environmental conditions (fluxes, currents, presence of mud and silt, etc.) due to which the distribution of microbes is affected. The under-treated effluents from the coastal population and discharges from industrial belt regions often pose an adverse impact on marine and estuarine species. The members like Salmonella sp., E. coli, faecal coliform, etc., can multiply and survive in the estuarine environment for weeks. The Enterobacteriaceae (Salmonella, E. coli, etc.) occur in the water as a result of contamination from the animal or human origin. This contamination has been normally associated with faecal contamination or pollution of natural waters or water environments, where these organisms survive for a long time (months) or through direct contamination of products during processing. In the entire Gangetic plain, it is the river Hugli that is subjected to heavy pollution load from the industrialized and highly urbanized cities of the Kolkata and Howrah. The discharges from the port–cum–industrial complex of Haldia have aggravated the magnitude of pollution. The marine ecosystem nearest to the city of Kolkata is the Indian Sundarbans, which is the most biologically productive, taxonomically diverse and aesthetically celebrated ecotone in the Indian subcontinent. The untreated and the under-treated sewage of the city of Kolkata and Howrah is responsible for the microbial load. Among microbial flora, the presence of pathogens such as Salmonella, Streptococcus sp., Vibrio sp. and E. coli has been determined. It is thus clear that the present zone of investigation is under severe stress due to municipal discharge containing appreciable amount of sewage generated from municipal and several categories of anthropogenic microbial activities.

7.2.2 2. Aims and Objectives

The present study aims to evaluate the microbial load (total coliform and faecal coliform) in water sample in and around lower stretch of Hooghly river estuary. The area is stressed due to industrial and anthropogenic activities. Now-a-days bacterial indicators are measured instead of pathogenic organisms because the indicators are safer and can be measured with faster, less expensive methods than the pathogen of concern (McGee et al. 1997).

The main objectives of the present study are highlighted:

• To monitor monthly variation of physico-chemical variables during the study periods

• To observe the spatial variation of the selected physico-chemical variables in the study area

• To scan the microbiological parameters during 3 months of the study period

• To monitor the spatial variation of the microbiological parameter in the study area

7.2.3 3. Physiography

7.2.3.1 3.1. The Ecological Profile

The Indian Sundarbans Delta (ISD) is part of the delta of the Ganga–Brahmaputra–Meghna (GBM) basin in Asia. The Sundarbans shared between Indian and Bangladesh is home to one of the largest mangrove forests in the world. The ISD spread over about 9630 km² between 21°40′04″ N and 22°09′21″N latitude and 88°01′56″ E and 89°06′01″ E longitude is the smaller and western part of the complete Sundarbans Delta.

The Indian Sundarbans Delta is bounded by the Ichamati–Raimangal River in the east, by the Hooghly River in the west, by the Bay of Bengal in the South and by the Dampier-Hodges line drawn in 1829–1830 in the north. A little over half of this area has human settlements on 54 deltaic islands; the remaining portion is under mangrove vegetation. Soils of ISD are principally alfisols (older and alluvial soil) and aridisols (coastal saline soil).

The landscape is characterized by a web of tidal water systems. The average tidal amplitude is between 3.5 m and 5 m, with the highest amplitudes in July–August and the lowest in December–January. Of the eight rivers that dominate the landscape, only the Hugli and Ichamati–Raimangal carry freshwater flow of some significance. Being the moribund part of the lower delta plain of the GBM system, the ISD is experiencing both declining freshwater supplies and net erosion, as has been recorded since 1969 (Hazra et al. 2002; Hazra et al. 2010).

The Indian Sundarbans at the apex of the Bay of Bengal (between 21°13′N and 22°40′N latitude and 88°03′E to 89°07′E longitude) is located on the southern fringe of the state of West Bengal (a maritime state in the north-east coast of India). The area of the Indian Sundarbans is 9630 Km². of which the forest area is about 4200 Km². The region is bordered by Bangladesh in the East, the Hooghly river (a continuation of the Ganges river) in the west, Dampier and Hodges Line in the north and the Bay of Bengal in the south. With a considerable degree of maritime characteristics in major portion of the ecosystem, the important morphotypes of deltaic Sundarbans are beaches, mud flats, coastal dunes, sand flats, estuaries, creeks, inlets and mangrove swamps.

The rivers are the live matrix of deltaic complex, on which the unique spectrum of biological diversity is embedded. In Indian Sundarbans, approximately 2069 Km² area is occupied by tidal river system or estuaries which finally end up in the Bay of Bengal. The deltaic complex of Indian Sundarbans is also noted for its seasonality in terms of climatic condition and wind action as highlighted here in brief. Frequent nor’westers are also common in the premonsoon season.

7.2.3.2 3.2. Climate of Indian Sundarbans

The deltaic lobe of Indian Sundarbans experiences a moderate type of climate because of its location adjacent to the Bay of Bengal as well as due to regular tidal flushing in the estuaries. Wave actions, micro- and macrotidal cycles and long-shore currents are recorded in most of the islands of the ecosystems. Coastal processes are very dynamic and are accelerated by tropical cyclones, which is locally called ‘Kal Baisakhi’ (nor’wester). The seasonal climate in study area may be conveniently categorized into premonsoon (March–June), monsoon (July–October) and postmonsoon (November–February). Each season has a characteristics feature of its own, which is very distinct and unique. The oscillations of various physico-chemical variables in different seasons of the year are discussed here in brief.

7.2.3.3 3.3. Wind

The direction and velocity of wind system in the coastal West Bengal are mainly controlled by the north-east and southwest monsoons. The wind from the north and north-east commences at the beginning of October and continues till the end of March. The months of January and February are relatively calm with an average wind speed around 3.5 km/h. Violent wind speed recommences from the southwest around the middle of March and continues till September. During this period, several low-pressure systems occur in this region, a number of which take the form of depressions and cyclonic storms of varying intensity. The air temperature of Sundarbans area varies from 19.0 °C to 34.0 °C and velocity of wind from 0.85 to 4.54 m/s (Saha et al. 1998).

7.2.3.4 3.4. Waves and Tides

The wind is the basic driving force for generating surface waves in the coastal zone of West Bengal. Sea waves in this region rarely become destructive except during cyclonic storms. During nor’westers the wind speed rises above 100 km/h. and is usually accompanied by huge tidal waves. When the cyclonic incidences coincide with the spring tides, wave height can rise over 5 m above the mean sea level. Ripple waves appear in the months of October, November and December when wind-generated wave height varies approximately between 0.20 and 0.35 m. In the months of April to August, large wavelets are formed in the shelf region, and they start breaking when they approach towards the coastal margin. Wave height rises up to 2 m during this period, which causes maximum scoring of land masses. The average tidal amplitude in the estuaries of the Sundarbans ranges from 3.5 to 4.0 m. Wave actions, micro- and macrotidal cycles and long-shore currents are recorded in most of the islands in this ecosystem.

7.2.3.5 3.5. Surface Water Temperature

In coastal West Bengal, the seasonal variation of surface water temperature is not so drastic between premonsoon and monsoon seasons. The premonsoon period (March to June) is characterized by a mean surface water temperature around 34 °C. The monsoon period (July to October) shows a surface water temperature around 32 °C (mean), and the postmonsoon period (November to February) is characterized by cold weather with a mean surface water temperature around 23 °C.

7.2.3.6 3.6. Rainfall

The average annual rainfall in deltaic Sundarbans region is 1920 mm. Rainfall is usually maximum during the month of August/September, and the monsoon period lasts from July to October. The southwest wind triggers the precipitation in the monsoon period with an average rainfall of about 165 mm (Human Development Report, South 24 Parganas, 2009). The postmonsoon (November to February) is characterized by negligible rainfall, and the premonsoon period (March to June) is basically dry but occasionally accompanied by rains and thunderstorms.

7.2.4 4. Materials and Methods

The present programme encompasses the evaluation of microbial load (water) and some related physico-chemical variables such as:

• (a) Surface water temperature

• (b) Surface water salinity

• (c) Surface water pH

• (d) Surface water dissolved oxygen (DO)

• (e) Surface water nitrate (NO₃ ⁻)

• (f) Surface water phosphate (PO₄ ²⁻)

• (g) Surface water silicate (SiO₂)

The work was carried out on a monthly basis from February 2013 to April 2013. Samplings have been carried out at eight different stations in Indian Sundarbans, namely:

• 1. Haldia

• 2. Daimond Harbour

• 3. Lot 8

• 4. Kachuberia

• 5. Chemaguri

• 6. Sagar Island

• 7. Namkhana

• 8. Frasergaunje

The entire work procedure has been divided into four procedural phases as mentioned below:

• Phase A: Site selection.

• Phase B: Analysis of physico-chemical variables of water.

• Phase C: Analysis of microbial load (total bacterial count, total coliform, faecal coliform, E. coli, Vibrio sp., Streptococcus sp., Salmonella sp.) in ambient water media.

• Phase D: Statistical analysis.

Phase A: Site Selection

The first phase of the work involves selection of eight sampling stations (Table 7B.1) in the deltaic region of Sundarbans (Figs. 7B.1A and 7B.1B).

Table 7B.1 Sampling stations with coordinates

Fig. 7B.1A

Map of Indian Sundarbans

Fig. 7B.1B

Map showing sampling stations

Phase B: Analysis of Physico-chemical Variables of Water

• (a) Surface water temperature: The surface water temperature was measured using 0–100°C mercury thermometer.

• (b) Surface water salinity: The surface water salinity was recorded by means of an optical refractometer (Atago, Japan) and cross-checked in the laboratory by employing more Knudsen method (Strickland and Parsons 1972). The correction factor was found out by titration of the silver nitrate (AgNO₃) solution against standard seawater (IAPO Standard Seawater Service Charlottenlund, Slot Denmark, Chlorinity 19.376 ppt).

• (c) Surface water pH: The surface water pH was measured by using a portable pH-meter sensitivity = ±0.02.

• (d) Surface water dissolved oxygen (DO): The surface water DO was measured by DO meter in the field and subsequently cross-checked in the laboratory by Winkler’s method.

• (e) Surface water nutrient analysis: Surface water was collected for nutrient analysis in cleaned Tarsons bottles and transported to the laboratory in iced freeze condition. Triplicate samples were collected from same collection sites to maintain the quality of the data. The standard spectrophotometric method of Strickland and Parsons (1972) was adopted to determine the nutrient concentration in surface water.

  • (i) Nitrate analysis: Nitrate was analyzed by oxidizing it to nitrite by means of passing the sample with ammonium chloride buffer through a glass column packed with amalgamated cadmium filings and finally treating the samples with sulphonyl amide. The resultant diazonium ion was coupled with N-(1-naphthyl)-ethylene diamine to give an intensely pink azo dye.

  • (ii) Phosphate analysis: Determination of the phosphate was carried out by treatment of an aliquot of the sample with an acidic molybdate reagent containing ascorbic acid and a small proportion of potassium antimony tartrate.

  • (iii) Silicate analysis: Dissolved silicate was determined by treating the sample with acidic molybdate reagent. The resultant silico-molybdic acid was reduced to molybdenum blue complex by ascorbic acid and incorporating the oxalic acid to prevent the formation of similar blue complex phosphate.

Phase C: Analysis of Microbial Load in Ambient Water

• 1. Sampling:

  • (i) Sampling of the water: Water samples were collected fortnightly aseptically in sterilized glass container (sterilized in autoclave) with utmost care from February 2013 to April 2013. The collected samples were immediately transferred in icebox and brought to the laboratory for further analysis.

  • (ii) Preparation of culture media for the microbial analysis :

    • (a) Preparation of the Lauryl Tryptose Broth (LTB) for presumptive test: In order to prepare the LTB, at first a dehydrated amount of ingredients for single strength (SS) and double strength (DS) was required to dissolve separately in each 1 l of sterilized distilled water, and it was thoroughly mixed and slightly heated by proper swirling. The pH was adjusted up to 6.8 ± 0,2 by either 0.1(N) sodium hydroxide (NaOH) or 0.1 (N) hydrochloric acid (HCl). After that it was distributed as required (10 ml SS and 10 ml DS) in test tube containing inverted Durham’s tube and then placed in the autoclave for sterilization at 121°C and 15 lbs for 15 min. The general ingredients of the LTB are given in Table 7B.2.

      Table 7B.2 Ingredients of LTB

    • (b) Preparation of Brilliant Green Lactose Bile Broth (BGLB) for confirmed test: At first the required amount of the dehydrated ingredients was dissolved in 1 l of sterilized distilled water which was thoroughly mixed and slightly heated by proper swirling, and then pH was adjusted up to 7.2 ± 0.2 by either 0.1(N) sodium hydroxide (NaOH) or 0.1(N) hydrochloric acid (HCl). After that it was distributed in test tubes (10 ml each) containing inverted Durham’s tube and then placed in autoclave for sterilization at 121 °C and 15 lbs for 15 min. The general ingredients of BGLB are as follows (Table 7B.3):

      Table 7B.3 Ingredients of BGLB

• 2. Preparation of the collected water samples:

  • (i) Preparation of the water samples: The collected water samples were mixed thoroughly before analysis.

  • (ii) Microbial analysis of the water samples: For microbial analysis in terms of total coliform load, the most probable number (MPN) procedure by multiple fermentation techniques (MFT) is stated in APHA (1998). The techniques involve inoculating the sample and/ or its several dilutions in a liquid medium of Lauryl Tryptose Broth (LTB). After completion of the incubation period, the tubes were examined for growth, acid and gas production by the coliform organisms. This test is known as the presumptive test. Since the organisms other than coliforms may also produce the reaction, the positive tubes from the presumptive test were subjected to a confirmatory test. The density of bacteria was calculated on the basis of positive and negative combination of the tubes. For water samples, the results were expressed in MPN/100 ml (APHA 1998).

Presumptive Test for Total Coliform

Presumptive test for total coliform and Lauryl Tryptose Broth was used as culture media. For analysis of water five test tubes each of 10 ml, 1 ml, 0.1 ml sample portions were used as the presumptive test.

First set of contained five numbers of 10 ml (DS) broth tubes. Second and third sets contained ten numbers of 10 ml (SS) broth tubes for analysis of water. Each tube in a set of five 10 ml, 1 ml and 0.1 ml of water sample was inoculated in the first, second and third sets of media tube, respectively, and mixed thoroughly. In each case a controlled set was run parallelly. The inoculated test tubes were incubated at 36 ± 1 °C after 24 ± 2 h, and the inoculated tubes were examined for growth of gas and acidic reaction. If there was no gas and acid reaction, the tubes were re-examined and re-incubated at the end of 48 ± 2 h. Within each tube, Durham’s tubes were invertedly placed to show the bacterial growth with the emission of gas. Production of gas bubbles and acids with growth in the tubes within 48 ± 2 h contributes presumptive reaction. After the incubation period of 48 h, the number of positive tubes were counted and preceded for confirmatory test.

Confirmatory Test for Total Coliform

For the total coliform test, the culture medium used was Brilliant Green Lactose Bile Broth (BGLB). The positive presumptive tubes were gently shaken with a sterile loop (3.5 mm-5 mm in diameter); one or two loopfuls of culture were transferred to a test tube containing BGLB with an invertedly placed Durham’s tube. The inoculated BGLB tubes were incubated at 36 ± 1 °C. Formation of any gas within 48 ± 2 h constituted the confirmed test. The results were obtained in MPN/100 ml by comparing with the MPN table.

Phase D: Statistical Analysis

In order to find the differences between months and stations, ANOVA was done using Excel under Windows 2007.

7.2.5 5. Results

Marine and estuarine ecosystems are being threatened by the discharge of untreated sewage wastes and industrial effluents which ultimately affects the sustainability of living resources and public health.

Some microbial pathogens in the coastal environment are indigenous to the oceans, including Vibrios, whereas others like Escherichia coli, Salmonella sp. and Shigella sp. are allochthonous which are introduced through agricultural, urban surface run-off, wastewater discharges and from domestic and wild animals. Most of the Vibrios and Salmonella sp. are pathogenic to humans and some have fatal infections (Blake et al. 1980; Grimes 1975; Carlson et al. 1968; Gerba and Schaiberger 1975). Infections with Vibrios are known to be associated with either consumption of seafood or exposure to marine environment (Raveendran et al. 1990). The presence of faecal coliforms forms representative for the assessment of coastal recreational water quality. The present investigation highlights the occurrence distribution pattern of enteric pathogens in marine water. It also evaluates the influence of anthropogenic inputs and raw sewage on the incidence of these bacteria in and around Indian Sundarbans.

The microbial load is also influenced by physico-chemical variables like temperature, salinity, pH, etc. The level of DO also fluctuates depending on the microbial load and action. The present dissertation was therefore undertaken to focus the spatio-temporal variations of physico-chemical and microbiological parameter as highlighted here:

7.2.5.1 5.1 Physico-chemical Parameters

7.2.5.1.1 5.1.1 Surface Water Temperature

In February 2013, the surface water temperature ranged from 26.8 ± 0.1 °C to 27.1 ± 0.1 °C during the study period. The station-wise order of surface water temperature is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) = Sagar Island (Stn. 6) = Lot 8 (Stn. 3) > Chemaguri (Stn. 5) = Haldia (Stn. 1) > Diamond Harbour (Stn. 2) = Kachuberia (Stn. 4) (Fig. 7B.2).

Fig. 7B.2

Surface water temperature (°C) in the selected stations during February 2013

In March 2013, the surface water temperature ranged from 28.8 ± 0.1 °C to 30.7 ± 0.1 °C during the study period. The station-wise order of surface water temperature is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Kachuberia (Stn. 4) = Haldia (Stn. 1) > Lot 8 (Stn. 3) = Diamond Harbour (Stn. 2) > Chemaguri (Stn. 5) (Fig. 7B.3).

Fig. 7B.3

Surface water temperature (°C) in the selected stations during March 2013

In April 2013, the surface water temperature ranged from 32.2 ± 0.2 °C to 33.1 ± 0.2 °C during the study period. The station-wise order of surface water temperature is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) = Sagar Island (Stn. 6) > Kachuberia (Stn. 4) = Chemaguri (Stn. 5) > Lot 8 (Stn. 3) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) (Fig. 7B.4).

Fig. 7B.4

Surface water temperature (°C) in the selected stations during April 2013

7.2.5.1.2 5.1.2 Surface Water Salinity

In February 2013, the surface water salinity ranged from 1.05 ± 0.05 psu to 20.89 ± 0.34 psu during the study period. The station-wise order of surface water salinity is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.5).

Fig. 7B.5

Surface water salinity (‰) in the selected stations during February 2013

In March 2013, the surface water salinity ranged from 2.89 ± 0.05 psu to 24.89 ± 0.20 psu during the study period. The station-wise order of surface water salinity is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.6).

Fig. 7B.6

Surface water salinity (‰) in the selected stations during March 2013

In April 2013, the surface water salinity ranged from 7.12 ± 0.08 psu to 29.55 ± 0.05 psu during the study period. The station-wise order of surface water salinity is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.7).

Fig. 7B.7

Surface water salinity (‰) in the selected stations during April 2013

7.2.5.1.3 5.1.3 Surface Water pH

In February 2013, the surface water pH ranged from 7.89 ± 0.01 to 8.28 ± 0.02 during the study period. The station-wise order of surface water pH is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.8).

Fig. 7B.8

Surface water pH in the selected stations during February 2013

In March 2013, the surface water pH ranged from 7.90 ± 0.01 to 8.29 ± 0.02 during the study period. The station-wise order of surface water pH is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.9).

Fig. 7B.9

Surface water pH in the selected stations during March 2013

In April 2013, the surface water pH ranged from 8.10 ± 0.02 to 8.32 ± 0.01 during the study period. The station-wise order of surface water pH is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) = Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.10).

Fig. 7B.10

Surface water pH in the selected stations during April 2013

7.2.5.1.4 5.1.4 Surface Water Dissolved Oxygen (DO)

In February 2013, the surface water dissolved oxygen ranged from 4.99 ± 1.23 (mg/L) to 5.98 ± 1.35 (mg/L) during the study period. The station-wise order of surface water DO is Sagar Island (Stn. 6) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Diamond Harbour (Stn. 2) > Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Kachuberia (Stn. 4) > Haldia (Stn. 1) (Fig. 7B.11).

Fig. 7B.11

Surface water DO (mg/L) in the selected stations during February 2013

In March 2013, the surface water dissolved oxygen ranged from 4.93 ± 1.23 (mg/L) to 6.02 ± 1.03 (mg/L) during the study period. The station-wise order of surface water DO is Namkhana (Stn. 7) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.12).

Fig. 7B.12

Surface water DO (mg/L) in the selected stations during March 2013

In April 2013, the surface water dissolved oxygen ranged from 4.88 ± 1.33 (mg/L) to 5.45 ± 1.13 (mg/L) during the study period. The station-wise order of surface water DO is Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Haldia (Stn. 1) > Namkhana (Stn. 7) (Fig. 7B.13)

Fig. 7B.13

Surface water DO (mg/L) in the selected stations during April 2013

7.2.5.1.5 5.1.5 Surface Water Nitrate

In February 2013, the surface water nitrate ranged from 18.32 ± 1.04 (mg/L) to 29.88 ± 1.31 (mg/L) during the study period. The station-wise order of surface water nitrate is Frasergaunje (Stn. 8) > Haldia (Stn. 1) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) (Fig. 7B.14).

Fig. 7B.14

Surface water nitrate (mg/L) in the selected stations during February 2013

In March 2013, the surface water nitrate ranged from 15.30 ± 0.76 (mg/L) to 26.33 ± 1.04 (mg/L) during the study period. The station-wise order of surface water nitrate is Haldia (Stn. 1) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) (Fig. 7B.15).

Fig. 7B.15

Surface water nitrate (mg/L) in the selected stations during March 2013

In April 2013, the surface water nitrate ranged from 14.21 ± 0.76 (mg/L) to 24.33 ± 1.01 (mg/L) during the study period. The station-wise order of surface water nitrate is Haldia (Stn. 1) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Sagar Island (Stn. 6) (Fig. 7B.16).

Fig. 7B.16

Surface water nitrate (mg/L) in the selected stations during March 2013

7.2.5.1.6 5.1.6 Surface Water Phosphate

In February 2013, the surface water phosphate ranged from 1.32 ± 0.49 (mg/L) to 3.14 ± 0.91 (mg/L) during the study period. The station-wise order of surface water phosphate is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Chemaguri (Stn. 5) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) (Fig. 7B.17).

Fig. 7B.17

Surface water phosphate (mg/L) in the selected stations during February 2013

In March 2013, the surface water phosphate ranged from 1.29 ± 0.10 (mg/L) to 2.83 ± 0.81 (mg/L) during the study period. The station-wise order of surface water phosphate is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Chemaguri (Stn. 5) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) (Fig. 7B.18).

Fig. 7B.18

Surface water phosphate (mg/L) in the selected stations during March 2013

In April 2013, the surface water phosphate ranged from 1.09 ± 0.11 (mg/L) to 2.11 ± 0.81 (mg/L) during the study period. The station-wise order of surface water phosphate is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Chemaguri (Stn. 5) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Sagar Island (Stn. 6) (Fig. 7B.19).

Fig. 7B.19

Surface water phosphate (mg/L) in the selected stations during April 2013

7.2.5.1.7 5.1.7 Surface Water Silicate

In February 2013, the surface water silicate ranged from 49.84 ± 3.42 (mg/L) to 81.22 ± 3.93 (mg/L) during the study period. The station-wise order of surface water silicate is Sagar Island (Stn. 6) > Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Chemaguri (Stn. 5) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.20).

Fig. 7B.20

Surface water silicate (mg/L) in the selected stations during February 2013

In March 2013, the surface water silicate ranged from 44.32 ± 3.42 (mg/L) to 76.57 ± 1.99 (mg/L) during the study period. The station-wise order of surface water silicate is Sagar Island (Stn. 6) > Namkhana (Stn. 7) > Chemaguri (Stn. 5) > Frasergaunje (Stn. 8) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Haldia (Stn. 1) (Fig. 7B.21).

Fig. 7B.21

Surface water silicate (mg/L) in the selected stations during March 2013

In April 2013, the surface water silicate ranged from 41.90 ± 3.42 (mg/L) to 66.44 ± 2.05 (mg/L) during the study period. The station-wise order of surface water silicate is Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) (Fig. 7B.22).

Fig. 7B.22

Surface water silicate (mg/L) in the selected stations during April 2013

7.2.5.2 5.2 Microbial Load

7.2.5.2.1 5.2.1 Total Coliform

In February 2013, the total coliform count ranged from 22 ± 4 (MPN/100 ml) to 391 ± 80 (MPN/100 ml) during the study period. The station-wise order of total coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Sagar Island (Stn. 6) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) (Fig. 7B.23)

Fig. 7B.23

Total coliform count (MPN/100 ml) in the selected stations during February 2013

In March 2013, the total coliform count ranged from 20 ± 5 (MPN/100 ml) to 356 ± 80 (MPN/100 ml) during the study period. The station-wise order of total coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Sagar Island (Stn. 6) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) (Fig. 7B.24).

Fig. 7B.24

Total coliform count (MPN/100 ml) in the selected stations during March 2013

In April 2013, the total coliform count ranged from 12 ± 1 (MPN/100 ml) to 309 ± 80 (MPN/100 ml) during the study period. The station-wise order of total coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Sagar Island (Stn. 6) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Kachuberia (Stn. 4) > Chemaguri (Stn. 5) > Lot 8 (Stn. 3) (Fig. 7B.25).

Fig. 7B.25

Total coliform count (MPN/100 ml) in the selected stations during April 2013

7.2.5.2.2 5.2.2 Faecal Coliform (FC)

In February 2013, the faecal coliform count ranged from 2 ± 1 (MPN/100 ml) to 354 ± 190 (MPN/100 ml) during the study period. The station-wise order of faecal coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) (Fig. 7B.26).

Fig. 7B.26

Faecal coliform count (MPN/100 ml) in the selected stations during February 2013

In March 2013, the faecal coliform count ranged from 10 ± 1 (MPN/100 ml) to 300 ± 80 (MPN/100 ml) during the study period. The station-wise order of faecal coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) = Sagar Island (Stn. 6) (Fig. 7B.27).

Fig. 7B.27

Faecal coliform count (MPN/100 ml) in the selected stations during March 2013

In April 2013, the faecal coliform count ranged from 5 ± 1 (MPN/100 ml) to 267 ± 75 (MPN/100 ml) during the study period. The station-wise order of faecal coliform count is Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) (Fig. 7B.28).

Fig. 7B.28

Faecal coliform count (MPN/100 ml) in the selected stations during April 2013

7.2.5.2.3 5.2.3 Total Bacterial Count (TBC)

In February 2013, the total bacterial count ranged from 5.76 ± 0.01 (CFU × 10⁶/ml) to 17.11 ± 0.12 (CFU × 10⁶/ml) during the study period. The station-wise order of TBC is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Kachuberia (Stn. 4) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) (Fig. 7B.29).

Fig. 7B.29

TBC (CFU × 10⁶/ml) in the selected stations during February 2013

In March 2013, the total bacterial count ranged from 0.68 ± 0.01 (CFU × 10⁶/ml) to 16.94 ± 0.02 (CFU × 10⁶/ml) during the study period. The station-wise order of TBC is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) > Sagar Island (Stn. 6) > Chemaguri (Stn. 5) (Fig. 7B.30).

Fig. 7B.30

TBC (CFU × 10⁶/ml) in the selected stations during March 2013

In April 2013, the total bacterial count ranged from 2.50 ± 0.01 (CFU × 10⁶/ml) to 16.00 ± 0.15 (CFU × 10⁶/ml) during the study period. The station-wise order of TBC is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) > Chemaguri (Stn. 5) > Diamond Harbour (Stn. 2) > Haldia (Stn. 1) > Sagar Island (Stn. 6) (Fig. 7B.31).

Fig. 7B.31

TBC (CFU × 10⁶/ml) in the selected stations during April 2013

7.2.5.2.4 5.2.4 E. coli Count

In February 2013, the E. coli count ranged from 0.01 ± 0.001 (CFU × 10⁶/ml) to 19.89 ± 0.12 (CFU × 10⁶/ml) during the study period. The station-wise order of E. coli count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Haldia (Stn. 1) > Sagar Island (Stn. 6) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) (Fig. 7B.32).

Fig. 7B.32

E. coli count (CFU × 10⁶/ml) in the selected stations during February 2013

In March 2013, the E. coli count ranged from 0.002 ± 0.001 (CFU × 10⁶/ml) to 18.55 ± 0.12 (CFU × 10⁶/ml) during the study period. The station-wise order of E. coli count is Frasergaunje (Stn. 8) > Lot 8 (Stn. 3) > Namkhana (Stn. 7) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) (Fig. 7B.33).

Fig. 7B.33

E. coli count (CFU × 10⁶/ml) in the selected stations during March 2013

In April 2013, the E. coli count ranged from 0.01 ± 0.001 (CFU × 10⁶/ml) to 17.89 ± 0.05 (CFU × 10⁶/ml) during the study period. The station-wise order of E. coli count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Diamond Harbour (Stn. 2) > Sagar Island (Stn. 6) > Haldia (Stn. 1) > Kachuberia (Stn. 4) (Fig. 7B.34).

Fig. 7B.34

E. coli count (CFU × 10⁶/ml) in the selected stations during April 2013

7.2.5.2.5 5.2.5 Vibrio sp. Count

In February 2013, the Vibrio sp. count ranged from 0.10 ± 0.01 (CFU × 10⁶/ml) to 2.20 ± 0.09 (CFU × 10⁶/ml) during the study period. The station-wise order of Vibrio sp. count is Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Lot 8 (Stn. 3) > Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) (Fig. 7B.35).

Fig. 7B.35

Vibrio sp. count (CFU × 10⁶/ml) in the selected stations during February 2013

In March 2013, the Vibrio sp. count ranged from 0.00 (CFU × 10⁶/ml) to 16.0 ± 0.11 (CFU × 10⁶/ml) during the study period. The station-wise order of Vibrio sp. count is Chemaguri (Stn. 5) > Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Lot 8 (Stn. 3) > Haldia (stn1) > Diamond Harbour (Stn. 2) > Kachuberia (Stn. 4) > Sagar Island (Stn. 6) (Fig. 7B.36).

Fig. 7B.36

Vibrio sp. count (CFU × 10⁶/ml) in the selected stations during March 2013

In April 2013, the Vibrio sp. count ranged from 0.00 (CFU × 10⁶/ml) to 0.90 ± 0.01 (CFU × 10⁶/ml) during the study period. The station-wise order of Vibrio sp. count is Chemaguri (Stn. 5) > Namkhana (Stn. 7) > Frasergaunje (Stn. 8) > Haldia (stn1) > Lot 8 (Stn. 3) > Diamond Harbour (Stn. 2) = Kachuberia (Stn. 4) > Sagar Island (Stn. 6) (Fig. 7B.37).

Fig. 7B.37

Vibrio sp. count (CFU × 10⁶/ml) in the selected stations during April 2013

7.2.5.2.6 5.2.6 Streptococcus sp. Count

In February 2013, the Streptococcus sp. count ranged from 0.00 (CFU × 10⁶/ml) to 0.33 ± 0.02 (CFU × 10⁶/ml) during the study period. The station-wise order of Streptococcus sp. count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) = Lot 8 (Stn. 3) > Kachuberia (Stn. 4) = Chemaguri (Stn. 5) = Sagar Island (Stn. 6) (Fig. 7B.38).

Fig. 7B.38

Streptococcus sp. count (CFU × 10⁶/ml) in the selected stations during February 2013

In March 2013, the Streptococcus sp. count ranged from 0.00 (CFU × 10⁶/ml) to 0.30 ± 0.01 (CFU × 10⁶/ml) during the study period. The station-wise order of Streptococcus sp. count is Frasergaunje (Stn. 8) > Haldia (stn1) > Namkhana (Stn. 7) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) = Chemaguri (Stn. 5) = Sagar Island (Stn. 6) (Fig. 7B.39).

Fig. 7B.39

Streptococcus sp. count (CFU × 10⁶/ml) in the selected stations during March 2013

In April 2013, the Streptococcus sp. count ranged from 0.00 (CFU × 10⁶/ml) to 0.30 ± 0.01 (CFU × 10⁶/ml) during the study period. The station-wise order of Streptococcus sp. count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) = Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Kachuberia (Stn. 4) = Chemaguri (Stn. 5) = Sagar Island (Stn. 6) (Fig. 7B.40).

Fig. 7B.40

Streptococcus sp. count (CFU × 10⁶/ml) in the selected stations during April 2013

7.2.5.2.7 5.2.7 Salmonella sp. Count

In February 2013, the Salmonella sp. count ranged from 0.02 ± 0.001 (CFU × 10⁶/ml) to 0.82 ± 0.04 (CFU × 10⁶/ml) during the study period. The station-wise order of Salmonella sp. count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Kachuberia (Stn. 4) (Fig. 7B.41).

Fig. 7B.41

Salmonella sp. count (CFU × 10⁶/ml) in the selected stations during February 2013

In March 2013, the Salmonella sp. count ranged from 1.65 ± 0.01 (CFU × 10⁶/ml) to 90.8 ± 0.03 (CFU × 10⁶/ml) during the study period. The station-wise order of Salmonella sp. count is Lot 8 (Stn. 3) > Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Haldia (Stn. 1) > Diamond Harbour (Stn. 2) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Kachuberia (Stn. 4) (Fig. 7B.42).

Fig. 7B.42

Salmonella sp. count (CFU × 10⁶/ml) in the selected stations during March 2013

In April 2013, the Salmonella sp. count ranged from 1.25 ± 0.01 (CFU × 10⁶/ml) to 75.40 ± 0.13 (CFU × 10⁶/ml) during the study period. The station-wise order of Salmonella sp. count is Frasergaunje (Stn. 8) > Namkhana (Stn. 7) > Haldia (stn1) > Diamond Harbour (Stn. 2) > Lot 8 (Stn. 3) > Chemaguri (Stn. 5) > Sagar Island (Stn. 6) > Kachuberia (Stn. 4) (Fig. 7B.43).

Fig. 7B.43

Salmonella sp. count (CFU × 10⁶/ml) in the selected stations during April 2013

7.2.6 6. Discussion

Microbiological water quality investigations of lotic and lentic ecosystems are very rare, despite their importance in accompanying the role of large water bodies for cases of recreation, tourism and aquaculture. An attempt to adequately monitor scientific data in large-scale river bodies is a priority to some organizations in Europe as stipulated by Kirschner et al. (2009). This microbiological data in the Sundarbans estuary gives a strong signal to the environmental community to embark on the creation of water treatment facilities in order to prevent the transmission of communicable diseases by population that explore its water, as total and faecal pollution is a crucial problem affecting most urban water systems (Eleria 2002).

The monthly values are very important with values reaching 391 ± 80 (MPN/100 ml) in February at Haldia (Stn. 1) for total coliforms. These pathogens will keep on accumulating in the open system (Bell et al. 1994). The values obtained could be spatio-temporarily linked to the number of visitors in this ecosystem and also the role played by point and non-point sources in the biocontamination of aquatic ecosystem (Cieslak et al. 1993; Kelsey et al. 2004). These pathogens could be free living, particle associated or in an intermediary state, depending on the organic and inorganic condition of the medium as stipulated in the findings of Basemer et al. (2005).

Rainfall–storm water run-off is a significant source of pollutants to the river, which can include bacteria, viruses and sediment, to which the substrate pollutants attached as indicated by Mallin et al. (2000). Storm rainfall characteristics and conditions prior to the storms are significant factors in the transport and concentrations of pollutants in the river. Stream flow–river flow is the primary transport media of faecal coliform bacteria (Christensen et al. 2000).

Among the diseases associated with poor microbial water quality, those causing dehydrating diarrhoea are of critical importance as they could lead to death within 48 h after the initial symptoms as analyzed in the findings of Manja et al. (1982). These extreme cases are more predominant in countries where overcrowding and poor sanitary conditions are the norm (Francy et al. 2002). The presence of faecal coliforms indicates the contamination of water with faecal waste that may contain other harmful or disease-causing microorganisms, including bacteria, viruses, protozoa or other infectious agents (Brewster et al. 1994). Drinking water contaminated with these organisms can cause stomach and intestinal illness including diarrhoea and nausea.

The Hooghly estuary is the lifeline of the highly urbanized city of Kolkata and supports industry of crucial economic importance. The surrounding area is a complex mixture of commercial, industrial, agricultural and residential development. The watershed provides important services for drinking water, wildlife habitat, recreation (swimming, fishing, boating), pilgrimage and transportation. The mixed use of the watershed results in a complex pattern of waste and pollutant input that alters ecosystem health. Microbes play an important role in determining water quality (nutrient concentration, clarity, oxygen levels, pathogen load) by controlling the internal transformations, but their activity is modulated by the system’s variable environmental conditions.

The present dissertation focuses the following points:

• There is an increasing trend in surface water temperature, salinity, pH and silicates while approaching from upstream to downstream region. This may be because of the effects of the tidal action from Bay of Bengal, which is in the south of selected stations. The surface water dissolved oxygen concentration, nitrate and phosphate did not show any general spatial trend. The anthropogenic activities basically control the concentration of dissolved oxygen, nitrate and phosphate through sewage and other waste disposals. Haldia (Stn. 1), Namkhana (Stn. 7) and Frasergaunje (Stn. 8) sustain port, industries, hotels and tourism units and fish landing stations. These point sources generate wastes of complex characters due to which the nitrates and phosphates exhibited comparatively higher values in these stations.

• ANOVA revealed significant monthly variations (p < 0.01) in surface water temperature, salinity, pH, dissolved oxygen, nitrate, phosphate and silicate. However, the statistical difference is not significant between stations in case of surface water temperature as F_cal (2.71) is less than F_crit (2.76). In case of other physico-chemical variables like surface water salinity, pH, DO, nitrate, phosphate and silicate, significant differences between stations were observed (Table 7B.4). All these are related to nature and magnitude of human/anthropogenic activities.

  Table 7B.4 ANOVA: showing variation of hydrological parameters between stations and months (for physico-chemical parameters)

• ANOVA revealed significant monthly variations (p < 0.01) in total coliform count, faecal coliform count, total bacterial count, E. coli count, Vibrio sp. count, Streptococcus sp. count and Salmonella sp. count (exceptions are observed in case of E. coli count and Vibrio sp. count). However, the statistical difference is not significant between stations in case of Vibrio sp. count as F_cal (1.58) is less than F_crit (2.76). In case of Salmonella sp. count, the statistical difference between stations is also not significant as F_cal (2.47) is lower than F_crit (2.76) (Table 7B.5).

  Table 7B.5 ANOVA: showing variation of microbial load between stations and months (for microbial parameters)

7.2.7 7. Conclusion

It is very difficult to come to a solid conclusion with a meagre data of 3 months. A long-term study is required (at least 2 years) to monitor the seasonal effects of physico-chemical parameters.

With these snapshots of 3 months, it is very clear that the unplanned urbanization, tourism units and agricultural activities are mainly responsible for deterioration of water quality along the Hooghly estuary stretches. It is interesting to note that the salinity, pH and silicate level increases from upstream to downstream, that is, from Haldia to Frasergaunje. This is exclusively the marine effect of the Bay of Bengal. However, the microbial parameters in some stations like Haldia (Stn. 1), Diamond Harbour (Stn. 2), Namkhana (Stn. 7) and Frasergaunje (Stn. 8) increase abruptly because of release of untreated waste from hotels, fish landing stations and market places. These activities have not only increased the coliform load in the water bodies, but also pathogenic strains, such as Salmonella sp. and Vibrio sp., have also been observed in stations like Chemaguri (Stn. 5), Namkhana (Stn. 7) and Frasergaunje (Stn. 8) where shrimp culture (Penaeus monodon) activities are a major issue. Overstocking of tiger prawn feed and periodic release of the wastewater in the surrounding estuarine is also one of the important reasons for enhanced microbial load in these stations.

Continuous monitoring of the system and strict regulation by concerned government departments and agencies are essential to restore the ecological health of the system.