Intra-annual variability in nutrients in the Godavari estuary, India (original) (raw)
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Indian Journal of Geo-Marine Sciences
Present study is about the impact of macronutrient enrichment on phytoplankton biomass and community structure in a tropical monsoonal estuary. In situ experiments carried out during the pre-monsoon period (February-March 2006), showed that the response time of phytoplankton to nutrient enhancement was 24-32 h. Phytoplankton biomass increased sizably, indicating nitrate and silicate limitation for phytoplankton growth. An increase in 23µg chl a l-1 resulted in an uptake of 10µM nitrate, 0.6µM phosphate and 17µM silicate. Phytoplankton showed high growth rates with an average value of 1.36µg chl l-1 d-1 .This phytoplankton community was largely dominated by diatoms (>96%), particularly chain forming species. Relative preference index (RPI) value for nitrate was >1, suggesting that, irrespective of the ambient ammonium concentration, estuarine autotrophs preferred nitrate. Few species like Skeletonema costatum and Thalassionema nitzschioides exhibited the ability to withstand hypoxic condition.
Intra- and inter-seasonal variability of nutrients in a tropical monsoonal estuary (Zuari, India)
Continental Shelf Research, 2014
A study was conducted to understand the intra-and inter-seasonal variability of dissolved oxygen and nutrients in a tropical monsoon estuary (Zuari in Goa, India). We adopted a dual sampling approach with (a) daily or alternate day sampling at a fixed location in the mid estuarine zone and (b) longitudinal transect sampling from freshwater end to mouth during spring and neap tides of each month for about a year. Multivariate statistical analyses of oxygen and nutrients were carried out to evaluate the hypotheses (i) biogeochemical processes chiefly regulate their variability and (ii) anthropogenic inputs lead to material accumulation in the estuary. Multivariate statistical analyses helped identify the controlling factors of the oxygen and nutrient variability. Our results significantly revealed (i) physical forcings (freshwater discharge and tidal circulation, these also facilitate sedimentary releases) are more important than biogeochemical processes in determining oxygen and nutrient variability in the water column and (ii) the monsoon driven regular annual flushing makes the system resilient to human interference as the Zuari estuary returns to normalcy by postmonsoon every year. Our study identified the significance of subsurface discharges in transporting mining effluents from the river basin. Results also suggest that extrapolation of controlling factors of biogeochemical variables at a fixed location to the entire estuary is untenable since the relative dominance of forcings vary in time and space in the estuary.
Marine Ecology, 2012
Ongoing climate change and anthropogenic activities are introducing stressors that affect the structure and function of coastal ecosystems. This paper focuses on the fluvial fluxes and estuarine transport of nutrients from a tropical river (Mahanadi River) in Northeastern India and compares select nutrient and water quality parameters between 1983 and 2008. This estuary acts as a perennial source of CO 2 with a net annual flux to the atmosphere of about 135 tons. The non-conservative fluxes showed a net annual removal of 650 and 140 tons of phosphorus and nitrogen from the water column, respectively. Negative biogeochemical feedbacks that decreased the availability of N and P in 2008 relative to 1983 levels indicate major changes in biogeochemical responses towards fluvial fluxes of nutrient.
The present investigation deals with the perpendicular (Surface, Middle and Bottom) variations on the physico-chemical and chlorophyll 'a' concentration of neritic (Palk Bay) and estuarine (Pambanar) waters of Muthukuda, Southeast coast of India. In this study we have examined the physico-chemical parameters such as water temperature, salinity, pH, and inorganic nutrients viz., nitrate, nitrite, phosphate ammonia and reactive silicate concentration for a period of four months (January-April 2012). The study inferred that the water temperature, salinity, pH, total hardness and calcium hardness was varied from 26.9-31.0 o C, 25-32‰, 7.05-7.86, 51.5-56.8 mg/l and 43.7-53.3 mg/l respectively. The concentration of inorganic nutrients such as nitrate (0.02 to 2.73µmol/l), nitrite (0.02-2.12µmol/l), ammonia (0.06 and 13.92µmol/l), phosphate (0.05 to 8.56µmol/l) and reactive silicate (0.06 to 25.45µmol/l) were found to be varied in respect to depth of water. Chlorophyll 'a' concentration was noticed in the range between 0.001 and 0.062µg/l. The present study obviously indicated that the physico-chemical and phytoplankton biomass (chlorophyll 'a') varied autonomously in subject to the depth of coastal system.
Decadal Variation of Nutrient Level in Two Major Estuaries in Indian Sundarbans
jordan journal of biological sciences, 2015
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.
Our Nature, 2014
Variations of hydro-chemical characters were recorded at three sites of Mahi estuary, near J-point (Lat. 22º10.3′N and Long. 72º44.28′E) during the pre-monsoon period. The concentration of the nutrients was relatively high due to the elevated atmospheric temperature, evapo-transpiration of water, slow saline intrusion as well as low inflow of surface water from Mahi River. On the contrary, dissolved oxygen (DO) was at its minimum level during this investigated period. The trophic status of all the three study stations was determined in terms of DO, phosphate, nitrate and sulphate in relation to phytoplankton as key pollution indicators species like Navicula, Nitzchia, Oscillatoria, Scenedesmus, Syndra and others. The results revealed that all the three sites are organically polluted as per the Palmer’s species diversity indices.DOI: http://dx.doi.org/10.3126/on.v11i2.9533 Our Nature 2013, 11(2): 85-95
Journal of Marine Systems, 2006
The Ganges drains much of the southern slopes of the Himalayas and yields high-suspended sediment load during the monsoon. The Hooghly estuary, the first deltaic offshoot of the Ganges and flows through the western part of the Sundarbans mangrove forest is a source for inorganic nutrients due to the high input of litter and sediment associated nutrients that are released during estuarine transport. Dissolved inorganic carbon (DIC), dissolved inorganic nitrogen (DIN), dissolved reactive phosphate (DRP) and silicate budgets and fluxes of the coastal zone of the Hooghly River system have been done by biogeochemical modeling and their annual fluxes were calculated to be 230 × 10 9 mol (2.76 × 10 6 t), 4705 × 10 6 mol (65.8 × 10 3 t), 415 × 10 6 mol (12.8 × 10 3 t), 15.28 × 10 9 mol (42.8 × 10 3 t), respectively. Out of the total transport, monsoonal runoff could account 64% for DIC, 71% for DIN and 76% for both DRP and silicate. Annual load of sediment out of the estuary to the NE coast of Bay of Bengal was estimated to be 65.19 × 10 6 t. During the estuarine transport 7.5% of DIC and 7.0% of silicate were removed while addition for DIN and DRP were found to be 59% and 44%, respectively. Occurrence of light limited conditions and auto-heterotrophic coupling within the estuary results regeneration of nutrients from organic matter originated from external source. Comparison was made with the estimates of nutrient fluxes through the some mangrove dominated Southeast Asian estuaries.
Chemistry and Ecology, 2017
Dissolved nutrients, Chl-a and primary productivity were measured from seven transects along the coastal waters of the southeastern Arabian Sea during northeast monsoon. Ten major estuaries were chosen to study the influence of estuarine discharge on the nutrient dynamics in the coastal waters. The mean water discharge of the estuaries in the north (64.8 ± 18 × 10 5 m 3 d −1) was found to be higher than those in the south (30.6 ± 21.4 × 10 5 m 3 d −1), whereas the nutrient concentrations were found to be higher in the estuaries of the south. The results from the offshore waters were discussed in accordance with the depth contour classification, that is, shelf (depth ≤ 30 m) and slope waters (depth ≥ 30 m). Our results suggest that the estuarine discharge plays a major role in the nutrient distribution in near shore shelf waters, whereas in shelf and slope waters, it was mainly controlled by in situ biological processes. The inorganic form of N to P ratios were found to be higher than Redfield ratio in slope waters when compared with shelf waters, suggesting that PO 4 3− (<0.15 µmol L −1) is a limiting nutrient for primary production. The multivariate statistical analysis revealed that the nutrient dynamics in the coastal waters was controlled by both biological and physical processes.
Environmental …, 2010
Changes in the phytoplankton biomass (chlorophyll a), production rate and species composition were studied over two seasons using the time series measurements in the northern limb of the Cochin estuary in relation to the prevailing hydrological conditions. The present study showed the significant seasonal variation in water temperature (F = 69.4, P<0.01), salinity (F = 341.93, P <0.01), dissolved inorganic phosphorous (F = 17.71, P <0.01) and silica (F = 898.1, P <0.01) as compared to nitrogen (F = 1.646, P >0.05). The uneven input of ammonia (3.4 -224.8 µM) from the upstream (from Periyar River) leads the inconsistency in the N:P ratio (range 6.8 -262). The distinct seasonality was observed in Si:N (F = 382.9, P <0.01) and Si:P (F = 290.3, P <0.01) ratios as compared to the N:P ratio (F=1.646, P >0.05). The substantial increase in chlorophyll a (av. 34.8 ± 10 mgm -3 ) and primary production (av.1304 ± 694 mgC m -3 d -1 ) were indicated the mesotrophic condition of the study area during the pre-monsoon and it was attributed by the large increase in the population of nanoplankton (size <20µ) such as Skeletonema costatum, Thalassiosira subtilis, Nitzschia closterium and Navicula directa. In contrast during the post monsoon, prevalence of less chlorophyll a concentration (av. 9.3 ± 9.2 mgm -3 ) and primary production (av. 124 ± 219 mgC m -3 d -1 ) showed the predominance of heterotrophic condition. It can be stated that the preponderance of favourable environmental conditions (optimum nutrients and light intensity) prevailing during the pre-monsoon have been enhanced the abundance of nanoplankton community in the estuary, whereas during post monsoon, the light limitation due to high turbidity can reduces the nanoplankton growth and abundance, even though high nutrient level exists.
Seasonal variability of phytoplankton population in the Brahmani estuary of Orissa, India
Journal of Applied Sciences and …, 2010
The dynamic relationship of water physico-chemical characteristics with phytoplankton has long been of great interest in both experimental ecology and environmental management. This study was carried out at the Brahmani Estuary (East coast, Bay Of Bengal, India) from March 2007 to November 2007. Based on the collected samples from six stations, phytoplankton population, DO, BOD, salinity and nutrient (o-PO4, NO3+NH3) were examined. The phytoplankton abundance varies with the seasonal variation. Due to wave action and circulation patterns DO distribution shows a marginal variation at different sampling points but the DO are relatively higher in the upstream compared to downstream, as oxygen solubility is higher for fresh water. In tropical climates higher light energy and temperature allow faster cycling of nutrients, thus seasonal maxima and minima of nutrient level are more difficult to asses and in general the nutrient concentration are low. Phytoplankton abundance increased through the increasing trend in salinity to the extent found in this investigation. A regression plot analysis exhibit a positive value i.e. R 2 = 0.7897, or correlates with each other up to 78.97%.. @ JASEM