Distribution of Urea in the Waters of the West Coast of India

230-233Urea concentrations at the surface are high both in coastal and offshore waters in the region north of 15° N (0.3-7.76 µg at N/litre) and low in the region south of this latitude (0-1.5 mu g at N/litre). Vertical distribution shows peak at some levels and very low concentrations at others. Urea concentration increases towards the central west coast of India. Comparison with the other inorganic nutrients indicates that urea constitutes >10% of the available nitrogen in the euphotic zone (0-100 m). This shows that urea forms a significant nitrogen source for marine phytoplankton in the west coast of India

Urea as Nitrogen Source for Phytoplankton Production in Coastal Waters of Goa

93-97Annual variation of urea in coastal waters off Goa, India is 0 to 2.92 mu g-at N.1/1 and 0 to 4.69 mu g-at N.1/1 in adjacent estuarine waters of Mandovi. Peaks of phytoplankton production accompanied with the decrease in urea in June and October, when ammonia and nitrate were high, indicate that urea is utilised or decomposed by phytoplankton organisms. Seasonal fluctuation of urea is between 7 and 55U+0025 of total utilizable nitrogen, which is a large reserve of nitrogen for phytoplankton growth. Assimilation ratio (delta N: P) indicates that nitrate is in short supply. However, urea available in these waters can substitute nitrogen deficiencies for the high rate of phytoplankton production

Effect of urea on growth of marine phytoplankters

132-134Growth rates of 3 phytoplankters - Asterionella japonica, Synechocystis sp. and Chlorella sp.- were studied as a function of urea by enriching the nutrient-depleted water with varying concentrations (0 to 50 µg- at N/litre) of urea; growth rate was calculated from the increase in chlorophyll a content of the organisms. Maximum growth of these phytoplankters was observed between concentrations 1 and 2 µg-at urea-N/litre

Water quality characteristics at Velsao and Colva beaches of Goa

111-113Chemical and biological factors were studied at two beaches, viz. Velsao and Colva, of Goa, India. High fluctuations of nitrogen and phosphorus compounds were found at Velsao while they were of normal range at Colva. High nitrogen and phosphorus values were due to the effluents discharged from a fertilizer factory at Velsao. Phytoplankton cell counts also showed higher values at Velsao than at Colva. Results indicate continuous eutrophication problem associated with the discharge of ammonium salts and a long term effect of this eutrophication may prove adverse on fishery resources of that region

Particulate organic matter in the coastal and estuarine waters of Goa and its relationship with phytoplankton production

In the coastal and estuarine waters of Goa, particulate organic carbon (POC) varied from 0.52 to 2.51 mg l-1 and from 0.28 to 5.24 mg l-1 and particulate phosphorus (PP) varied from 0.71 to 5.18 μg l-1 and from 0.78 to 20.34 μg l-1, respectively. The mean values of chlorophyll and primary productivity were 1.94 mg m-3 and 938.1 mg C m-2 day-1 in the coastal waters and 4.3 mg m-3 and 636.5 mg C m-1 day-1 in the estuarine waters, respectively. POC/chl ratios were low in June and October even when POC values were quite high. The POC in surface waters was linearly correlated with the chlorophyll content. Also PP increased when chlorophyll and primary productivity remained high. The results suggest that the phytoplankton was sharply increasing and contributed to POC and PP content. The percentage of detritus calculated from the intercept values of chlorophyll on POC varied from 46 to 76% depending on season. Results indicate that the major portion of POC and PP during postmonsoon (October–January) is derived from phytoplankton production while the allochthonous matter predominate during monsoon (June–September)

Production of organic matter In Antarctic sea Shelf

1-5Particulate organic matter (POM) collected from 3 discrete depths (0, 10 and 30 m) at a single station in the waters off the ice shelf of Princess Astrid Coast (70-degrees-S-11-degrees-E), Antarctica during austral summer, winter and spring of 1986 was analysed for phytoplankton biomass (as chl a), particulate organic carbon (POC) and constituent fractions. Chlorophyll a varied from 0.026 to 3.1-mu-g l-1. POC ranged from 0.280 to 1850-mu-g l-1, particulate carbohydrate (PCHO) from 8 to 193-mu-g l-1, particulate protein (PP) from 16 to 200-mu-g l-1 and particulate lipids (PL) from 8 to 209-mu-g l-1. Large variations during summer signified patchy distribution. Phytoplankton population in 30 m deep water column during winter was dominated by unicellular blue green algal forms while during spring, diatoms such as Thalassiothrix longissima, Thalssiosira sp. were dominant. Sea-ice microalgal communities showed dominance of diatoms whereas dinoflagellates were poorly represented. The cell count varied from 0.15 to 142 x 10(4) cells l-1 with lowest counts during winter. In the zooplankton communities copepods were dominant in all months averaging 24.985%. The maximum zooplankton density of 2280 per 100 m3 was observed in December. Significant correlation was observed between POC and chl a and PL at 10 m depth. Variation in POC was due to variation in community structure, composition and production of the sea-ice algae and phytoplankton in the water column during different months

Primary productivity and nutrients in the Indian sector of the Southern Ocean

6-12Hydrography, nutrient and biological productivity data collected from 1981 to 1986 in the Indian sector of the Southern Ocean between 11-degrees to 53-degrees-E longitude are reported. The physical processes are most active in this region, with nutrient rich water upwelling at the Antarctic divergence (AD) at 65-degrees-S and water downwelling at the Antarctic convergence (AC) or subtropical convergence (STC) to the north. Chlorophyll a, primary producitivity and zooplankton estimations suggest that the regions south of AC are more productive than others. Higher productivity at the continental ice-edge than in oceanic waters is accounted for by the stability of the water column brought about by low salinity due to ice melting. Sharp depletion of Si near the AC where NO3 and PO4 maintain high values, as in the higher latitudes, reflects a unique behaviour of this element (Si) as regards to its biological uptake and regenerative mechanisms. Nutrient anomaly studies indicate that N regeneration is sufficiently fast in surface waters while most of the Si incorporated in diatoms and silicoflagellates tend to escape to deeper waters or to bottom sediment. The importance of microbial population is stressed to understand the food chain dynamics of Antarctic ecosystem

Seasonal changes in suspended particulate component in Bombay High oil field (Arabian Sea)

135-142Investigation on the influence of seasonal changes in physico-chemical factors on particulate matter in the ''Bombay High'' region from February'85 to January'86 suggests that dominance of physical factors in monsoon largely influence the production of phytoplankton biomass. Ratio of silicate and nitrate to phosphate was 16:16:1 for monsoon and postmonsoon periods. Annual values of particulate carbohydrates, particulate proteins and particulate lipids in surface waters ranged from 40 to 265 mu g l(-1), 21 to 56 mu g l(-1) and 14 to 51 mu g l(-1) respectively. Significant correlation of particulate carbohydrate, particulate proteins and particulate lipids with chlorophyll a suggested that plankton biomass comprised a substantial percentage of these constituent fractions. Almost uniform ratios of particulate lipid to particulate organic carbon (PL/POC) during all the three seasons indicated incorporation of petroleum hydrocarbons in the suspended particles

Physicochemical Characteristics Of Fishing Grounds Off Mangalore, West-Coast Of India

201-205In the regions off Mukka and Hosbettu, Karnataka coast, salinity attains maximum value of 35.1 x 10-3 in May. Similarly silicate, nitrate and phosphate show high values (27, 0.12 and 1.32 µM respectively) in May. This indicates upwelling of nutrient rich bottom waters. Changes in chl a and nitrate, phosphate and NO3:PO4 ratio suggest nitrate deficiency. Multiple correlation coefficient of temperature and salinity towards oil sardine landing is highly significant (r = 0.9917; P a content