Geochemical evidence for enhanced upwelling and organic productivity during the late Quaternary on the continental margin of northern California

EXTRACT (SEE PDF FOR FULL ABSTRACT): Laminated sediments are preserved in upper Pleistocene sections of cores collected on the continental slope at water depths within the present oxygen-minimum zone from at least as far north as the Klamath River and as far south as Point Sur. Comparison of sediment components in the laminae with those delivered to sediment traps as pelagic marine "snow" show the dark/light lamination couplets are indeed annual (varves). ... The presence of carbon-, sulfur-, and metal-rich sediments, as well as lack of bioturbation, all support the theory that the oxygen-minimum zone in the northeastern Pacific Ocean was more intense - in fact, anoxic - during the late Pleistocene in response to greater coastal upwelling and higher organic productivity.

Meteorological signals in primary productivity at two mountain lakes

Fluctuations in primary productivity at two subalpine lakes reveal both meteorological and biological influences. At Castle Lake, California, large-scale climate events such as the El Niño/Southern Oscillation affect total annual production and, combined with human fishing activity, modify the seasonal pattern of productivity. At Lake Tahoe, California-Nevada, local spring weather conditions modulate annual production and its seasonality by determining the depth of mixing and resulting internal nutrient load. Climatic conditions also contribute to deviations from the long-term trend in productivity by increasing the incidence of forest fires and through anomalous external nutrient loads during precipitation extremes. A 3-year cycle in productivity of as yet unknown origin has also been detected at Lake Tahoe.

High productivity and upwelling in the California Current during Oxygen-Isotope Stage 3: diatom evidence

Evidence for vigorous coastal upwelling and enhanced diatom productivity during the latter part of Oxygen-Isotope Stage 3 (OIS-3) is suggested by changes in diatom assemblages in laminated sediment from the northern California margin and in bioturbated and laminated sediment from Santa Barbara Basin. These conditions require strong along-shore or off-shore wind stress off California preceding the onset of global glacial conditions.

Biological productivity and fishery potential in the coastal waters off Bombay

Fishery potential of the nearshore waters of Bombay is estimated from the observed values of biological productivity at different trophic levels. The rate of primary and secondary production is relatively higher in the polluted coastal waters of Versova, Mahim and Thana. Observed mean benthic standing stock in the polluted creek waters is far less than the relatively unpolluted coastal regions off Bombay. Results suggest that the higher productivity at the lower trophic levels due to pollution, may not end up with high tertiary production. Therefore, such polluted regions are to be classified as special ecosystems where the transfer coefficient may be far less than the assumed 10% conversion factor.

Nutrient Enhanced Coastal Ocean Productivity (NECOP). Data report: CTD and hydrographic data, R/V Pelican cruise, April 3-11, 1993

The Nutrient Enhanced Coastal Ocean Productivity (NECOP) Program is a component of NOAA's Coastal Ocean Program. The central hypothesis of this research is: Anthropogenic nutrient inputs have enhanced coastal ocean productivity with subsequent impacts on coastal ocean water quality, living resource yields, and the global marine carbon cycle. The initial study area for this program is the Mississippi/Atchafalaya River Outflow and adjacent Louisiana shelf region.

Primary productivity in polluted environments of Bombay

The coastal areas of Bombay are generally turbid and the euphotic zone in these waters hardly exceeds 6 m. Primary productivity is largely confined to surface layers. Nearshore polluted stations have low values of dissolved oxygen, salinity and pH. Nutrients, on the other hand, are high. Primary productivity in these areas was 16.86 mg C m super(-3) d super(-1) in October. Column production for all the 4 stations ranged from 10.32 to 2511.30 mg C m super(-2) d super(-1). A direct correlation was found between nutrients and productivity values.

General features and productivity of the Wadge Bank trawl fishery

For several years one of the world's few successful tropical trawl fisheries has been carried on off the southern tip of India. Much of it has been under the auspices of the Government of Ceylon. Records covering the entire history of the fishery are remarkably complete and those of the last ten years are unusually detailed. The purpose of this paper is to summarize these records and relate them to information from other sources in such a way as to illustrate the principal features of the fishery and permit comparisons with other fisheries. This should provide a sound basis for clear thinking about the industry's present problems and prospects. This is important because the fishery is expanding.

Rearing of Labeo bata in sewage-fed fish culture pond

Labeo bata is a highly priced fish which commanding good consumer preference, even if the size is very small (15 to 20 g each), especially in West Bengal. With a view to evaluating the culture potential of this fish, repeated experiments were conducted at the Wastewater Aquaculture Division of the Central Institute of Freshwater Aquaculture, Rahara, West Bengal, during 1991-93 in ponds fed with treated domestic sewage effluent. An average production of 1270.63 kg per ha was obtained within 6 to 10 months for a uniform stocking density of 50,000 seed per ha. The average size attained by the fish in the different sets of experiments varied from 23.3 to 37.9 g as against the initial weight of 0.096 to 0.193 g. Details of management, growth, survival, quantity of sewage used and pond nutrient status and productivity are dealt with in this communication.

Ecology and settlement of marine fouling in the Suez Bay, Egypt

This study deals with seasonal variations, natural correlations and similarities of fouling assemblages on exposure panels in the Suez Bay during January 1992 to January 1993. Three main sources of pollutions flow into the bay; industrial waste products, domestic drainage of Suez city and ships' oil and refuse.The fouling assemblages on the test pan els after various periods (1, 2 and 3 months) belonged mainly to the algae (Ulva rigida), polychaetes (Hydroides elegans), Cirripedes (Balanus amphitrite) and amphipods. The fouling at the lst station was relatively more dense than at the 2nd station during the summer and autumn seasons. The lowest productivity was achieved at the 3rd station which was considered less polluted being offshore water. The overall paucity of fouling in the bay is because of the silt covering the submerged surfaces, particularly at the 2nd station, leading to the prevention of the settlements or establishment of fouling organisms. The seasonal changes in the intensity of fouling assemblages on submerged surfaces in seawater seems to be closely related to seasonal variations in water temperature. The great fouling communities on the buoys and long exposure panels showed a remarkable variety of species and density rather than on short term exposures, which were more dense during warmer months.

Resource productivity and economic performance of producing fish seeds in government and private fanns in Bangladesh

The effect of various factors on spawn and fingerlings production in government and private farms was measured in this study. Primary data were collected from 45 private and 11 government farms from 9 selected districts covering major fish seed producing areas of Bangladesh. Results from Cobb-Douglas production function analysis indicated that the included variables had some positive impacts on returns from spawn and fingerlings. No input was found to be over used and increasing returns to scale was observed. Tabular analysis indicated that higher amount of input use produced higher level of yield, gross return and net return. The government farms were under utilized. For increased supply of fish seeds in the country more amount of specified inputs (feed and fertilizer) should be used for producing spawn and fingerlings especially in government farms.

Water quality of two semi-closed areas in the United Arab Emirates Coast along the Arabian Gulf:a comparative study

A comparative study was carried out between the two biggest creeks along the Arabian Gulf coast of the United Arab Emirates to evaluate impacts of sewage and industrial effluents on their hydrochemical characteristics. Surface and bottom water samples were collected from Abu Dhabi and Dubai creeks during the period from October 1994 to September 1995. The hydrochemical parameters studied were: temperature (21.10-34.00°C), salinity (37.37-47.09%), transparency (0.50-10.0 m), pH (7.97-8.83), dissolved oxygen (1.78-13.93 mg/l) and nutrients ammonia (ND- 13.12,ug-at N/1), nitrite (ND-6.66 ,ug-at N/1), nitrate (ND- 41.18 ,ug-at N/1), phosphate (ND- 13.06 ,ug-at P/1), silicate (0.68-32.50 ,ug-at Si/1), total phosphorus (0.26- 21.48 ,ug-at P/1), and total silicon (0.95- 40.32 ,ug-at Si/1). The present study indicates clearly that seawater of Abu-Dhabi Creek was warmer (28.l2°C) than Dubai (27.56°C) resulting in a higher rate of evaporation. Owing to more evaporation, salinity levels showed higher levels at Abu Dhabi (43.33%) compared to Dubai (39.03%) seawater. The study also revealed higher secchi disc readings at Abu Dhabi Creek (4.68 m) as compared to Dubai Creek (2.60 m) suggesting more transparency at Abu Dhabi Creek. Whereas, seawater of Dubai exhibited higher levels of pH (1.03 times), and dissolved oxygen (1.05 times) than Abu Dhabi seawater due to an increase in productivity. Meantime, seawater of Dubai showed higher tendency to accumulate ammonia (8.22 times), nitrite (10.93 times), nitrate (5.85 times), phosphate (10.64 times), silicate (1.60 times), total phosphorus (3.19 times), and total silicon (1.54 times) compared to Abu Dhabi seawater due to the enrichment of seawater at Dubai with domestic sewage waters which has distinctly elevated the levels of the nutrient salts particularly in inner-most parts of the creek leading to eutrophication signs. The changes occurred in the receiving creek water of Dubai as a result of waste-water disposal that have also reflected on the atomic ratios of nit: Effect of pollution rogen: phosphorus: silicon.

Nutrient profile of pond water in north-eastern state of Tripura and impact of water acidity on aquaculture productivity

Physicochemical parameters of 31 fish pond water samples of Tripura were studied to ascertain the nutrient profile of acidic soil zone and the impact of water acidity towards aquaculture productivity. The pH was acidic (mean 6.63±0.44) with high Fe (mean1.04±0.40 mglˉ¹) and AI (mean 2.67±2.41 mglˉ¹) contents. These were mostly responsible for pond water acidity and poor productivity with low nitrogen, phosphate and total alkalinity. The study also showed strong negative relationship between water pH and redox potential (R²=0.5251). However, pH was positively significant with electrical conductivity. The roles of redox potential and electrical conductivity in water acidity were found highly important. Available calcium content was also found low (mean 2.91±2.96 mglˉ¹). Elevating level of pH of pond water could be the possible management practices in acidic water so that such unproductive water might be productive enough with higher phosphate and nitrogen levels for better biological production.

Adoption, productivity and profitability of rice-fish and fingerling culture in three selected districts of Bangladesh

The study aimed to investigate the productivity and profitability of rice-fish farming. It also determined the factors affecting rice-fish and fingerling production in Bangladesh. Among the total respondents about 55% were involved in rice-fish farming, 37% in pond fish culture and rest 9% in fish nursery. Integrated rice-fish farming contributed about 83% of the annual farm income in Comilla while it was about 20% in both Kishoregonj and Chandpur districts. Among the different farming systems integrated rice-fish culture and rearing fingerlings in the nursery pond were more profitable at the farm level. Farmers earned a net return of Tk. 49,714/ha from integrated fish culture with boro rice while the net return of boro rice-alone was only Tk. 11,179/ha. This indicated that farmer could earn 218% higher net return from integrated rice-fish farming than that of boro rice only farming. Moreover, integrated rice-fish culture also reduced pesticides cost to about 77% and weeding cost to about 51% in boro season. Fingerling nursing earned highest net returns among the three technologies.