Showing papers on "Water column published in 1969"

Fayetteville green lake, new york. ii. precipitation and sedimentation of calcite in a meromictic lake with laminated sediments1

Abstract: The activities of calcium and carbonate in Fayetteville Green Lake were estimated from detailed seasonal measurements of pH, calcium, and titration alkalinity. By comparison of observed ion activity products (IAP) for Ca2+ and CO32− with the calcite equilibrium activity product (Kcq), the water column was found to be supersaturated throughout the year. In the surface waters of the mixolimnion, the ratio IAP: Keq increased from 2 to 4 in winter to 6 to 8 during late May through October. Precipitation of calcite was confirmed by collection of crystals in the water column by filtration, identification by X-ray diffraction, and quantitative measurement by a gas chromatographic technique. Maximal crystal loads of 35 g CaCO3 m−2 in the water column occurred in June and July (1965–1967), while calcite loads in fall, winter, and early spring were reduced by an order of magnitude. From isopleths of suspended calcite, settling rates of 2–4 in day−1 were estimated for spring, which was close to values predicted from Stokes’ Law. About 90% of the total sedimentation occurred from June through October, and 80% of this mass was calcite. The laminae occurring in monimolimnetic sediments were regarded as annual couplets resulting from seasonal sedimentation of calcite, with deposition of organic matter throughout the year. The sedimentation rate derived from sediment trap data was 300 g dry matter m−2 yr−1. From the chemical composition of these samples, sedimentation rates were derived for CaCO3, acid insoluble organic carbon, acid insoluble nitrogen, and total nitrogen, sulfur, phosphorus, silicon, and iron.

Responses to salinity change as a tidal transport mechanism of pink shrimp, penaeus duorarum

Abstract: 1. The inshore movements of postlarval pink shrimp and the subsequent offshore movements of the juveniles are facilitated by flood and ebb tides, respectively. This investigation concerns the behavioral mechanisms involved in the selective use of one tide and the evasion of the other.2. Salinity changes, similar to those occurring with change in tide in the inshore environment usually occupied by pink shrimp, were imposed on both postlarvae and juveniles in a constant-current apparatus.3. Juvenile shrimp were almost invariably positively rheotactic. However, with a decrease in salinity the sign of the response was reversed, resulting in active downstream swimming. This often gave way to passive drifting.Under conditions of low light intensity postlarvae were active in the water column, and being unable to withstand even slow currents, were easily displaced. With a decrease in salinity they sank to the substrate or remained low in the water column where they were better able to maintain position.4. Respons...

Thermal Stratification in the Arctic Ocean

Abstract: Fine scale measurements of the vertical temperature profile in an Arctic water column show the presence of several cascaded isothermal layers. Layers between the depths of 300 anid 350 meters range from 2 to 10 meters in thickness, while the temperature change between adjacent layers is approximately 0.026 degrees C. The individual layers are isothermal to within +/- 0.001 degrees C.

Composition and Horizontal Distribution of Crustacean Plankton in Lake Ontario

Abstract: The horizontal distribution of planktonic crustaceans was determined in Lake Ontario at monthly intervals from June to October 1967, based on net hauls from 50 to 0 m at 32–62 stations. A separate study conducted over a 24-hr period at one station showed that on the average 90% of the zooplankters occupied the 0–50-m stratum through which the net was hauled. Eleven species of copepods and 11 species of cladocerans were found. The most abundant forms were Cyclops bicuspidatus thomasi, Daphnia retrocurva, Bosmina longirostris, Bosmina coregoni coregoni, Tropocyclops prasinus mexicanus, and Ceriodaphnia lacustris. Most species appeared in the collections during June–July in the eastern part of the lake with abundance patterns later moving westward, contrary to the general movement of wind and water. At the time of maximal population density there was a strong positive correlation between zooplankton abundance and heat content of the water column from 0 to 25 m. The eastern part of the lake averaged 1.7 times...

Mesopelagic fishes and thermal fronts in the western Sargasso Sea

Abstract: Analysis of 25 midwater trawl collections, disposed along the meridian 70°20′W from off Hispaniola to the Gulf Stream, showed a change in the mesopelagic fish fauna at about 27°N. The point of faunal change corresponded to a change in the temperature structure of the upper part of the water column, i.e., at a (the?) so-called “thermal front”, perhaps identical to the so-called “North Atlantic subtropical convergence”. Of 44 species occurring in four or more collections, 13 species were collected only to the north of the front and 1 species only to the south. By most criteria, north-of-the-front collections were larger than southern ones. This is in accord with the north-south difference in primary production noted by other workers which, in turn, seems atributable to the north-south difference in temperature structure. To the north the upper part of the water column is well stratified in summer only, while to the south it is well stratified at all seasons. Taken altogether, what is now known suggests that the thermal front logically divides the upper Sargasso Sea into northern and southern portions that differ in many ways.

Current System in the Northern Irish Sea

Abstract: IN the past four years direct measurements of the tidal streams in the northern Irish Sea have been made synoptically over an extensive area and at various points in the water column. Before these studies, the circulation of the sea was largely a matter of qualitative deduction, based on surface temperature and salinity charts, the movement of surface drift bottles and a few rather broad-based estimates of water transport derived from consideration of the continuity equations for a variety of parameters1.

Salinity and water circulation in the vellar estuary

Abstract: This paper reports a series of measurements of salinity, temperature, and current velocity in the Vellar estuary. This typical bar-built estuary is shown, by comparison with dimensionless stratification parameters, to be a salt wedge at high river discharge and well stratified at low river discharge. During the tidal cycle, the salt wedge near the bottom became isolated in a series of basins during ebb tide; short period diffusion along the intense halocline seems to have been an important process in the salt balance of the water column. The water circulation at high river discharge was dominated by a meander system of alternating scour holes, with the high seaward flow in the deepest areas. Superimposed on this was a secondary lateral circulation system that broke down and reversed its sense at low river flows when the saline inflow developed.

Selective Withdrawal from Density-Stratified Reservoirs

Abstract: In lakes and reservoirs stable density stratification is caused primarily by the temperature variation with depth, and secondarily by a variable concentration of dissolved and suspended solids. In the summer the surface layers are heated strongly by the sun, while wind and surface evaporation cause mixing in a surface zone, called the epilimnion, which is fairly uniform in temperature. Below this is the thermocline through which the temperature decreases rapidly to that of the lower zone, the hypolimnion, which feels negligible effect of the surface heating. During the fall and winter, the epilimnion cools, often to such an extent that the whole water column overturns and becomes fairly well mixed. In the spring the stratification is gradually reestablished. This is briefly the annual regime of lakes with little inflow or outflow. Man-made reservoirs have thermal regimes similar to lakes, but with the added effects if substantial inflows and outflows, which contribute to the heat and mass balance. Incoming river flows may sometimes spread out on the lake surface, if they are less dense than reservoir water, or may plunge to the bottom or to some intermediate level of neutral buoyancy, where an internal density current is formed. The river water density depends on its concentration of dissolved salts and suspended sediments as well as its temperature.

Temperature Measurements in the Bottom Layers of the Red Sea Brines

Abstract: Detailed measurements of temperatures in the water layers immediately above the sediments in Atlantis II and Discovery Deeps are presented. In the bottom 60m of Discovery Deep there is a cooling of 0.5°C as the sediment is approached; above 60m the temperature gradient is adiabatic except for a discrete temperature change at 80m. The water column at the bottom in Atlantis II Deep is stable. These results suggest periodic outflow of hot saline water from Atlantis II Deep into Discovery Deep.

Methane distribution in Holocene marine sediments in the Bornholm Basin, southern Scandinavia

Abstract: The Baltic Sea is an ideal natural laboratory to study the methane cycle in the framework of diagenetic processes. In this paper we present preliminary geological mapping results from project Baltic Gas, a research project with the overall aim to contribute to the development of a scientific basis for long term sustainable use and protection of the Baltic Sea ecosystem. The Baltic Sea is a marginal sea with a strong permanent haline stratification, which leads to oxygen-poor bottom waters, and which is sometimes interrupted by oxygen-rich saltwater flowing in from the North Sea. The history of the Baltic Sea has resulted in deposition of organic-rich Holocene marine sediments that overlie glacial, late-glacial and early Holocene organic-poor sediments. The aims of Baltic Gas, a project within the BONUS-169 Joint Baltic Sea Research Programme running from 2009 to 2011, were (1) to map the occurrence of free shallow gas in Holocene sediments, (2) to quantify methane fluxes through the sediments and into the water column and the atmosphere, and (3) to investigate the processes and parameters governing methane generation and consumption. The contribution by the Geological Survey of Denmark and Greenland, reported here, was to map the thickness and structure of organicrich marine deposits and the distribution of gas-bearing sediments in co-operation with partners. The authors have also compiled acoustic data which were used to select sites for a comprehensive coring programme. The sediment cores were used for physical characterisation of the gas-bearing sediments and for biogeochemical analyses. These included measurements of the concentrations of methane, sulphide, sulphate, iron and other elements and compounds. Here we present data from the Bornholm Basin, one of several key study areas (Fig. 1).