Showing papers on "Water column published in 1974"

Measurement of microbial oxidation of methane in lake water

Abstract: A radiotracer method which measures rates of oxidation of methane to cell material, extracellular products, and carbon dioxide has been applied to two lakes and indicates that methane oxidation occurred in a narrow band where methane and oxygen occurred together in the water column. Oxidation rates of 1.0 µM hr−1 were recorded in a eutrophic lake; rates in a meromictic lake reached 0.15 µM hr−1. Usually a third of the carbon from oxidized methane was found in cell material and extracellular products and the rest was converted to carbon dioxide. This ratio was observed to change at very low oxygen concentrations.

Primary Production in the Plankton Community of a Tropical Lake

Abstract: The primary production of Lake Lanao, Philippines, was studied over a 15—mo period by in situ application of C—14 and oxygen—difference techniques. Supporting data include weather, water chemistry, light penetration, and standing crop of both autotrophs and heterotrophs. A statistical treatment of production estimates precedes the presentation of data. Extensive comparison of the oxygen and C—14 methods indicates that the C—14 method as applied in Lake Lanao measures net primary production. Data from time—course experiments show no evidence of diurnal rhythms in the efficiency of photosynthesis per unit area of lake surface. Heterogeneity studies based on transect data indicate that at low to moderate levels of production, the probability that production at an index station will differ from the average for the lake on a given date by more than 30% is less than .05, while the comparable probability for high levels of production is .35. There is no significant difference between stations in mean primary production for the study period. Vertical profiles of photosynthesis exhibit light inhibition on all but the most overcast days. The threshold for inhibition at the surface is near 133 kerg/cm2°s during calm weather and somewhat lower in windy weather. The mean threshold for inhibition 1 m or more below the surface is lower than at the surface (101 kerg/cm2°s). The lake is exceptionally transparent (mean extinction coefficient, 0.38) considering its high productivity and has a vertical dispersion of production that is similar to temperate oligotrophic lakes. The characteristic is explained in terms of the low amounts of dissolved and suspended matter in the euphotic zone, high production per unit of standing crop, and great amount of mixing in the upper water column. Net primary production average 1.7 gC/m2°day, and gross primary production is 2.6 gC/m2°day. Autotrophs account for 80% of respiration in the euphotic zone. Factors controlling seasonal variation are related to resource supply rather than to temperature or biomass removal. Between 12 and 30% of seasonal variation in production can be accounted for by variations in incident light. Light limitation also occurs due to thickening of the zone of mixing during the circulation period and during storms. Nutrient supply is the dominant controlling factor during stratification. Nutrient depletion is relieved at frequent intervals by changes in the depth of mixing associated with storms. High sustained production on a low nutrient base is explained by rapid transfer of nutrients from the zone of decomposition back to the euphotic zone. General conclusions are drawn concerning the relative importance of seasonal and aperiodic variation in regulating the resource supply of temperate and tropical plankton communities.

Suspended solids in water.

Abstract: I. Principles of Studying Suspended Material and Its Settling Velocities.- Principles of Studying Suspended Materials in Water.- Stokes' Settling and Chemical Reactivity of Suspended Particles in Natural Waters.- II. Principles of Optical Techniques.- Beam Transmissometers for Oceanographic Measurements.- Volume-Scattering Functions in Ocean Waters.- Mie Theory Models of Light Scattering By Ocean Particulates.- Spatial Distribution of the Index of Refraction of Suspended Matter in the Ocean.- Absolute Calibration of a Scatterance Meter.- III. Nearshore Studies.- Effects of Tropical Storm Agnes on the Suspended Solids of the Northern Chesapeake Bay.- Distribution and Transport of Suspended Particulate Matter in Submarine Canyons Off Southern California.- Continuous Light-Scattering Profiles and Suspended Matter Over Nitinat Deep-Sea Fan.- Physical, Chemical, and Optical Measures of Suspended-Particle Concentrations: Their Intercomparisons and Application to the West African Shelf.- The Distribution of Particulate Matter in a Northwest African Coastal Upwelling Area.- The Suspended Material of the Amazon Shelf and Tropical Atlantic Ocean.- IV. Offshore Studies.- Turbidity Distribution in the Deep Waters of the Western Atlantic Trough.- Variations in Benthic Boundary Layer Phenomena: Nepheloid Layer in the North American Basin.- Distribution of Suspended Particles in the Equatorial Pacific Ocean.- Suspended Matter and the Stability of the Water Column: Central Caribbean Sea.- Light-Scattering Measurements and Chemical Analysis of Suspended Matter in the Near-Bottom Nepheloid Layer of the Gulf of Mexico.- Light Scattering and Suspended Particulate Matter on a Transect of the Atlantic Ocean at 11 N.- List of Contributors and Participants.

Internal surges in coastal waters

Abstract: A multiple element thermistor chain was installed at the end of Scripps pier in La Jolla, California, in 5 m of water along with a pressure sensor to record sea surface fluctuations. Temperature fluctuations throughout the water column are characterized by the occurrence of events, times during which a significant thermal gradient, of the order of or greater than those associated with the seasonal thermocline in deeper waters, exists in the water column. Temperature differences between the bottom and the surface of up to 5°C have been measured in events that are similar to those reported by Cairns (1967). The contributions of this work are to report (1) that the onset of events can be very rapid, occurring during times of the order of 1 s, (2) that motions exist in the water column at frequencies much higher than the buoyancy frequency that are not directly coupled to the surface wave field, and finally (3) that events are likely to be strongly three-dimensional in such shallow waters. Extrapolations of observations at Scripps pier on a worldwide scale indicate that such events could be responsible for an energy flux into shoal waters ranging between 2×105 kW and 2×107 kW, an estimate which is to be compared with the 2.5×106 kW proposed by Wunsch and Hendry (1972) on the basis of estimates of the power, in the form of internal waves, incident on the coastline of the world.

Sediment turnover by a deposit‐feeding polychaete1

Abstract: Monthly determinations of the size frequency distribution of specimens in a population of Pectinaria caZiforniensis, a deposit-feeding polychacte from Puget Sound, Washington, and laboratory measurements of sediment turnover by the same species reveal seasonal patterns in the rate at which the population processes the sediment during feeding. The relation between numbers of specimens and mean specimen size results in the most intense scdimcnt turnover in late autumn or early winter ( 1 kg dry sediment mm2 month-l), when recently scttlcd animals dominate the biomass. Annual turnover was 8.6 kg dry sediment m-‘. This intense activity is potentially important in the transfer of dissolved materials from sediment to the water column. Rhoads (1973) has suggested that sediment turnover by benthic invertebrates (whereby subsurface material expelled as fecal or pseudo-fecal material into the water column is redeposited on the substrate surface) may be responsible for much of the turbidity of overlying water and perhaps for the recycling of nutritive material from sediment to the water column. Equally important, the activity of such organisms may result in the resuspension or solution of other tract substances (pollutants or otherwise) found in deposited scdimcnt. For example, Bothner ( 1973) suggested that resuspension of bottom sediments by benthic organisms may partly account for the observed dccrcase of mercury with time from contaminated estuarine sediments in Bcllingham Bay, Washington. Increased knowledge of the processes of sediment turnover by bottom dwelling organisms would help us to understand the mechanisms of the flux of trace substances at the scdimcnt-water interface. Several investigators (Fox et al. 1948; Rhoads 1963; Mangum 1964; Gordon 1966; Rhoads 1967) h avc mcasurcd rates of sediment turnover by a variety of intertidal and shallow subtidal invertebrate speciesthe amount of time required by species populations to rework completely all the sediment in a given area to the depth ac1 The research was supported in part by National Science Foundation Grant GB 13205. cessiblc to ( adult?) individuals. Estimates of population size (used to convert laboratory-determined turnover rates of individuals to annual rates on areal bases) were made by these workers primarily from data from one season, usually summer. The turnover or reworking rates of individual species so determined vary from a low of once every 15 years to a high of once every 10 weeks (disregarding species diffcrenccs and slight differences in the reworking depth used in the calculations). Most rates, however, fall in the range of 1 to 5 years for populations of individual species (Mangum 1964; Rhoads 1967). The investigation described here represcnts an extension of a study of the dynamics and energetics of three depositfeeding benthic invertebrates ( Nichols 1972), in which rates of sediment turnover by one of these, the polychaetous annelid Pectinaria calif orniensis Har tman, were measured. Watson (1927) provided detailed dcscriptions of feeding and tube-building processes of adult specimens of Pectinaria koreni. The animals burrow, head down, into the sediment with the small end of the cone-shaped tube protruding slightly from the sediment surface. They handle sand grains individually with tentacles, ingcsting some grains, cementing others of precise size and .texture onto the large end of the tube, and propelling unused material out through the upper end of the tube. UnLIMNOLOGY AND OCERNOGRAPIIY 945 NOVEMBER 1974, V. 19 (6)

Summer phytoplankton blooms in Auke Bay, Alaska, driven by wind mixing of the water column1

Abstract: Winds blowing from the southeast along the only significant fetch into Auke Bay mixed nitrate into the photic zone from deeper in the water column; major summer phytoplankton blooms in the bay resulted. The wind-mixing effect could bc monitored by measuring salinity changes in the water column caused by mixing of freshwater from the glacially originating Mender-mall River down into the water column. Phytoplankton productivity in an estuary depends on the interaction of physiological characteristics of endemic phytoplankton populations, the particular hydrographic characteristics of the esturay, local meteorological conditions, and nutrient input from the land. Smayda (1957) found that in the relatively shallow Narragansett Bay, where tidal mixing prevented development of a stable water column, stability was not important in controlling phytoplankton blooms, but stability of waters outside the bay acted to contain phytoplankton populations within the bay and allowed blooms to develop. Gilmartin ( 1964)) on the other hand, observed that seasonal variability in stability of the water column was the primary factor controlling phytoplankton production in a British Columbia fjord. Much of the annual variation in primary production in St. Margaret’s Bay, Nova Scotia, could be attributed to the influence of weather on the hydrographic regime of the bay (Platt 1971). Bruce (1969 ) described a succession of phytoplankton blooms in Auke Bay, Alaska, throughout the summer in a water column ‘This work was supported in part by National Marine Fisheries Service Coastal Oceanographic Laboratory, Auke Bay, Alaska, Contract 14-l70005-297 and by National Oceanic and Atmosshperic Administration Institutional Sea Grant 2-35187, and is part of a Ph.D. thesis presented to Oregon State University by R.L.I. which was always positively stable. Auke Bay ( Fig. 11) is a small embayment in a large fjord-estuarine system in Southeast Alaska near Juneau. It is 110 km from the ocean and relatively isolated from oceanic effects and from major currents within the large estuarine system, with an area of about 11 km2 and deep enough that tidal effects (spring tide range 6 m) do not destroy water column stability. Bruce (1969) showed that availability of nitrate-nitrogen limited phytoplankton growth in the bay during summer. A mechanism for producing major summer phyoplankton blooms in Auke Bay, based on wind mixing of nitrate-rich water from deeper layers into the photic zone, is

Deep sea sedimentation

Abstract: An important problem in the study of microparticles in the marine environment, suspended in the water column or deposited as sediment on the ocean bottom, is the determination of provenance of the ...

Ecological studies on Chaoborus (Diptera, Chaoboridae) in Lake George, Uganda

Abstract: Summary (1) Chaoborus anomalus and Chaoborus ceratopogones were found together throughout the year in Lake George, Uganda, the larvae forming 65-85% by number of the macro-benthos of the central lake area. (2) First and second instar larvae were wholly planktonic and third and fourth instar larvae mainly benthic during the day, migrating into the water column at night. A proportion of the third and fourth instar larvae were found in the water column during the day in the centre of the lake where light attenuation was greatest. C. anomalus showed a greater tendency to be benthic than C. ceratopogones. (3) Planktonic larvae were distributed in dense patches thought to be cohorts resulting from oviposition by swarms of adult females. The maximum density of planktonic larvae recorded was 31.7 × 102/m2 column. Third and fourth instar larvae were more evenly distributed in the benthos of the central lake area, the maximum density recorded was 79.9×102/m2. (4) First and second instar larvae occurred mainly in the inshore regions, very few were found in the centre of the lake. Oviposition is likely to take place inshore. The patches of planktonic larvae were not stationary. Dispersal of larvae away from the shore may be active or may result from complex oscillations of the water mass produced by storms. In C. ceratopogones the floating egg batches could he carried away from the north shore by currents produced by inflows and prevailing winds. (5) Adults of C. ceratopogones were more numerous during the rainy seasons than during the dry seasons. A similar, though less marked seasonality was found in the occurrence of C. anomalus adults. The biomass of benthic larvae of C. ceratopo-gones was estimated at 387.0 mg C/m2 in the dry season, June 1970, and 130 0 mg C/m2 in the rainy season, October 1970. That of C. anomalus was constant at 241.7 and 254.3 mg C/m2 in June and October, 1970 respectively. (6) No difference was found in the horizontal distribution of the larvae, or in the size and weight attained by the various stages. (7) Interspecific differences were found in the mean number of eggs per adult female (309, C. anomalus and 224, C. ceratopogones); in the nature ofthe egg batches; n i the morphology of the larval mouthparts and pharyngeal sphincters, as well as i n the vertical distribution of the larvae and seasonal occurrence of the adults. On the basis of these differences the co-existing species are thought not to be competing for the same resources.

Turbidity Distribution in the Deep Waters of the Western Atlantic Trough

Abstract: The “background” turbidity (clearest water of the water column) has been mapped in the western Atlantic using standardized nephelometer measurements taken on R/V Conrad cruises 15 and 16. This background has then been utilized as a reference turbidity to map features of the bottom-water turbidity using older unstandard-ized relative nephelometer profiles. Variations in background turbidity of a factor of 3 apparently reflect the pattern of biological productivity in the overlying surface waters: high background in an equatorial belt and in latitudes greater than the subtropical convergences, but low background in the temperate latitudes. The resulting distributions of near-bottom turbidity values show a maximum in the southwestern Argentine Basin and a lesser maximum along the continental rise of the North American Basin. Bottom turbidity in the nepheloid layer decreases from both basins toward the equator and appears to be both a function of bottom current velocity and proximity to terrigenous sediment sources.

The seasonal succession and vertical distribution of the phytoplankton in Abbot's Pond, North Somerset, U.K.

Abstract: Abbot's Pond provided constrasting environments through the year which supported differing algal populations. Permanent thermal stratification and the depletion of oxygen in the hypolimnion together with accumulation of nutrients within the latter provided two distinct regions that supported different algal populations. In the photic epilimnion, Chlamydomonas, Pandorina, Scenedesmus and Stephanodiscus formed dominant populations whereas in the lower regions, to where very little light penetrated, Cryptomonas rufescens and Trachelomonas volvocina formed dominant populations. The irregular occurrence of the “other main phytoplankters” indicated that their ecological niches were smaller than those of the Diatoms and Chlorophyceae which occur each year. Chrysococcus was able to develop large populations in conditions of low turbulence and to maintain itself again in low turbulent conditions at the limit of light penetration when turbulence did increase in the upper regions of the water column. The occurrence of the small Rhodomonas appeared to be associated with high nutrient levels in the water and not with temperature of water. Similarly Trachelomonas volvocina populations were associated with high nutrient levels but in conditions of very low oxygen levels, as were C. rufescens populations. Trachelomonas volvocina var. minuta occurred for the first time in 1969 and appeared to die as the water column became more stable and nutrient levels in the epilimnion fell. Therefore, growth of algal populations of Abbot's Pond was dependent upon the physical, chemical and biological factors found within the water column.

Simulation model for wind-driven summer phytoplankton dynamics in Auke Bay, Alaska

Abstract: A model was developed for use in simulating effects of short-term wind-mixing of the water column on estuarine phytoplankton dynamics. Simulation results, using parameter values estimated from field data, exhibited maxima observed in phytoplankton standing crop over a summer in Auke Bay, Alaska. Short-term wind-mixing of the water column can be important in determining the time of occurrence of phytoplankton community productivity pulses in deep estuaries.

Phytoplankton productivity in findley lake

Abstract: Findley Lake is a dimictic, oligotrophic, subalpine lake located in the western Cascade Mountains, Washington. The lake is snow covered for most of the year so that the growing season was 3.5 months in 1971 and 4.5 months in 1972. Rapid melt of the lake's snow cover in summer allowed the sudden development of a phytoplankton productivity maximum (as measured by the 14C tracer method) of 86 mg m−2 hr−1 and a peak of 48 mg chlorophyll a per m1 within two weeks of surface clearing in 1972, followed by a rapid decline of productivity and biomass. Annual production (between 10 October, 1971 and 21 October, 1972) was 36 g/m2 in the 27.5 m water column. Autotrophic carbon assimilation during the snow-covered period was insignificant. The total production for the lake in 1972 was 530 kg carbon. The concentration of available nitrogen (NO2 + NO3 + NH3 as N) at 15 m ranged from 12 to 76 mg/m3 while PO4-P ranged from 0.5 to 8.3 mg/m3. In vitro nutrient enrichment experiments with natural phytoplankton communities from the lake indicated that while N and P together were growth limiting, P alone produced a growth response while N alone did not. Contributions to production from net-, nanno-, and ultraplankton were determined by fractional filtration of 14C-labeled phytoplankton samples. The nannoplankton, dominated by diatoms, accounted for 58% to 94% of productivity.

On thermal stratification in large bodies of water

Abstract: A method of predicting water temperature in large bodies of water has been presented in this paper. The vertical water column is subdivided into two layers: an isothermal surface layer and a temperature-stratified diffusion layer. Meteorological data, either real or imposed, are used for calculating the variation of water temperature with time in the surface layer utilizing the thermal budget method. Then in the diffusion layer the temperature profiles are obtained by solving the time-dependent energy equation by the similarity technique with variable density, conductivity, and diffusivity and zero velocity. Calculated water temperatures are compared with the measured values. The comparison shows favorable agreement.

Suspended Matter and the Stability of the Water Column: Central Caribbean Sea

Abstract: Total suspended matter, TSM, was measured in the water column at 4 stations in the central Caribbean Sea in relationship to the vertical profile of static stability. It is postulated that the several TSM maxima at depth are associated with zones of low turbulence, and the near-bottom nepheloid layer observed in many areas of the world ocean is a function of a near-bottom density increase coupled with a bottom shear capable of suspending fine sediment. The absence of one or both of these criteria explains the reported lack of a nepheloid layer in the Caribbean.

Measurement and interpretation of nonvolatile hydrocarbons in the ocean. part i. measurements in atlantic, mediterranean, gulf of mexico, and persian gulf

Abstract: Little quantitative data are available on the amount and composition of hydrocarbons in the sea. To obtain such data, water samples were taken from tankers along four main routes in the Atlantic and adjacent seas and in other locations from oceanographic research vessels. Floating oil or tar balls were not collected. The water samples were extracted with carbon tetrachloride. The amount of extractable organic material and the amount and composition of nonvolatile hydrocarbons were measured. Hydrocarbons (with a mean of 4 ppb) were log-normally distributed in the samples collected through the top to meters of the water column. In deeper ocean waters hydrocarbon content generally declined with depth, and the median value was less than 1 ppb. Based on relative amounts of hydrocarbons and of total CCL4 extractable material, it is estimated that the hydrocarbons are mostly petroleum-derived in locations where petroleum input into the sea is likely. Additional work is needed to confirm and extend these findings.

Man-made plutonium in freshwater and marine environments

Abstract: Significant concentrations of plutonium isotopes are found in lake and coastal marine sediments accumulating at rates of 1–5 mm/yr The activity levels of239, 240Pu range between 0·7–3·3 dpm/g for post 1960 sediments The measured and the calculated integrated activities of239Pu in the lake sediments are in agreement This suggests that plutonium is chemically reactive in freshwater environments and it is removed to sediments from the water column shortly after its injection

Distribution studies of plutonium in the Great Lakes

Abstract: The distribution of residual fallout plutonium in Lake Michigan between water and various trophic levels of the food chain has been studied. Concurrent measurements of the conservative fallout radioisotope $sup 90$Sr in the water column are used to estimate the cumulative fallout deposition on Lake Michigan; these data indicate that ca 97 percent of the fallout $sup 239$Pu (and ca 94 percent of the fallout $sup 137$Cs) presently constitute a sediment reservoir pool. The results of analyses of comparison samples of water, plankton, and fish indicate that the residual fallout $sup 239$Pu remaining in the water column has attained a consistent physicochemical form in all 5 Great Lakes.

Suspended matter and the stability of the water column

Abstract: TotaZ suspended matter, TSM, was measured in the water aoZumn at 4 stations in the aentraZ Caribbean Sea in reZationship to the ver­ tiaaZ profile of statia stability. It is postuZated that the sevel"­ aZ TSM maxima at depth are assoaiated with zones of Zow turbuZenae, and the near-bottom nepheZoid Zayer observed in many areas of the worZd oaean is a funation of a near-bottom density inarease aoupZed with a bottom shear aapabZe of suspending fine sediment. The ab­ senae of one or both of these ariteria expZains the reported Zaak of a nepheZoid Zayer in the Caribbean.

The Hydrography of Estuary, Delaware z the Murderkill

Abstract: The hydrography of the lower Murderkill River, a small, Shallow estuary in southeastern Delaware, was studied from July, 1967, through December, 1970. Variations of current velocity, tide stage, salinity, water temperature, and dissolved oxygen were measured at one station in the estuary during periods of mean and high freshwater runoff. The flushing time and mixing characteristics of the estuary during mean runoff were determined using a water-tracer dye. Seasonal and tidal variations of salinity, water temperature, dissolved oxygen, pH and turbidity were measured at seven stations along the estuary from September, 1969 through December, 1970. The Murderkill Estuary has characteristics of both a well-mixed and partiaUy-mixed estuary. The prevailing hydrographic regime is maintained by tidal mixing and forced river flow which disrupt density-induced, internal circulation. Approximately 90% of the upsffeam salt flux is maintained by diffusion. During mean freshwater runoff the estuary discharges 1.7  l0 s m 3 of freshwater seaward per tidal cycle and has a flushing time of 4.4 tidal cycles. The flushing time decreases from 18.4 tidal cycles during low runoff, 3.1  104 m 3 per tidal cycle, to 2.6 tidal cycles during high runoff, 3.1  l0 s m 3 per tidal cycle. The proposed daily discharge of 3.8  104 m 3 of sewage effluent into the estuary will shorten the flushing time of the estuary at the discharge site from 4.4 to 3.9 tidal cycles during mean runoff. Salinity distributions in the estuary are highly variable. At high water, the lower reaches of the estuary are occupied by moderately saline water, 15.7 to 28.2 o/oo, from lower Delaware Bay. Vertical and longitudinal salinity gradients are small. In the central section of the estuary, salinity decreases from values characteristic of lower Delaware Bay to 1.0 o/oo. Mean vertical salinity differences are 2.0 o/oo, and the mean longitudinal salinity gradient is 2.7 o/oo per km. In tidal freshwater, salinity does not exceed 1.0 o/oo, and salinity gradients, vertical and longitudinal, are small. At low water, salinity in the lower reaches of the estuary is reduced substantially. The water column is well mixed, and the mean longitudinal salinity gradient is 2.4 o/oo per km. Tidal freshwater occupies the upstream 30% to 70% of the estuary with increasing runoff. Dissolved oxygen concentrations in the estuary range from 10 to 12 rag/liter during the winter to 2 to 3 mg/liter during the summer. A zone of oxygen depletion appears in the central section of the estuary. This section will receive the effluent from the sewage-treatment facility. Oxygenated water presently enters the central section of the estuary from inland freshwater runoff and from lower Delaware Bay.