Showing papers on "Water column published in 1978"

Sedimentation of particulate matter during a phytoplankton spring bloom in relation to the hydrographical regime

Abstract: Data presented and discussed here were collected continuously during April/May 1975 in the Bornholm Basin of the Baltic Sea. Sedimentation rates of particulate matter were recorded with 5 multisample sediment traps from different depths in the water column at 2 positions 170 km apart. Current meter data collected during the same period and depths indicated that the positions remained hydrographically distinct during the investigation. Particulate matter from the euphotic zone including diatom cells formed the bulk of the material collected by all traps. This flux of organic particles to the bottom was unimpeded by the strong density stratification present in the water column. The upper traps always collected less material than lower ones. This paradox has been ascribed to diminishing current speeds with depth, concomitant with an increase in sinking rates of phytoplankton and phytodetritus. Both factors influence the sampling efficiency of sediment traps, which are thought to have underestimated actual sedimentation rates here. A time lag of 2 to 3 weeks in bloom development seemed responsible for the characteristic differences between the two positions. The phase of major sedimentation at one position covered about 18 days, and a distinct sequence in the composition of the material collected by the 6 glasses of each trap indicated phases of a progressively deteriorating phytoplankton population in the water column contributing the particulate material. A total of 6.2 g C m-2 in 34 days was recorded at this station. Apart from a trap situated in an oxygen deficient layer which collected 0.44 g C m-2 of zooplankton corpses, zooplankton mortality was overestimated by the traps. Large-scale sedimencation of “fresh” organic matter produced by the spring bloom is probably a regular feature in areas with low over-wintering zooplankton populations and, as such, possibly has a direct stimulatory effect on growth and reproduction of the benthos.

Wind events and food chain dynamics within the New York Bight 1, 2

Abstract: Time series of wind, current, nutrients, chlorophyll, and zooplankton are used to examine the effect of storm events on the food chain dynamics of the New York Bjght. Storms cause dilution of phytoplankton concentration in the vertical plane, but lead to aggregation of chlorophyll in the horizontal field. Nutrients are made available with onshore flow in response to wind events favorable for upwelling. A series of nutrient budgets suggest that storm-induced mixing and upwelling of nitrate may satisfy at least 33% of the productivity demand of this system. Examples of the biological response to storms are drawn from 20 cruises during January, March, April-May, and August-September 1974, 1975, 1976, and 1977 under mixed and stratified conditions of the water column. The interaction of storms and seasonal stratification suggests predictable structure and frequency of chlorophyll distribution across the shelf which mav influence both the survival strategies of herbivores and the loci of energy transfer to the rest of the food chain.

Detritus in the Lake Ecosystem

Abstract: Present views of the roles of detritus are not consistent with the ecosystem concept, and result in an underestimation of the importance of carbon and energy pathways involving detritus. Nonpredatory losses from a plant-herbivore transfer, particularly as dissolved organic matter and egestion, may be greater than the amount of material and energy transmitted up the grazer food chain. Ecosystem efficiencies are significantly higher than Lindeman (food chain) efficiencies. Benthic anaerobic metabolism (CO2 production) is greater than benthic oxygen uptake estimates indicate, and the energy-rich intermediate products which undergo deferred respiration (O2 uptake) far from their origin may create redox gradients, drive chemosynthesis, and subsidize bacterial photosynthesis in the water column. Thus, aquatic detrital material, particulate and dissolved, and its metabolism create a dynamic structure in lake sediments and water somewhat analogous to the trophic-dynamic aspect of the biota. However, detrital-dyna...

In situ methane production in a small, hypereutrophic, hard‐water lake: Loss of methane from sediments by vertical diffusion and ebullition 1

Abstract: The rate and quantity of methane produced by sediments of Wintergreen Lake were estimated by separately measuring methane lost by ebullition using bubble traps and by estimating methane lost to the water column by diffusion. The maximum rates of methane loss by ebullition occurred in late summer and were 35 mmol. rnw2. d-i in 1972 and 37 in 1973. The average dissolved methane flux for 1972 was estimated to be in the range of lo-46 mmol. rnw2. d-l. The minimum value was estimated by summing dissolved methane concentrations in the water column for each sampling date. The maximum value was estimated using the eddy diffusion coefficient of 4.9 x 10e3 cm2-s-l, calculated from the temperature method of Hutchinson. This methane diffusion rate was about two times the average rate of methane lost by ebullition (21 mmol*m-2*d-1) over the same time period. Dissolved methane was detected only in anoxic waters during summer stratification and within a meter of both the sediment and ice during winter. Ebullition also occurred during winter.

Aspects of water column primary productivity in the Chukchi Sea during summer

Abstract: Measurements of primary productivity, chlorophyll a, incident solar radiation, phosphate-P, silicate-Si, nitrate-N, nitrite-N, ammonium-N, temperature and salinity were made in the Marginal Ice Zone of the Chukchi Sea in summer 1974. Low to moderate levels of primary productivity (0.07 to 0.97 g C m-2 half-day-1) were observed; primary productivity exceeded 3 g C m-2 half-day-1 at two stations. Surface primary productivity was nitrogen-limited at most stations. Mean chlorophyll a concentration in the photic zone varied from 0.4 to 17.8 mg m-3. Higher concentrations and significant subsurface accumulation of chlorophyll a, reaching 40 mg m-3, were observed in July at stations near the ice-edge than those in open water. No chlorophyll maximum was noted in September, when values ranged from 0.4 to 2.2 mg m-3. It is postulated that the contribution of sea-ice algae to the total chlorophyll content can be substantial, but that the stay of these cells in the water column may not be long. Non-linear regression estimates from solar radiation and chlorophyll-specific primary productivity data showed a maximal photosynthetic rate of 18 mg C mg chlorophyll a -1 half-day-1, an optimal light intensity of 54 langleys half-day-1, and markedly reduced primary productivity at moderately higher light intensities. These features indicate that phytoplankton was shade-adapted.

Pollution indicators and other microorganisms in river sediment.

Abstract: Bacterial indicators of the potential presence of human pathogens in aquatic systems have traditionally been enumerated from the water column. However, recent literature has in cluded several reports of increased numbers of both indicators and pathogens in sediments. Downstream of a wastewater effluent, Hen dricks;1 found approximately 90 percent of Salmonella isolates in the sediments, and dem onstrated a higher recovery rate from sediments than from water. Van Donsel and Geldreich 2 recovered 100 to 1 000 times more fecal coli forms in river mud than in the overlying water. Grimes 3 showed increased numbers of fecal coliforms in the Mississippi River during and after channel dredging and concluded that the resuspended sediments had released coliforms into the water. Reports of survival and multiplication of indicators and pathogens in sediments are even more significant in terms of basic pollution indicator theory. Enteric organisms have been shown to metabolize freshwater sediment eluates,4 and grow and reproduce in predator free marine sediment systems.5 Thus, rapid die-off from the water column may result in increased sediment populations from settlement. The importance of benthic microorganisms is recognized in shallow water systems, since the benthic community accounts for most of the system's biomass 6_8 and metabolic activ ity.6? 7' 9?10 It is clear that sediment analysis for indicators can provide additional water quality information. In the light of this recent evidence, data collected during a 3-year study of indicator and other bacteria and yeasts in the Shetucket River basin in northeastern Connecticut will be presented. For all microorganisms considered, higher concentrations were noted in sediments than in subsurface waters, and a sufficient sup

Distribution, abundance, and metabolic states of microorganisms in the water column and sediments of the Black Sea1

Abstract: The vertical distribution, abundance, and metabolic states of microorganisms have been measured within the water column of the Black Sea. Samples collected from the O2–HS− interface revealed a vertically restricted layer (<20–30 m) of metabolically active cells. Within the anoxic portion of the water column (200–2,100 m), ATP concentrations were 5–10 times greater than in oxygenated environments of comparable depth; biomass and various metabolic activities increased with increasing water depth, implying a vertical gradient in specific organic substrates required for bacterial growth and metabolism. The vertical distribution of ATP was also measured in two sediment cores raised from the western basin of the Black Sea. The ATP concentration within the uppermost sediment layer (0–10 cm) was 4 orders of magnitude greater than in the overlying water column, on a per volume basis (150 ng ATP · cm−3 for the sediments, vs. 10 ng ATP · liter−1 for the water column). Scanning electron micrographs are presented depicting early stages in the diagenesis of framboidal iron sulfide.

Interleaving at the subsurface front in the slope water off Nova Scotia

Abstract: It has been known for some time that a frontal zone exists in the slope water, which lies between the Gulf Stream and the shelf break off Nova Scotia, where the temperature jumps from 7°C to 11°C and the salinity from 34.8‰ to 35.2‰ in a horizontal distance of a few kilometers. Data taken from this area with a yo-yoing CTD (conductivity-temperature-depth probe) have been analyzed and show that at the front the two water masses interleave with a vertical scale of the order of 10 m. The interleaving layers are coherent for several kilometers in the cross-frontal direction and for at least 17 km in the long-frontal direction. The data suggest that considerable vertical mixing, through double diffusive processes, and horizontal mixing, through interleaving processes, occur in the frontal zone. Vertical eddy coefficients of 8 × 10−4 m2/s for heat and 3 × 10−4 m2/s for salt are calculated for the water column between 40 and 160 m at the front by using Turner's (1965, 1967) formulae to calculate the double diffusive fluxes across the interfaces of the layers. The horizontal eddy diffusion coefficients at the front are calculated to be 10 m2/s for heat and 9 m2/s for salt. The estimated annual vertical heat flux at the front into the coastal water is 15% of the solar input to the shelf water, and the salt flux is 10% of that needed to produce shelf water from the freshwater runoff. Horizontal mixing across the front is shown to be large enough to explain the observed annihilation of the Labrador Slope Water during the time that it takes to travel along the Scotian Shelf. The high vertical mixing at the front may provide a significant vertical nutrient flux.

Transport of particulate organic matter by bubbles in marine waters 1

Abstract: Flotation experiments with surface marine waters collected from estuarine, continental shelf, slope, and open ocean waters showed that about half of the originally present particulate organic carbon and nitrogen was adsorbed and transported by bubbles to the surface froth. Recovery values were a function of primary production and other environmental parameters. In only one instance was there evidence of selective removal of particles with C:N ratios differing from those left behind. The estimated open ocean transport of POC by bubbles was five times higher than an earlier estimate due to the unexpected efficiency of the flotation column at low concentrations of open ocean POC. Budget calculations indicated little or no conversion of dissolved to particulate organic carbon. Large macroscopic particles quickly formed in the froth produced by bubbling, an aggregation phenomenon which may be of importance in the transport of large particle POC to deep waters. Particulate matter concentrated in the surface microlayer of the sea may be living or nonliving and is not limited to organic matter (e.g. Parker and Barsom 1970; Liss 1975a,b). Microlayer concentrations of particulate organic carbon (POC) and nitrogen (PON) are substantially greater than the concentrations in the water column below the microlayer (Williams 1967; Nishizawa 197 1). Our work is an attempt to better define processes that lead to the enrichment of organic substances at the air-sea interface and the chemical and physical nature of the concentrated material. An adsorptive bubble separation technique was used to determine the removal and transport of POC and PON by rising bubbles from estuarine, coastal, and open ocean surface seawater samples. The fraction of organic particulate matter in surface waters that possessed an affinity for the air-water interface was thus empirically defined. Baylor and Sutcliffe (1963), Riley (1963), and others have investigated the role of bubbles in the transfer of organic carbon in marine waters from a dissolved

The Saline Lakes of Saskatchewan II. Locale, Hydrography and other Physical Aspects

Abstract: The geology and physiography, climate, soils and vegetation of the saline lakes region of southern Saskatchewan are briefly reviewed. The location and morphometry of 60 saline lakes was determined. Some of them are large (307 km2) but mean depths do not exceed 10 m and many are very shallow. Light penetration varied considerably from very turbid shallow lakes to Redberry Lake where the 1% light level was below 16.5 m. Light extinction coefficients for the entire water column of deeper lakes (7) varied from 0.256 to 2.558. Shallow lakes failed to stratify thermally but a dozen deeper lakes stratified for at least several months. Higher salinity tends to prolong stratification. Thermal stratification augmented chemical stratification in two meromictic lakes. Maximum temperature up to 30 °C in very saline shallow waters was recorded while temperatures as low as-3 °C occurred under the ice. Freezing was delayed and thawing accelerated in more saline lakes. Annual heat budgets varied from 3350 to 13,900 g cal cm-2 in seven lakes. Oxygen concentration was reduced below thermoclines and was virtually absent below the ice in very shallow lakes and, at times, in a very productive lake.

Importance of Mixing, Thermal Stratification and Light Adaptation for Phytoplankton Productivity in Lake Tahoe (California-Nevada)

Abstract: Lake Tahoe is highly transparent (Secchi readings 20—42 metres) and never freezes over. Deep mixing throughout its 500—metre water column occurred in March 1974 and 1975. Between June and October 1974, a distinct epilimnion of 15— to 30—metre thickness existed. Phytoplankton, which is dominated by diatoms, showed no significant vertical shifts in species composition. Chlorophyl α concentrations were highest at the bottom of the trophogenic zone (75—100m) during thermal stratification. Maximum photosynthetic rates were observed at greater depths during winter mixing of the lake than during thermal stratification. In situ experiments, in which incubations flasks containing phytoplankton from 3 discrete depths were distributed over the trophogenic zone, were conducted to study light adaptation. Results indicated that seasonal variation in the vertical distribution of photosynthesis was controlled to a greater extent by algal adaptation to prevailing subaquatic light conditions than by variations in solar irr...

Dissolved silica in pore waters of Lakes Ontario, Erie, and Superior sediments

Abstract: The distribution of dissolved silica in pore waters from Lakes Ontario, Erie, and Superior sediments is not directly related to the deposition of diatomites from the overlying water. It is proposed that silica concentrations in the pore waters are controlled by dissolution of fcrroaluminum silicate, AI,,Fe,,“+(SiO,),(OH)~~,-~~. The cryptocrystalline complex is formed in the sediments by the reaction of biogenic silica with aluminum and ferric oxyhydroxides or by the hydrolysis of clay minerals. A massive episodic flux of biogenic silica to the sediments follows the crash of diatom blooms. Most of the biogenic silica is however dissolved in the water column or at the sediment-water interface; a small fraction is fixed permanently in the sediments as the cryptocrystalline complex. Budget calculations show that regeneration of silica from Ontario and Erie sediments far exceeds annual input from external sources. Considerable insight into the diagenesis of aluminosilicates in Great Lakes sediments can be gained from studies of dissolved silica in interstitial waters, Silica concentrations in pore waters from Lakes Ontario, Erie, and Superior sediments reported by Kramer (1967), Callender (1969), Sutherland (1970), Weiler (1973), and Glass and Poldoski (1975) are subject to possibly large errors due to “temperature of squeezing” effects (see Fanning and Pilson 1971). I report here dissolved silica concentrations in interstitial waters from the three lakes obtained at in situ temperatures and propose a deterministic reaction model to explain the observed concentrations. It is now believed that pollutant phosphorus has stimulated extensive diatom production in the Great Lakes (e.g. Schelske and Stoermer 1971; Duthie and Sreenivasa 1971). An increase in phosphorus loading while the input rate for silica remains constant should result in a net decrease in silica concentration in the lake water, because of increased sedimentation of diatoms. Diatom blooms can deplete silica concentrations in lake water to deficiency levels (Munawar and Munawar 1975). Biological activity in the overlying lake water should therefore increasingly demand silica from the sediments. I present silica budgets to show that regeneration of silica from Lakes Erie and Ontario sediments exceeds the annual input of this nutrient from external sources.

The influence of turbidity on net phytoplankton photosynthesis in some Irish lakes

Abstract: SUMMARY. An important influence on gross photosynthetic rates per unit area is the success with which phytoplankton competes for the available light with non-algal suspended material and dissolved organic compounds. Using a range of Irish lakes, with euphotic zones varying between 0.7 and 20 m and with chlorophyll-α values between 1 and 860 mg m−3, the effect on gross rates of photosynthesis is analysed for changes in the balance between the factors contributing to light attenuation. Net values per unit area are also likely to be modified in well-mixed systems as the ratio of light to dark regions in the water column are altered with changes in light penetration. Depth gradients in dark respiration are reported for L. Neagh which vary according to previous light history and nutrient stress. Possible cases of restraint on phytoplankton growth are discussed for optically deep situations.

Dinoflagellate cysts in the plankton

Abstract: SUMMARY The geographical and seasonal occurrences of dinoflagellate cysts at a depth of 10 m in the North Atlantic and North Sea are described from samples taken by the Continuous Plankton Recorder between June 1973 and December 1975. A special study was made of the large cyst of Polykrikos schwartzii Butschli in the autumn of 1973 when CPR samples were supplemented by vertical sampling in the upper 500 m with a Longhurst-Hardy Plankton Recorder at Ocean Weather Station, INDIA. Only ten isolated records of cysts were made in the western Atlantic. All others occurred to the east of 30° W in both oceanic and neritic waters and especially in the shallow waters of the North Sea. Cysts were found in the spring plankton but were most abundant in the autumn. They have been recorded down to 500 m but occur most frequently in the top 30 m of the water column. Large aggregations of cysts in bottom sediments probably reflect concentration over many years since they cannot be explained by the low numbers found in the plankton. Generally, the distribution of cysts in the plankton is reflected in bottom sediments but concentrations in sediments may be outside the centres of production, implying movement by currents or sediment transport.

Organic 14 C activity in an abyssal marine sediment

Abstract: ONE measure of transport rates and residence times of organic carbon within the various organic carbon pools in the ocean is to follow perturbations from the 1952–58 and 1961–62 atmospheric thermonuclear bomb tests on the natural 14C activities of living, detrital and dissolved organic matter. We report here our measurement of the 14C activity of the total sedimentary organic carbon (SOC) in an abyssal red clay, as no such data were available for this organic carbon pool. Ultimately, these sedimentary organic 14C activities may be compared with the 14C activity of the source organic material in the water column and estimates made of the magnitude of organic carbon consumption at the seawater–sediment interface. What was found, unexpectedly, was evidence for the penetration of recent organic carbon from the 4 cm mixed layer at the sediment–seawater interface down to at least 12 cm in the sedimentary column. This suggests a different and more rapid mechanism for the sedimentation of some fraction of the SOC other than direct association with clay minerals.

Phytoplankton Distribution and Light Attenuation in Port Hacking Estuary

Abstract: The distribution of phytoplankton in a marine dominated estuary is described in terms of in vivo chlorophyll fluorescence, phytoplankton photosynthesis rates at constant irradiance, and the attenuation of solar irradiance by the water column. The phytoplankton distribution was consistent with the physiography and water circulation in the estuary. A method is described for estimating the proportions of suspended sediments, introduced with runoff from the land, which are removed from the estuary by tidal exchange or by sinking. Estimates of the proportions of phytoplankton and detritus in the water column are derived from the relationship of chlorophyll concentration to the extinction coefficient.