Postulated responses of phytoplankton and bacteria to predicted increases of inorganic suspended sediments in oligotrophic lakes     

Marc Schallenberg  Udo Friedrich  Carolyn W. Burns 《新西兰海洋与淡水研究杂志》2013,47(4):763-779

We establish the relationships between concentrations of inorganic suspended sediments (ISS) on light, nutrients, phytoplankton, and bacteria in three oligotrophic lakes (four sites) and we use these relationships to predict the impacts of increasing concentrations of ISS on the biomass and productivity of phytoplankton and bacteria in the lakes. Increased concentrations of ISS contributed little available nutrient to the lakes. The relationships between ISS and underwater light attenuation differed among lakes because of variation in sediment size‐structure, and composition. Only at the site with the highest ISS concentrations and a relatively deep mixing depth, were phytoplankton apparently light‐limited and, thus, predicted to decline with increased ISS concentrations. In contrast to previously published studies, bacterial abundance and production were not highly correlated to suspended sediment concentrations in these lakes. However, bacterial biomass, productivity, and specific productivity were more strongly correlated to phytoplankton production. As a result of light limitation and stimulation of bacterial production, increases in ISS concentrations are not predicted to significantly shift the metabolic balance in the planktonic ecosystem of three of the sites towards greater heterotrophy. Where light limits phytoplankton production, increases in ISS are predicted to reduce the productivity of both phytoplankton and bacteria by direct inhibition of phytoplankton production, again without a large shift towards greater importance of the microbial loop. By reducing phytoplankton production and inhibiting larger cladoceran grazers, we predict that high concentrations of ISS will reduce available energy and its flow up the food chain.  相似文献   

Paired comparison models in biostratigraphy     

Carolyn Brauer Hudson  Frederik P. Agterberg 《Mathematical Geology》1982,14(2):141-159

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Intertidal mudflat properties, currents and sediment erosion in the partially mixed Tamar Estuary, UK     

Reginald J. Uncles  Anthony J. Bale  Mary D. Brinsley  Patricia E. Frickers  Carolyn Harris  Roy E. Lewis  Nicholas D. Pope  Frederick J. Staff  John A. Stephens  Carol M. Turley  John Widdows 《Ocean Dynamics》2003,53(3):239-251

Results are presented from a 1-year campaign to measure the seasonal variability of some key physical and biological properties of intertidal mudflats over a section of the central Tamar Estuary and to relate these to the physical environment. Seasonal variations in physical mudflat properties, such as grain size, density and moisture content were relatively small. With the exception of the particulate organic carbon content in the upper 0.002 m of surface sediment, biological variations were large. Redox potential exhibited considerable seasonal variation and showed that the sediments were less reduced in winter and more reduced in summer. Chlorophyll a and extracellular polymeric substances (EPS) within the surface 0.002 m of sediment (due to the presence of benthic diatoms) were strongly correlated and exhibited a pronounced seasonal pattern, with smallest values during winter and greatest values during late summer and early autumn. EPS had a dominating influence on sediment erosion, as determined from annular flume measurements. Velocity measurements and velocity modelling indicated that during the flood, and for much of the time during benthic diatom bloom conditions of high chlorophyll a and EPS sediment contents, the stresses exerted by tidal currents were too small to cause significant suspension of sediments over much of the middle and upper mudflats. Suspended fine sediment in the turbidity maximum zone was transported down-estuary and deposited in the main channel at low-water (LW) slack. Some of this sediment, in the form of relatively large aggregates, was subsequently transported onto the mudflats during the flooding tide, where slack currents and fast settling velocities may have enhanced sediment deposition there.Responsible Editor: Hans Burchard  相似文献   

The groundwater geochemistry of the Bengal Basin: Weathering, chemsorption, and trace metal flux to the oceans     

Carolyn B. Dowling  Robert J. Poreda 《Geochimica et cosmochimica acta》2003,67(12):2117-2136

Sixty-eight groundwater samples from the Ganges-Brahmaputra floodplain in the Bengal Basin were analyzed to assess the groundwater geochemistry, the subsurface hydrology, the buffering effects of sediments on trace metal concentrations and their isotopic compositions, and the magnitude of the subsurface trace element flux to the Bay of Bengal and to the global ocean. Samples obtained from depths of 10 to 350 m were measured for major and trace elements, dissolved gas, and tritium. On the basis of the ³He/³H ages, the groundwater at depth (30-150 m) appears to be continually replenished, indicating that this recharge of groundwater to depth must ultimately be balanced by a significant quantity of submarine discharge into the Bay of Bengal. Using the ³He/³H groundwater age-depth relationship to calculate a recharge rate of 60 ± 20 cm/yr, we estimate a subsurface discharge into the Bay of Bengal of 1.5 ± 0.5 × 10¹¹ m³/yr, or 15% of the surface Ganges-Brahmaputra river (GBR) flux. Several trace elements, especially Sr and Ba, display elevated concentrations averaging 7 to 9 times the surface GBR water values. The submarine groundwater fluxes of Sr and Ba to the oceans are 8.2 ± 2 × 10⁸ and 1.5 ± 0.3 × 10⁸ mol/yr, or 3.3 and 1.2%, respectively, of the world total, or equal to the surface GBR Sr and Ba estimated fluxes. Our groundwater flux for Ba agrees with the estimate of Moore (1997) (3 × 10⁸-3 × 10⁹ mol/yr), on the basis of measured Ba and Ra excesses in the Bay of Bengal. Other trace metals, such as U and Mo, are at low but measurable levels and are not major contributors to the global flux in this river system. A comparison of the Sr and Ba concentrations, plus ⁸⁷Sr/⁸⁶Sr ratios in groundwater to the oxalate extractable fractions of a coastal sediment core, suggests that weathering of carbonates and minor silicates, coupled with cation exchange plus adsorption and desorption reactions, controls the trace element concentrations and ⁸⁷Sr/⁸⁶Sr isotopic compositions in both the groundwater and river water. Our data also imply that other coastal floodplains (e.g., the Mekong and the Irrawaddy rivers) that have high precipitation rates and rapid accumulation of immature sediments are likely to make significant contributions to the global oceanic trace metal budgets and have an impact on the Sr isotopic evolution in seawater.  相似文献   

A Comparison of Three Functional Forms for Representing Soil Moisture Characteristics     

Amar C. Bumb  Carolyn L. Murphy  Lome G. Everett 《Ground water》1992,30(2):177-185

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Preliminary petrographic description and geologic implications of the Apollo 17 Station 7 boulder consortium samples     

E.C.T. Chao  Jean A. Minkin  Carolyn L. Thompson 《Earth and Planetary Science Letters》1974,23(3):413-428

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The sedimentary record of drifting ice (early Wisconsin Sunnybrook deposit) in an ancestral ice-dammed Lake Ontario, Canada     

Nicholas Eyles  Carolyn H. Eyles  Todd A. Randall 《Quaternary Research》2005,63(2):171-181

Outcrops of pebbly mud (diamict) at Scarborough in Southern Ontario, Canada (the so-called Sunnybrook ‘Till’) are associated with the earliest incursion of the Laurentide Ice Sheet (LIS) into mid-continent North America some 45,000 years ago. The Sunnybrook is a blanket-like deposit containing deepwater ostracodes and occurs conformably within a thick (100 m) succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake. Contextual evidence (associated facies, sedimentary structures, deposit geometry and landforms) indicates a low energy depositional setting in an ice-dammed ancestral Lake Ontario in which scouring by floating ice masses was an important process. U-shaped, iceberg-cut scours (with lateral berms) up to 7 m deep, occur on the upper surface of the Sunnybrook and are underlain by ‘sub-scour’ structures that extend several meters below the scour base. Ice-rafted concentrations of clasts (‘clast layers’), grooved surfaces formed by floating ice glissading over a muddy lake floor (‘soft sediment striations’) and melanges of sand and mud mixed by grounding ice keels (‘ice keel turbates’) are present and are all well known from modern cold environments. The wider significance of this depositional model is that the LIS margin lay east of Scarborough and did not overrun Southern Ontario. This finding is in agreement with recent data from the Erie Basin of Canada, Ohio, and Indiana where deposits formerly correlated with the Sunnybrook (and thus implying an extensive early Wisconsin ice sheet) are now regarded as Illinoian. A speculative hypothesis is proposed that relates deposition of the Sunnybrook and two younger deposits of similar sedimentology, to surge-like instabilities of the southern LIS margin.  相似文献   

Exchange dynamics of a shallow contaminated wetland   总被引：1，自引：0，他引：1  

Heidi M. Nepf  Carolyn E. Oldham 《Aquatic Sciences - Research Across Boundaries》1997,59(3):193-213

Flux pathways are investigated for a wetland system comprised of a river flowing through two shallow forebays and then entering the main basin of a lake. The hydrodynamic exchanges between these three components influence the fate and transport of heavy metals in the system. During non-storm summer flows the river plume, comprised of river water and entrained forebay water, was cooler than the lake surface water and so plunged as it entered the main basin and inserted near the seasonal thermocline. Because the river plume plunged, only a fraction of its metals flux was available to the epilimnion. A return flow into the forebay was always observed immediately above the river inflow, ensuring a predominantly two-layer exchange system. However during days of negative heat flux (surface heating), an additional exchange mechanism existed when the surface waters from the forebay formed a buoyant plume, flowing out into the main basin. This heated outflow produced a significant, but short-lived, arsenic flux from the forebay into the surface waters of the lake.  相似文献   

Grain size partitioning of metals in contaminated,coarse-grained river floodplain sediment: Clark Fork River,Montana, U.S.A.     

Johnnie N. Moore  Edward J. Brook  Carolyn Johns 《Environmental Geology》1989,14(2):107-115

The traditional concept of the relationship between metal content and grain size assumes that the fine fraction carries most of the metals in natural sediments. This concept is supported in many cases by strong, significant linear relationships between total-sediment metal concentrations and percentages of various fine-size fractions. Such observations have led to development of methods to correct for the effects of grain size in order to accurately document geographical and temporal variations and identify trends in metal concentrations away from a particular source. Samples from the floodplain sediment of a large, coarse-grained river system indicates that these concepts do not hold for sediments contaminated by mining and milling wastes. In this particular system, the application of methods to correct for grain-size effects would lead to erroneous conclusions about trends of metals in the drainage. This indicates that the a priori application of grain-size correction factors limits interpretation of actual metal distributions and should not be used unless data indicate that correlations exist between metals and particular size fractions.  相似文献   

Petroleum systems modeling in tectonically complex areas — A 2D migration study from the Neuquen Basin, Argentina     

Carolyn Lampe  Kristijan Kornpihl  Simone Sciamanna  Toms Zapata  Gonzalo Zamora  Roberto Varad 《Journal of Geochemical Exploration》2006,89(1-3):201

A roughly 30 km 2D section across the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina, is the basis for a petroleum systems study, including structural restoration through time, deposition and erosion, pressure, temperature and migration modeling. Integrating tectonic and petroleum systems modeling proved critical to properly evaluate sub-thrust plays. Multi-dimensional modeling of dynamic processes allows accurate assessment and prediction of the potential of petroleum systems in tectonically complex areas such as the Neuquen Basin.  相似文献