Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 23 for “"photic zone"”.
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Testing the ancient marine redox record from oxygenic photosynthesis to photic zone euxina
… may have transiently accumulated in the marine photic zone (i.e. photic zone euxinia; PZE) during mass extinctions and oceanic anoxic events. Here, the molecular fossil evidence for oxygenic photosynthesis and eukaryotes is reevaluated, where the results imply that currently existing lipid …
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Testing the ancient marine redox record from oxygenic photosynthesis to photic zone euxina
… may have transiently accumulated in the marine photic zone (i.e. photic zone euxinia; PZE) during mass extinctions and oceanic anoxic events. Here, the molecular fossil evidence for oxygenic photosynthesis and eukaryotes is reevaluated, where the results imply that currently existing lipid …
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Comparison of water column properties derived from an autonomous underwater vehicle and satellite based sources in Lake Michigan
… measure features such as the extent of the photic zone, which provides the opportunity to compare these in situ measured features to those represented by surface sampling regimes. This study validates a data processing method for AUV—sampled data showing a strong match with satellite-derived …
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The influence of differential production and dissolution on the stable isotope composition of planktonic foraminifera
… species), collected in plankton tows in the photic zone, show light isotopic compositions possibly in slight negative deviation from oxygen isotopic equilibrium. Radioactive tracer experiments using 14C and 45Ca were conducted on shallow dwelling benthonic foraminifera and hermatypic corals. …
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Context-dependent controls of periphyton across the littoral-benthic habitat of deep, clear lakes
… studies examining production across the photic zone in deep lakes are limited. This study investigates the role of nutrient limitation and inhibition from the shallow to deep (lower limit of the photic zone) littoral-benthic habitat of lakes with varying trophic states. To achieve this …
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Trophic transfer of nearshore basal resources: interpreting fatty acid and stable isotope biomarkers
Benthic heterotrophs living in aphotic aquatic habitats rely upon subsidies of detrital energy, in the form of complex organic molecules, which are synthesized by macrophytes and phytoplankton in the photic zone. Identifying the relative importance of different basal energy resources to consumers …
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Stable isotope and organic biomarker analysis of the late Proterozoic Coppercap formation in the MacKenzie Mountains
… hydrogen sulfide rich waters in the shallow photic zone persisted until the Sturtian.
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Chlorophyll diagenesis in the water column and sediments of the Black Sea
… synthesized by the phytoplankton living in the photic zone at the time of production. Analysis of pyropheophorbide-a steryl esters in sediments shows the distribution of sterols to be quantitatively and qualitatively more similar to the distribution of free sterols in sediment traps than in …
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Late cretaceous (Maestrichtian) calcareous nannoplankton biogeography with emphasis on events immediately preceding the cretaceous/paleocene boundary
… paleoenvironmental conditions in the marine photic zone during the latest Cretaceous. Different theories explaining the biospheric turnover at the Cretaceous/Paleocene (KIP) boundary have alternatively suggested or denied substantial environmental perturbations during the last ~500 ky of the …
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Wind induced entrainment in the Strait of Georgia and the possible consequences for fish survival
… by supplying nitrate rich deep water to the photic zone and increasing primary productivity. Historical records of winds and Fraser River discharge were used to drive the combined GF4/MULES physical/biological model, to simulate entrainment and nitrate concentration in the upper layer of the …
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Growth Characterization of Mesophotic Rhodoliths in the Northern Gulf of Mexico Using Radiocarbon Dating
… and they are distributed from the intertidal zone to the lower limits of the photic zone. While growth rates and patterns in rhodoliths from shallower depths and simpler morphologies have been assessed using incremental and geochemical analyses, rhodoliths from mesophotic depths have rarely …
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Geochemical and Paleontological investigations of the Neoproterozoic-Cambrian Transition: Case Studies on geochemical clast provenance, emerging paleo redox proxies, and ambiguous dubiofossils
… in marine redox, such as the development of photic zone euxinia. In the third chapter, I investigate the identity of Brooksella alternata, a purportedly cnidarian fossil that was later suggested to be a hexactinellid sponge fossil. My morphological and compositional analysis reveals B. …
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Biogeochemical proxies for environmental and biotic conditions at the Permian-Triassic boundary
… dominated by bacterial inputs in which photic zone euxinia was prevalent for extended time periods. Additional findings from compound-specific isotope data suggest that at isolated intervals, the chemocine may have extended even closer to the surface. The timing of these intervals …
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Sedimentology, Diagenesis and Reservoir Characteristics of Eocene Carbonates Sirt Basin, Libya
… under shallow-marine conditions within the photic zone, as indicated from their richness in phototrophic fauna and flora. These include lagoon (back-bank), main bank, fore-bank and open-marine facies, all of which were deposited on a homoclinal ramp type of carbonate platform. The type and …
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Controls on Carbonate Factory Distribution in a Restricted Intraplatform Basin: Upper Jurassic Smackover, Southwest Alabama
… sandstone, recording high saturation in the photic zone. Effective wave agitation and current flushing of nutrients contributed to supersaturation and the abiotic precipitation of oolites in shallow, near-shore environments. Alternating wet and dry climates resulted in high variability, …
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The geochemistry of water-filled sinkholes at Bitter Lake National Wildlife Refuge, Roswell, NM : implications for hydrochemical evolution and trophic support
… were found to organize at the bottom of the photic zone. High NH4 and CO2 accompanying low O2 dissolved gas values confirm the increased biological control in stratified sinkholes. Resident fish populations are affected by water chemistry which reduces reproductive success or exceed the …
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Phytoplankton Ecology and Dynamics in the James River Estuary Virginia, U. S. A.
… with phytoplankton and the reduction of the photic zone due to the turbidity maximum.</p> <p>Furthermore, autotrophic abundance upriver may indirectly regulate the onset of the spring bloom in the more estuarine portions of the river by controlling the amount of nutrients available. This is …
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Habitat relationships for alewives and blueback herring in a Virginia stream
… downstream sites in size, vegetation, hydrology, photic zone depth, pH, and vegetation. At times, pH levels in the upstream site were within the range of lethality reported for blueback herring larvae. Relationships between habitat variables and occurrence of river herring life stages in the …
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Deep coral forests from the Island of Sardinia
… ‘vegetal’ forest in shallow depths (within the photic zone) to the ‘animal’ forest (dwelling in the circalittoral zone) throughout the depth gradient. ‘Animal forest’ concept refers to forests entirely constituted by animals, that substitute to the vegetal canopy in the three dimensional …
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Fluxes, dynamics and chemistry of particulates in the ocean
… than 3% of the organic carbon produced in the photic zone at the trap sites was collected as primary flux 500 m above the sea floor. The primary flux measured at two sites was enough to supply 75% on the upper Rise and 160% on the mid Rise of the organic carbon needed for respiration and for …
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