Why is the relative abundance of Asterionella formosa increasing in a Boreal Shield lake as nutrient levels decline?     

Branaavan Sivarajah  Kathleen M. Rühland  Andrew L. Labaj  Andrew M. Paterson  John P. Smol 《Journal of Paleolimnology》2016,55(4):357-367

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Tracking the long-term responses of diatoms and cladocerans to climate warming and human influences across lakes of the Ring of Fire in the Far North of Ontario,Canada     

Kathryn E. Hargan  Clare Nelligan  Adam Jeziorski  Kathleen M. Rühland  Andrew M. Paterson  Wendel Keller  John P. Smol 《Journal of Paleolimnology》2016,56(2-3):153-172

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EAF implementation in Southern Africa: Lessons learnt     

Barbara Paterson  Samantha L. Petersen   《Marine Policy》2010,34(2):276-292

The practical implementation of an ecosystem approach to fisheries (EAF) management has proved difficult to achieve. Without simple and structured guidelines for implementing an EAF, managers are grappling with the complexity of implementation and the need to prioritise resources and management actions. Ecological risk assessment has been put forward as a structured procedure. There is a need to review regularly whether progress is being made in addressing the issues and priorities identified through ecological risk assessment. Such reviews require a framework providing clear objectives for the respective fishery and delineating the steps required towards their achievement. This paper proposes a generic framework for reviewing ecological risk assessments through stakeholder workshops. This framework is aided by a fuzzy logic tool to track EAF implementation and informs the development of proactive work plans which incorporate EAF objectives. The advantages and disadvantages of a generic and participatory approach are discussed and compared with other related methods for evaluating progress in implementing an EAF.  相似文献   

Magmatic erosion of the solidification front during reintrusion: the eastern margin of the Tuolumne batholith, Sierra Nevada, California     

Jiří Žák  Scott R. Paterson 《International Journal of Earth Sciences》2010,99(4):801-812

The Tuolumne batholith, Sierra Nevada, California, consists of several nested granitoid units and is an example of upper-crustal normally zoned intrusions. The two outermost units of the batholith are separated by a wide gradational contact in what is interpreted to represent a large magma chamber. In the Potter Point area near the eastern margin of the batholith, the gradational contact is cross-cut by a network of interconnected mafic–felsic sheets, which grade into zones of magmatic erosion by stoping where the host granodiorite between the sheets was entirely removed and replaced by younger enclave-rich quartz diorite. We interpret these features to record disruption of a steep solidification front, which migrated inwards from the eastern batholith margin and separated the mushy to solidified margin from the remaining active magma chamber. When intersecting the gradational contact, the solidification front started to break up via a network of tectonically driven fractures accompanied by simultaneous injection of localized magma pulses. The solidification front break-up is interpreted here as an initial stage of a “recycling” process, whereby older magma mush is disrupted and incorporated into younger magma batches, a process we propose to have been widespread along internal contacts in the Tuolumne magma chamber.  相似文献   

Changes since the onset of acid deposition among calcium-sensitive cladoceran taxa within softwater lakes of Ontario, Canada     

Adam Jeziorski  Andrew M. Paterson  John P. Smol 《Journal of Paleolimnology》2012,48(2):323-337

Aqueous calcium (Ca) concentrations are currently decreasing in many softwater lakes on the Boreal Shield. As the onset of these declines often pre-date direct monitoring programs, indirect techniques are required to examine the impacts of reduced Ca availability on aquatic communities with relatively high Ca demands such as the Cladocera (Class: Branchiopoda). Among the Cladocera, the family Daphniidae has been identified as a taxonomic group potentially useful for inferring past Ca concentrations due to their high Ca demands and preservation in lake sediments. Here, we use a ??top/bottom?? paleolimnological analysis to compare present-day cladoceran communities preserved in the surface sediments of 36 softwater lakes in south-central Ontario, Canada, which are potentially vulnerable to Ca decline (i.e. small headwater systems with present-day lakewater [Ca]?<?3?mg?L^?1), with the communities present in lake sediments deposited prior to the onset of regional acid deposition. To distinguish the potential impacts of lake acidification from those of Ca availability (as Ca and pH trends are strongly correlated in this region), the study lakes were chosen to be evenly distributed about a present-day lakewater pH of 6 and Ca concentration of 1.5?mg?L^?1 (threshold values). Despite the importance of pH as an explanatory variable for the present-day assemblages, a comparison of the sedimentary remains from the two time periods indicate there have been large declines since pre-industrial times in the relative abundances of Ca-rich Daphnia spp. (particularly of the Daphnia longispina species complex), regardless of present-day pH, accompanied by increases in the Ca-poor species Holopedium glacialis. These observations suggest that recent declines in Ca concentration may have already fallen below baseline conditions, with marked implications for ecosystem function due to the differential responses among cladoceran taxa.  相似文献   

Identification and geochemical modeling of processes controlling leaching of Cr(VI) and other major elements from chromite ore processing residue   总被引：1，自引：0，他引：1  

Jeanine S Geelhoed  Johannes C.L MeeussenStephen Hillier  David G LumsdonRhodri P Thomas  John G FarmerEdward Paterson 《Geochimica et cosmochimica acta》2002,66(22):3927-3942

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Sustainable development, sustainable decisions and the precautionary principle     

John Paterson 《Natural Hazards》2007,42(3):515-528

One of the key foundations of sustainable development is the precautionary principle, a concept that has given rise to a considerable amount of controversy. For some, it is a barrier to technological progress and development, for others a means of preventing potentially harmful applications of science. What does this principle actually mean? What is its contribution to sustainable development in general and to decision-making in response to natural hazards in particular? How should it be applied? This paper will consider whether an examination of the relationship between science and law can assist in answering questions such as these, and thus provide some greater clarity about this important principle.  相似文献   

Metamorphism of the deepest exposed arc rocks in the Cretaceous to Paleogene Cascades belt, Washington: evidence for large-scale vertical motion in a continental arc   总被引：2，自引：0，他引：2  

P. M. Valley  D. L. Whitney  S. R. Paterson  R. B. Miller  H. Alsleben 《Journal of Metamorphic Geology》2003,21(2):203-220

The Swakane Gneiss and the overlying Napeequa Complex in the North Cascade range, Washington, were metamorphosed and deformed during development of a Cretaceous‐Paleogene continental arc, and are among the structurally deepest exposed rocks within the Cordilleran arcs of North America. Peak metamorphic conditions in both the Swakane Gneiss and Napeequa Complex were c. 640–750 °C, 9–12 kbar. Clockwise paths and widespread evidence for high‐P metamorphism in meta‐supracrustal rocks (burial to >40 km) document major vertical tectonic motion during arc construction and unroofing. These and other moderately high‐pressure rocks in the North Cascades‐Coast Mountains experienced a dramatically different tectonometamorphic history than metamorphic rocks within other Cordilleran arcs. The exhumed arc complexes of the Sierra Nevada and Peninsular Ranges are dominated by relatively low‐P metamorphic and plutonic rocks (typically <6 kbar). There is no evidence that the northern Cordillera was thickened to a greater degree than these other belts, suggesting that the greater magnitude of vertical motion in the Cascades may have been related to exhumation mechanisms: Eocene extension in the northern Cordillera vs. erosional unroofing in the central and southern Cordillera.  相似文献   

Igneous origin of K-feldspar megacrysts in deformed granite of the Papoose Flat Pluton, California, USA     

R. H. Vernon  S. R. Paterson 《Visual Geosciences》2002,7(1):1-28

Many points of evidence, especially igneous microstructures and structures resulting from solid-state deformation, indicate that K-feldspar megacrysts in deformed granites of the Papoose Flat pluton are residual phenocrysts, not porphyroblasts. Evidence of an igneous origin includes features such as crystal shapes, simple twinning, zonally arranged euhedral plagioclase inclusions, oscillatory compositional zoning, and local occurrence in microgranitoid enclaves. Evidence of solid-state deformation of the megacrysts (which is consistent with their existence prior to the mylonitic deformation) includes marginal recrystallization and neocrystallization, microcline twinning, marginal replacement by myrmekite, and recrystallized/neocrystallized “tails”. Evidence of porphyroblastic growth, such as overgrown inclusion trails, is absent. This appears to be the situation in most felsic augen gneisses and mylonites.  相似文献   

Micrometeorological study of an urban valley     

R. D. Paterson  K. D. Hage 《Boundary-Layer Meteorology》1979,17(2):175-186

Winds, temperatures, and carbon monoxide concentrations were measured in a cross-section of the North Saskatchewan River Valley in central Edmonton on a clear October evening with cross-valley winds. The evolution of a complex asymmetrical valley inversion with vertical temperature gradients up to 12C (100 m)^–1 on the north-facing slope and 6C (100 m)^–1 on the south-facing slope is described. The inversion is accompanied by downslope winds of about 0.4 m s^–1 and a reversal from upvalley to downvalley winds. Carbon monoxide concentrations on the south-facing slope exhibit a well-defined evening maximum and an immediate response to the reversal from upslope to downslope winds.  相似文献