Environmental impact of salmon net-pen culture on marine benthic communities in Maine: A case study   总被引：1，自引：0，他引：1  

Robert H. Findlay  Les Watling  Lawrence M. Mayer 《Estuaries and Coasts》1995,18(1):145-179

The environmental impacts of salmon net-pen aquaculture on the benthic environment were investigated at a commercial fish farm located in coastal Maine waters. This site has a sandy mud bottom and low current velocities, is subjected to episodic sediment resuspension, and way in production for 3 yr prior to this study: We examined both the increase in carbon flux to the benthos caused by the net-pen and the effects of the elevated flux on sediment biogeochemistry and the microbenthic communities. The experimental design involved the establishment of two study sites, an ambient site ca. 100 m from the net-pen and a treatment site around the pen. Sediment traps deployed 1 m above the sediment-water interface indicated that carbon flux to the benthos was increased 1-fold to 6-fold (to a maximum of 5 g m^?2d^?1) at the edge of the net-pen with little or no increase in carbon flux 10 m from the pen. Unlike carbon flux rates, sediment organic matter inventories showed a complex pattern of change over time. Mineral surface area, organic carbon and nitrogen, digestible protein, and sterol content were initially (April 1991) lower beneath the pen than in ambient sediments. During 1991 ambient sediment accumulated organic matter until July after which it decreased, to a low during November. In contrast, organic matter inventories of sediment beneath the pen remained low until July and then increased to a high during November. These latter gains were associated with the development of bacterial mats at the sediment-water interface. Beneath the pen, microbial and macrofaunal communities were shifted toward those commonly associated with organic enrichment but seasonal trends and storm-related resuspension events also significantly affected these sediment communities. When abundant, most epibenthic organisms were more numerous near the pen than in adjacent ambient areas. These results suggest that net-pen aquaculture can alter the benthic ecosystem in Maine Coastal waters but indicate that the effects are spatially limited.  相似文献   

Directions     

Lawrence J. Drew 《Natural Resources Research》1993,2(1):1-2

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Is there a metric for mineral deposit occurrence probabilities?     

Lawrence J. Drew  W. David Menzie 《Natural Resources Research》1993,2(2):92-105

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Survey of Microbial Populations in Buried-Valley Aquifer Sediments from Northeastern Kansas   总被引：1，自引：0，他引：1  

James L. Sinclair  Stephen J. Randtke  Jane E. Denne  Lawrence R. Hathaway  William C. Ghiorse 《Ground water》1990,28(3):369-377

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A synopsis of climatic and vegetational change in Southeast Asia     

Lawrence R. Heaney 《Climatic change》1991,19(1-2):53-61

Tropical rain forest in Southeast Asia has developed within an extensive archipelago during the past 65 million years or more. During the Miocene (beginning 25 million years BP), rain forest extended much further north (to southern China and Japan); since that time it has contracted. During the Pleistocene (beginning 2.0 million years BP), development of continental glaciers at high latitudes was associated in Southeast Asia with lowered sea level, cooler temperatures, and modified rainfall patterns. Fossil pollen records demonstrate that Southeast Asian vegetation during the last glacial maximum (ca. 18 000 BP) differed substantially from that of today, with an increase in the extent of montane vegetation and savannah and a decline in rain forest. These data show that the distribution and extent of rain forest in Southeast Asia has historically been quite sensitive to climatic change.  相似文献   

Arctic hazes in summer over Greenland and the North American Arctic: II. Nature and concentrations of accumulation-mode and giant particles     

Yutaka Ishizaka  Peter V. Hobbs  Lawrence F. Radke 《Journal of Atmospheric Chemistry》1989,9(1-3):149-159

Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents.  相似文献   

The use of general circulation models in the analysis of the ecosystem impacts of climatic change   总被引：4，自引：0，他引：4  

W. Lawrence Gates 《Climatic change》1985,7(3):267-284

The use of general circulation models in the estimation of the impact of climatic change on the global ecosystem is seen to depend primarily on their ability to reliably depict the seasonal and geographical distribution of the changes in surface climate variables. While present GCMs generally simulate the observed distribution of surface air temperature reasonably well, they show significantly different changes in the equilibrium temperature as a result of doubled CO₂, for example. These disagreements are attributed to differences in the model's resolution and parameterization of subgrid-scale processes. Such model-dependent errors notwithstanding, much more information of possible use in impact analysis can be extracted from general circulation model simulations than has generally been done so far. The completeness, consistency and experimental possibilities offered by simulated data sets permit the systematic extraction of a wide variety of statistics important to the surface ecosystem, such as the length of the growing season, the duration of rainless periods, and the surface moisture stress.Assuming further model improvements, the elements of a model-assisted methodology for climate impact analysis are seen to be: (1) the determination of the seasonal and geographical distribution of that portion of simulated climatic changes which are both statistically and physically significant; (2) the transformation of the (significant) large-scale climatic changes onto the local scale of impact (the climate inversion problem); and (3) the design of specific statistical parameters or functions relevant to local ecosystem impacts.  相似文献   

Erratum     

Vanavan Ekambaram  Iwao Kawabe  Tsuyoshi Tanaka  Andrew M. Davis  Lawrence grossman 《Geochimica et cosmochimica acta》1985,49(5):1293

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Accretionary rims on inclusions in the Allende meteorite     

Glenn J. MacPherson  Akihiko Hashimoto  Lawrence Grossman 《Geochimica et cosmochimica acta》1985,49(11):2267-2279

Many inclusions in Allende, particularly those with irregular shapes, are surrounded by a sequence of thin layers which differ from one another in texture, mineralogy and mineral-chemistry. The layer underlying all others contains either: IA, pyroxene needles + olivine + clumps of hedenbergite and andradite; IB, olivine doughnuts; or IC, rectangular olivine crystals. The next layer outward, II, contains tiny (<5 μm) olivine plates and Layer III large (5–10 μm) olivine laths. The final layer, IV, occurs as clumps of andradite + hedenbergite surrounded by magnesium-rich pyroxene needles. It separates Layer III from the Allende matrix which is more poorly sorted and more sulfide-rich than Layer III. Nepheline and iron sulfide are common constituents of most layers, the latter being particularly fine-grained and abundant in Layer II. Although not every layer is present on every inclusion, the sequence of layers is constant. Evidence that the rims are accretionary aggregates includes the presence of highly disequilibrium mineral assemblages and the fact that they are highly porous masses consisting of many euhedral crystals with few intergrowths. In addition, the layers are thickest in topographic hollows on the surfaces of inclusions and the inner layers are absent or discontinuous beyond such irregularities, suggesting that the probability of accretion of crystals was low initially, except in pockets, and became greater later, after a soft cushion of accreted condensate crystals had already formed. Separation of assemblages of different mineralogy, mineral-chemistry and texture into different rim layers seems best explained by nebular models in which long, slow cooling histories allow differentiation during condensation by grain/gas separation processes.  相似文献   

Germanium geochemistry and mineralogy   总被引：1，自引：0，他引：1  

Lawrence R. Bernstein 《Geochimica et cosmochimica acta》1985,49(11):2409-2422

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