Seasonal and regional patterns in egg production of Calanus glacialis/marshallae in the Chukchi and Beaufort Seas during spring and summer, 2002     

Stphane Plourde  Robert G. Campbell  Carin J. Ashjian  Dean A. Stockwell 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3411

Understanding the physical and biogeochemical processes that control the exchange of biogenic carbon within and between the arctic shelves, slopes, and deep basins is a key objective of the Western Arctic Shelf-Basin Interaction program (SBI). Here, egg production (EP) of the dominant copepod Calanus glacialis/marshallae was used as an indicator of food limitation for the mesozooplankton community in the Chukchi and Beaufort Seas in spring and summer, 2002. Both C. glacialis and C. marshallae may occur in this region but the two cannot easily be differentiated visually. Four oceanographic regions were objectively identified that roughly corresponded to the different pathways in circulation of nutrient-rich Pacific water. A ‘transition’ region characterized by ‘older’ Pacific water was located at the shelfbreak and separated the nutrient-rich shelf water and the low-nutrient waters of the deep basin. The observed spatial pattern in EP in C. glacialis/marshallae in spring and summer resulted both from the different water mass environments and from the reproductive cycle of the species. EP was greater on the shelf than in the basin, corresponding to differences in body size and nitrogen condition factor (NCF) in females, while the egg viability was generally high throughout the study area. EP showed no relationship with low-chlorophyll a biomass under heavy ice-cover in spring, while a significant relationship was observed in the more open water in summer. Adult female carbon condition factor (CCF) was much higher in summer, reflecting the accumulation of lipids during the growth season. Small animals with a markedly greater NCF dominated on the shelf. The shelfbreak region contained a mixture of females from the shelf and the basin with intermediate sizes, conditions, and EP rates. The occurrence of water typical of the ‘transition’ shelfbreak region and elevated EP in C. glacialis/marshallae offshore on the Barrow Canyon and East Barrow sections indicated offshore transport of productive shelf water and the associated plankton community. The input of nutrient-rich Pacific water and accompanying elevated production to the northern Chukchi Sea and the Chukchi-Beaufort shelfbreak region may contribute to the reproductive success of C. glacialis/marshallae in this region.  相似文献   

The reliability of the thermodynamic constants for the dissociation of carbonic acid in seawater     

Kitack Lee  Frank J. Millero  Douglas M. Campbell 《Marine Chemistry》1996,55(3-4)

Laboratory measurements of all four CO₂ parameters [f_CO2 ( = fugacity of CO₂), pH, TCO₂ ( = total dissolved inorganic carbon), and TA ( = total alkalinity)] were made on the same sample of Gulf Stream seawater (S = 35) as a function of temperature (5–35 °C) and the ratio of TA/TCO₂ (X) (1.0–1.2). Overall the measurements were consistent to ±8 μ atm in f_CO2, ± 0.004 in pH, ± 3 μ mol kg⁻¹ in TCO₂, and ± 3 μ mol kg⁻¹ in TA with the thermodynamic constants of Goyet and Poisson (1989), Roy et al. (1993), and Millero (1995). Deviations between the measured pH, TCO₂, TA and those calculated from various input combinations increase with increasing X when the same constants are used. This trend in the deviations indicates that the uncertainties in pK₂ become important with increasing X (surface waters), but are negligible for samples with the lower X (deep waters). This trend is < 5 μ mol kg⁻¹ when the pK₂ values of Lee and Millero (1995) are used.The overall probable error of the calculated f_CO2 due to uncertainties in the accuracy of the parameters (pH, TCO₂, TA, pK₀, pk₁, and pK₂) is ± 1.2%, which is similar to the differences between the measured values and those calculated using the thermodynamic constants of Millero (1995).The calculated values of pK₁, (from f_CO2-TCO₂-TA) agree to within ± 0.004 compared to the results of Dickson and Millero (1987), Goyet and Poisson (1989), Roy et al. (1993), and Millero (1995) over the same experimental conditions. The calculated values of pK₂ (from pH-TCO₂-TA) are in good agreement (± 0.004) with the results of Lee and Millero (1995) and also in reasonable agreement (± 0.008) with the results of Goyet and Poisson (1989), Roy et al. (1993), and Millero (1995). The salinity dependence of our derived values of pK₁ and pK₂, (S = 35) can be estimated using the equations determined by Millero (1995).  相似文献   

Carrying capacity of the eastern ecological gradient of Kenya     

Bernard FE  Campbell DJ  Thom DJ 《National geographic research》1989,5(4):399-421

Kenya's rate of natural population increase exceeds 4.0%/year. At this rate, Kenya's population of 23.5 million will expand to 35 million by the year 2000. Rural migrants are being forced out of the highlands into marginal arid and semiarid regions to the east and south in the eastern ecological gradient including Meru, Kitui, Machakos, and Kajiado districts. The people have become victims of marginalization by which the productivity of a unit of land declines relative to the demands of its occupants. The concept of carrying capacity means the number of people a given area can sustain over the long term. In Maasailand, 3.5 standard stock units (450 kg each) are required per adult equivalent for full subsistence, about 7 cows/person. For the Maasai pastoralists, carrying capacities were examined at 2 levels of subsistence: 100% from the herds and 80% from the herds; 2 technological levels; and population-growth rates of 2%, 2.5%, and 3%/annum. Using the median, 3.5%/year, population-growth scenario these districts will have almost 5 million inhabitants in the year 2000. Poverty at technology level I for 40% of them, or for 2 million people, is implausible. Technology level II implies that current rural-development programs will succeed with technological innovations for farm households, access to credit, and markets for their produce. Level II is likely to prevail toward the end of the century for the majority of farmers. Level III necessitates best agricultural and livestock technology as well as the best management. At most, 25% of the households of the eastern ecological gradient could enter this realm by the year 2000. Current strategies of voluntary family planning, rural development emerging from an antiquated extension system, inability to address inequity in land distribution, and laissez-faire resource management are inadequate to deal with the pace of change.  相似文献   

Fixing marine governance in Fiji? The new scalar narrative of ecosystem-based management     

Leila Sievanen  Rebecca L. Gruby  Lisa M. Campbell 《Global Environmental Change》2013,23(1):206-216

Although there is widespread concern over degrading marine environments, there is debate within the global marine conservation agenda about the nature of the problem and appropriate solutions. At the center of this debate lie questions about the appropriate scale at which to plan and implement marine resource management. In the late 1990s, Fiji became recognized as one of the most successful examples of community-based marine resource management in the world. Recently, there has been a move to manage human–environment interactions at larger “natural” scales. We draw from the political ecology and “politics of scale” literatures, and a critical realist understanding of nature and politics, to explain the emergence of large-scale management and conservation in Fiji. We contribute to a “political ecology of scale” by developing the concept of a scalar narrative to show how social and ecological scales are reworked in the development of an ecosystem-based approach to marine management in Fiji. In doing so, we consider implications of the struggle to define the appropriate scale of marine management, which is closely bound to debates about the role of science and local participation. Our findings suggest that the struggle to define the scale at which marine management should be planned and implemented is inseparable from the struggle over who should define, inform, and conduct the governance process. We aim to clarify marine policy debates as policy actors worldwide move forward to implement ecosystem-based management, increase marine protected area coverage, and pursue sustainable development.  相似文献   

Evaluation of a low‐cost temperature measurement system for environmental applications     

Jason Hubbart  Timothy Link  Colin Campbell  Doug Cobos 《水文研究》2005,19(7):1517-1523

Thermochron iButtons incorporate the latest in digital technology, making them smaller, less expensive, durable and potentially more reliable than many other temperature logging devices. The objective of this study was to test the accuracy of an inexpensive air temperature measurement system, composed of a Thermochron iButton and radiation shield. Sixty‐one iButtons were subjected to a sequence of two water baths (0 °C and 24·9 °C) to assess the absolute accuracy of the sensors. Five solar radiation shields were tested in a greenhouse setting to evaluate the reduction in radiative heating. Significant differences (p < 0·05) were detected between instruments subsequent to both water‐bath treatment analyses. The accuracy of the sensors was well within the manufacturer's stated specification of ±1·0 °C with a collective temperature variance of ±0·21 °C. Temperature responses generated by the Thermochron iButtons in different radiation shields were consistent, but varied significantly (p < 0·05) from 28 to 44 °C based on diurnal temperature ranges. Results indicate that the Thermochron iButton is an accurate, inexpensive alternative to more expensive temperature data‐logging systems, and is well suited for obtaining quality spatially distributed data for hydrologic and water quality investigations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Survey evaluations to assess marine bioinvasions     

Campbell ML  Gould B  Hewitt CL 《Marine pollution bulletin》2007,55(7-9):360-378

Countries need to know what species are present within their waters to effectively manage the issue of non-indigenous marine species. Five survey methods are currently employed to detect introduced marine species: the Hewitt and Martin protocols (66% of effort; 73 ports, 12 countries); Rapid Assessment Surveys (7% of effort; 8 regions, 4 countries); the Bishop Museum protocols (7% of effort; 8 ports, 3 countries); the Chilean aquaculture surveys (1% of effort; numerous regions; 1 country); and Passive Sampling protocols (18% of effort; 20 ports, 2 countries). These methods use either quantitative, qualitative, or a mixture of the two sampling techniques and tend to target locations that are potential inoculation sites (i.e., such as ports, marinas and aquaculture facilities). To date, introduced marine species surveys have been implemented in 19 countries and have detected more than 1185 non-indigenous, 735 cryptogenic and 15,315 native species.  相似文献   

Seasonal variations in the north toroidal sporadic meteor source     

M. Campbell‐Brown  P. Wiegert 《Meteoritics & planetary science》2009,44(12):1837-1848

Abstract— Determining the origins of the sporadic meteoroid sources helps determine their current properties. We have analyzed four years of orbital radar data, looking at how the rates, radiants, and orbits of meteoroids in the north toroidal sporadic source change throughout the year. Twelve broad radiant concentrations, separated in either time or radiant location, are identified. Six are broad distributions associated with more focused shower activity, and six are not associated with major showers. Four of the six concentrations not associated with showers have been named Toroidal, Toroidal A, Toroidal B, and Toroidal C, because of their constant location at the north toroidal centre. The other two, which appear close to the north toroidal source and drift toward the helion and antihelion sources respectively, have been named the Helion Arc and the Antihelion Arc. The twelve radiant concentrations generally last for more than ten degrees solar longitude, and those which may have a single parent are likely composed of orbitally evolved material.  相似文献   

Geo-political genetics: Claiming the commons through species mapping     

Lisa M. Campbell  Matthew H. Godfrey 《Geoforum》2010,41(6):897-907

Genetic techniques are increasingly employed in the field of conservation biology; our understanding of sea turtle biology, and particularly of sea turtle migrations and population structures, has increased through genetic analyses that ‘match’ turtles found in various and often widely distributed habitats (e.g. nesting beaches, foraging grounds, migratory corridors). This relatively recent technological development has implications for how sea turtles are conceived, both as resources and as objects of conservation. Traditionally, sea turtle populations have been identified with nesting beaches, and most conservation efforts have been focused on these discrete geographic locations and undertaken by the state. The more complete understanding of relationships among turtles found in geographically disparate areas, achieved via genetic analysis, can take conservation beyond the beaches and territorial waters of individual states; foraging populations can now be linked to nesting populations sometimes hundreds of kilometers distant. In this paper, we explore the implications of genetic analysis for sea turtle conservation, the scale at which it is undertaken, and the variety of actors with competing interests in it. We focus on the case of hawksbill sea turtles in the Caribbean, where genetic data are invoked in conservation conflicts. We are particularly interested in the way genetic data can support the scaling-up of sea turtle conservation, creating new ‘conservation territories,’ and we draw on political ecology and common pool resource theory to explore the implications thereof.  相似文献   

Earth-based 12.6-cm wavelength radar mapping of the Moon: New views of impact melt distribution and mare physical properties     

Bruce A. Campbell  Lynn M. Carter  Michael Nolan  Rebecca R. Ghent  Ross F. Anderson 《Icarus》2010,208(2):565-181

We present results of a campaign to map much of the Moon’s near side using the 12.6-cm radar transmitter at Arecibo Observatory and receivers at the Green Bank Telescope. These data have a single-look spatial resolution of about 40 m, with final maps averaged to an 80-m, four-look product to reduce image speckle. Focused processing is used to obtain this high spatial resolution over the entire region illuminated by the Arecibo beam. The transmitted signal is circularly polarized, and we receive reflections in both senses of circular polarization; measurements of receiver thermal noise during periods with no lunar echoes allow well-calibrated estimates of the circular polarization ratio (CPR) and the four-element Stokes vector. Radiometric calibration to values of the backscatter coefficient is ongoing. Radar backscatter data for the Moon provide information on regolith dielectric and physical properties, with particular sensitivity to ilmenite content and surface or buried rocks with diameter of about one-tenth the radar wavelength and larger.Average 12.6-cm circular polarization ratio (CPR) values for low- to moderate-TiO₂ mare basalt deposits are similar to those of rough terrestrial lava flows. We attribute these high values to abundant few-centimeter diameter rocks from small impacts and a significant component of subsurface volume scattering. An outflow deposit, inferred to be impact melt, from Glushko crater has CPR values near unity at 12.6-cm and 70-cm wavelengths and thus a very rugged near-surface structure at the decimeter to meter scale. This deposit does not show radar-brightness variations consistent with levees or channels, and appears to nearly overtop a massif, suggesting very rapid emplacement. Deposits of similar morphology and/or radar brightness are noted for craters such as Pythagoras, Rutherfurd, Theophilus, and Aristillus. Images of the north pole show that, despite recording the deposition of Orientale material, Byrd and Peary craters do not have dense patterns of radar-bright ejecta from small craters on their floors. Such patterns in Amundsen crater, near the south pole, were interpreted as diagnostic of abundant impact melt, so the fraction of Orientale-derived melt in the north polar smooth plains, 1000 km farther from the basin center, is inferred to be much lower.  相似文献   

‘Strange changes’: Indigenous perspectives of climate change and adaptation in NE Arnhem Land (Australia)     

L. Petheram  K.K. Zander  B.M. Campbell  C. High  N. Stacey 《Global Environmental Change》2010,20(4):681-692

Despite growing global attention to the development of strategies and policy for climate change adaptation, there has been little allowance for input from Indigenous people. In this study we aimed to improve understanding of factors important in integration of Yolngu perspectives in planning adaptation policy in North East Arnhem Land (Australia). We conducted workshops and in-depth interviews in two ‘communities’ to develop insight into Yolngu peoples’ observations and perspectives on climate change, and their ideas and preferences for adaptation. All participants reported observing changes in their ecological landscape, which they attributed to mining, tourism ‘development’, and climate change. ‘Strange changes’ noticed particularly in the last five years, had caused concern and anxiety among many participants. Despite their concern about ecological changes, participants were primarily worried about other issues affecting their community's general welfare. The results suggest that strategies and policies are needed to strengthen adaptive capacity of communities to mitigate over-arching poverty and well-being issues, as well as respond to changes in climate. Participants believed that major constraints to strengthening adaptive capacity had external origins, at regional, state and federal levels. Examples are poor communication and engagement, top-down institutional processes that allow little Indigenous voice, and lack of recognition of Indigenous culture and practices. Participants’ preferences for strategies to strengthen community adaptive capacity tended to be those that lead towards greater self-sufficiency, independence, empowerment, resilience and close contact with the natural environment. Based on the results, we developed a simple model to highlight main determinants of community vulnerability. A second model highlights components important in facilitating discourse on enhancing community capacity to adapt to climatic and other stressors.  相似文献