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81.
Dietmar Grimm Ivan Barkhorn David Festa Kate Bonzon Judd Boomhower Valerie Hovland Jason Blau 《Marine Policy》2012,36(3):644-657
What are the effects of transitioning traditionally managed fisheries to incentive-based catch shares fisheries? In a study of all major United States federal catch share fisheries and associated shared stock fisheries in British Columbia, catch shares result in environmental improvements, economic improvements, and a mixture of changes in social performance, relative to the race for fish under traditional management. Environmentally, compliance with total allowable catch increases and discards decrease. Economically, vessel yields rise, total revenues grow, and long-term stock increases are encouraged. Socially, safety increases, some port areas modestly consolidate, needed processing capacity often reduces, and labor markets shift from part time jobs to full time jobs with similar total employment. Newer catch shares address many social concerns through careful design. 相似文献
82.
In the high mountain oligotrophic Seven Rila Lakes (2 095–2 535 m a.s.l.) bacterial abundance was recorded in July and September
2006. In July, bacterial abundance (average (3.32±2.5)×105 cell/ml) in the lakes correlated negatively with elevation, while in September (average (26.39±7.1)×105 cell/ml) this pattern was altered and the greatest abundance of bacteria occurred at the highest ((39.05±1.5)×105 cell/ml) and the lowest ((30.63±6.0)×105 cell/ml) elevated lakes. Regression analyses suggested that the principal factor controlling bacterial abundance, in both
July and September, was inorganic nitrogen (NO3-N and NH4-N; R
2=0.70, P<0.05). Other major regulating factors were temperature (R
2=0.66, P<0.03) in July and filter-feeding zooplankton (R
2=0.95, P<0.01) in September. All factors, except NO3-N, had a positive effect on bacterial abundance. 相似文献
83.
Laura Gaggero Laura Buzzi Ivan Haydoutov Luciano Cortesogno 《International Journal of Earth Sciences》2009,98(8):1853-1877
Eclogitic rocks were sampled from two zones in the basement of the Sredna Gora terrane (central western Bulgaria): (1) partially
retrogressed eclogites and amphibolites embedded in sillimanite-bearing garnet-micaschists with kyanite relics and migmatites
and (2) banded amphibolites associated with muscovite-bearing metagranites within two-mica paragneisses. Rutile relics and
oligoclase + green hornblende + epidote ± biotite pseudomorphs after garnet suggest an eclogite facies event. A tholeiitic,
transitional affinity was determined for the protoliths, suggesting a continental rift environment, consistent with several
eclogite-bearing complexes in the eastern segments of the Variscan belt that arose from the Cambro-Ordovician Gondwana break-up.
Decreasing pressure after the eclogite overprint was demonstrated by (a) diopside-albite symplectite, and (b) plagioclase
+ red–brown to green amphibole kelyphite. The early static re-equilibration, dated to 398 ± 5.2 Ma by 40Ar–39Ar technique, was followed by an amphibolite facies foliation, which was pervasive in amphibolites, gneisses and micaschists,
and poorly developed in eclogites. The lithospheric PT paths corresponding to higher and lower metamorphic gradients reflect
the juxtaposition of crustal and lithospheric mantle units, respectively. In the build-up of the basement of the Balkan orogen,
the physical properties of the lithological complexes might have influenced the collisional pattern of involved microplates. 相似文献
84.
Meiobenthic fauna is complex and essential part of the stream benthos and it is known as intermediaries from bacteria to higher trophic levels. However, the dynamics and mechanisms regulating this community at small-scale largely have been neglected. This study was carried out to determine meiofaunal dynamics in a small scale-patterns influenced by flow velocity and other abiotic and biotic factors. We examined meiofauna within bryophytes on a tufa barrier in Plitvice Lakes National Park using a detailed taxonomic approach of various meiofaunal groups and their feeding guilds. We choose three microhabitats (slow, medium, fast) differing significantly in flow velocity above bryophytes. Bdelloid rotifers were the most abundant group in microhabitat with highest flow velocity, while in other two microhabitats nematodes and monogonont rotifers prevailed in abundance. Data on environmental variables and main meiofaunal taxa and feeding guilds were analyzed using redundancy analysis. This analysis indicated that microfilter feeding guild (e.g. bdelloid rotifers) was strongly affected by interaction of flow velocity and POM fractions. Other feeding guilds were influenced by temperature, oxygen and/or pH and did not prefer high flow velocity. Suction-feeder nematodes and microfilter-feeder rotifers were dominant on temporal and spatial scale, indicating their good adaptations on frequently disturbed conditions that prevailed on bryophyte covered tufa barrier. Our results provide comprehensive survey of diversity, density as well as trophic structure of meiofauna in aquatic bryophytes. Differences in meiofaunal composition and density between three microhabitats suggest that the meiofauna is relevant indicator of environmental changes even at small-scale pattern. 相似文献
85.
Unreclaimed strip mine dumps near Henryetta, Oklahoma were employed as a natural laboratory for the study of slope evolution. These dumps were created by similar technologies and from similar materials but at different times. Modern, 30-year-old and 60-year-old slopes were compared through morphometric analysis and by the direct measurement of current rates of denudation. Slope evolution may be generalized as slope decline. This was effected through reduction of the slope crest, burial of the slope foot, and extension of the upper convexity and lower concavity at the expense of the rectilinear main slope of the original mine dump. There was a progressive reduction in rates of surface erosion, and the balance between weathering and suffosion became skewed towards the latter on the oldest dumps. 相似文献
86.
Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions
B?rje Dahren Valentin R. Troll Ulf B. Andersson Jane P. Chadwick Màiri F. Gardner Kairly Jaxybulatov Ivan Koulakov 《Contributions to Mineralogy and Petrology》2012,163(4):631-651
Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing
at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite
of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene
composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage
in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s),
at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km,
while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage
regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage
at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified
a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods
are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological
surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes. 相似文献
87.
Ryoko Fujiyoshi Hikaru Amano Yousuke Sakuta Kazumasa Okamoto Takashi Sumiyoshi Ivan Kobal Janja Vaupoti? 《Environmental Earth Sciences》2012,67(1):133-140
Carbon sources were estimated by measuring carbon isotope ratios (??13C and ??14C) with accelerator mass spectrometry (AMS) in forest soils of different lithology. Six locations were selected in temperate deciduous and coniferous stands in Slovenia (?irovski vrh, Idrija, Ko?evski Rog, Pohorje, Gori?nica, and Rakitna), where carbonate rocks consisting of limestone and dolomite are abundant as underlying bedrock. Carbon isotope fractionation would not have occurred in two carbonaceous soils, since the values of both ??13C and ??14C changed consistently in these soils after thermal (550°C, 2?h) or chemical (1?M HCl, 24?h) treatments. Organic components were found to be predominant carbon sources (70?C100%) in the uppermost portions (0?C2?cm in depth). In deeper portions at a depth of about 30?C35?cm, soil carbon may be derived completely from underlying carbonate minerals in Idria, western part of Slovenia. The Combination of heat and chemical treatments with AMS provides practical information on soil carbon sources in carbonaceous soils. 相似文献
88.
Boitsov S Petrova V Jensen HK Kursheva A Litvinenko I Chen Y Klungsøyr J 《Marine environmental research》2011,71(5):357-368
Subsurface sediments from a pockmark area in South-Western Barents Sea have been earlier found to contain elevated levels of petroleum-related polycyclic aromatic hydrocarbons. This work describes a comprehensive analysis of various biomarkers, including the highly source-specific hopanes, in a 4.5?m long gravity core from the same area, together with subsurface sediment samples from other areas in the region without pockmarks present ("background samples"). A clear difference between the pockmark gravity core and the background sediment cores was found, both with regard to genesis and the level of transformation of organic matter. A number of indicator parameters, such as methylphenanthrene index (MPI-1), point towards a significantly higher maturity of hydrocarbons in the pockmark core throughout its length as compared to the other sampled locations. Higher contents of microbial hopanoids (hopenes) may indicate the former presence of petroleum. These findings confirm the hypothesis of a natural hydrocarbon source in the deeper strata present in the studied location with pockmarks. 相似文献
89.
To assess responses and recovery of salt marsh grass species, we manipulated external nutrient supply and removed shoots of
Spartina alterniflora or Spartina patens from fertilized and control plots in a Massachusetts marsh. The pulse-and-recovery experiment included treatments for 5 years,
and recovery for an additional 7 years. Responses of these potential competitors sensitively depended on local contingencies
of elevation and nutrient dose, and, moreover, the differences in outcomes were emphasized at longer time scales. Local contingencies
became manifest as differences in responsiveness and resiliency of the different grass species, with differing time courses
and longer-term outcomes as to what species were present. These features might explain the diverse results obtained in shorter-term
salt marsh experiments, and provide a view of the complex suite of species-specific and external environmental variables that
may control competitive interactions in general. 相似文献
90.
The structure of the Tasmanian dolerite at Great Lake 总被引:1,自引:1,他引:0
A gravity survey over Great Lake on the central plateau of Tasmania shows that the structure of the dolerite that intrudes gently dipping Permian and Triassic sediments has appreciable thickening under the northern end of Great Lake and by means of alternate dykes and sills the dolerite moves up and out from the central feeder. This structure facilitates the formation of grano‐phyre over the dykes. The Great Lake intrusion is not unique but a typical form for the Tasmanian dolerite. 相似文献