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排序方式: 共有209条查询结果,搜索用时 234 毫秒
91.
Kiran Liversage Victoria J. Cole Christopher D. McQuaid Ross A. Coleman 《Marine Biology》2012,159(12):2777-2786
Patchy distributions within landscapes may be caused by migration in response to different types of habitat patches. Intertidal boulder fields are landscapes in which boulders are discrete habitat patches, often with chitons attached to their under-surfaces. Chiton densities and associations with patch edges differed between boulders overlying coarse- versus fine-sediment types, with greater densities occurring over fine sediments. We tested whether adult migration caused between-boulder distributions by measuring immigration and emigration following experimental replacement of coarse sediments with fine sediment under boulders. We also assessed whether the manipulations altered chiton positions relative to patch edges, and large-scale generality was tested by including data from two continents. The manipulations did not influence the association of chitons with edges or amounts of emigration, but chitons did display positive density-dependent immigration that mirrored their distributional patterns, indicating the importance of immigration. Strikingly, all results were consistent between continents despite involving different species and even genera of chitons. By using boulder fields as a small-scale, easily manipulated landscape, we show that, even in sedentary organisms, patchy distributions within landscapes can be caused by migration alone, without the need to invoke mortality or larval recruitment. 相似文献
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Burachevskaya Marina Minkina Tatiana Mandzhieva Saglara Bauer Tatiana Nevidomskaya Dina Shuvaeva Victoria Sushkova Svetlana Kizilkaya Ridvan Gülser Coşkun Rajput Vishnu 《Environmental geochemistry and health》2021,43(4):1655-1672
Environmental Geochemistry and Health - In recent years, the study of the influence of nanoparticles (NPs) on the environment has attracted much interest as nanotechnology is becoming the key... 相似文献
96.
The pattern of growth (biomass accumulation) in Ecklonia radiata throughout the year and across a depth profile was investigated using the traditional hole-punch method, and the information presented in context with concurrently measured in situ net productivity rates. The rate of net daily productivity showed a lack of consistent seasonal variability, remaining constant throughout the year at two of the four depths measured (3 m and 12 m), and becoming higher during winter at another (5 m). Throughout the year, rates of net daily productivity differed significantly across the depth profile. Net daily productivity rates averaged 0.017 g C g–1 dwt day–1 and 0.005 g C g–1 dwt day–1 at a depth of 3 m (1,394 mol O2 g–1 dwt day–1) and 10 m (382 mol O2 g–1 dwt day–1) respectively. In contrast, the biomass accumulation rate of E. radiata was highly seasonal, with low rates of growth occurring in autumn (0.002 g dwt g–1 dwt day–1 at both 3 and 10 m) and summer (0.007 and 0.004 g dwt g–1 dwt day–1 at 3 and 10 m respectively) and higher rates in spring (0.016 and 0.007 g dwt g–1 dwt day–1 at 3 and 10 m respectively) and winter (0.015 and 0.008 g dwt g–1 dwt day–1 at 3 and 10 m respectively). The proportion of assimilated carbon used for biomass accumulation varied throughout the year, between 5% and 41% at 3 m and between 28% and 128% at 10 m. The rates of biomass accumulation at all depths represented only a small proportion of the amount of carbon assimilated annually.Communicated by P.W. Sammarco, Chauvin 相似文献
97.
A. V. Krusche F. P. de Garvaiho J. M. de Moraes P. B. de Camargo M. V. R. Ballester S. Hornink L. A. Martinelli R. L. Victoria 《Journal of the American Water Resources Association》1997,33(5):1117-1123
ABSTRACT: The spatial and temporal variability of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate concentration and total coliform (TC) were investigated at nine sampling stations distributed along the main rivers of the Piracicaba River Basin, a 12,400 km2 catchment located in São Paulo State, one of the most developed regions of Brazil. Spatially, a downstream impoverishment of water quality conditions was observed, as seen by the decrease of DO, and increase of BOD, nitrate, and TC. These changes were probably caused by accumulating downstream discharge of domestic and industrial sewage. Temporal evaluation of 18 years of data showed that DO decreased with time for the majority of the sampling stations, while BOD, nitrate, and TC increased. A law, approved at the end of 1991, proposed a new water tax for river water extraction for industrial and agricultural use. The amount of this tax is determined according to the water quality of the extracted water. Therefore, the evaluation of the water quality status in this basin is a first step to help resources managers to determine the values for this tax. 相似文献
98.
George R. Robinson Steven N. Handel Victoria R. Schmalhofer 《Environmental management》1992,16(2):265-271
With the advent of modern sanitary landfill closure techniques, the opportunity exists for transforming municipal landfills
into urban woodlands. While costs of fullscale reforestation are generally prohibitive, a modest planting of clusters of trees
and shrubs could initiate or accelerate population expansions and natural plant succession from open field to diverse forest.
However, among woody species that have been screened for use on landfills, these ecological potentials have not yet been investigated.
We examined a 14-yr-old landfill plantation in New Jersey, USA, established to test tolerance of 19 species of trees and shrubs
to landfill environments. We measured survivorship, reproduction, and recruitment within and around the experimental installation.
Half of the original 190 plants were present, although survival and growth rates varied widely among species. An additional
752 trees and shrubs had colonized the plantation and its perimeter, as well as 2955 stems of vines. However, the great majority
(>95%) of woody plants that had colonized were not progeny of the planted cohort, but instead belonged to 18 invading species,
mostly native, bird-dispersed, and associated with intermediate stages of secondary plant succession. Based on this evidence,
we recommend that several ecological criteria be applied to choices of woody species for the restoration of municipal landfills
and similar degraded sites, in order to maximize rapid and economical establishment of diverse, productive woodlands. 相似文献
99.
Berzas Nevado JJ García Bermejo LF Rodríguez Martín-Doimeadios RC 《Environmental pollution (Barking, Essex : 1987)》2003,122(2):261-271
The world's largest mercury mine is placed at Almadén, Spain. However, there is a lack of information about the environmental impact of these mining activities in the ecosystem that surrounds this area. The aim of this article is to document the concentration of mercury in waters, sediments and bivalves of the aquatic system impacted by historic mine wastes. Simultaneously, a comprehensive study has been undertaken to characterise this hydrosystem and to determine the influence of some major physico-chemical parameters on the fate of mercury. Samplings were carried out for the last few years. Concentration of mercury in waters ranged from not detectable to 20 microg/l. For the sediments study, samples have been taken both from contaminated and non-contaminated sites within the basin. The regional background mercury concentration is higher than values typically cited for natural backgrounds. At exposed sites the mercury concentrations between 5 and 1000 microg/g were measured. These values are one to four order of magnitude greater than regional background levels. In the comparison between the results obtained at the present moment and those available for the 1974-1977 period, a general diminution of mercury levels is observed. Mercury concentrations in fresh water bivalves ranged between 1 and 4 microg/g (d.w.), with around 30% as monomethylmercury. In the discussion of the implications for risk assessment data available for other areas affected both for mine activities and mercuriferous belt are included. 相似文献
100.
Trophic State in Voyageurs National Park Lakes before and after Implementation of a Revised Water‐Level Management Plan
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Victoria G. Christensen Ryan P. Maki 《Journal of the American Water Resources Association》2015,51(1):99-111
We compiled Secchi depth, total phosphorus, and chlorophyll a (Chla) data from Voyageurs National Park lakes and compared datasets before and after a new water‐level management plan was implemented in January 2000. Average Secchi depth transparency improved (from 1.9 to 2.1 m, p = 0.020) between 1977‐1999 and 2000‐2011 in Kabetogama Lake for August samples only and remained unchanged in Rainy, Namakan, and Sand Point Lakes, and Black Bay in Rainy Lake. Average open‐water season Chla concentration decreased in Black Bay (from an average of 13 to 6.0 μg/l, p = 0.001) and Kabetogama Lake (from 9.9 to 6.2 μg/l, p = 0.006) between 1977‐1999 and 2000‐2011. Trophic state index decreased significantly in Black Bay from 59 to 51 (p = 0.006) and in Kabetogama Lake from 57 to 50 (p = 0.006) between 1977‐1999 and 2000‐2011. Trophic state indices based on Chla indicated that after 2000, Sand Point, Namakan, and Rainy Lakes remained oligotrophic, whereas eutrophication has decreased in Kabetogama Lake and Black Bay. Although nutrient inputs from inflows and internal sources are still sufficient to produce annual cyanobacterial blooms and may inhibit designated water uses, trophic state has decreased for Kabetogama Lake and Black Bay and there has been no decline in lake ecosystem health since the implementation of the revised water‐level management plan. 相似文献