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991.
Francesca Porri Gerardo I. Zardi Christopher D. McQuaid Sarah Radloff 《Marine Biology》2007,152(3):631-637
Settlement is a major determinant of intertidal populations. However, the energy costs of lost larvae are very high. Accordingly,
arrival and attachment on suitable substrata are essential requirements for species’ survival. On the intertidal, the presence
of cues left by adult or juvenile conspecifics could be vital for the successful establishment of larvae arriving on the shore.
Two mussel species, the indigenous Perna perna and the invasive Mytilus galloprovincialis, co-occur on the lower eulittoral zone on the south coast of South Africa. P.
perna dominates the low and M. galloprovincialis the high mussel zones, with co-existence in the mid mussel zone. This study tested the hypothesis of settlement selectivity
for conspecifics in these two mussel species, to understand whether the final adult distribution of mussels on the shores
is determined by active behavioural and chemical mechanisms. Preferential selection by larvae for conspecifics was tested
in the field during the peak settlement period in 2004 in natural mussel beds across zones and through manipulative experiments
in the mid-zone where the species co-exist. On natural beds, settlement was determined by counts of settlers attached over
48 h onto artificial collectors. Collectors were placed on beds of P. perna and M. galloprovincialis present at both high- and low-adult densities, as well as in mixed beds. On such natural beds, settlers of both species consistently
favored low-zone P. perna beds. Settlement patterns over 24 h onto experimentally created mussel patches consisting of P.
perna, M. galloprovincialis or the two species combined beds, set in the mixed zone, did not conform with the results of the natural beds study: settlers
of both species settled with no discrimination among different patches. The results indicate that mussels, which are sedentary,
lack attraction to conspecifics at settlement. This highlights the importance of tidal height in setting settlement rates,
and of post-settlement events in shaping populations of these broadcast spawners. 相似文献
992.
This paper is concerned with the sustainable development of a self-drive tourist destination in the remote region in Northern
Australia. It first compares officially used data on visitor profiles to the information collected in the survey. Differences
between data collected and available secondary data imply that tourism planning should include collection of region-specific
tourism information to guide and mitigate potential environmental changes. Natural landscape features are the key attraction
for visitors to the region. Visitor satisfaction levels with the current state of the destination are high. However, local
residents reported perceived negative impacts of tourism, in particular on amenities and the ecology of the landscape. Visitors
also reported behavior that might contribute to environmental impacts. Implications of the findings, in the context of future
destination planning, are discussed. 相似文献
993.
Direct solid sampling Zeeman atomic absorption spectrometric methods were developed and successfully applied to the determination of mercury, cadmium, lead and manganese in aquatic plants. Mercury was determined using a specially designed furnace. The other elements were determined by a third generation spectrometer. In 3-field- and dynamic mode the working range was substantially extended and high amounts of analyte were detectable without laborious dilution of solid samples. The measurements were based on calibrations using certified reference materials of organic origin. No matrix effects were observed under the optimised conditions. Results obtained were in good agreement with the certified values. 相似文献
994.
Zrinka Dragun Marijana Erk Dušica Ivanković Roko Žaja Vlatka Filipović Marijić Biserka Raspor 《Environmental science and pollution research international》2010,17(4):977-986
Purpose
The aim of this study was to compare the level of metal contamination in two bays in the middle part of the Eastern Adriatic coastal zone in Croatia using the gills of mussels Mytilus galloprovincialis as indicator tissue. Despite the existing sources of contamination, previous studies with caged mussels only indicated moderate metal contamination of the Kaštela Bay, contrary to the Trogir Bay in which marina and shipyard present a probable source of Cu- and Zn-contamination. 相似文献995.
Stream fish bioassessment methods assume that fish assemblages observed in sample sites reflect responses to local stressors, but fish assemblages are influenced by local factors as well as regional dispersal to and from connected streams. We hypothesized that fish movement to and from refugia and source populations in connected rivers (i.e., riverine dispersal) would weaken or decouple relations between fish community metrics and local environmental conditions. We compared fish-environment relations between streams that flow into large rivers (mainstem tributaries) and streams that lack riverine confluences (headwater tributaries) at multiple spatial grains using data from the USEPA's Environmental Monitoring and Assessment Program in the mid-Atlantic highlands, USA (n = 157 sites). Headwater and mainstem tributaries were not different in local environmental conditions, but showed important differences in fish metric responses to environmental quality gradients. Stream sites flowing into mainstem channels within 10 fluvial km showed consistently weaker relations to local environmental conditions than stream sites that lacked such mainstem connections. Moreover, these patterns diminished at longer distances from riverine confluences, consistent with the hypothesis of riverine dispersal. Our results suggest that (1) the precision of fish bioassessment metrics may be improved by calibrating scoring criteria based on the spatial position of sites within stream networks and (2) the spatial grain of fish bioassessment studies may be manipulated to suit objectives by including or excluding fishes exhibiting riverine dispersal. 相似文献
996.
Fabio Orecchini 《Sustainability Science》2007,2(2):245-252
Human society consumes resources that it is not able to reproduce. Human activities are still based on “open cycles,” starting
from a condition of natural environmental balance and reaching an environmental imbalance. The challenging scope of scientific
and technological research towards sustainability appears clear if it is based on this analysis: to find development systems
based on “closed cycles” of resources. The challenging objective of realizing closed cycles leads to a definition of sustainability
that indicates the path to sustainable development, as well as stating the general principle. It also provides a key to the
qualitative measurement of sustainability. This means that the sustainability level of a system can be measured by measuring
its capacity to avoid the consumption of resources. Zero consumption is a necessary condition for sustainability, and brings
about as a side effect the highly desired “zero-waste” result. Materials entering the proposed endless scheme pass through
the process of usefulness without losing their capacity to feed the system again after being used. Thus, the concept of “consumption”
itself is replaced by one of “use” when resources are inserted into closed loops capable of feeding human development. The
application of the closed cycle sustainability criterion particularly displays its feasibility, and a theoretical guiding
role, in the energy sector. Energy vectors such as hydrogen and electricity enable the closure of the energy resources loop
by effectively approaching the objective of “zero consumption” (and the side result of “zero waste”) through already demonstrated
technological solutions. 相似文献
997.
Advanced terrestrial ecosystem analysis and modelling 总被引:1,自引:0,他引:1
Wolfgang Cramer 《Regional Environmental Change》2008,8(3):89-90
998.
Olanike O. Aladenola Ayodele E. Ajayi Ayorinde A. Olufayo Babatunde Ajayi 《The Environmentalist》2008,28(2):123-127
The performance of a mixture of a forest bye product and cement for the production of storage structure for harvested rainwater
was assessed. Three mix ratios of Cement: Gmelina arborea sawdust 3.0:1.0 (specimen A), 2.5:1.0 (specimen B) and 2.0:1.0 (specimen C) were considered. Engineering properties and dimensional
stability of the different mix-ratios were monitored from prototypes cylindrical pots and test billet specimens. Possible
change in quality of stored rainwater, with time was monitored in all the three cases. Water quality parameters monitored
include pH, hardness, total suspended solids, alkalinity, acidity and total dissolved CO2. The tensile stress obtained were 110, 104, and 95 N/mm2, while the compressive strength were 5,000, 3,000, and 2,000 kN for specimens A, B and C respectively. Accelerated aging
test showed that sample A were more resistant to deformation, while specimen C were more susceptible to change in structure
over time. Similarly, the values of tensile and compressive strength after accelerated aging test increased in the order of
specimen A > B > C. Except in specimen C where significant differences in alkalinity and acidity were observed, there were
no significant differences in quality of the water stored in the pots after 2 months of storage. The results indicate the
suitability of the Gmelina arborea waste as an alternative in constructing water storage structures in rural communities. 相似文献
999.
Haber W 《Environmental science and pollution research international》2007,14(6):359-365
Humans’ superiority over all other organisms on earth rests on five main foundations: command of fire requiring fuel; controlled
production of food and other biotic substances; utilization of metals and other non-living materials for construction and
appliances; technically determined, urban-oriented living standard; economically and culturally regulated societal organization.
The young discipline of ecology has revealed that the progress of civilization and technology attained, and being further
pursued by humankind, and generally taken for granted and permanent, is leading into ecological traps. This metaphor circumscribes
ecological situations where finite resources are being exhausted or rendered non-utilizable without a realistic prospect of
restitution. Energy, food and land are the principal, closely interrelated traps; but the absolutely decisive resource in
question is land whose increasing scarcity is totally underrated. Land is needed for fulfilling growing food demands, for
producing renewable energy in the post-fossil and post-nuclear era, for maintaining other ecosystem services, for urban-industrial
uses, transport, material extraction, refuse deposition, but also for leisure, recreation, and nature conservation. All these
needs compete for land, food and non-food biomass production moreover for good soils that are scarcer than ever. We are preoccupied
with fighting climate change and loss of biodiversity; but these are minor problems we could adapt to, albeit painfully, and
their solution will fail if we are caught in the interrelated traps of energy, food, and land scarcity. Land and soils, finite
and irreproducible resources, are the key issues we have to devote our work to, based on careful ecological information, planning
and design for proper uses and purposes. The article concludes with a short reflection on economy and competition as general
driving forces, and on the role and reputation of today’s ecology.
Updated version of the keynote lecture presented at the EcoSummit 2007 in Beijing, China, May 24. The article is gratefully
dedicated to the memory of my late colleague and friend Frank B. Golley. 相似文献
1000.
This study estimates efficient nitrogen load reductions to the Stockholm archipelago, a Swedish coastal zone in the Baltic
Sea, and compares these with politically determined and implemented nitrogen abatement programs. The region is relatively
well equipped with necessary data, and a simple programming model is constructed. The results show a large divergence in efficient
nitrogen reductions, mainly due to the divergences in benefit estimates from water quality improvements in the archipelago.
However, the results need to be interpreted with caution due to all uncertainties related to predicting net values from changes
in nitrogen load to a coastal zone. In spite of this, it is still of policy relevance to infer results which show that the
politically determined target coincides with an efficient nitrogen reduction at relatively low benefit estimate, but that
actual net benefits could be increased from a reallocation of abatement measures towards more low cost measures. 相似文献