Open- and closed-loop equilibrium control of trophic chains

If a nearly natural population system is deviated from its equilibrium, an important task of conservation ecology may be to control it back into equilibrium. In the paper a trophic chain is considered, and control systems are obtained by changing certain model parameters into control variables. For the equilibrium control two approaches are proposed. First, for a fixed time interval, local controllability into equilibrium is proved, and applying tools of optimal control, it is also shown how an appropriate open-loop control can be determined that actually controls the system into the equilibrium in given time. Another considered problem is to control the system to a new desired equilibrium. The problem is solved by the construction of a closed-loop control which asymptotically steers the trophic chain into this new equilibrium. In this way, actually, a controlled regime shift is realized.     

The effects on welfare of the imposition of individual transferable quotas on a heterogeneous fishing fleet

This paper examines the determination of effort levels, the rental price of quotas and the number of participants in a fishery managed with a total allowable catch and individual transferable quotas. How these variables change is determined for three phases of the management process. Potential participants in the fishery are assumed to be heterogeneous in their catching capabilities so that almost all active fishers earn positive net profits from fishing activities. It is shown that these quasirents are reduced during any of the management phases considered here. The impact of free allocations of permanent quota rights on fishers’ welfare is also considered. This may increase the welfare of all fishers if the allocation is based on catch history. However, an example is provided where the welfare of some highliners is reduced when the allocation is based on effort history.     

The Application of A Tiered Testing Approach to the Management of Dredged Sediments for Disposal at Sea in Canada

Canada, and other signatories to the London Convention 1972 on the prevention of marine pollution by dumping, are preparing to ratify a 1996 Protocol to this convention. Among the improvements to this international agreement, is a new process for the Assessment of Waste and Other Matter, which is to be adopted by signatory parties. the process includes a step in which material considered potentially acceptable for sea disposal must be characterized by chemical, physical and biological properties. Canada's interpretation and intended implementation of this characterization step is presented for the assessment of dredged sediments. This tiered testing approach involves using chemical screening limits for contaminants, and biological testing when screening levels are exceeded. Dredged material containing specified substances (e.g., cadmium, mercury, PAHs, PCBs, etc.) below or at screening levels would generally be considered of little environmental concern for disposal at sea. Wastes above the screening levels would require more detailed assessment before their suitability for disposal at sea could be determined.     

An improved index for monitoring metal pollutants in surface sediments

An approach for defining the quality of surface sediments of limited areas in terms of heavy metal contents is proposed. Sediments were taken on a bi‐dimensional mapping, for checking possible different sources of pollution in the case study, a harbour zone. Non residual metals were determined by ICP‐AES in cold diluted hydrochloric acid leachates of sediments. An “enrichment factor”;, r, can be computed for each metal: metals with r values exceeding unity can be considered as indicators of metal pollution. A “total enrichment factor”;, R, was proposed in order to assess the degree of pollution of sediments for each site. R is an adimensional value that accounts for the presence of metals that exceed threshold values determined by background concentrations.     

西葫芦对土壤持久性有机氯化物污染的指示性研究

西葫芦(Cucurbita pepo L.)对土壤中持久性有机氯化物的超强吸收能力已被证实,意味其具有指示区域土壤持久性有机氯化物污染状况的潜能。本研究采用农田小区试验,考察了西葫芦不同组织器官(根、过渡茎、茎、叶和果实)在6个生长期对有机氯化物的累积吸收行为;采用同位素稀释高分辨气相色谱-高分辨质谱法,分析了种植土壤及西葫芦各组织器官中的21种有机氯农药(OCPs)和18种多氯联苯(PCBs)。结果表明,西葫芦可将根吸收的OCPs和PCBs传递到过渡茎和茎。不同生长期采集的西葫芦根、过渡茎和茎中的OCPs和PCBs浓度基本稳定,无明显生物稀释效应,且此3个组织器官中OCPs和PCBs的分布模式与土壤中的分布模式基本一致。因此,可以用西葫芦根和茎中持久性有机氯化物的浓度指示土壤中持久性有机氯化物的污染水平,根和茎的采样时间可以不受西葫芦生长期的限制。     

The Application of A Tiered Testing Approach to the Management of Dredged Sediments for Disposal at Sea in Canada

Canada, and other signatories to the London Convention 1972 on the prevention of marine pollution by dumping, are preparing to ratify a 1996 Protocol to this convention. Among the improvements to this international agreement, is a new process for the Assessment of Waste and Other Matter, which is to be adopted by signatory parties. the process includes a step in which material considered potentially acceptable for sea disposal must be characterized by chemical, physical and biological properties. Canada's interpretation and intended implementation of this characterization step is presented for the assessment of dredged sediments. This tiered testing approach involves using chemical screening limits for contaminants, and biological testing when screening levels are exceeded. Dredged material containing specified substances (e.g., cadmium, mercury, PAHs, PCBs, etc.) below or at screening levels would generally be considered of little environmental concern for disposal at sea. Wastes above the screening levels would require more detailed assessment before their suitability for disposal at sea could be determined.     

The assessment of environmentally sensitive forest road construction in Calabrian pine forest areas of Turkey

Forest road construction by bulldozers in Calabrian Pine (Pinus brutia Ten.) forests on mountainous terrain of Turkey causes considerable damage to the environment and the forest standing alongside the road. This situation obliges a study of environmentally sound road construction in Turkey. This study was carried out in 4 sample sites of Antalya Forest Directorate in steep (34-50% gradient) and very steep terrain (51-70% gradient) conditions with bulldozer and excavator machine and direct damages to forest during road construction was determined, including forest area losses and damages to downhill trees in mountainous areas. It was determined that in steep terrain when excavators were used, less forest area (22.16%) was destroyed compared to bulldozers and 26.54% less area in very steep terrain. The proportion of damage on trees where bulldozer worked was nearly twofold higher than excavator was used. The results of this research show that the environmentally sensitive techniques applied for the road construction projects are considerably superior to the traditional use of bulldozers on steep slopes. The environmentally sound forest road construction by use of excavator must be considered an appropriate and reliable solution for mountainous terrain where areas of sensitive forest ecosystems are to be opened up.     

Heavy metals in albanian coastal sediments

Heavy metals (Fe, Mn, Cr, Ni, Cu, Cd, Pb, Sn) concentration has been determined on 39 coastal sediment samples collected in Albania. The relationship between the heavy metals content and the grain size has been considered. All metals, except Cu and Cd, resulted accumulated in the finest fraction, which constituted up to 95% of most of the considered sediments. A good correlation has been found for Ni, Cr, Fe, Zn, Cu in the entire area, indicating a common origin for these metals in the analyzed sediments. Concentration values fall in the range reported for Dinaric chain derived sediments, revealing, generally, a natural origin of the metal contents. Though in some selected areas such as the Drin and the Skumbin Bay, an antropogenic input of Cr, Fe, Ni and Cu can be observed, as the result of discharging of mines and smelter activities.     

Inorganic pollution in water—the analyst's viewpoint†

Inorganic pollution comprises both major and minor constituents, although only 12 chemical elements may be considered major components. Twenty‐eight elements constitute a group of common minor elements and an additional 13 elements comprise a group of less common minor constituents. Reliable quantitative data are required on the occurrence of these substances in a wide variety of water types, usually at extremely low concentrations. The analysis of standard reference water samples provides information on the overall reliability of water‐quality data. Although most major constituents may be determined with acceptable reliability, determinations of certain minor constituents lack comparable precision; for example, determinations of boron, nickel, and chromium. Few precision data are available on the determination of the less common trace elements. Several comparatively new analytical techniques, such as flameless atomic absorption spectrophotometry, voltammetry, and emission spectroscopy with plasma excitation, appear capable of providing improved sensitivity.     

Identifying and mapping local bycatch hotspots of loggerhead sea turtles using a GIS-based method: implications for conservation

Fisheries bycatch of marine megafauna is a worldwide conservation issue. In this study, we propose a method for generating reliable maps of sea turtle bycatch hotspots. Based on a well-defined area of fishing effort determined from the longline sets monitored in 2007 and 2010, we calculated the fishing area with the highest turtle bycatch density for both years. Our results show that it is important to consider all the components of fishing effort (area, number of hooks and soak time) in order to standardize the bycatch events, and thus the spatial density of the captures can be considered an index of abundance and aggregation of the species. Moreover, the high-resolution level of the analyses was useful for investigating the cumulative effect of the longline sets, which often overlap, and made it possible to correctly map the capture density and the intensity of the fishing effort at any given location.     

Nutrient distribution in locations of the Gulf of Trieste (northern Adriatic sea) suspected of pollution

Nutrients (ammonium‐nitrogen, nitrite, nitrate, orthophosphate and dissolved silica) as well as some chemical‐physical parameters (temperature, pH, salinity, dissolved oxygen and total suspended matter) were determined in filtered seawater samples taken at the surface, at middle depth and at the bottom, in 6 open‐sea locations of the Gulf of Trieste (northern Adriatic Sea) close to pipeline exits that discharge wastewaters from treatment plants. The collected data allow a comparison of the quality of these open‐sea waters with coastal waters and constitute a reference for successive monitoring in these locations suspected of pollution. A multivariate statistical analysis by the principal component method shows that the considered ecosystem can be modeled with two factors: the first one is referenced to the marine environment, in particular to the decomposition of the organic debris in deep water; whereas the second factor is referenced to the input of freshwaters in the Gulf, driving nitrates from agricultural lands.     

Microstructural growth in otoliths of conger eel (Conger myriaster) leptocephali during the metamorphic stage

Otolith growth during metamorphosis and some aspects of the early life history of conger eel (Conger myriaster) were determined as indicated from microstructure in otoliths of the leptocephali collected from Cheonsu Bay, Korea during May and June 1988. The leptocephali occurred from early May to late June in the study area. Larvae collected in early May were in the late leptocephalus stage, and the proportion of the metamorphosing leptocephali increased over time. Otoliths in the late leptocephalus stage showed a translucent zone only. Although the fish did not feed and the body length diminished during metamorphosis, the otolith continued to grow and, consequently, the opaque zone was formed outside the translucent zone. The inner translucent zone can be considered a leptocephalus zone, and the outer opaque zone a metamorphic zone. Assuming that the growth increments were deposited daily from hatching, the conger eel can be considered to have hatched between September and February. The number of increments in the inner hyaline zone ranged from 124 to 239, and was assumed to represent the number of days from hatching to the onset of metamorphosis. The duration of metamorphosis was estimated as 51 to 75 d based on the number of increments in the opaque zone at the end of the metamorphic stage.     

Zum Stichprobenfehler im Human-Biomonitoring

Goal and Scope

Human biomonitoring determines the concentration of xenobiotics in populations by means of smaller samples, thus necessarily arising sampling errors. These are determined.

Methods

For a fictitious population of 200,000 persons, differently broad xenobiotic concentration distributions were simulated. Samples of varying size were randomly drawn and the sampling error, defined as the proportional difference between the geometric means of sample and population, was determined.

Results and Conclusions

The sampling error depends on the sample size and the width of the concentration distribution; its estimation is possible for any xenobiotic, given it has lognormal distribution, and the sample size is between 10 and 50,000. For its estimation an equation was derived.

Outlook

When presenting and interpreting results of human biomonitoring, the sampling error must be considered, together with the uncertainty of the measurement.     

Social feedback and attractiveness in zebra finches

The attractiveness of an individual (i.e. its ability to arouse interest in a potential mate) has important implications for its reproductive success. However, attractiveness is not a fixed trait. Previous work has shown that male birds can adjust the intensity of their courtship display in response to variation in female behaviour, but little is known about how males adjust their behaviour during mate choice in response to social feedback about their own attractiveness independent of their intrinsic quality. Such information may help to maximize the potential mating success of males. Here, we provide experimental evidence that the amount of attention given by male zebra finches to females is dependent upon the manipulated attractiveness of males. This demonstrates that, in this socially monogamous species of bird, attractiveness of males could be considered to be a social construct, at least partially determined via social feedback from females.     

Prediction of response of zooplankton biomass to climatic and oceanic changes

This paper examines the long-term variation in zooplankton biomass in response to climatic and oceanic changes, using a neural network as a nonlinear multivariate analysis method. Zooplankton data collected from 1951 to 1990 off the shore of northeastern Japan were analyzed. We considered patterns of the Kuroshio and the Oyashio, sea surface temperature, and meteorological parameters as environmental factors that affect zooplankton biomass. Back propagation neural networks were trained to generate mapping functions between environmental variables and zooplankton biomass. The performance of the network models was tested by varying the numbers of input and hidden units. Changes in zooplankton biomass could be predicted from environmental conditions. The neural network yielded predictions with smaller errors than those of predictions determined by linear multiple regression. The sensitivity analysis of networks was used to extract predictive knowledge. The air pressure, sea surface temperature, and some indices of atmospheric circulation were the primary factors for predictions. The patterns of the Kuroshio and the Oyashio demonstrated different effects among sea areas.     

利用微核试验和彗星电泳试验评价黄河兰州段水质致遗传毒性作用

利用微核和彗星电泳试验对黄河兰州段鲤鱼(Cyprinuscarpio)红细胞大小及其DNA损伤(微核、核异常、单链断裂和遇碱不稳定点、双链断裂)进行了研究,并以刘家峡水库为对照.结果显示,黄河兰州段采得的鲤鱼其红细胞微核率显著增加(P<0.05),DNA单链断裂和遇碱不稳定点损伤比例和程度加重,但两样点差异不显著(P>0.05),这表明兰州段黄河水质有明显的致遗传毒性作用.同时两种检测结果显示,不同的遗传毒性检测手段具有不同的检测终点和机制,建议在监测环境污染致遗传毒性作用时考虑检测方法的统一和标准化,从而得到更可靠、全面的结果.图4表3参15     

Ökonomische Ansätze zur Ökosystembewertung am Beispiel des Bodens

As it is practically impossible in an industrial society to reduce impacts into ecosystems to a level that would preclude any damages, the need for damage valuation arises. One of the available valuation tools is the economic approach. Subsequent publications present this approach using the example of soils. In the first part, soils as part of ecosystems are considered from an ecological and a conventional economic point of view. In the following so-called ecological-economic perspective, more recent developments in economic valuation research are introduced. It is shown how ecological and economic valuation can complement one another. It is emphasized that economic valuations should be restricted to a critical soil structure which, in economic terms, is determined by the non-substitutable services of the ecological asset.     

Biomass measurements and weight-to-weight conversion factors: a comparison of methods applied to the mussel Mytilus galloprovincialis

Wet weight to ash-free dry weight conversion factors were calculated for the bivalve Mytilus galloprovincialis Lamarck; specimens were collected in November 1989 in the Magra Estuary (eastern Ligurian Sea, Italy). Ash-free dry weight was determined by four different methods: (A) mechanical separation of shell and body; (B) shell dissolution with HCl; (C) dissolution of organic matter with NaClO; (D) incineration of the whole organism. The results obtained by these four methods were significantly different, indicating that caution is necessary when comparing biomass data obtained by different methods. Incineration and decalcification with HCl seem to be the best procedures: they not only combine accuracy with speed, but are also the most universally applicable, being equally suitable for soft-bodied or hard-bodied organisms. Mechanical separation can lead to an underestimation of the biomass, whereas treatment with NaClO can lead to its overestimation. However, no method can be considered the best in absolute terms, the final choice depending on the particular weight measurement required (e.g. shell-free dry weight) and the nature of the organism concerned (e.g. an organism with a large carbonate content).     

The role of organic matter components in soil on partitioning of Chlorohydrocarbons

Triolein, farnesol, humic acid, methyl salicylate, lignin and cellulose were selected as representative soil organic matter components. Equilibrium partition coefficients between these materials and water were experimentally determined for lindane, aldrin and a series of chlorobenzenes. Theoretical values for the chlorobenzenes were also determined using a Regular Solution Theory approach. The molecular size and polarity of the sorbent or organic matter components were identified as factors influencing the magnitude of the partition coefficient. Both experimental and theoretical partition coefficients were compared with soil/water values expressed on an organic matter basis. For the chlorobenzenes considered, experimental values for humic acid agreed most closely with those from soil, although triolein and lignin were also similar. Theoretical partition coefficients were in general lower than experimental values, but within a factor of 10 . Closest agreement was noted with triolein. Soil/water partition coefficients were consistent with partitioning between humic acid and water.     

Implications of Intratropical Migration on Reserve Design: A Case Study Using Pharomachrus mocinno

As habitat loss continues, natural protected areas will become islands in human-modified landscapes; maintenance of functional communities and ecosystems will depend on properly designed protected areas. We demonstrate that incorporating regional habitat linkages that allow for seasonal migrations of intratropical resident species must be a major design criterion for establishing protected areas. Using radiotelemetry, we monitored the seasonal movements of one such migrant, the Resplendent Quetzal ( Pharomachrus mocinno ), a large, frugivorous bird, one of many tropical residents known to migrate altitudinally within Mesoamerica. Based on three years of data we determined that quetzals followed a complicated local migration that linked four montane life zones. Using this species as an indicator revealed that the configuration of the Monteverde reserve complex in the Tilaran Mountains in west-central Costa Rica lacked sufficient habitat distribution to conserve montane biodiversity. On the basis of these results, we propose that the three-step process proposed by Soulé and Simberloff (1986) for estimating minimum sizes of reserves be amended to include a fourth step: The critical habitats used throughout the annual cycles of target or keystone species must be identified and adequately protected. Natural protected areas can be considered adequately designed only when sufficient area with a full complement of ecologically linked habitats is included.