Mercury bioaccumulation and trophic transfer in sympatric snapper species from the Gulf of Mexico.

Consumption of marine fish is a major route of toxic methyl mercury (MeHg) exposure to ocean apex predators and human populations. Here we explore the influence of trophic structure on total mercury (Hg) accumulation in red snapper (RS, Lutjanus campechanus) and gray snapper (GS, Lutjanus griseus) from the coastal Louisiana region of the Gulf of Mexico, west of the Mississippi River. The objectives of this investigation were to: (1) determine the effectiveness of the use of offshore recreational fishing charter boats and marinas as sources of fish samples and (2) compare species differences in Hg bioaccumulation, trophic position, and carbon sources. Our data show that length-normalized Hg concentrations (> or = 97% as MeHg in tissue of both species) were 230% greater in GS in comparison to RS collected from the same general area. Stable C and N isotope signatures (delta15N and delta13C) indicate that GS occupy a slightly higher trophic position (approximately 30% of one trophic position higher) on the Gulf food web in comparison to RS and that GS appear to incorporate higher trophic positioned prey, continually and at smaller sizes. Mercury was strongly correlated with combined delta15N and delta13C in pooled species data, arguing that most of the substantial difference in Hg bioaccumulation between RS and GS can be explained by modest differences in their trophic position and, to a lesser degree, carbon sources, which had low variation and high overlap among species. These observations demonstrate that even minor to moderate differences in trophic position and food habits in sympatric species can create relatively large differences in bioaccumulation regimes and underscores the importance of quantitative characterization of trophic structure in marine MeHg bioaccumulation studies.     

ECONOMIC EVALUATION OF ON-FARM WATER MANAGEMENT PROJECTS1

ABSTRACT: During the last three decades, developing countries have invested enormous amounts of resources (running into billions of dollars) in the development of large surface irrigation systems. Investment funds were largely spent on the development of the main systems such as dams, canals and distributaries. Very little attention and resources have been spent on the development of below-the-outlet subsystems, in spite of very low levels of water use efficiency due to lack of proper land leveling, high water losses in field channels, and skewed distribution of available water among farmers served by individual water courses. This state of affairs has resulted in a lack of confidence on the part of most farmers in the reliability of surface irrigation systems to deliver water on time and in adequate quantities which, in turn, has resulted in farmers using below optimum levels of all other complementary inputs except labor. Realizing the importance of improving water use efficiency, both the domestic governments and donor agencies are increasingly paying serious attention to these problems. On-Farm Water Management (OFWM) as a strategy to improve water use efficiency and consequently agricultural production in many developing countries has been currently receiving very wide and vigorous consideration among economists, water management experts, policymakers, and donor agencies. A judicious use of the newly allocated funds of OFWM projects obviously needs proper evaluation procedures so that money could be allocated for the most deserving purposes and projects. In particular, recently, private profitability calculations due to public investments in OFWM activities have received attention from economists and decision makers in developing countries’governments and in donor agencies are very much interested in knowing the impacts of their investments in OFWM activities on farmers’income and welfare. However, the evaluation procedures commonly used in empirical studies, using a production function approach, seem to be at variance and sometimes inconsistent with proper comparative-static procedures. Thus, the primary objective of this paper is to develop consistent procedures for evaluating the impacts created by OFWM investments on farmers’income and resource use. In this context, the paper examines the critical relationship between the market price of the agricultural output and production function parameters which are affected by the OFWM investments.     

The relation between caste ratios and division of labor in the ant genus Pheidole (Hymenoptera: Formicidae)

Summary Ten species of Pheidole, representing as many species groups from various localities in North and South America, Asia, and Africa, were analyzed to probe for possible relationships between caste ratios and division of labor.Minor workers are behaviorally almost uniform among the species, but major workers vary in repertory from 4 to 19 behavioral acts (Table 1, Fig. 2). The major repertory size increases significantly across the species with the percentage of majors in the worker force (Fig. 3). This trend is consistent with the basic prediction of ergonomic optimization models under an assumption of colony-level selection. There is also a trend toward reduction of behavioral repertory with increase of size in the major relative to the minor, a second relation expected from theory, but the data are not sufficient to reach statistical significance.When the minor:major ratio was lowered to below 1:1 (from the usual 3:1 to 20:1, according to species), in three widely different species (guilelmimuelleri, megacephala, pubiventris), the repertory size increased by 1.4–4.5X and the rate of activity by 15–30X (Table 1, Figs. 4–6). The change occurred within 1 h of the ratio change and was reversed in comparably short time when the original ratio was restored.This abrupt and important shift in behavior permitted the major workers to serve as an emergency stand-by caste, available to be summoned to a nearly full repertory when the minor worker caste was depleted. The majors also restored 75% or more of the missing minor workers' activity rate under laboratory conditions. Their transformation allowed continued oviposition by the queen and the rearing of larvae to the adult stage.In line with these findings, a distinction is made between programmed elasticity in the repertory of individual workers and castes and the resiliency of the colony as a whole, which depends upon the pattern of caste-specific elasticity.     

Polychlorinated chemical residues in fish from major watersheds near the Great Lakes, 1979

Over 50 non-PCB polyhalogenated organic chemicals have been identified by GC/MS in fish from the Great Lakes and other major watersheds near the Great Lakes. p,p′-DDE, hexachlorobenzene, and components of tech-chlordane were the most frequently found chemicals. Also described are advances in sample preparation methodology which allow the identification of many frequently occuring unusual chemicals. Several chemicals not previously reported in environmental samples are identified.     

Employee influence on decisions: An analysis

Attitude data from a national sample of 2300 working adults are reported. The data show that employees feel they should have more influence on a number of decisions. This feeling is stronger for decisions affecting how their job is done, than for matters of corporate policy and personnel decisions. However, it is in the policy and personnel areas that they perceive the greatest discrepancy between the amount of influence they presently have and the amount of influence they feel they should have. Older, better educated, and higher-paid respondents felt they should have more influence on all decisions. The implications of these findings for the Quality of Work Life movement were considered. The data suggest a favourable future climate for certain types of employee influence/Quality of Work Life projects.     

THE ENGINEER'S ROLE IN WATER RESOURCES PLANNING1

Engineers have traditionally led the planning effort in water resources developments. The engineer's leadership role in water resources, as well as in many other planning activities, has been challenged by technical and scientific people as well as by the general public for insensitivity to social, aesthetic, ecological, and political problems created by planning. The paper draws attention to the fact that the engineer cannot continue to expect the role of leadership to fall to him unless he prepares himself properly for that role. However, it is brought out that the engineer, by his education and training, is still the best qualified among all the representatives of the various disciplines associated with water resources planning to lead the planning effort if he prepares himself for the task. The requirements for preparation for leading water resources planning are outlined.     

Sanitary aspect of using partially treated landfill leachate as a water source in green waste composting

Shredded green wastes were composted in windrows, at the Harewood Whin landfill, near the city of York, in West Yorkshire, UK. Landfill leachate were added twice during the second and fourth week of the process in two piles. One pile was turned once every week for eight weeks and the other was turned twice, during the same period. Each time approximately, 2 m3 of leachate was added, into each pile. The two piles each contained about 45 m3 of shredded green waste. The effect of adding leachate on the sanitisation of the green waste during composting, was evaluated based on the changes in the levels of faecal coliforms and faecal streptococci. The results suggested that using leachate as the moisture source had no significant effect (tested with two factors ANOVA test) on the sanitisation process when compared with two similar piles, used as the control, for which tap water was used for moisture addition. In all four piles sanitisation was almost complete and below the acceptable levels. Additionally, the results indicated that there was no significant effect on the sanitisation process of the turning frequency.