Toxicity and bioaccumulation of thallium in Hyalella azteca, with comparison to other metals and prediction of environmental impact

Thallium (Tl) is an extremely toxic but little studied metal. For Hyalella azteca exposed in Lake Ontario water, a 25% reduction in survival (the LC25) occurred at about 48 nmol litre(-1) after 4 weeks. Body concentrations of Tl, which were proportional to water concentrations, averaged 290 nmol g(-1) dry mass at the LC25. Growth was reduced at slightly lower concentrations. Concentrations affecting reproduction were variable at < 50% of the LC25. On a water-concentration basis Tl was more toxic than Ni, Cu or Zn, but less toxic than Cd or Hg to Hyalella; toxicity to Pb was similar. On a body-concentration basis, the toxicities of Tl, Cd, Hg and Pb were all similar. Unlike Cd, Tl toxicity and uptake was affected by K concentrations in the water, and not by Ca, Mg, Na or other ions. Toxicity was proportional to uptake, and body concentrations were better predictors of toxicity than water concentrations in media with varying K concentrations. Preliminary measurements of Tl and Cd uptake by Hyalella from Hamilton Harbour and Lake Ontario sediments suggested that total bioavailable metal concentrations were greater in deep-water sediments from Lake Ontario than in sediments from the harbour. The ratio of bioavailable metal to the toxic threshold was slightly higher for Cd than for Tl, but well below 1 for both metals.     

Levels of polychlorinated biphenyls, organochlorine pesticides, mercury, cadmium, copper, selenium, arsenic, and zinc in the harbour seal, Phoca vitulina, in Norwegian waters

Residue levels of the chlorinated hydrocarbons polychlorinated biphenyls (PCBs), total DDT, alpha-, beta- and gamma-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), and oxychlordane in blubber, and the elements mercury, cadmium, copper, selenium, arsenic, and zinc in liver, of 82 harbour seals, Phoca vitulina, were determined. The seals were found dead or dying in Norwegian waters during the disease outbreak caused by a morbilli virus in 1988. Of the chlorinated hydrocarbons, the highest concentrations were found of PCBs, which were 2-4 times higher than the total DDT concentrations. P,p'-DDE was the main contributor to the total DDT, and constituted about 80%. The PCB and total DDT concentrations ranged from 0.4-38 and 0.1-8.8 mg kg(-1), respectively. The mercury concentrations ranged from 0.1-89 mg kg(-1). Significantly higher mean levels of PCBs (13 mg kg(-1) and mercury (16 mg kg(-1)) were found in blubber and liver, respectively, of seals from the Southern coast of Norway, as compared to the corresponding mean levels in seals from the Oslofjord (8.8 and 4.1 mg kg(-1)), and at the Northwestern coast (5.8 and 7.9 mg kg(-1)), respectively. A significant positive correlation was found between the concentrations of selenium and mercury. When the seals were grouped according to sex and age, females of ageclass > 1 and pups of both sexes had significantly lower PCB and total DDT levels than males ageclass > 1. Significantly higher hepatic mercury levels were found in seals ageclass > 1 as compared to pups. Only low levels of the other organochlorines, cadmium and arsenic, were found. Copper and zinc were considered to be present at normal physiological levels. The present organochlorine and heavy metal concentrations gave no support to suggestions that organochlorines and heavy metal pollution may be directly involved in the observed seal deaths.     

The Effects of Selective Logging on Inbreeding in Shorea megistophylla (Dipterocarpaceae) from Sri Lanka

The mating system of Shorea megistophylla , an endemic canopy tree from Sri Lanka, was quantified by allozyme analysis of progeny arrays using a mixed-mating model. Two adjacent populations were compared: one in forest that was selectively logged about 20 years ago, and the other in undisturbed primary forest. The selectively logged population had a lower multilocus outcrossing rate (t_m, = 0.71) compared to that of the undisturbed forest (t_m = 0.87). Only the progeny from the logged population showed evidence of either biparental inbreeding or Wablund effect, and the genotypic frequencies violated the assumptions of the mixed-mating model. Apomixis was detected in one isolated tree in the Royal Botanical Garden in Peradeniya by a multilocus test of progeny genotypic frequencies relative to the maternal genotype. However, significant levels of apomixis were not discerned in the natural (logged and unlogged) populations. These findings indicate that a reduction in population density of S. megistophylla following selective logging can significantly elevate the proportion of seeds produced through inbreeding. Adventive embryony may also increase in isolated trees that lack the chance to outcross.     

Fly-ash induced synthesis of phytochelatins in chickpea (Cicer arietinum L.) plants

Phytochelatins and related metabolites (cysteine and GSH) were found to be induced in the shoots of two varieties of Cicer arietinum viz., CSG-8962 and C-235 grown under different amendments of fly-ash with garden soil and press mud. Cysteine, GSH, PCs and its speciation were found in higher concentrations in amended fly-ash than in the control 100% soil. Two species of metal binding peptides i.e., PC2 and PC4 were found in both varieties and in amendments, however, their concentration varied depending upon the fly-ash concentrations in both amendments. Further, var. CSG-8962 was found more tolerant than var. C-235 because of higher concentrations of PCs and related metabolites.     

Biochemical responses of Camellia sinensis (L.) O. Kuntze to heavy metal stress

Three heavy metals-mercury (II), copper (II) and nickel (II), each at a concentration of 10 and 100 micrograms/ml, were tested for their effects on various biochemical constituents of tea leaves. Both NI (II) and Hg (II) decreased the phenolic contents, while Cu (II) increased it to some extent. The metal treatments enhanced the activity of phenyl alanine ammonia lyase (PAL), while the activity of poly phenol oxidase (PPO) showed a decline. Heavy metal stress also decreased the chlorophyll content of the leaves, along with a significant reduction in Hill activity. Proline content increased significantly in all treatments.     

Copepod nutritional condition and pelagic production during autumn in Kosterfjorden,western Sweden

The in situ grazing rate and nutritional condition of copepods were studied during October/November 1985, by analyzing gut fluorescence (feeding), body size and lipid composition (nutritional state), and electron transport system (ETS) activity (respiration rate) of copepods from surface-and deep-water in Kosterfjorden on the Swedish west coast. These parameters were related to the physical and biological environment, as defined by light, hydrography, autotrophic and bacterial production and seston in the water column. The results show a gradual build-up of the autumn phytoplankton bloom in the uppermost meters, with a peak in total autotrophic production in mid October of ca 550 mg C m^–2 d^–1, and a bacterial net production corresponding to 15% of this. Phytoplankton exudates made up, on average, 47% of the primary production and more than 50% of this was utilized by the bacteria. Copepods occurring in the surface-water exhibited grazing rates corresponding to between 11 and 18% of their body C d^–1 and potential growth rates of 0 to 9% d^–1. Copepod populations in the surface water were composed of individuals with higher average body-weight and lower lipid-proportion than those from the deep-water.Calanus finmarchicus in the deep-water showed characters indicating diapause condition, while this was not observed forAcartia clausi. Differences in lipid content and composition indicate thatC. finmarchicus, Pseudocalanus sp. andA. clausi represent three successive points on a scale of tolerance for fluctuations in the food environment. Adult femaleMetridia longa was the only one among seven species/stages of copepods in the deep-water ( 50 m depth) that contained phytoplankton pigments.Study performed through Tjärnö Marine Biological Laboratory, University of Göteborg, S-452 00 Strömstad, Sweden     

Optimal investment policies with exhaustible resources: An information-based model

An information-based model of the “optimal control” type is developed using concepts from information theory to explore the dynamics of fossil resource exhaustion and the phenomenon of substitution by other forms of capital and technological knowledge. All exhaustible resources stocks and forms of capital (and knowledge) are taken to be equivalent to forms of information in the physical sense. It is shown that, with optimal policies, the planning period, or cycle, has several distinct phases, with different optimal investment patterns. The model has two important qualitative implications: (1) economic growth rates are inherently discontinuous and (2) the model predicts an evolutionary structural change, viz., the creation of a new sector in response to the progressive exhaustion (or obsolescence) of previously essential resources or capital stocks. A multiperiod extension is suggested, leading to a tentative explanation for the Kondratieff long-wave phenomenon.     

Seasonal variations in compostability and production of vermiprotein by Eisenia fetida

The potential of E. fetida to degrade wastes into vermicompost and to produce vermiprotein in the form of worm-biomass during different seasons was evaluated. Results revealed that the environmental factors prevailing during different seasons did influence directly the life activities of the worm and indirectly the compostability of the wastes. Feeding activities of E. fetida reduced the time of production of an efficient organic pool with energy reserves as vermicompost. Further, the amount of vermicompost produced by the worm activity depended primarily on the environmental factors and secondarily on the nature of organic wastes.