Bioavailability, accumulation and effects of heavy metals in sediments with special reference to United Kingdom estuaries: a review

Using mainly United Kingdom estuaries as examples, various factors governing the bioavailability, bioaccumulation and biological effects of heavy metals in sediment-dominated estuaries are reviewed. Estuaries and metals primarily discussed include the Mersey (Hg, methylmercury; Pb, alkyllead), the Loughor (Cr, Sn), the Severn (Ag, Cd), the Fal (As, Cu, Sn, Zn), Poole Harbour (Cd, Hg, Se, tributyltin) and Southampton Water (tributyltin). Concentrations and bioavailabilities of metals in estuarine sediments depend on many different processes. Examples include (1) mobilisation of metals to the interstitial water and their chemical speciation, (2) transformation (e.g. methylation) of metals including As, Hg, Pb and Sn (3) the control exerted by major sediment components (e.g. oxides of Fe and organics) to which metals are preferentially bound, (4) competition between sediment metals (e.g. Cu and Ag; Zn and Cd) for uptake sites in organisms, and (5) the influence of bioturbation, salinity, redox or pH on these processes. Under field conditions, identification of dominant processes can be achieved by observing the goodness of fit between metal concentrations in ubiquitous deposit-feeding species and levels in various types of sediment extract over a wide spectrum of sediment types. Factors of more local importance are often indicated by the marked deviation of some points from otherwise excellent relationships. For example, points lying above the line relating tissue Sn concentrations in the clam Scrobicularia plana to those in 1 n HCl extracts of sediments were found to reflect the accumulation of tributyltin, a more readily bioavailable form of Sn. In the same species, unexpectedly high tissue-Cu concentrations were characteristic of very anoxic in sediments and tissue And As and Pb concentrations were suppressed in sediments having high concentrations of Fe oxides. Under field conditions, examples of deleterious effects on benthic organisms that can be attributed to specific metallic pollutants are comparatively rare. Effects of tributyltins from antifouling paints on oysters and neogastropods have been documented and their toxicity has undoubtedly led to environmental degradation in many UK estuaries and coastal areas. In estuaries contaminated with metal-mining wastes, the effects of Cu and Zn on species distribution can be observed, but they are generally less obvious than would be predicted from experimental data. Effects are ameliorated by the induction of metal tolerance mechanisms in some species and in others by the appearance of tolerant strains. The induction of metal detoxification systems involving the formation of granules or metal-binding proteins leads in some species to tissue concentrations that are orders of magnitude higher than normal. For example, high concentrations of Cd and Ag have been found in some species from the Severn Estuary, although there is no unequivocal evidence that either metal has caused deleterious effects on benthic populations. On the other hand, experimental studies with Ag, Cd, Cr, Cu, Hg and Zn show that they are toxic to some species at environmentally realistic levels. Since pollutants rarely occur singly, it is likely that in many moderately contaminated estuaries metals contribute to the stress to organisms caused by substances requiring detoxification. There has been much speculation over the years concerning the biomagnification of metals with increasing trophic levels along food chains. Whilst animals having higher metal concentrations than their prey are sometimes found, the only consistent evidence of biomagnification concerns methylmercury. When estuarine birds are considered, there are relatively few instances in which deleterious effects can unequivocally be attributed to metals or their compounds. However, the Mersey bird kill was attributable to alkyllead pollution from industry. Among other organometals, methylmercury has proved toxic to birds but, so far, no evidence for the toxicity of tributyltin has been reported. However, the compound may have affected bird populations through its effects on the abundance of prey organisms, particularly estuarine molluscs. Of the inorganic forms of metals, Pb in the form of shot has caused problems in many areas and Cd, Hg and Se are suspected of causing toxic effects. There is little field evidence that birds have been affected by Ag, As, Cr, Cu or Zn individually. On the other hand, it is difficult to exclude the possibility that, additively, these metals may produce a significant effect. In part, the lack of evidence reflects the fact that relatively little research has been done. There is scope for more work on metals and organometals in estuarine birds, particularly with regard to their metabolism and their effects on juveniles and individuals subjected to stresses such as starvation.     

The Next Chapter Begins: Announcing Prof. Bram F. Noble,Editor in Chief of Environmental Management

Environmental Management -     

THE CENTRAL ARIZONA WATER CONTROL STUDY: A COMPARISON OF ALTERNATE PLANS USING CONCORDANCE ANALYSIS AND MULTI-DIMENSION SCALING1

ABSTRACT The Central Arizona Water Control Study (CAWCS) was initiated by the Bureau of Reclamation in 1978. The study attempted to identify and evaluate alternate water management schemes for Central Arizona. By 1981 a set of seven plans had been developed and for each an assessment on a number of economic, environmental, and social factors had been undertaken. This paper offers a formal procedure, using concordance analysis and multi-dimension scaling, to compare alternate plans using multiple factors in order to produce a classification of the attractiveness of the alternatives. Empirical data for the CAWCS are used to clarify the procedure. The results of the formal analysis are compared to those produced by the CAWCS. A critique of the formal procedure is offered, and it is suggested that it may have utility to assist in the collection of data as well as in the search for a best plan. The procedure allows a number of different types of sensitivity tests to be conducted.     

Environment as the Stage for Economic Actors

The relative importance of economics and environment in debate may soon be reversed due to the influence of three fac- tors. Firstly, in the global economy it is hard to hide the unwanted products of economic processes. Secondly, huge advances in sci- ence will reduce the imperfect knowledge of markets, making some monitoring and analyzing tools show the design of sensible and equitable livelihood in communities, which is more important than the motivation of maximising profits for some individuals or firms. Thirdly, China, as the last major player on the planet to take on economic growth, comes from traditions fundamentally differ- ent from those economies that have experienced the Industrial Revolution previously. Its challenges with sustainability and en- vironmental conservation predate Western economics by millennia, and it is implementing policies domestically and starting to work on the world stage that acknowledges that the surroundings are the host for any economic and socio-political system.     

Development of food preferences: social learning by Belding's ground squirrels Spermophilus beldingi

Summary The mechanisms by which food selection behavior develops may constrain the evolution of optimal foraging, yet these mechanisms have received relatively little attention in recent optimal foraging studies. We used cafeteria-style feeding trials to examine the role of social learning in the development of food preferences by a generalist mammalian herbivore, Spermophilus beldingi. Naive young spent relatively little time feeding and showed no preferences among five plant species offered in their feeding trials. This random pattern persisted for one set of young during two subsequent trials in the absence of their mother. A second group of young squirrels was tested initially alone, once with their mothers, and then once more alone. These squirrels fed more than those in the control group during their final trials, and showed significant preferences among plant species. These paralleled the preferences of their mothers. These results suggest that social learning may be important in the development of feeding behavior in ground squirrels, and provide a possible mechanism for cultural differences in food preferences among populations.     

Proposed guidelines for diagnosis of chromosome mosaicism in amniocytes based on data derived from chromosome mosaicism and pseudomosaicism studies

Currently, accepted protocol which has been developed at the Prenatal Diagnosis Laboratory of New York City (PDL) requires that when a chromosome abnormality is found in one or more cells in one flask, another 20–40 cells must be examined from one or two additional flasks. Chromosome mosaicism is diagnosed only when an identical abnormality is detected in cells from two or more flasks. In a recent PDL series of 12 000 cases studied according to this protocol, we diagnosed 801 cases (6.68 per cent) of single-cell pseudomosaicism (SCPM), 126 cases (1.05 per cent) of multiple-cell pseudomosaicism (MCPM), and 24 cases (0.2 per cent) of true mosaicism. Pseudomosaicism (PM) involving a structural abnormality was a frequent finding (2/3 of SCPM and 3/5 of MCPM), with an unbalanced structural abnormality in 55 per cent of SCPM and 24 per cent of MCPM. We also reviewed all true mosaic cases (a total of 50) diagnosed in the first 22000 PDL cases. Of these 50 cases, 23 were sex chromosome mosaics and 27 had autosomal mosaicism; 48 cases had numerical abnormalities and two had structural abnormalities. Twenty-five cases of mosaicism were diagnosed in the first 20 cells from two flasks, i.e., without additional work-up, whereas the other 25 cases required extensive work-up to establish a diagnosis (12 needed additional cell counts from the initial two culture flasks; 13 required harvesting a third flask for cell analysis). Our data plus review of other available data led us to conclude that rigorous efforts to diagnose true mosaicism have little impact in many instances, and therefore are not cost-effective. On the basis of all available data, a work-up for potential mosaicism involving a sex chromosome aneuploidy or structural abnormality should have less priority than a work-up for a common viable autosomal trisomy. We recommend revised guidelines for dealing with (1) a numerical versus a structural abnormality and (2) an autosomal versus a sex chromosome numerical aneuploidy. Emphasis should be placed on autosomes known to be associated with phenotypic abnormalities. These new guidelines, which cover both flask and in situ methods, should result in more effective prenatal cytogenetic diagnosis and reduced patient anxiety.     

Genetic structure and phylogeography of the lined shore crab, Pachygrapsus crassipes, along the northeastern and western Pacific coasts

Marine invertebrates with high larval dispersal capacity typically exhibit low degrees of population differentiation, which reflects both contemporary and historical processes. We sampled 346 individuals from seven populations of the lined shore crab, Pachygrapsus crassipes Randall, along the northeastern Pacific Coast and Korea during summer 2003. DNA sequence analysis of 613 bp of the mitochondrial COI gene showed that overall gene diversity (h) was high (0.92±0.01), whereas overall nucleotide diversity (π) was low (0.009±0.005). A total of 154 mtDNA haplotypes were identified; however, 114 were present in only one individual. Analysis of molecular variance revealed significant genetic structuring at Point Conception, CA, USA, that is likely due to the oceanographic circulation patterns, which result in asymmetrical migration of haplotypes. However, genetic variation among eastern Pacific populations was generally low, probably because of high contemporary gene flow and recent common ancestry of haplotypes. Mismatch analysis and nested clade analysis suggested that the population history of this region is characterized by two contiguous northwards range expansions, which are congruent with Late Pleistocene glacial cycles. Highly significant genetic differentiation was detected between eastern Pacific populations and Korea, indicating transpacific gene flow is restricted. Time of divergence between the two transpacific lineages was estimated between 0.8 and 1.2 Myrs ago. The small, recently founded population of P. crassipes at Bamfield, BC, Canada, did not appear to have undergone a founder effect.     

The morphology and behavior of dimorphic males in Perdita portalis (Hymenoptera : Andrenidae)

Summary In Perdita portalis, a ground nesting, communal bee, males are clearly dimorphic. The two male morphs are easily distinguished based on head size and shape into (1) a flight-capable, small-headed (SH) morph that resembles the males of other closely related species and (2) a flightless, large-headed (LH) morph that possesses numerous derived traits, such as reduced compound eyes, enlarged facial foveae and fully atrophied indirect flight muscles. The SH morph occurs exclusively on flowers while the LH morph is found only in nests with females. While on flowers, SH males are aggressive, fighting with conspecific males and heterospecific male and female bees, and they mate frequently with foraging females. Using artificial observation nests placed in the field, I observed the behavior of females and LH males within their subterranean nests. LH males are aggressive fighters; males attacked each other with mandibles agape, and male-male fights always ended in the death of one male. LH males are highly attentive to the reproductive behavior of females; they spend increasing amounts of time near open cells during cell provisioning, and mating only takes place immediately prior to oviposition when females are forming the accumulated pollen and nectar into a ball. Based on larvae reared to adulthood in the laboratory, the two male morphs occur in equal proportions. The behavior of males in closely related species, especially P. texana, and the origin and maintenance of male dimorphism are discussed.     

Snapping turtles - a biological screen for PCB's

Snapping turtles are capable of storing extremely high concentration of organochlorine compounds in their fat without any apparent detrimental effect. This tolerance, to high bioconcentration, permits a wide gradation between the extremes in pollution levels and facilitates the detection of extremely toxic substances present in trace amounts. Consequently snapping turtles provide an excellent biological screen for these compounds.