Eco-toxicological impact of “metals” on the aquatic and terrestrial ecosystem: A comparison between eight different methodologies for Life Cycle Impact Assessment (LCIA)

The assessment of eco-toxicological impacts related to the emission of contaminants into the environment has peculiar characteristics in the context of Life Cycle Assessment (LCA), and many different Life Cycle Impact Assessment (LCIA) methodologies can be used. However, previous studies recognized the presence of high uncertainties in the process, in particular when the analysis focuses on metal emissions. Metals are diverse inorganic substances relevant for their characteristic environmental chemistry, their high persistency into the environment and their toxicity at even low environmental concentrations. This study aims at expanding the discussion about how, and how differently, various methods for LCIA are estimating the impacts related to metals emissions, with a focus on eco-toxicological impacts. A comparison between eight different LCIA methods is presented in relative terms, using a contribution analysis at two levels: general and specific. Results show that there is a poor agreement between methods in the determination of the total eco-toxic impact attributable to metals, and in defining which metal provokes the highest eco-toxic impact per unitary emission. Furthermore, the characterization phase is critical in determining the disagreement between methods. However, some similarities were found: there is the tendency in most methods to associate the largest share of the total eco-toxicological impacts to metals. Theoretical and practical differences between methods are discussed and suggestions for the choice of the proper, case-specific, LCIA method are provided.     

Developing markets for recyclate: perspectives from south Wales

This paper introduces the problems of a market-driven waste management strategy in the UK and the momentum towards developing markets for recycled materials. It focuses on the demand side barriers and principally the need for market stimulation in the end uses for recyclables. The important role, which small- and medium-sized manufacturing enterprises (SMEs) have to play in developing existing markets for recyclate, is discussed. SMEs also have the potential to contribute to the radical new approach of identifying and developing a broad range of new, more diverse and higher value uses for recyclate. If these enterprises are to be engaged effectively then regional action is essential. The paper then reports on research work focusing on SMEs that has taken place as a component of the CWMRE (Creating Welsh Markets for REcyclate) market development initiative in Wales. As a foundation for this, a series of semi-structured interviews with SMEs has been conducted with those operating in sectors that are known to have the potential to provide novel applications for secondary materials or to have the potential for material displacement. Some of the barriers and corresponding needs within the case study companies involved are discussed. The implications of these findings for a regional market development programme are considered and in particular how these case studies support the need to engage SMEs in the use of secondary materials.     

Plant genes link forests and streams

Although it is understood that the composition of riparian trees can affect stream function through leaf litter fall, the potential effects of genetic variation within species are less understood. Using a naturally hybridizing cottonwood system, we examined the hypothesis that genetic differences among two parental species (Populus fremontii and P. angustifolia) and two groups of their hybrids (F1 and backcrosses to P. angustifolia) would affect litter decomposition rates and the composition of the aquatic invertebrate community that colonizes leaves. Three major findings emerged: (1) parental and hybrid types differ in litter quality, (2) decomposition differs between two groups, a fast group (P. fremontii and F1 hybrid), and a slow group (P. angustifolia and backcross hybrids), and (3) aquatic invertebrate communities colonizing P. fremontii litter differed significantly in composition from all other cross types, even though P. fremontii and the F1 hybrid decomposed at similar rates. These findings are in agreement with terrestrial arthropod studies in the same cottonwood system. However, the effects are less pronounced aquatically than those observed in the adjacent terrestrial community, which supports a genetic diffusion hypothesis. Importantly, these findings argue that genetic interactions link terrestrial and aquatic communities and may have significant evolutionary and conservation implications.     

The influence of nectar secretion rates on the responses of bumblebees (Bombus spp.) to previously visited flowers

Bumblebees can avoid recently depleted flowers by responding to repellent scent-marks deposited on flower corollas by previous visitors. It has previously been suggested that avoidance of visited flowers for a fixed period would be a poor strategy, since different plant species vary greatly in the rate at which they replenish floral rewards. In this study, we examined the duration of flower repellency after an initial bumblebee visit, using wild bumblebees (Bombus lapidarius, B. pascuorum and B. terrestris) foraging on four different plant species (Lotus corniculatus, Melilotus officinalis, Phacelia tanacetifolia and Symphytum officinale). We constructed a model to predict flower visitation following an initial visit, based on the nectar secretion pattern of the different plant species, the insect visitation rate per flower, and the search and handling times of bumblebees foraging on the plant species in question. The model predicts an optimal duration of flower avoidance which maximises the rate of reward acquisition for all bees. However, this optimum may be open to cheating. For two plant species, the evolutionary stable strategy (ESS) is a shorter duration of flower avoidance than the optimum. We found the duration of flower avoidance was markedly different among flower species and was inversely related to nectar secretion rates. The predicted ESSs for each plant species were close to those observed, suggesting that the key parameters influencing bumblebee behaviour are those included in the model. We discuss how bees may alter the duration of their response to repellent scents, and other factors that affect flower re-visitation.     

Morphology of<Emphasis Type="Italic"> Ecklonia radiata</Emphasis> (Phaeophyta: Laminarales) along its geographic distribution in south-western Australia and Australasia

Ecklonia radiata (C. Ag.) J. Agardh is a common macroalga on reefs in the warm-temperate parts of the southern hemisphere. It is a dominant habitat-former and as such has a strong structuring effect on associated algal assemblages. Morphological variation in E. radiata potentially affects its interactions with the surroundings and contributes to confusion about its taxonomy. We quantified the magnitude of morphological variation in fully developed E. radiata sporophytes across Australasia and tested the hypotheses that E. radiata has different morphology at different locations and that the degree of morphological difference depends on spatial distances among locations. A total of 11 morphological characters were sampled from 11 locations along the Australian coastline from Kalbarri in Western Australia to Sydney in New South Wales as well as from Doubtful Sound, New Zealand. Most morphological characters varied considerably from one location to another. For example, the average (±SE) thallus length was 135.2±12.5 cm in Kalbarri and only 69.7±5.5 cm in Sydney. There were no consistent spatial patterns of variation among individual morphological characters, and, generally, variations among individual characters were poorly correlated (-0.5< R<0.5). This suggests that individual morphological characters develop independently of each other in response to processes operating at different spatial scales. Multivariate measures of morphology were found to be different among some locations and similar among others (-0.37=Clarke's  R=1), but there was no correlation (Spearman's R=0.08) between morphological similarity and distance between locations. Consequently, our results do not support clinal variation in E. radiata morphology. Rather, they suggest the presence of discrete morphologically different populations, in which the morphology at any one location reflects multiple forcing factors operating on different morphological characters at different spatial scales.     

Sex ratios and life-history patterns of a solitary wasp,Trypoxylon (Trypargilum) politum (Hymenoptera : Sphecidae)

Summary Werren and Charnov (1978) and Seger (1983) proposed a model to explain a fairly common pattern of alternating sex ratio biases between generations in partially bivoltine insects. When first-generation males overlap and mate with females of the second generation, then females should bias sex ratios in favor of sons for the first generation and daughters for the second generation. In an intensive, 7-year study at four sites in northern Florida, pipe-organ mud-daubing wasps (Trypoxylon (Trypargilum) politum; Hymenoptera: Sphecidae) were found to have strongly male-biased sex ratios in the first or overwintering generation and 1:1 or female-biased sex ratios in the second or summer generation. These differences were not due to differences in mortality of the two sexes but rather resulted from changing female sex-allocation decisions. In some respects the mud dauber results fit Seger's model well: alternating sex ratios in partially bivoltine populations, first-generation males overlapping second-generation females and perhaps most convincingly, northern, univoltine populations do not have a male bias. Despite this qualitative fit, however, our data do not meet the quantitative predictions of the model. This could result from the fact that some assumptions of the model are not met by the life history of T. politum. Alternative explanations for alternating sex ratios include split sex ratios, seasonal differences in cost ratios, facultative maternal investment rules and facultative overwintering decisions by offspring. Despite the position that sex ratios have achieved in the modern study of evolution, it is clear that accurate, quantitative predictions on sex-allocation patterns demand the same detailed understanding of the biology of the organism that is required for the study of other adaptations.     

Interspecific associations of Cape ground squirrels with two mongoose species: benefit or cost?

Mixed-species associations have been described in many vertebrate species, but few behavioral studies have investigated associations between species from different mammalian orders. Cape ground squirrels (Xerus inauris) are highly social rodents that inhabit burrows with two species of mongoose, but the benefits of these interspecific associations to ground squirrels remain unresolved. We compared the behavior of squirrels while solitary, with conspecifics, and in the presence of suricates (Suricata suricatta) and yellow mongooses (Cynictis pencillatus). Squirrels spent less time alert and more time feeding when suricates were present, but increased vigilance in the presence of yellow mongooses. In a series of mobbing trials with a puff adder (Bitis arietans), a common predator of all three species, Cape ground squirrels were the most active in mobbing the snake. Our results suggest that Cape ground squirrels benefit from associating with suricates, but not necessarily with yellow mongooses. Both mongoose species benefit from the burrowing activities of the squirrels for thermoregulation and escape from predators, and a suite of other organisms may similarly benefit from the habitat modifications by Cape ground squirrels, suggesting they could be considered ecosystem engineers of the arid and semi-arid regions of southern Africa. Thus, the association between Cape ground squirrels and suricates appears mutually beneficial, whereas yellow mongooses may merely be commensals of the squirrels.     

Preponderance of a few diatom species among the highly diverse microphytoplankton assemblages in the Bay of Bengal

The microphytoplankton assemblages were studied from water samples collected at eight discrete depths in the top 120 m at five central (open ocean) and four western (shelf/slope region) locations in the Bay of Bengal. The Bay is a low-productive warm pool regime with poor inorganic nutrient inputs to its intensely stratified surface layer despite the very large riverine influx. In addition, the prolonged cloud cover has an adverse effect on the top 25–40 m, on primary production, chlorophyll concentration and phytoplankton assemblages. Microphytoplankton were the most abundant in the northern area of the Bay. A total of 153 phytoplankton species were identified during this study. The most abundant species (at least 1,800 individual cells belonging to a given species or ≥2% of the total counts of identified specimens) during this study were: Thalassiothrix longissima, Thalassiothrix fauenfeldii, Rhizosolenia styliformis, Nitzschia angularis, Thalassionema nitzschioides, Coscinodiscus radiatus, Chaetoceros eibenii, Skeletonema costatum, Coscinodiscus concinnus and Chaetoceros coarctatus. Similarly, there were 20 moderately abundant (≥0.5 but <2%) species. Thirty-three of the least abundant species (<0.5%) occurred at one station. Diatom species, T. fauenfeldii and T. longissima were ubiquitous in the study area. The exclusive occurrence of S. costatum in the northernmost stations suggests that it proliferates only in the low-salinity regions with adequate silica from the land inputs. Abundance of pennate diatoms was higher in the open Bay compared to that of centric diatoms in the more productive northern locations and the western Bay. There appears to be a basic difference between near shore flora and offshore flora. This first analysis of phytoplankton assemblages from the offshore Bay suggests that while there is predominance of only a few species, the Bay harbors very diverse diatom communities that seem to be syntrophic, non-competitive and co-habiting in the generally low nutrient, stratified surface waters.