The use of Bacillus thuringiensis var. israelensis to control the nuisance fly Sylvicola fenestralis (Anisopodidae) in sewage filter beds

The effectiveness of using the microbial insecticide Bacillus thuringiensis var. israelensis (Bti) to control the nuisance fly Sylvicola fenestralis at Rossendale Sewage Works, Lancashire, was investigated. Following a provisional trial in 1987, the whole Works (28 filter beds) was treated with a two-stage application of Bti in 1988; the first application in late April was separated from the second in late May by about half the length of the Sylvicola life-cycle. The Bti treatment was timed to reduce fly nuisance in June, the month when most complaints (71%) had been received. For each application, 0.161. of the Bti preparation, containing nearly 10¹⁰ spores·cm⁻³, was applied per square metre of bed surface. An 80 and 98% kill of Sylvicola larvae was recorded following the first and second applications respectively. The lower kill achieved by the first application was believed to be due to insufficient mixing of the Bti with the settled sewage prior to dosing. Nuisance caused by the flies was considerably reduced; there were no complaints from the public during June, although a few were received in late July, early August. Sewage purification efficiency was not affected by Bti treatment. The maximum concentration of Bti spores in the Works' effluent was 7 × 10⁴ spores·cm⁻³. This concentration did not appear to affect the already impoverished macro-invertebrate fauna of the receiving river.     

The dynamics of mercury and cadmium uptake into different organs of Anodonta cygnea L.

The bioaccumulation of Hg and Cd into various organs of the freshwater mussel Anodonta cygnea was investigated during an 840 h experimental period. Parallel with the metal concentrations the periodicity of activity and the body weight of the animals were also checked.The accumulation of Hg in all of the investigated organs, and that of the Cd into the kidney have two phases, up to 24 h it was non linear, between 24 and 72 h it became linear in most organs up to 840 h, and could be characterized by a regression line. For Hg accumulation the gills while for Cd accumulation the kidney and viscera were exceptions, here saturation was observed after 504 and 672 h, respectively.The speed of Hg and Cd uptake was different in various organs of Anodonta cygnea. Into the kidney the accumulation of Hg was six times faster than that of Cd. As compared to the adductor muscles the Hg and Cd uptake of the kidney was 20 and 10 times faster, respectively.The factor of concentration was in all organs except adductor muscles over 1000, in case of the kidney the rate of bioconcentration for Hg reached nearly 100,000.The dry weight of organs dropped during the metal uptake by 20–60%, but no mortality was observed up to 840 h.In the presence of Hg and Cd the filtering activity of the mussels became reduced as a result of increase of inactive rest periods. Nevertheless, the decrease of activity did not prevent the linear uptake of metals into the animal     

The influence of substrate, pH, diet and temperature upon cadmium accumulation in the asiatic clam (Corbicula fluminea) in laboratory artificial streams

The influence of substrate, pH, diet and temperature upon the accumulation of cadmium (0.05 mg l⁻¹ dose < 0.001 mg l⁻¹ control) in the visceral mass of the Asiatic clam Corbicula fluminea was studied in laboratory artificial stream systems at intervals of 0, 3, 5, 7, 10 and 14-day exposures. Four substrate conditions, sand; sand, silt and clay (SSC); sand, clay and organic matter (SCO); and no substrate (NoS), were considered. The greatest tissue accumulation of cadmium in C. fluminea occurred at 0.05 mg l⁻¹ Cd in NoS and the lowest in clams occupying SCO. Complexation of available metals, lower clam filtering rates and physical protection by the substrate were attributed to the depressed cadmium accumulation of clams exposed in the SCO substrate. Lower pH exposures (5.0 vs 7.8) significantly (P 0.05 level) reduced cadmium uptake at 21°C but had little effect at 9°C. Uptake was higher in clams fed with cadmium-exposed Chlamydomonas reinhardt at 21°C but not at 9°C. In temperature exposures alone at 0.05 mg l⁻¹ Cd, accumulation was significantly higher in C. fluminea exposed at 21°C than at 9°C. The results are discussed relative to the importance of standardized laboratory protocol and the use of C. fluminea as a bioindicator of heavy metal stress.     

Trace nutrient deficiency in Daphnia magna cultured in standard medium for toxicity testing. Effects of the optimization of culture conditions on life history parameters of D. magna

The suitability of various synthetic media for the culture of Daphnia magna was tested. Daphnids cultured in a standard medium for toxicity testing proposed by ISO showed low reproduction, reduced growth, high numbers of undeveloped parthenogenetic eggs and high mortality of neonates and adults. As a feature, animals cultured in the ISO medium lost parts of their second antennae. It could be shown that this was caused by selenium deficiency. The addition of selenium to the ISO medium clearly improved the quality of this medium. However, results of several tests were more variable than when a medium with a complex trace element composition (medium M4) was used. Medium M4 has allowed continuous culture of daphnids for three years up to now without any signs of reduced viability or reproduction. A mean reproduction rate of about 140 progeny/parent daphnid was calculated from 19 non simultaneous experiments. Neither a fourfold increase nor a reduction to one tenth of the trace element concentration of M4 had any effect on reproduction, growth or survival of daphnids. It was shown in this study that ion-exchanger cartridges can leach detrimental substances into the matrix water. Therefore, only ultrapure matrix waters should be used for the preparation of culture media.     

Uptake of Kepone® by the estuarine bivalve Rangia cuneata, during the dredging of contaminated sediments in the James river, Virginia

The uptake of the pesticide Kepone was monitored in situ in the wedge clam, Rangia cuneata, during the dredging of Kepone-contaminated sediments in the James River estuary, Va. After 2 weeks of dredging, residue levels in Rangia at sites along the disposal area were significantly elevated above background; however, Kepone levels in clams at sites downstream of the dredging were not elevated. The increase in tissue contamination (0.01–0.04 μg g⁻¹, mean values) was persistent 2 weeks after dredging was completed. The ecological significance of the Kepone uptake documented during dredging is discussed in relation to the overall Kepone contamination in the James River ecosystem.     

The effects of variation in climatic temperature (1980–2001) on breeding activity and tadpole stage duration in the common toad, Bufo bufo

The effects of variation in climatic temperature on breeding behaviour and tadpole growth were investigated using data collected during a 22-year study of a single population of common toads, Bufo bufo, in southern England. Although the start of the breeding season each year, taken as the day when adult toads first arrived at their breeding pond in large numbers, showed no trend over time (1980–2001) it was highly correlated with climatic temperature. Thus, toads started breeding approximately 50 days earlier in the year following very mild winters (1993: February 2nd) compared with very cold ones (1986: March 23rd). Regression analysis of the relationship between the mean temperature of the 40 days immediately preceding the main arrival of toads at the breeding pond revealed that for every 1° increase (or decrease) the toads arrived 12 days earlier (or later). Although the duration of the tadpole stage was longer when spawning was early, toadlets still emerged from the pond earlier than when spawning was late. The increased length of the tadpole stage, in years when spawning was early, was due to an increase in the proportion of cold days when the minimum ground temperature was at or below 0 °C. Thus, the tadpole stage was approximately 6 days longer (or shorter) for every 5% increase (or decrease) in the proportion of cold days the tadpoles were exposed to.     

Modeling spatially explicit population dynamics of Pterostichus melanarius I11. (Coleoptera: Carabidae) in response to changes in the composition and configuration of agricultural landscapes

The intensification of agricultural practices has induced the local, national and regional extinction of many species and also affected ecosystem services provided by biodiversity such as biological control of agricultural pests. We model the population dynamics of Pterostichus melanarius (Coleoptera: Carabidae), a carabid beetle often used as indicator species of habitat changes, by a joint model that combined a matrix model of population dynamics including local dispersal with an explicit model of the patchy landscape of the polders of the Bay of Mont St. Michel (Brittany, France). We used this model to evaluate the effects of landscape composition and configuration on the spatial population dynamics of this carabid beetle, and also investigated the consequences that different management strategies of the structure and composition of an agricultural landscape can have on its abundance and spatial distribution. The results of this study highlight that semi-habitats (field edges, dykes, hedgerows) usually considered as shelters for wintering play a key role as well for summer recruitment. We find that there is an optimal cluster size of patches for population viability that is induced by the seasonal movement of P. melanarius. However, the effect of increasing the amount of semi-natural habitats patches on the viability of this population critically depend on the spatial arrangement, connectivity and spatial alternation of the network of semi-natural habitats, a feature that should be considered in the conservation and management actions in the landscape context.     

The feasibility of using disused water treatment filter beds for rearing carp (Cyprinus Carpio L.) in the U.K.

The feasibility of rearing carp (Cyprinus carpio) at a disused water treatment works in East London (U.K.) was investigated. The 10 ha of filter beds represented an atypical site for carp culture; in order to assess whether in-house aquaculture would enable a Water Authority to gain advantage in cost, availability and disease-free status of stock, a series of trials was undertaken. These enabled comparison of the weight of carp produced in relation to: extensive cultivation, artificial feeding, a range of stock densities and a range of ages and sizes. The filter beds were unsuitable for natural spawning, early fry production and the rearing of first year fish (0⁺ age group). However, growing-on of subsequent stages (i.e. 0⁺ − 1⁺ or 1⁺ − 2⁺) gave good survival (60–80%) and growth rates. Fish stocked at 20 g in April/May reached 200–400 g by September and 1 kg plus, 1 yr later. Production levels of 300–350 kg ha⁻¹ yr⁻¹ without artificial foods (i.e. extensive cultivation) and up to 2.2 tonnes ha⁻¹ yr⁻¹ with supplementary feeding were comparable with mainland European fish farms. These high values reflect the eutrophic nature of this site and successful exploitation of the available secondary production. It was possible to harvest 15,000–20,000 carp yr⁻¹ for restocking. Carp rearing integrated with existing operations and activities on site (e.g. pipe and equipment stores) and represents a novel, alternative use of a semi-redundant site. Cost benefit assessment showed that fish production was economically viable returning nominal profit margins of between £1.10 and £2.06 kg⁻¹ of carp harvested. The resultant cost/benefit ratios per kilogram harvested were 1:1.9 for extensive production (without feeding) and 1:1.34–1.43 when intensive cultivation employing artificial foods was used.