No description available.

Anti-atrazine and anti-mecoprop single chain antibody fragments (scAbs) were cloned from monoclonal cell lines and expressed in <I>Escherichia coli</I>. The anti-atrazine and anti-mecoprop scAbs showed the same specificity for atrazine and mecoprop respectively as the parental mAb, but showed a 2-3 fold increase in sensitivity for free atrazine. Antibody fragments against mecoprop and diuron were stabilised by the introduction of inter domain disulphide bonds and were capable of remaining more than 90% functional in 10% methanol and other harsh denaturing conditions. BIAcore analysis and competition ELISAs confirmed the stabilised antibodies (stAbs) bound to free pesticide with the same affinity and specificity as the scAb fragments. <I>Lux</I> marked bacteria were used to predict the toxicity of 7 pesticides over a range of concentrations in aqueous solutions and finally in aqueous and non aqueous fractions extracted from soil. The toxicity of pesticide mixtures was further investigated and synergistic interactions identified. <I>Lux</I> marked <I>E. coli</I> HB101 cells and 4 anti-pesticide stAbs were used as a tool-kit to measure firstly toxicity and secondly to quantify the pesticides present in both the aqueous and non aqueous fractions of soil. The <I>E. coli</I> HB101 biosensor was able to detect pesticides from soil at 10-100 times lower concentrations than would have had an effect in water, showing improved sensitivity. The pesticide concentration solvent extracted soil was analysed using either stab fragment in an indirect competition ELISA or by HPLC and in each case the results were almost identical. This toolkit combines the specificity of stAb antibodies, as a rapid and robust alternative to chemical analysis, with toxicity assessment of <I>lux</I> biosensors as a safety net to identity presence of unknown toxins and toxin mixtures in the field.

Anthropogenic inputs of copper into the marine environment have increased in recent decades due to a ban on tributyl tin as an antifoulant and its subsequent replacement by copper. Dose-response experiments were conducted to assess the impact of copper on environmentally relevant biota: phytoplankton, brown alga, mussels, and amphipods.  Both alga and amphipods assimilated dose-dependent copper concentrations, while mussels did not.  Effects of copper exposure included reduced growth of algae, increased superoxide dismutase activity (SOD; an indicator of stress) in mussels and increased mortality in amphipods.  Reduced carbon and nitrogen assimilation and a change in diversity were measured in phytoplankton. Environmental surveys were employed to assess the dispersal of copper into water, sediment and biota from fish farm nets.  Alga and mussels transplanted to waters adjacent to fish farms were employed to assess copper uptake and impact.  A zone of increased copper concentration was found around farms with concentrations decreasing over distance.  Within the contaminated zone, or footprint, decreased growth in algae and increased stress in mussels were recorded. By incorporating different trophic levels into an ecotoxicological study this project provided a more detailed view of copper in the coastal ecosystem than those based on one species.  Of the methods employed, algae were the most consistent in showing a farm based impact.  The different methods and species used together showed the complexity of fish farm copper in the coastal environment.  Copper interacts with other farm outputs such as organic matter, which results in an impact over a limited distance from the cages.

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The adsorption behaviour of dissolved zinc and cadmium present in River Tawe freshwater in the presence of added clay mineral and naturally occurring suspended seawater particles was monitored using differential pulse polarography and differential pulse anodic stripping voltammetry. Zinc and cadmium were both found to be rapidly adsorbed on to suspended particles added to membrane filtered freshwater. Duplication of these experiments using Swansea Bay seawater and sodium chloride solution (3.2% w spiked with ionic zinc and cadmium) revealed an overall reduction in the extent of zinc adsorption and no cadmium adsorption, in comparison with the freshwater experiments. Mixing experiments where freshwater possessing a high trace metal content and low suspended load (natural particles or the clay mineral illite) demonstrated non-conservative behaviour with addition for cadmium over the time scale of an 8-10 hour mixing experiment. The scatter of data produced by the mixing experiments, with respect to zinc, is quite large and offers only a qualitative rather than a quantitative measure of non-conservatism with zinc removal. The additions of calcium and magnesium ions (to freshwater suspensions containing adsorbed zinc, in quantities to produce concentrations of these ions equivalent to those found in seawater), did not initiate any desorption of zinc within 3-4 hours. The reaction is thought to proceed via a mechanism possessing an irreversible step whereby the adsorption of zinc becomes specific rather than simply electrostatic. Some adsorbed cadmium (12-40%) is released into solution when particulate bearing freshwater is rendered saline. The formation of a monochlorocadmium complex in seawater may contribute to drive the equilibrium of cadmium away from the adsorbed state. The standard addition of lead to water samples was found useful for the estimation of the complexing capacity of freshwater and seawater (with respect to non-labile complex dissociation). L3 camination of lead at naturally occurring concentrations was hampered by contamination and sample interactions with borosilicate glassware.

Self-incompatible annual weed species, with similar flowers, flowering time and ecology were used to investigate the relationship between relative abundance, pollinator service and seed-set in two-species mixtures. In mixed stands of the mayweeds <i>Anthemis cotula</i> L. and <i>Tripleurospermum inodorum</i> (L.) Schultz Bip. the common capitulum-visiting insects (hoverflies and other diptera) seemed to find the two species equally attractive, frequently flying from one to the other. In a survey of wild populations of these species the number of insect visitors per capitulum was independent of the number of capitula per m<SUP>2</SUP>. These observations suggest that where <i>A. cotula</i> and <i>T. inodorum</i> co-occur the number of insect visits to each is not affected by the presence of the other. However, when mixtures of <i>A. cotula</i> and <i>T. inodorum</i> were grown in garden plots the number of insect visitors per capitulum was lowest in the plots where the number of capitula per m<SUP>2</SUP> was highest. Thus it would seem that sometimes when <i>A. cotula</i> and <i>T. inodorum</i> grow together each species reduces the number of insect visits to the other. In 9:1 and 1:9 mixtures of <i>A. cotula</i> and <i>T. inodorum</i> the percentage of seeds set by each species when the minority type was sometimes significantly lower than when forming the majority in a nearby plot. It is likely that this occurred because most pollinators visited both species (ie. they were not 'constant'), and thus there were few direct flights between minority individuals, so that pollination of these plants was very ineffective. Container-grown <i>Sinapis arvensis</i> L. and <i>S. alba</i> L. were placed in an experimental garden in single-species groups (6 plants) and 1:9 and 9:1 mixtures (60 plants, a 'majority' of 54 and a 'minority' of 6). Individuals were moved between sites and their seed-set assessed when in single-species, majority and minority situations. Majority and single-species seed-sets were similar, but minority seed-sets were significantly lower (in both species). The low minority seed-sets were due to ineffective pollination which occurred because most insects visited both species whilst foraging in the mixed groups, and thus few visits to minority flowers were immediately preceded by visits to flowers on another minority plant. The incompatibility system of <i>Sinapis arvensis</i> was studied in plants collected from farmland in South Wales. The results obtained are consistent with there being a single locus, multiallelic, sporophytic incompatibility system in this species. In the population investigated there were at least 14 S-alleles, and probably more than 24. By labelling individuals it was shown that females of the solitary bee species <i>Colletes daviesanus</i> Smith returned repeatedly to forage at the same sites.