The impact of climate change on the physical characteristics of the larger lakes in the English Lake District

1. The larger lakes of the English Lake District have been the subject of intensive scientific study for more than 60 years. Year‐to‐year variations in the weather have recently been shown to have a major effect on their physical characteristics. The area is mild but very wet and the dynamics of the lakes are strongly influenced by the movement of weather systems across the Atlantic. 2. Here, we combine the results of long‐term measurements and the projections from a Regional Climate Model (RCM) to assess the potential impact of climate change on the surface temperature and residence times of the lakes. 3. The RCM outputs used were produced by the U.K. Hadley Centre and are based on the IPCC ‘A2’ scenario for the emission of greenhouse gases. These suggest that winters in the area will be very much milder and wetter by the 2050s and that there will be a pronounced reduction in the summer rainfall. 4. An analysis of the meteorological data acquired between 1940 and 2000 shows that there have been progressive increases in the winter air temperature and in the rainfall which are correlated with the long‐term change in the North Atlantic Oscillation. The trends reported during the summer were less pronounced and were correlated with the increased frequency of anticyclonic days and a decrease in the frequency of westerly days in the British Isles. 5. A simple model of the year‐to‐year variations in surface temperatures showed that the highest winter temperatures were recorded in the deeper lakes and the highest summer temperatures in the lakes with the shallowest thermoclines. When this model was used to predict the surface temperatures of the lakes in the 2050s, the greatest winter increase (+1.08 °C) was observed in the shallowest lake and the greatest summer increase (+2.18 °C) in the lake with the shallowest thermocline. 6. The model used to estimate the seasonal variation in the residence time of the lakes showed that the most pronounced variations were recorded in lakes with a short residence time. Average winter residence times ranged from a minimum of 10 days to a maximum of 436 days and average summer values from a minimum of 23 days to a maximum of 215 days. When this model was used to predict the residence time of the lakes in the 2050s, the greatest winter decrease (−20%) was observed in the smallest lake and the greatest summer increase (+92%) in the lake with the shortest residence time. 7. The results are discussed in relation to trends reported elsewhere in Europe and the impact of changes in the atmospheric circulation on the dynamics of the lakes. The most serious limnological effects were those projected for the summer and included a general increase in the stability of the lakes and a decrease in the flushing rate of the lakes with short residence times.     

Short-term movements of chalk-stream invertebrates

SUMMARY 1. Trays of gravel were implanted for 24 h periods in several chalk streams. The trays were variously modified to monitor colonization from different sources, particularly drift (D), other downstream movements (DSM), upstream movements (USM), and all sources combined (ALL).
2. The abundance of invertebrates in the streams was high (maximum of 717 per 0.04 m²) and colonization of the trays was extensive, especially by Gammarus pulex , the predominant species in all but one of the streams (maximum number of individuals of G. pulex per tray: for D, 473; for DSM, 462; tor USM, 286; and tor ALL, 639). In some cases benthic densities were achieved in the trays in the 24 h exposure period, and in most cases any one source of colonization could provide benthic densities in a few days.
3. Patterns of movement differed between species, between size classes of G. pulex , and between sites for particular species. No one source of colonization could be regarded as generally predominant although downstream movements in total (D + DSM) usually far exceeded USM. DSM was usually an important source of colonization.
4. The extent and direction of movement appeared to be determined by local factors and were explained in terms of the high densities of invertebrates and the current and substratum characteristics of each site.
5. Estimates of the relative importance of different sources of colonization varied greatly according to the criteria used in determining proportions.     

The Effect of Hypoxia and Sulphide on Culture-Grown Wetland and Non-Wetland Plants: II. METABOLIC AND PHYSIOLOGICAL CHANGES

Pearson, J. and Havill, D. C. 1988. The effect of hypoxia andsulphide on culture-grown wetland and non-wetland plants. II.Metabolic and physiological changes.—J. exp. Bot. 39:431–439. Two non-wetland (Agropyron pungens, Hordeum vulgare) and fivewetland species (Oryza sativa, Aster tripolium, three Salicorniaspp.) were grown in aerated, unaerated and sulphide-treatedculture solution. Changes in the activity of alcohol dehydrogenase(ADH) and cytochrome oxidase (COase) in the roots were measured.In the non-wetland species, treatment with hypoxia or sulphideincreased ADH activity by 900–1 800%, whereas COase activitydecreased by 80–92% of the aerated control. In the wetlandspecies, except S. europaea which was not affected, hypoxiaincreased ADH activity by 350–550%, while COase activitywas little affected. Generally, when treated with sulphide theactivity of ADH increased to about 750% in most of the wetlandspecies, but increases as low as 175% (S. europaea) and as highas 1400% (S.fragilis) were recorded. The effect of sulphideon the COase activity in the wetland plants was not as markedas in the non-wetland plants. The Salicornia spp. were the leastaffected by the sulphide treatment and they also had intrinsicallyhigher levels of COase activity than the other species sampled.Of the wetland plants the Salicornia species had the lowestvalue for root aerenchyma, 3–6%. Therefore, there wasno correlation between the possession of aerenchyma and thephysiological changes measured. Measurement of malate, lactateand ethanol in roots of the first four species listed abovegave no evidence for alternative anaerobic fermentation pathways.While in the flood-intolerant species, high ADH activities werenot able to maintain the energy charge. It is suggested thatmaintenance of relatively high COase activity in wetland plantsmay help to ‘scavenge’ any available oxygen withinroots and thus help reduce energy loss. Key words: Cytochrome oxidase, alcohol dehydrogenase, metabolic adaptation     

Diversity and seasonality of adult Trichoptera captured in a light-trap at Yuccabine Creek,a tropical Australian rainforest stream

Seventeen light-trap samples were taken over a 20 month period at Yuccabine Creek, an upland rainforest stream in north-eastern Queensland. Seventy-eight species of Trichoptera were recorded from a total catch of 6431 individuals. The fauna was dominated by the Hydroptilidae (25 species and 5131 individuals) and, though composed primarily of Torresian genera, some Bassian elements were recorded. A seasonal pattern of change of abundance was observed with the majority of tax a exhibiting maxima between December and January (summer) and minima between July and September (winter).     

New prosauropod material from South Wales

New prosauropod material from a cave filling of Upper Triassic/Lower Jurassic age in Pant-y-ffynnon Quarry, South Wales, is described. The Panl-y-ffynnon fauna also includes thecodont, coelurosaur, crocodile and lepidosaur material.
Most of the prosauropod skeleton is represented. An almost complete but disarticulated skull is preserved. The skull and whole skeleton of the prosauropod are reconstructed. Evidence from the size and relative proportions of the bones, also the state of ossification, indicates that the prosauropod remains represent juveniles.
The level of the jaw articulation combined with the form of the teeth would suggest that the Pant-y-ffynnon prosauropod was omnivorous.
The Pant-y-ffynnon prosauropod resembles closely the much less complete Durdham Down (Bristol) remains of Thecodonlosaurus antiquus Morris; the Welsh material could well be juveniles of that species. Here the Pant-y-ffynnon material is ascribed to Thecodonlosaurus sp.
The mode of deposition of the fossil material is discussed, to account for the deposit containing only juveniles of the prosauropod.     

Acid resistance of attached organisms and its implications for the pathogenicity of plasmid-bearing Escherichia coli

Organisms of Escherichia coli attached to glass beads in a model attachment system were more resistant to acid than were unattached organisms and this applied to cultures exposed to either pH 2·5 or 3·5. Attached organisms of both Col^- and Col V, I-K94⁺ strains showed the effect but with prolonged exposure to pH 2·5, the attached Col V⁺ organisms appeared more resistant than the attached Col^- ones, possibly because they formed a thicker surface layer. It is proposed that the increased resistance of attached organisms to pH 2·5 might allow the survival, in gastric acid, of organisms attached to food particles. This would be more significant for the Col V⁺ strains because the plasmid enhances enterobacterial attachment properties. The increased resistance of attached organisms to pH 3·5 might be significant for survival of particle- or surface-bound organisms in the acidic environment of the phagocyte especially since lactate (which occurs in phagocytes) enhanced the effect of exposure to pH 3·5.     

Cytogenetic Effects of Cyclohexylamine and N-OH-Cyclohexylamine on Human Leucocytes and Chinese Hamster Bone Marrow

SOME humans metabolize the commonly used artificial sweetener, cyclamate, to cyclohexylamine (CHA) and N-hydroxycyclo-hexylamine (N-OHCHA). There have been three reports^1–3 that cyclamate and its metabolic byproducts cause a significant amount of cytogenetic damage in cultured human cells and the bone marrow and spermatogonial cells of the rat, but unfortunately they do not give quantitative cytogenetic data, other than the percentages of cells with “breaks”. In our experiments, we attempted to detect significant cytogenetic damage to human leucocytes treated in vitro or in a host-mediated assay system with CHA or N-OHCHA. At the same time, bone marrow from Chinese hamsters was studied for cytogenetic effects after daily injections of CHA.