ALBERT

Notes: The resistance often early, ten medium late and ten late flowering ryegrass populations to two rates of dalapon (2.8 and 5.6 kg ha-1 acid equivalent) was measured in a box experiment. There was no difference in the mean effect of dalapon on the maturity groups at the time of greatest yield reduction, but the recovery of the late flowering population was, on average, better than that of the medium late group. There was a range of reaction to herbicide within all three maturity groups and, in general, the high yielding populations without dalapon were the most resistant, but there were exceptions. Assessment at 2.8 kg ha-1 acid equivalent gave a similar ranking order to that using twice the amount of dalapon. The results of the current box experiment with seedlings were consistent with those obtained in the field at another location (Faulkner, 1974) for the eleven cultivars common to both trials. The resistance of a permanent pasture population was much lower than that of some cuttivars.

Notes: Scale and length/weight data from 2071 Llyn Tegid grayling and 1803 River Dee grayling were used for age and growth determinations. The time of scale annulus formation varied from autumn in some years to spring in other years. Seasonal changes in length, weight and the condition factor were described. The main growth period was from spring to autumn with very little growth occurring during the winter. Annual growth in length was back-calculated from scale measurements, and von Bertalanffy's model was fitted to the resulting length for age data. Comparisons were made between the specific growth rates and ultimate lengths (Lx) of Llyn Tegid and River Dee grayling, and between the growth of male and female grayling. Males grew faster than females after the onset of sexual maturity. Calculated lengths were converted to weights using a combined length/weight relationship for Llyn Tegid and River Dec grayling. Changes were evident in this relationship throughout the life of the fish.

Notes: SUMMARY. Increased sensitivity in the determination of ATP in fresh water and sediment samples was achieved by incorporating protein, EDTA and extra luciferin in the reconstruction of the firefly lantern preparation. Maximum recovery was only obtained when samples were extracted in actively boiling Tris buffer. The method was sufficiently sensitive for the determination of ATP in 1 ml water samples injected directly into the boiling buffer. Concentration of water samples on membrane filters, even volumes as small as 1 ml, caused a significant drop in the ATP recovered. This was thought to be due, at least in part, to cell lysis and the concentration of interfering detrital material on the membrane. Further interference was observed when sediment samples were analysed. This was only partly overcome by dilution of the sample and the importance of the inclusion of internal standards (bacterial cultures) is emphasized.

Notes: SUMMARY. The difference between the results of viable and total counting procedures for bacteria are exemplified by vertical profiles from a deep and a shallow lake and from seasonal changes in the epilimnion and hypolimnion of a shallow eutrophic lake. The viable count was, on average, 0.25% of the total count, the greatest difference being noted in the anoxic hypolimnion, probably due to the inadequacy of the viable counting procedure for the isolation of bacteria from such samples. There was a general trend for the more nutrient-rich waters to support larger bacterial populations but such observations did not provide any further information on the factors responsible for the population changes observed. Seasonal fluctuations in the counts are studied and the qualitative and quantitative changes resulting from artificial enclosure of water are discussed. Not all the temporal changes could be explained and short-term changes resulting from nutrient additions to the experimental enclosures were not always reproducible. Horizontal variability was examined, found to be significant and could play an important role where water movement and turbulence is considerable. Results from six sites sampled between 1969 and 1974, representing total and viable bacterial population estimates and a total of eighteen independent or regressor variables were then subjected to principal components analysis. Results taken from the whole water column showed the overwhelming effect of the process of stratification on the bacterial population accounting for 30%-60% of its variability. Secondary components representing algal productivity could account for 10% to 20% of the variability. Many of the chosen regressor variables were acting as measures of the same phenomenon without providing significant information on what affected the bacterial population. To overcome this problem results from the hypolimnion and epilimnion were analysed separately. The analysis demonstrated the importance of seasonal changes in nutrient concentrations in the epilimnion and the development of anoxic conditions in the hypolimnion. Algal biomass, phosphate concentration and the interaction of pH and ammonia appeared to be important. It was concluded that most of the variability in the bacterial population estimates could have been explained by five of the regressor variables and that the factors most likely to provide more information would include some measure of predation and lake retention time.

Notes: SUMMARY. Epilithic algae in a small softwater stream in the English Lake District were studied using a direct counting epifluorescence technique. A small trickling filter sewage treatment plant discharged into the stream and cattle grazed in fields adjoining the upper reaches. Both increased the inorganic nitrogen and phosphorus concentrations in the stream but the effect of the cattle was of a more intermittent nature. Cocconeis placentula was the dominant diatom but large numbers of encrusting green, blue-green and red algae also occurred in samples from the middle reach, which was heavily shaded by trees in summer. Although it was possible to demonstrate the effect of the sewage effluent on the rate of colonization of clean surfaces placed in the stream, it was only during periods of stable water flow that this was reflected in the standing crop of algae on the stones. The Cocconeis counts below the sewage outfall tended to be highest in the autumn whereas those of the other diatoms were highest in the spring. The results were, however, extremely variable and apart from the effect of the nutrient inputs, the Cocconeis standing crops were largely related to the rate of water flow. Counts decreased and the variability between and within stones increased as higher rainfall and flow caused instability and scouring of the stones. A similar decrease in standing crop and high variability occurred in conditions of very low water flow but this could not be explained.

Notes: SUMMARY. Changes in bacterial populations and certain physical and chemical variables in Esthwaite Water between June and September 1975 were studied and compared with results obtained from 1972 to 1974 in the hypolimnia of Blelham Tarn and the Lund tubes. The counts of total bacteria ranged between 1 and 7 × 106ml−1 and were highest in the anoxic hypolimnion. The bacterial genera examined in more detail constituted only a small percentage of this count and included Ochrobium (104ml−1), Naumanniella (103ml−1), Leptothrix (102ml−1), Planctomyces (103ml−1), and Metallogenium (102ml−1). The iron bacteria appear to grow best in the oxycline where there was not only sufficient oxygen for aerobic growth but also a plentiful supply of reduced iron. Planctomyces numbers increased as the thermocline became depressed in September. The results from Blelham Tarn might be interpreted as further evidence of growth by iron bacteria in the absence of dissolved oxygen, but other explanations are possible. Examination of the results by multiple regression analysis showed that it was possible to explain a significant proportion of the bacterial variation (with the notable exception of the Planctomyces counts) in spite of considerable intercorrelation of the regressor variables.

Notes: SUMMARY. In the summer of 1971 the village of Grasmere was converted from septic tank to mains drainage with sewage treatment at an activated sludge plant. The effluent was discharged into the River Rothay, the main inflow of a nearby small lake (Grasmere). This paper describes some of the effects on the lake. The mean areal hypolimnetic oxygen deficit increased from 274 to 434 mg O2 m−2 day−1 with an accompanying marked increase in the degree of deoxygenation in the hypolimnion. Plate counts of bacteria in the surface water increased for 2 years but this increase was not sustained. The mean summer soluble reactive phosphorus concentration did, however, increase significantly (P= 0.05), but the same was not true of nitrate levels. This paper is particularly concerned with inorganic nitrogen transformations and analyses of the main inflow have shown that 50–98% of the ammonia and 10–40% of the nilrate entering in this river was derived from the sewage effluent. The concentrations in the main body of the lake were usually lower, possibly due to assimilation and denitrification in the shallower reaches of the lake. Seasonal changes in the inorganic nitrogen species in the hypolimnion showed three distinct phases of activity, ammonification, nitrification and denitrification. Nitrification accounted for approximately a quarter of the oxygen uptake in the hypolimnion.

Notes: SUMMARY. Estimates of the fecundity of dace were made on 105 mature females using the dry method of Simpson (1959). The reliability of the counting procedure was assessed and found to be satisfactory. Fecundity was examined in relation to fork length (cm), somatic weight (g), ovary weight (g) and age (years). Logarithmic multiple regressions of fecundity on these variables showed that neither log fork length nor log somatic weight contributed significantly towards explaining the observed variations in fecundity. The best prediction equation for fecundity, incorporated both log ovary weight and log age. Incidents of extensive follicular atresia were found in the ovaries of 19% of the female dace examined and the frequency of occurrence of this phenomenon increased with age.