Production of a stream shredder, Peltoperla maria (Plecoptera: Peltoperlidae) in disturbed and undisturbed hardwood catchments

SUMMARY. (1) The average benthic density of Peltoperla maria in an undisturbed southern Appalachian stream was more than twice that of a nearby stream draining a previously clear-cul catchment in its tenth year of natural secondary succession.
(2) Peltoperla production estimates, using three methods, do not show a significant difference in production between streams draining the two catchments. We attribute these results to quicker growth and slightly higher densities of larger nymphs in the disturbed stream. Production estimates for the disturbed stream ranged from 498 to 560 mg (ash free dry weight) m⁻²y⁻¹ while those for the undisturbed stream were 41–4–515 mg m⁻² y⁻¹.
(3) Our results reinforce the view that conclusions based solely upon numerical densities may lead to erroneus interpretations about the roles organisms play in ecosystems.
(4) Annual frass production by this shredder is about 20 times (10 g m⁻² y⁻¹) the secondary production of P. maria.     

Immunogold localization of LHC II proteins in chloroplasts with different degrees of grana stacking induced by SAN-9789.

The amount and distribution of proteins of the light-harvesting complex associated with photosystem II (PS II) were investigated using immunogold labelling of chloroplasts of wheat ( Triticum aestivum L. cv. Walde). The seedlings were grown in weak red light (16 mW m⁻²) after imbibition of grains with SAN-9789 (Norflurazon, 0.028 to 28 mg I⁻¹). Chloroplasts of these plants exhibited thylakoids with different degrees of stacking. Thylakoids of untreated plants grown in a greenhouse had most gold particles per unit membrane length in both appressed and non-appressed regions compared to red light grown plants. The ratios of labelling between appressed and non-appressed membranes were fairly constant in red light- and greenhouse-grown plants. The labelling densities were 2.5–3 times higher in the appressed thylakoids compared to the non-appressed thylakoids. However, at a SAN concentration of 2.8 mg I⁻¹ there was a sharp decrease in thylakoid appressions and in labelling density of both appressed and non-appressed membranes. The total amount of particles per chloroplast was also much lower as compared to that at lower SAN concentrations. Plants treated with the highest concentration of SAN (28 mg I⁻¹) contained chloroplasts devoid of normal grana structures. In these plastids, the thylakoids were elongated and single. The labelling density in these membranes was ca 50% of that observed at 2.8 mg I⁻¹. This paper thus supports earlier observations that proteins of the light-harvesting complex of PS II (LHC II) are mainly localized in the appressed regions of the grana membranes, and may be involved in the formation of grana.     

Effects of temperature and current discharge on the concentration and photosynthetic activity of the phytoplankton in the upper Mississippi River

SUMMARY. Temperature and current discharge regulated phytoplanktonic concentration, chlorophyll-a concentration, the light-saturated rate of photosynthesis (P_max), and photosynthetic capacity (P_cap) in the Mississippi River at Prairie Island, Minnesota. The chlorophyll-a maximum was 48 mg m⁻³ in 1975, a wet year with a high current discharge, and 190 mg m⁻³ in 1976, a relatively dry year. The highest values of P_max were 0.37 (mgO₂ I⁻¹h⁻¹) in 1975 and 1.60 in 1976. P_cap varied from 3 to 21 (gO₂ per g chlorophyll-a h⁻¹) both years, and its value was highly correlated with temperature. The temperature optimum shifted from 16°C for P_cap in the spring, to greater than 28°C in the summer. Multiple regression analysis indicated a second-order relationship of P_cap in the spring to temperature. Other independent variables explained only negligible variation of P_cap.     

Microbial activity associated with seston in headwater streams: effects of nitrogen, phosphorus and temperature

SUMMARY 1. The influences of temperature and dissolved nitrates and phosphates on microbial activity associated with suspended fine particulate organic matter (seston) were evaluated in four headwater streams in the southern Appalachian Mountains.
2. Temperature manipulations of ± 5°C always induced significant changes in [¹⁴C] glucose mineralization (ANOVA; P <0.05) and [³H]thymidine incorporation (ANOVA; P <0.05).
3. Nutrient amendments of 1.0 mg NO₃ I⁻¹ and 0.05 mg PO₄I⁻¹ induced no significant alterations in bacterial mineralization of [¹⁴C]glucose (ANOVA; P >0.05) or incorporation of [³H]thymidine (ANOVA; P >0.05) in short-term (i.e. 3 h) experiments.
4. Microorganisms attached to refractory particulate organic matter do not appear to be limited by nitrogen or phosphorus even in streams with ambient nutrient concentrations as low as 0.06 mg NO₃ I⁻¹ and <0.03 mg PO₄ I⁻¹.
5. Our results indicate that variations in water temperature resulting from diurnal and seasonal temperature fluctuations, forest clear-cutting, and catchment elevation and aspect can have marked effects upon microbial activity and production, while short-term alterations in nutrient regime appear to have no significant effect on microbial activity associated with seston.     

A survey of the macro-invertebrate riffle fauna of the River Wye

SUMMARY. Surveys of the Wye catchment in March and September 1975, and July and September 1976 and 1977, yielded 227 macro-invertebrate taxa, 77 of which were Chironomidae. Total macro-invertebrate density ranged from 520 to 22020 m⁻². Total density estimates in July 1976. during a period of severe drought, were significantly higher than in July 1977 but no differences were established between estimates on other comparable dates in 1975, 1976 and 1977. The total number of taxa and total macro-invertebrates collected from sites with total dissolved solids concentrations less than 50 mg I⁻¹ were significantly lower than at sites with higher concentrations. In general, upstream sites were dominated numerically by Plecoptera in March; Ephemeroptera, Trichoptera and Diptera were relatively more abundant during the summer months. Sites lower in the catchment were more variable in composition with Oligochaeta, Ephemeroptera, Trichoptera and Diptera all abundant at certain sites and times. The densities of Ecdyonuridae (Ephemeroptera). Hydropsychidae (Trichoptera) and Elminthidae (Coleoptera) in the impounded R. Elan, a tributary of the R. Wye, were significantly lower than at nearby sites on the Wye although no differences in total macro-invertebrate density were established. Average linkage clustering of Spearman rank correlation coefficients between selected taxa allowed the comparison of taxa groups with contemporary site groups by nodal analysis. Six major taxa groups were established and these characterized five site groupings.     

Inputs and transformation of allochthonous particulate organic matter in a headwater stream

Inputs and outputs of allochthonous particulate organic matter were measured during 15 months in the upper part of a beech forest headwater stream. Inputs were estimated to 716 g m⁻² yr⁻¹, and leaves made up 71%. Outputs were estimated to 535 g m⁻² yr⁻¹ and consisted mainly of FPOM (92%). Therefore, a significant transformation of CPOM into FPOM took place. The mean FPOM concentration varied between 0.6 and 3.4 mg 1⁻¹, but the daily variations greatly surpassed the seasonal variations. As discharge was rather constant, the observed variations were due to external disturbances, especially precipitation.
A tentative scheme for leaf processing is established from the present data and previous studies in the area, indicating that a significant part takes place in the MPOM pool and that microbial and invertebrate processing make up about 50% each of total intra-system processing.     

The influence of drought on the fish and invertebrate populations of an upland stream in Wales

SUMMARY. 1. The exceptionally dry summer of 1976 presented an opportunity to assess the impact of drought on the fauna of an unregulated stream in Wales.
2. Total number of macroinvertebrates varied from 1808 m⁻² in September 1976 to 7412m⁻² in August 1977. Two main effects of drought were observed: an initial reduction in abundance during the drought and a change in community structure in the following year, probably through impaired reproduction.
3. Trout density ranged from 0.075±0.028 to 0.402±0.093 m⁻² and salmon parr density varied between 0.014±0.004 and 0.414±0.119 m⁻². The only detrimental effect of the drought on the fish fauna was the elimination of the 1976 year class of young salmon. probably due to prolonged high water temperature.     

Longitudinal variation in recolonization rates of macroinvertebrates along an upland river in south-eastern Australia

SUMMARY. 1. Recolonization rates of benthic invertebrates were estimated at five sites in the catchment of the Acheron River, in spring (October) and in summer (January), The sites ranged from those that experience short floods and high shear stress at the streambed (upstream sites) to those that experience prolonged floods and low shear stress (downstream sites). We hypothesized that these differences should affect recolonization rate.
2. In October, absolute rates of recolonization of taxa (number of taxa 0.05 m⁻² d⁻¹) onto 1-m² patches of substratum, which had been raked to remove fauna, did not vary between the three sites studied, nor did the relative rates of recolonization of taxa (absolute rate/mean number of taxa in control samples, which were taken from adjacent undisturbed patches of substratum). Absolute rates of recolonization of individuals (number of individuals 0.05 m⁻² d⁻¹) were proportional to the mean number of individuals in control samples; relative rates of recolonization of individuals (absolute rate/mean number of individuals in control samples) did not vary between sites.
3. In January, absolute rates of recolonization either of taxa or individuals were positively correlated with the mean densities of taxa or individuals in control samples; relative rates did not vary between the four sites studied.
4. We conclude that the benthic invertebrate communities at the various sites do not adapt to variations in flooding regime by altering relative recolonization rates. Absolute recolonization rates are directly proportional to the prevailing number of taxa or individuals at a site.     

The production of juvenile Atlantic salmon, Salmo salar in the upper Wye, Wales

The production of juvenile Atlantic salmon ( Sulmo salur L.) was investigated in 16 study sites in the upper Wye catchment during the period February 1975 to November 1976. The population structure was characterised by large numbers of 0+ fish whose abundance decreased with respect to time so that the numbers of each of the older year-classes was a function of the year-class strength of the original fry. The range of parr densities was similar to that recorded for other rivers: the estimates of 2+ smolts did not exceed about 0.04 m⁻². Production ranged from 0.3 to 11.0 gm⁻² a^−l; Of and 1+ fish contributed over 72% and 3+ fish less than 1 % of the total annug production. The relationship between production P (gm⁻² a⁻¹) and mean biomass B (gm⁻²) for all yeatclasses considered separately and in combination can be expressed by the relationship P=a^b . The values for a vary with age-composition and season but the values for b are not significantly different. Differences in growth rate of salmon between sites are small and differences in production result principally from differences in standing crop (biomass density). In most cases low values for salmon production can be attributed to poor spawning.     

A limnological investigation of the tarn Syslaktjønn, W Norway

An investigation covering hydrography, chemistry, vascular and cryptogamic plants, nitrogen fixation, phytoplankton biomass and production, and zooplankton was carried out from April to November 1976 in tarn in W Norway, The volume of the tarn was 18000 m³ and the turnover time about 30 d. Temperature ranged between 3.6 and 23.4°C and pH between 4.8 and 5.5. Nuphar luteum and Carex rostrata were the two dominating vasculars-with biomasses of 117 and 97 g m⁻², respectively The biomass of the bryophytes ( Sphagnum spp.) was about 510 g m⁻² and the production of the order 0.2–2.1 μg (mg d.w.)⁻¹h⁻¹. Nitrogen fixation in association with Sphagnum spp. was estimated at 25 g yr⁻¹ for the whole tarn. Phytoplankton was dominated by diatoms, green algae and chrysophyceans. The chlorophyll a content ranged from 2 to 20 mg m⁻³ and the carbon assimilation rates from 0.03 to 20 mg C m⁻³h⁻¹ at 0–4 m depths. Production in the period was of the magnitude 22 g C m⁻². The copepod Eudiaptomus gracilis was the most common netzooplankter. Large numbers of rotationrians were found during summer.     

Mortality patterns in trout (Salmo trutta and S. gairdneri) exposed to an anionic detergent in relation to concentration and mechanisms of toxic action

SUMMARY. Histological and electron microscopical study of the gills of fish poisoned by the anionic detergent sodium lauryl sulphate indicates that the nature of the toxic action changes at a concentration of about 120 mg I⁻¹. Toxicity tests were conducted to determine whether this change could be detected in the test data, using brown trout ( Salmo trutta ) and rainbow trout ( S. gairdneri ).
Toxicity curves showed no indication of the change in toxic action, but at concentrations of 120 and 130 mg I⁻¹ of sodium lauryl sulphate 'split' probit lines occurred, and the lines for 150 mg I⁻¹ consistently differed in slope from other lines.     

Effect of plant succession, ploughing, and fertilization on the microbiological oxidation of atmospheric methane in a heathland soil

Abstract: The effect of plant succession on methane uptake was measured on intact soil cores collected from seven heathland sites. Six of the sites had undergone either secondary succession with grass or oak, ammonium fertilization or ploughing, while the seventh site was located in the native heathland. There was a positive relationship between methane uptake rate and time elapsed since the plant invasion had taken place in the native heathland. The native heathland site showed an insignificant atmospheric methane uptake of 0.01 mg CH₄ m⁻² d⁻¹, whereas the established oak brushwood (70 years old) and the grass invaded heathland (13 years old) showed rates of 1.36 mg CH₄ m⁻² d⁻¹ and 0.73 mg CH₄ m⁻² d⁻¹, respectively. In the fertilized heathland plot (112 kg N ha⁻¹ six years prior to this study) grass had become the dominating species and showed a methane oxidation rate of 0.28 mg CH₄ m⁻² d⁻¹. Ploughing of the heathland resulted in methane oxidation rates seven times the rates measured in the native heathland. The results suggested that an increased future atmospheric nitrogen deposition in heathlands and other nutrient poor ecosystems may have a stimulating effect on the soil sink for atmospheric methane.     

Comparative primary productivity of algal epiphytes on three species of macrophyte in the littoral zone of Lake Ohrid, Yugoslavia

Primary productivity of algal epiphytes on the surfaces of Phragmites, Potamogeton , and Nuphar was measured seasonally from June 1978, through June 1979, in the littoral zone of Lake Ohrid, using ¹⁴C methodology. Surface areas of individual macrophytes were determined throughout the study period through the use of a non-miscible surfactant and a calibration curve of surfactant weight versus known, calculated surface areas.
Mean total surface area available for epiphytic colonization during the study period was 1.032 m² macrophyte surface per m² of littoral zone for Phragmites , 0.810 m² for Potamogeton , and 0.167 m² for Nuphar . Seasonal rates of mean primary productivity of algal epiphytes on Phragmites from the surface to the light-compensation depth ranged from 84–1406 mg C m⁻² littoral zone d⁻¹; ranges for epiphytes on Potamogeton and Nuphar were 77–586 and 69–268 mg C m⁻² littoral zone d⁻¹, respectively. Maximum rates were observed typically during June; minimum rates were observed typically during August to December. Mean daily productivity rates over the 12 month period were for epiphytes on Potamogeton 167.0, on Nuphar 100.4 and on Phragmites 671.2 mg C m⁻² littoral zone d⁻¹. Calculated annual production for epiphytes on Nuphar was 36.65, on Potamogeton 60.95 and on Phragmites 245.0 g C m⁻² littoral zone yr⁻¹. Epiphytic production data were typically considerably higher than production data obtained for littoral and pelagial planktonic algae and compare favorably with published data for epiphytic and periphytic production in Lawrence Lake, Marion Lake, and Borax Lake.     

A comparison of a new campylobacter selective medium (CAT) with membrane filtration for the isolation of thermophilic campylobacters including Campylobacter upsaliensis

The newly developed CAT campylobacter selective medium employing the blood-free charcoal-based agar containing cefoperazone (8 mg I⁻¹), amphotericin (10 mg I⁻¹) and teicoplanin (4 mg I⁻¹) was compared with the membrane filtration culture technique for isolation of Campylobacter spp. including Camp. upsaliensis. Nine hundred and fifty human, 275 dog and 65 cat faeces (in which modified CCDA medium was also compared) were tested. In addition, the recovery of Camp. upsaliensis from pure cultures and from spiked human faeces was examined after membrane filtration. A 50-fold reduction in recovery after filtration using the 0·65 μm filters and a 150-fold reduction using the 0·45 μm filters was found. Recovery of Camp. upsaliensis from spiked faeces was considerably improved using the CAT medium compared with filtration, especially with the lower concentration of organisms (approx. 10⁴ cfu ml⁻¹). Campylobacter upsaliensis was recovered from 91 specimens of animal faeces, with CCDA recovering 26 isolates (29%), CAT recovering 76 isolates (84%) and membrane filtration (0·65 μm) recovering 82 isolates (90%). CAT selective agar was found to be a suitable medium for the isolation of thermophilic campylobacters including Camp. upsaliensis from faecal samples.     

Production and litter processing by crayfish in an Appalachian mountain stream

SUMMARY 1. Mean annual density and biomass () of Cambarus bartonii in an Appalachian mountain stream (U.S.A.) was 12 individuals m⁻² and 1669 mg (ash-free dry weight) m⁻².
2. Annual production ( P ) of C bartonii was 961 mg AFDW m⁻². Despite high biomass, low growth rates resulted in low production and a low P/ ratio of 0.58.
3. While C bartonii constituted 61% of the total macroinvertebrate biomass, it contributed only 13% of annual community secondary production.
4. Litter processing was positively related to temperature and crayfish size. Cambariis bartotnii was estimated to comminute 36 g m⁻² y⁻¹ of leaf litter (>1 mm²) to 24 g m−^>2 y⁻¹ fine particulate material (<1 mm²). The annual pattern of litter comminution by crayfish was regulated by temperature. As a result, >5()% of shredding activity by crayfish occurred from June to September which was also the period of lowest litter standing crops and activity of other shredding macroinvertebrates.
5. We speculate that during summer crayfish play an important role in temperate woodland streams by converting slowly processed leaf litter species (e.g. Rhododendron ) to fine particles which are then available to collector-gatherers (e.g. Chironomidae, Oligochaeta).     

Respiration rate in maize roots is related to concentration of reduced nitrogen and proliferation of lateral roots

The relationship between specific rate of respiration (respiration rate per unit root dry weight) and concentration of reduced nitrogen was examined for maize ( Zea mays L.) roots. Plants with 2 primary nodal root axes were grown for 8 days in a split-root hydroponic system in which NO-₃ was supplied to both axes at 1.0 mol m⁻³, to one axis at 1.0 mol m⁻³ and the other axis at 0.0 mol m⁻³ or to both axes at 0.0 mol m⁻³ Respiration rates and root characteristics were measured at 2-day intervals. Specific rate of respiration was positively correlated in a nonlinear relationship with concentration of reduced nitrogen. The lowest specific rates of respiration occurred when neither axis received exogenous NO⁻³ and the concentration of reduced nitrogen in the axes was less than 9 mg g⁻¹. The greatest rates occurred in axes that were actively absorbing NO⁻³ and contained more than 35 mg g⁻¹ of reduced nitrogen. At 23 mg g⁻¹ of reduced nitrogen, below which initiation of lateral branches was decreased by 30–50%. specific rate of respiration was 17% greater for roots actively absorbing NO⁻³ than for roots not absorbing NO⁻³ Increases in specific rate of respiration associated with concentrations of reduced nitrogen greater than 23 mg g⁻¹ were concluded to be attributable primarily to proliferation of lateral branches.     

Development of leaf thickness for Plectranthus parviflorus – Influence of photosynthetically active radiation

Photosynthetically active radiation (PhAR) is apparently the environmental factor having the greatest influence on leaf thickness for Plectranthus parviflorus Henckel (Labiatae). A four-fold increase in leaf thickness from 280 to 1170 μm occurred as the PhAR was raised from 1.3 to 32.5 mol m⁻² day⁻¹. Compared to a constant PhAR of 2.5 mol m⁻² day⁻¹, a PhAR of 32.5 mol m⁻² day⁻¹ for one week during the first week (with return to 2.5 mol m⁻² day⁻¹ during the second and third weeks) led to an increase in final leaf thickness by 323 μm (to 802 μm). When increased PhAR was applied during the second week the increase in final thickness over the control was 217 μm, and when increased PhAR was applied during the third week it was 99 μm. However, leaf thickness was not simply responding to total daily PhAR, since a leaf 450 μm thick could occur at a low instantaneous PhAR for a long daytime (total daily PhAR of 1.5 mol m⁻² day⁻¹) and at a high PhAR for a short daytime (4.5 mol m⁻² day⁻¹). Total daily CO₂ uptake (net photosynthesis) was approximately the same in the two cases, suggesting that this is an important factor underlying the differences in leaf thickness. Leaf thickness is physiologically important, since thicker leaves tend to have greater mesophyll surface area per unit leaf area ( A ^mes/ A ) and hence higher photosynthetic rates.     

Ecological changes in a lake fishery and their effects on a stunted roach Rutilus rutilus population

Data for two sampling years (1969/70 and 1970/71) is presented to illustrate the changing composition, density and biomass of the macroinvertebrate fauna in a South Lancashire lake. Six faunal groupings are recognised for a non-parametric analysis of the data and significance levels are given for the between-station and between-year differences recorded. The mean density of macroinvertebrates (1.2 mm mesh sieve) estimated for the lake as a whole increased by 28.5% in the second year (2519 m⁻²-3237 m⁻²) whereas the estimated mean biomass in g m⁻² increased by 86% wet weight (8.61−16.01) and 196% dry weight (1.74−5.15). Molluscs contributed substantially to the increased standing crop which was accompanied by increased development of macrophytes.
A comparative study of the diets of roach in two size groups in winter and summer is described. The variety of food items consumed was found to be greater than in a preliminary study in May 1969 and, for the roach sampled, the average quantity of food consumed per fish increased after the 1969/70 winter. The possible relationships between invertebrate standing crop, roach diet and previously reported changes in the growth of the roach are discussed and an explanation is offered concerning the sequence of biological changes observed in the lake.     

Phytoplankton ecology in an Antarctic lake

SUMMARY. The ecology of the phytoplankton of Heywood Lake, Signy Island, South Orkney Islands, Antarctica was investigated during 1969–72. The lake, which is ice-covered for 8–10 months per year, is moderately eutrophic due to enrichment by seal excreta.
The annual cycle of the phytoplankton is described. During the winter (approximately May-September), very few algal cells could be detected in the water column and ¹⁴C fixation was below measurable limits. In spring (October-November), a rapidly-growing population of algae caused a large increase in the chlorophyll- a concentration (maximum value 170 mg m⁻²) but carbon fixation remained low, with values <500 mg C m⁻² day⁻¹. The algae contributing to this peak were mainly small chlorophytes and chrysophytes. The summer open-water period (December-March) was characterized by a different phytoplankton population dominated by cryptophytes. Chlorophyll levels were lower ( c . 40 mg m⁻²) but ¹⁴C fixation rates >3 g C m⁻² day⁻¹ were measured on bright days. Values for Assimilation Number were very high (maximum value 10.5 mg C h⁻¹ mg⁻¹ (chlorophyll- a ) in January (1971) though temperatures never exceeded 8°C. In autumn, the phytoplankton regressed to winter levels. Both spring and summer algal populations probably overwinter as resting stages.     

Phytoplankton production in relation to physico-chemical conditions in a small, oligotrophic subarctic lake in South Greenland

Phytoplankton production and physico-chemical parameters were measured during the summers of 1976 and 1977 in Lake 95 at 60°52'N, 46°01'W (area 8 ha, z 6.9 m). The duration of lake stratification during summer was weather dependent. Concentrations of total-CO₂ ranged from 2.04 mg l⁻¹ (surface) to 4.02 mg l⁻¹ (bottom during stratification). Nutrient concentrations were generally low, and systematic seasonal variation could not be detected with certainty. Vertical distribution of primary production typically showed a distinct maximum followed by a decline with depth. The low production, both per unit area (max. 60 mg C m⁻² d⁻¹) and per unit volume (max, 14.3 mg C m⁻³ d⁻¹), and the annual production of 4.7 g C m⁻² classified the lake as extremely oligotrophic.