摘要:

SummaryIn the course of investigations on the ecology of submerged aquatic macrophytes a narrow‐bandwidth spectroradiometer has been used to measure underwater spectral intensity (390–750 nm) in a series of lochs approaching the extremes in optical and chemical properties of Scottish fresh waters. Cosine response and immersion‐effect properties of the collector were determined in the laboratory with a colUmated hght source. Diffuse attenuation coefficients,Ee, ranged from 0·55 in Loch Croispol, a calcareous loch, to 2·9 in Loch Leven, a lowland eutrophic loch. Underwater spectral intensity (1 m) relative to subsurface values show a proportional increase in short‐wave radiation in the blue‐green water of Loch Croispol, while the converse is true of the peaty brown water of Loch Uanagan. Attenuation coefficients were derived over 25 nm wavebands in Lochs Croispol, Leven and Uanagan. The water in the latter two lochs is optically similar although Leven is rich in phytopiankton and has an extinction peak at 675 nm. Uanagan represents the brown‐water type of loch most common in Scotland. Loch Croispol has attenuation coefficients for shorter wave‐lengths at least ten times lower than the other two lochs and only approaches their values at 750 nm. Croispol resembles Crater Lake, Oregon. The colour range at the maximum colonizable depths by rooted macrophytes of brown (Uanagan 4 m) to blue‐green (Croispol 6 m) water is equivalent to 196·0 and 230·6 kJ/Einstein (48·2 and 55·6 kcal/Einstein). Red/far‐red ratios even in plankton‐rich water (Leven) were at least three times the value for sunlight (1·3) and within the total photic zone reached three‐figure proportions. Possible implications for light‐sensitive seeds of aquatic species and for morphogene

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01567.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SUMMARY(1) A survey of the macro‐invertebrates and fish in the River Cynon, a trout stream in south‐east Wales receiving industrial and domestic wastes, and nine of its tributaries, was carried out in the summer of 1970. Its principal purpose was to describe the structure of these communities before waste treatment facilities, in course of construction, reduce the degree of pollution.(2) The macro‐invertebrate communities changed dramatically at station C4, there being a very varied fauna upstream and one dominated by chironomids and oligochaetes downstream, principallyNais barbata., Cricotopus bicinctusandSyncricotopusrufiventris. It seems likely that coal particles, influencing the substrate, are largely responsible for this change. Further downstream, and below substantial organic discharges, tubificids and the enchytraeid,Lumbricillus rivalis, became increasingly abundant. The total density of macro‐invertebrates increased from about 2000/m2 in the headwaters to over 20,000/m2 in the lower reaches.(3) The fauna of the clean tributaries, Hir (C16) and Wenallt (C19) was similar to that ofthe unpolluted upper reaches ofthe Cynon (C1‐C3) whereas that of tributaries affected by coal particles was similar to the fauna of the Cynon downstream of C4.(4) Six species of fish were recorded (bullhead, eel, minnow, trout, stickleback and stoneloach) of which tbree (bullhead, eel and trout) were confined to reaches upstream (C8 and above) of industrial eflluents at Abercwmboi. For 0–8 km downstream of these effluents the river was fishless and further downstream, to the confluence with the River Taff, fish density and biomass were reduced.(5) In the upper Cynon and its tributaries the density and biomass of trout were within the range recorded elsewhere in the British Isles. The growth rate of trout in the catchment is low. Diflerences in growth rate and shape of trout in the main river and tributaries suggest that there is little interchange between these areas, except perhaps with very young fish. 0 +*fish were only caught in abundance at two tributary stations and their numbers, even if widely distributed, could not permanently support the current density of older fish throughout the upper catchment.(6) Stone loach and minnow reached a very large size and individuals caught of the latter species approached the maximum recorded length for the Br

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01568.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SUMMARY(1) Seasonal variation in the intensity of feeding activity was demonstrated in two chub populations. Feeding activity was higher in summer and more pronounced in the young age‐classes. The intensity of feeding activity was significantly correlated with temperature.(2) The diet of the total chub populations embraced a wide range of food items but vegetable material predominated. Substrate material was frequently encountered which suggested considerable feeding on the river bed. Fish were the most important animal food, by volume, in the River Lugg but Trichoptera larvae were most important in the Afon Llynfi. No remains of salmon parr or trout were found in chub stomachs but grayling were eaten. The most important prey fish, by volume, was the eel but cyprinids, especially minnows, were most important by frequency of occurrence.(3) Seasonal variation in the composition of the diet could be related to availability of food organisms but some selection was shown. Vegetable foods were most important in summer; animal foods, Trichoptera larvae in particular, were important in winter.(4) Analysis of the variation in the composition of the diet with age revealed several trends, notably a decrease in the importance of plant material, aquatic and aerial insects with age and a corresponding increase in the importance of larger prey foods such as fish, frogs and crayfish.(5) The commonly held view that chub are deleterious to salmonid stocks was examined. The absence of direct predation and the small likelihood of direct competition suggests that this view is incorrec

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01569.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SUMMARYMetabolically active phosphorus‐starved cultures of blue‐green algae assimilate32P rapidly in the light and in the dark. The uptake of phosphorus results in a rapid (within 15 min) stimulation in acetylene reduction byAnabaena cylindrica, A. flosaquae, Anabacnopsis circuiarisandChlorogloea fritschii, with a response being obtained to less than 5 μg/1 of phosphorus. Uptake of phosphorus also causes a rapid increase in respiration in the dark but not in photo respiration, and the size of the cellular ATP pool and the14CO2fixation rate both increase more slowly. The metabolism of phosphorus‐sufficient cells, which assimilate phosphorus more slowly, shows little response when phosphorus is provided.Excess phosphorus is stored in the vegetative cells of blue‐green algae as polyphosphate bodies which may form within 60 min of adding phosphorus to phosphorusstarved cells and which serve as a source of phosphorus for the algae when exogenous phosphorus is limiting. Preliminary results from Scottish waters suggest that urban effluents are important sources of available‐phosphorus for algal growth and that the levels entering fresh waters from agricultural land are, per unit volume, lower. In both types of water the levels of available‐phosphorus are rather similar to the levels of orthophosphate‐phosphorus present. Most detergents tested serve as a source of phosphorus for nitrogen‐fixing blue‐green algae and cause a rapid stimulation in reduction when added to phosphorus‐starved cultures. Of the detergents assayed, the biological types were richest in available phosphorus. The addition of detergents may result in a rapid increase in number of polyphosphate bodies present in the algae. Detergents in general also contain an inhibitor of algal metabolism. Whether a stimu‐lation or an inhibition occurs depends on the quantities of detergent added and on whether or not the alga i

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01570.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SUMMARYThough larger and more calcareous than a Lake District Beck, the River Bela now harbours a similar community of Ephemeroptera. Three species characteristic of small rivers were not recorded after the sides had been straightened and cleared of emergent vegetation and the bottom had been levelled.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01571.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

SUMMARYThe pattern of diel vertical migration ofChaoborus flavicanslarvae in a shallow Scottish loch varies according to the instar and, in third and fourth instars, according to the season.The planktonic phase of the migration is not exclusively concerned with predation, the larvae feeding at least equally actively in the benthos. Although there is no conclusive evidence as to the role of vertical migration inChaoborus flavicans, it has some of the characteristics of an epideictic display.Upward and downward locomotion can be induced experimentally in a plankton wheel by manipulating light intensity alone. However, the responses are complex and there is a great deal of individual variation, suggesting that additional factors are involved.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01572.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Sachs, L. (1970).Statistische Methoden, Ein Soforthelfer.Dansereau, Pierre (Ed.) (1970).Challenge for Survival: Land, Air and Water for Man in Megalopolis. 9½× 6 in.Electrical Energy Needs and Environmental Problems, Now and in the Future.Edmondson, W. T. and Winberg, G. G. (Eds) (1971).A Manual on Methods for the Assessment of Secondary Productivity in Fresh Water

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01573.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1971.tb01574.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY