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.     

Studies of tolerance to heavy metals in the flora of the rivers Ystwyth and Clarach, Wales

A survey of the river Ystwyth demonstrated that it was polluted with metals especially below the areas of old lead mines. Hormidium spp. Kütz in particular Hormidium rivulare Kütz were the most tolerant filamentous green algae present. Scapania undulata (L.) Dum. was a tolerant bryophyte on the Ystwyth and Clarach rivers and was found alone in polluted sites, but was less frequent in cleaner areas. Metal extracts of this bryophyte mirrored the variation in metal concentrations of the environment to some extent. In general, lower levels of Fe, Pb and Mn were found in Scapania as compared with the less tolerant Fontinalis squamosa Hëdw. When the latter was transplanted to polluted sites an increase in its Pb, Cu, Zn and Mn content occurred within 6 weeks and the plant started to die and decay after 18 weeks. Scapania survived when it was transplanted from its natural polluted habitat to a less polluted area, and there was no marked change in its metal content. Zn⁶⁵ tracing experiments, in the laboratory, demonstrated that both plants had similar uptake patterns for the metal, but that the amount taken up was slightly higher in the less tolerant Fontinalis. There was no change in the number of diatoms found upon Scapania when it was transplanted, but a reduction in numbers occurred on the transplanted Fontinalis when it started dying. The composition of these diatom floras was different in polluted sites as compared to that in the cleaner areas.     

The macro-invertebrate fauna of a small Andean stream

SUMMARY. The benthic fauna of a small headwater stream in the Amazon drainage in Ecuador was studied from August 1976 to July 1977. The sampling station was at an altitude of 3300 m in a typical paramo habitat of constant and cool temperatures. The fauna is dominated numerically by Hydracarina, Insecta, Copepoda and Oligochaeta, The major insect groups are Ephemeroptera, Plecoptera, Trichoptera, Elmidae (Coleoptera) and Chironomidae (Diptera). Benthos densities followed a bimodal pattern of rapid decreases and intervening gradual recoveries; similar patterns occur in most taxa, but are more pronounced in smaller animals such as Copepoda and Hydracarina. An analysis of the size-frequency distribution of three species of mayfly, two of stonefly and six of caddisfly suggest non-seasonal life-cycles except for Anacroneuria sp. Spates are thought to be the major factor regulating benthic densities in such non-seasonal environments.     

Channel changes and invertebrate faunas below Nant-Y-Moch dam,River Rheidol,Wales, UK

River impoundment is known to affect the physical, chemical, and biological characteristics of the downstream river, but little is known of the way in which changes of these characteristics interact or the time-scale required to attain a new quasi-equilibrium state. The data presented herein show that channel sedimentation below a tributary confluence, resulting from reduced flow competence and capacity within the regulated mainstream, has produced morphological changes associated with substrate particle-size alteration. Four physical compartments are identified, each representing a different stage of readjustment to the hydrological conditions imposed by the dam. Each stage is shown to have a characteristic fauna. Moreover, the species diversity, composition, and biomass were found to be most different from the natural data during the early stages of readjustment and to approach the natural data more closely as the channel attained a quasi-equilibrium form.     

The swimming endurance of threespine sticklebacks, Gasterosteus aculeatus L., from the Afon Rheidol, Wales

The endurance of threespine sticklebacks, Gasterosteus aculeatus , swimming with pectoral fin locomotion at 20° C in a laboratory flume was measured. Each trial lasted a maximum of 480 min. At a speed of 4 body lengths per sec (L s⁻¹) all fish were still swimming at the end of the trial, but endurance decreased at higher speeds. At speeds of 5 or 6 L s⁻¹ (20–30 cm s⁻¹) a few fish still maintained labriform locomotion for the 480 min. However, at a speed of 7 L s⁻¹ all fish furled their pectoral fins and used body and caudal fin propulsion but fatigued rapidly. During sustained swimming, fish could cover distances of 6 km or more. No significant differences between males and females were found.     

Numerical indices applied to the results of a survey of the macro-invertebrate fauna ofthe Tamar catchment (southwest England)

A survey ofthe macro-invertebrate fauna in the River Tamar revealed that a division ofthe catchment can be made which separates an organically enriched upper region from a more stable environment in the lower tributaries and reaches. Invertebrate species normally associated with organic pollution were found immediately downstream from farm waste and sewage effluent outfalls. Invertebrate species normally associated with an unpolluted condition were widely distributed throughout the catchment, and revealed that the Tamar is essentially free from gross pollution causing the continuous elimination of stream fauna. Systems used by pollution control organizations to codify biological results are reviewed and applied comparatively to the results. The Diversity index was found to be the most consistent method in assessing the biological state of the river. The Trent, Lothian, Chandler and Carpenter indices were found to give either anomalous figures or proved insensitive to conditions beyond a certain quality.     

A comparison of some classification methods used to determine benthic macro-invertebrate species associations in river survey work based on data obtained from the River Ely, South Wales

SUMMARY. The results of a survey of the macro-invertebrates of the polluted River Ely, South Wales, are used as a basis for comparing several classification methods which have been used previously in river survey work to determine species groupings. The methods compared are product-moment correlation (clustered by the nearest neighbour technique), Kendall's tau coefficient (clustered by the nearest neighbour and average linkage techniques), and Squared Euclidean-Distance coefficient (clustered by nearest neighbour and Ward's techniques). The species groupings determined by these methods were influenced both by the association coefficient and the technique used to cluster it. Some species were grouped together by all or most of the methods. The ecological validity of these robust groups is examined. A clear recommendation regarding the most appropriate method is frustrated by incomplete knowledge of the ecological requirements of most of the aquatic macro-invertebrates used in the data-set. However, Kendall's tau coefficient clustered by the average linkage technique appeared to produce ecologically meaningful species groups. Product-moment correlation was also reasonably successful and since it is based on absolute abundance data whereas Kendall's tau coefficient is based on relative abundance data, the use of the two together is recommended for determining robust groups.     

First survey of interstitial fauna in New Caledonian rivers: influence of geological and geomorphological characteristics

Despite zoogeographical implications and geological anomalies, the interstitial fauna of New Caledonian rivers remains unstudied. During this first survey, 15 different sized rivers varying in sediment grain size and geological substratum were sampled for both benthic (Surber sampler) and interstitial (Karaman-Chappuis pits) invertebrates during summer 1998–99. A total of 34 taxa was collected during the study, of which 22 were present in the sediment interstices. Interstitial assemblages were dominated by the Oligochaeta (present in 80% of the samples), the Chironomidae (in 73%), the Ceratopogonidae (in 73%), the Coleoptera Berosini (in 47%), the Turbellaria (in 47%), the OstracodaVestalenula sp. (in 40%) and the Copepoda Cyclopoida (in 40%). New amphipods close to Bogidiellidae were found in two stations. Some organisms, frequent and abundant in the benthic layer, were rare or absent in the sediment interstices (e.g. Decapoda Atyidae, Ephemeroptera Leptophlebiidae, Trichoptera Hydropsychidae and Leptoceridae, Diptera Simulidae). River size and distance between the station and the ocean were unassociated with abundance, taxonomic richness or composition of interstitial assemblages. In contrast, both abundance and taxonomic richness were significantly lower when sediment grain size decreased (probably because of low exchange with surface assemblages) and when the percentage of peridotitic substratum in the catchment increased (probably because of its high nickel and chromium contents). These preliminary results suggest that interstitial fauna can be used for ecological survey and river management even in tropical regions.     

The littoral fauna of Llyn Celyn, North Wales

Water level fluctuations of up to 5.5 m in the newly constructed reservoir, Llyn Celyn, were shown to result in a uniformly barren littoral zone in which Lumbriculidae, Pisidium sp. and Chironomidae were the only animals to occur in significant numbers throughout the year. Other groups of animals were unable to survive the big fluctuations in water level and this in turn affected the food and growth of trout in the environment.     

Rotifer fauna in the periphyton of Karst rivers in Croatia,Yugoslavia

Rotifers from periphyton communities of rivers in the Karst area of western Yugoslavia were examined. Thirty-two species, belonging to 10 families, were found. Rotifers were absent from locations without periphyton. Low densities of animals were noted at stations near urban centres and in the estuaries of the Mirna, Rãa, Rjeina and Krka rivers. Several species were found in all of the rivers studied, but always in low numbers. Most of these species are generally considered to be euryvalent and cosmopolitan.     

The three dimensional distribution of the fauna in a single riffle in a stream in Ontario

The surface and hyporheic fauna of a riffle area in Salem Creek near Elmira, Ontario, was investigated with a Surber and a corer sampler. A stratified random sampling design estimated the number of invertebrates at 154 561 (109 805–224 155) m^–2 in June and at 64 407 (40 905–97 996) m^–2 in October with more than 70% of the animals occurring below 5 cm. There was a great spatial variation of the hyporheos density in the three dimensions of the riffle, which seemed to be related mostly to hydrogeological characteristics (superficial groundwater flow and grain size). Upward water movement in the centre of the stream occurred in the upper two transects, especially from the upper right bank, while the lower transect showed little water transmission. Hyporheos composition is discussed in regard to life history and the input of organic materials. Only two of nine pairs of Surber samples showed a high degree of similarity (0.68, 0.81). The surficial spatial density and diversity were examined in relation to the available surface and to substrate heterogeneity. It is concluded that the great variations between samples caused by many factors present severe problems in the collection of reliable quantitative samples.

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Résumé La faune de surface et celle de l'hyporhélique d'un radier de Salem Creek près d'Elmira, Ontario, ont été étudiées à l'aide de l'échantillonneur de Surber et d'un carottier. Un échantillonnage aléatoire stratifié a permis d'estimer le nombre d'invertébrés a 154 561 (109 805–224 155) m^–2 en juin et à 64 407 (40 905–97 996) m^–2 en octobre. Environ 70% de la faune benthique a été retrouvée entre 5 et 65 cm. La densité de l'hyporhéos présente de grandes variations spatiales, et celles-ci semblent etre reliées aux caractéristiques hydrogéologiques (mouvement des eaux souterraines superficielles et taille des particules). Un net mouvement ascendant dirigé vers le centre du radier a été détecté dans les deux transects situés en amont; aucun mouvement n'a été mesuré dans un troisième transect situé an aval. La composition de l'hyporhéos est mise en relation avec les cycles vitaux et avec l'apport des matières organiques. Des 9 paires d'échantillons recueillis au Surber, deux seulement présentent un certain degré de similarité (0.68, 0.81). Les variations spatiales de la densité et de la diversité de la faune de surface furent mises en corrélation avec la surface disponible et l'hétérogénéité du substrat. On en conclu que la grande variabilité entre les échantillons dans les deux habitats est due à plusieurs facteurs et qu'elle pose de sérieux problèms pour l'estimation de paramètres quantitatifs.

     

The prediction of the macro-invertebrate fauna of unpolluted running-water sites in Great Britain using environmental data

SUMMARY. 1. A procedure has been developed which uses environmental data to predict the probabilities of macro-invertebrate taxa occurring at running-water sites in Great Britain.
2. Biological, physical and chemical data were collected from twenty- one sites on three river systems in order to evaluate the procedure.
3. For most sites the number and type of taxa recorded, using a standard sampling programme, were very close to those predicted using twenty-eight environmental variables.
4. Comparison with other studies at the same sites showed that most taxa whose probability of occurrence was ≥0.5 could be found with more intensive sampling.
5. Reducing the number of variables used in making the predictions from twenty-eight to five resulted in only a slight loss of predictive accuracy.
6. Combinations of chemical and physical variables gave better predictions than equivalent numbers of physical variables only but the latter may be more appropriate where chemical pollution is known, or suspected to occur.
7. The procedure is of practical value in the detection and assessment of pollution.
8. It may also be used to explore patterns in the structure and functioning of stream communities.     

Planktonic fauna of small salmon rivers in the Kola Peninsula

The zooplankton of 23 small salmon rivers of the White Sea and Barents Sea basins in the Kola Peninsula were studied. The species composition and quantitative indices in juvenile salmonids habitats are characterized. The maximum species diversity and abundance of planktonic fauna were recorded in lake-regulated rivers and places with large quantities of water. The quantitative development of zooplankton in rivers is low, which testifies to its minor role as a food resource for salmonid juveniles. The assessment of the ecological state of the river water is presented.     

The macroinvertebrate fauna of the drainage channels of the Gwent Levels, South Wales

SUMMARY. From a survey of the fauna at sixty sites in permanent drainage channels of the Gwent Levels during the spring of 1976 and at some of these sites (thirty-three) during the autumn, speeies and site associations were identified using classification and ordination techniques. Sites in some groups had identifiahly similar environmental characteristics and grouping seemed particularly related to the vegetational stage in the hydrosere, water How and the incidence of salt contamination from the Severn Estuary. Characteristics which were common within particular species groups and whieh, in part, explained their distributions were: adaptation to low oxygen concentrations, food preferences and dispersal mechanisms. Whilst there was some temporal stability in site groups between the spring and autumn surveys, such associations were not idenlical. The oxygen status of channels appeared a major factor determining faunal distribution. Twelve sites, representing a range of channel types, were sampled six times in a 12-month period. Far more species were colleeled within the water column and on plants than in the benthos. Several oligochaetes, e.g. Aulodrilus pluriseta, Dero digitata, Limnodrilus claparedeanus, were not recorded at most sites during the summer probably because of the SUStained lack of oxygen at these sites. Three contiguous reaches of channel were maintained during the period March—October 1977 with different plant cover (no Lemnu; complete Lemna cover: control with partial Lemna cover). The oxygen status of the reaches was different, that with complete Lemna cover being continuously anaerobic near the channel bed for several months, the control reach which had partial Lemna cover being anaerobic for a shorter period and that with no Lemna being only anaerobic at night. Whilst the distribution of macroinvertebrate species was prineipally related to this oxygen status, the control reach whieh was strueturally the most complex, having both submerged and floating plants, contained about twiee as many species as the other reaches during the summer (colleeted in the water column and on plants): benthic samples in this and the reach with complete Lemna cover contained only between zero and two species during the period May- September.     

Effects of nuisance submerged vegetation on the fauna in Norwegian rivers

Hydrobiologia - The abundance of aquatic vegetation is increasing in rivers and lakes worldwide. The aim of this study was to find how the macrophyte Juncus bulbosus Linnaeus affects salmonids and...     

Mountain streams of the Barberton area,Eastern Transvaal. Part I,A survey of the fauna

Summary This paper records the results of a faunistic survey of the mountain streams of the Barberton area of the Eastern Transvaal. Sampling was carried out in five different biotopes; cascades, sprayed flanking regions, stickles, backwaters and pools.Netting of the adults and imagos and breeding out of the larvae of Chironomidae, Odonata and Ephemeroptera was done.The faunal affinities were assessed by a comparison of the mayfly fauna of this area with that reported in other surveys conducted in Africa.     

The effects of silt and sand on the invertebrate fauna of streams and rivers

Summary Most of the literature concerned with the effects of silt and sand on the invertebrate fauna of streams and rivers has described changes taking place when biotopes are completely smothered by silt and sand. In few of these studies were the kinds of animals found recorded. There have been few studies of the effect of silt and sand on individual species. The invertebrate fauna of two biotopes in the streams and rivers of the Vaal River system, South Africa, changed with the amount of silt and sand in the watercourses. Where there were large amounts of silt and sand the variety of animals recorded from the stones in current biotopes was reduced, but the density of the fauna as a who did not change (Tables I and II, Unstable Depositing Zones, summer). However the density of many groups of animals was affected (Table III). Some of the animals adversely affected by silt and sand appeared in larger numbers below impoundments in which silt and sand would settle. In the sediment biotopes the summer density of the fauna was lowest where there was a lot of silt and sand (Table IV, the two Unstable Depositing Zones). Large amounts of silt and sand were associated with large summer declines in the surface dwelling animals as a proportion of the whole sediment fauna (Table IV). Differences between the summer proportions of surface dwelling forms in fine and coarse sediments were due to faunal differences. Sediments were not studied below impoundments.It is concluded that there may be considerable changes in the composition of the stones in current fauna due to silt and sand without the biotope being smothered, and that increases in the amount of silt and sand in river beds lead to increased instability of the sediments, which adversely affects their fauna.

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Zusammenfassung Die Abhandlungen, die sich mit dem Einflu von Schlamm und Sand auf die Invertebratenfauna von Bächen und Flüssen befassen, haben meistens die Veränderungen beschrieben, die sich ergeben, wenn Biotope ganz von Schlamm und Sand erstickt werden. In wenigen dieser Forschungen werden die Arten der gefundenen Tiere eingetragen. Es gibt wenige Arbeiten über den Einflu von Schlamm und Sand auf einzelne Arten.Die Invertebraten-Fauna zweier Biotope in Bächen und Flüssen des Vaalsystems, Süd-Afrika, hat sich mit der Menge von Schlamm und Sand in den Flüssen geändert. Wo es groe Mengen von Sand und Schlamm gab, ist die Verschiedenartigkeit der Tiere von Steinen in flüssigem Biotop vermindert worden, aber die Dichte der ganzen Fauna ist dieselbe (Tabellen I und II, Unstable Depositing Zones, Summer). Jedoch die Dichte vieler Tiergruppen ist beeinträchtigt worden (Tabelle III). Einige von Schlamm und Sand ungünstig beeinflute Tiere erscheinen in gröerer Anzahl unter Einsperrungen, wo Schlamm und Sand sich niederschlagen können. In Niederschlagbiotopen ist die Sommerdichte der Fauna am niedrigsten, wo es viel Schlamm und Sand gibt (Tabelle IV, Die zwei Unstable Depositing Zones). Groe Mengen von Schlamm und Sand gehen mit groen Sommerabnahmen der oberflächlich lebenden Tiere im Verhältnis zu der ganzen Niederschlagfauna zusammen (Tabelle IV). Unterschiede zwischen den Verhältnissen oberflächlich lebender Formen in feinen und groben Niederschlägen im Sommer sind die Folge faunaler Unterschiede. Niederschläge unterhalb von Einsperrungen sind nicht untersucht worden.Es wird geschlossen, da es beträchtliche Änderungen in der Zusammenstellung der Fauna der Steine in Flüssen wegen Schlammes und Sandes geben kann, ohne da der Biotop erstickt wird, und da Steigerungen der Menge von Schlamm und Sand in Flubetten zu vermehrter Instabilität der Sedimente führt, welche ungünstig auf die Fauna einwirkt.

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This work forms part of a dissertation submitted to Rhodes University Grahamstown, in fulfilment of the requirements for the degree of Doctor of Philosophy.