The impact of Cow Green Reservoir on invertebrate populations in the River Tees

Cow Green is a new reservoir situated in Pennine moorland. It has an area of 312 ha, a capacity of 40 . 9 x 10 SUP-6 m SUP-3 and a maximum depth of 22 . 8 m. The function of the reservoir is to regulate flow in the River Tees to provide industrial Teesside with sufficient water during the dry spells. Invertebrate studies were carried out in the Tees to monitor changes resulting from the construction of the reservoir both in the flooded basin and below the dam. The overall effect of the reservoir on the Tees has been to increase the numbers and biomass of certain taxa, but generally not at the expense of previous fauna. Some of the positive effects, ie. increase in number and biomass, and maintenance of faunal diversity, may in part be attributable to the presence of the rapids and waterfall. Turbulence resulting from this rapid flow over heterogeneous bottom is sufficient to prevent clogging of interstitial spaces by silt and to maintain the variety of ecological niches necessary for a diverse fauna.

Acid precipitation and its effects on aquatic systems in the English Lake District

There is no evidence of an increase in the acidity (lower pH or alkalinity) of water-bodies in the Lake District over the last 50 years. Brown trout occur in acid streams and upland tarns where pH is 4.5-5.2 throughout the year. Their occurrence in such waters in Britain and Ireland has been known for most of this century and there is no previous evidence of harmful effects on salmonid fisheries, though numbers of fish are naturally low. However, many benthic invertebrates that are common in hill-streams where pH is above 5.7 do not occur in more acid streams. This phenomenon occurs in the headwaters of several western rivers in Cumbria. It is not a recent response to "acid rain". Harmful effects of pH are undoubtedly more pronounced in waters that are poor in other dissolved ions. Low concentrations of sodium, potassium, calcium and chloride are especially important and may limit the distributions of some aquatic animals even where pH is above 5.7. The concentration of sulphate ions is usually relatively high but this is not important to the fauna; concentrations are at least two times higher in productive alkaline water-bodies than they are in unproductive acid waters.

The ecology of chalk-stream invertebrates studied in a recirculating stream

To study and qualify the factors influencing interactions between various trophic levels in natural hard-water streams, a recirculating artificial stream channel was constructed. This structure has enabled patterns of population change of stream fauna to be observed under partially controlled physical and chemical conditions. Initial colonization of the substratum by invertebrates and subsequent succession was studied along with depth distribution and growth and production studies of invertebrates.

The classification and prediction of macroinvertebrate communities in British rivers

This article describes the progress of the River Communities Project which commenced in 1977. This project aimed to develop a sensitive and practical system for river site classification using macroinvertebrates as an objective means of appraising the status of British rivers. The relationship between physical and chemical features of sites and their biological communities were examined. Sampling was undertaken on 41 British rivers. Ordination techniques were used to analyze data and the sites were classified into 16 groups using multiple discrimination analysis. The potential for using the environmental data to predict to which group a site belonged and the fauna likely to be present was investigated.

An introduction to RIVPACS

RIVPACS (River InVertebrate Prediction And Classification System) is a software package developed by the Institute of Freshwater Ecology (IFE). The primary application is to assess the biological quality of rivers within the UK. RIVPACS offers site-specific predictions of the macroinvertebrate fauna to be expected in the absence of major environmental stress. The expected fauna is derived by RIVPACS using a small suite of environmental characteristics. The biological evaluation is then obtained by comparing the fauna observed at the site with the expected fauna. RIVPACS also includes a site classification based on the macroinvertebrate fauna of the component reference sites. New sites, judged by their fauna to be of high biological quality, may be allocated to classification groups within the fixed RIVPACS classification. This has potential for evaluating sites for conservation. In this chapter, the origins and history of the RIVPACS approach are described, including major scientific and operational developments over the life of the project. RIVPACS III is described in detail and predictions at different taxonomic levels are demonstrated. The value of the reference dataset for river management and conservation is examined, and the chapter concludes with a brief consideration of some future challenges.

Resultados de las campañas oceanográficas Mar del Plata I-V. Contribución al trazado de una carta bionómica del área de Mar del Plata. Las asociaciones del sistema litoral entre 12 y 70 m. de profundidad

Under the name of Campañas Oceanográficas Mar del Plata I-V, five oceanographic surveys were done together with the Servicio de Hidrografía Naval, in the area between Faro Querandí and Mar del Sur. (Argentina, Province of Buenos Aires). A total of 82 oceanographic stations were covered and physical-chemical (temperature, oxygen, salinity determinations), sedimental and biological samplings (plankton and bottom organisms) were obtained. Bottom organisms collections were made with a conventional type of dredge 1 meter wide and 46 cm high grame with a net of thin mesh 2,60 m. Macrofauna components were only considered. This data allowed us to attempt a bionomic and litological chart of the studied area.As the sediments seem to have great heterogeneity over the hole studied area, in many cases the bottom fauna collections belonged to defferent associations which made difficult the limitations of areas covered by each one. Anyway we can draw that we are very near the minimun limits.