Phytobenthos of the River Tees and its tributaries

SUMMARY. A standard method is given for describing plant communities in fast-flowing streams and rivers. This involves the selection of a representative 10-m length of stream (termed a reach) which can be re-located exactly. Various estimates of the relative areas covered by different physiognomic forms and the relative proportions of species present are then combined to give a 'semi-quantitative' account, which can be compared with data collected at other sites or times. The method has been applied to six sites on the River Tees system. A site below Cow Green reservoir with markedly regulated flows, differs from the others in various ways. Bryophytes show a greater cover here than elsewhere throughout the year and a conspicuous cover of Phormidium occurs in autumn. Filamentous green algae of many different species are abundant at this site in late summer and early autumn. At the most downstream site where such seasonal growths also occur, a single species, Cladophora glomerata , is dominant. Conspicuous spring diatom 'bursts' occurred at the two upstream sites and a month later at the two downstream sites.