ISSN:
1573-5117
Keywords:
algae
;
biomass
;
chalk stream
;
soft water stream
;
chlorophyll content
;
epilithon
;
production
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Microscopic epilithic algae in the River Itchen at Otterbourne near Southampton and in the Ober Water in the New Forest were studied during 1984 and 1985. The River Itchen rises from chalk springs and has a steady pH near 8.2 and a mean alkalinity of 236 mg HCO3 1−1; at the study site the river is about 16 m wide and 20 cm deep, with a mean flow rate of 0.33 m s−1 and a discharge ranging through the year between 0.34 and 2.46 m3 s−1. The Ober Water, which drains sands and gravels, has a pH between 6.9 and 7.2 and a mean alkalinity of about 50 mg HCO3 1−1; at the study site it is about 6 m wide, with a mean flow rate of 0.27 m s−1 and a discharge ranging through the year between 0.08 and 1.0 m3 s−1. Epilithic algae removed from the pebbles that form the major part of the beds of both streams show seasonal changes in abundance and composition. Diatoms peaked in April/May and dominate the epilithic flora in both streams, comprising 70–95% of all algal cells; highest numbers of chlorophytes occurred in summer and cyanophytes increased in autumn. The species composition of the epilithic flora in the two streams was different, as was the population density; algal cell numbers ranged between 500 and 7000 cells mm−2 of stream floor in the River Itchen and between 8 and 320 cells mm−2 of stream floor in the Ober Water. The chlorophyll a content of epilithic algae in the River Itchen ranged between 115 and 415 mg m−2 of stream floor, representing an annual mean biomass of about 8 g m−2, whereas in the Ober Water a chlorophyll a content of 2.2 to 44 mg m−2 of stream floor was found, representing an annual mean biomass of about 1 g m−2. Cautious estimates of the annual production of epilithic algae in these streams suggest a value of about 600 g organic dry weight m−2 in the River Itchen and about 75 g m−2 in the Ober Water.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00005637
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