The production of algae growing on gravel in a chalk-stream

Marker, A.F.H. (1976) The production of algae growing on gravel in a chalk-stream. In: Forty-fourth annual report for the year ended 31st March 1976. Ambleside, UK, Freshwater Biological Association, (Annual Report, Freshwater Biological Association, Ambleside)

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Abstract

Epilithic algae, ie that growing on the surface of stones, was studied as part of the work on the energy flow of the chalk-stream ecosystem, by the River Laboratory. The study area was on Bere Stream and 2 neighbouring streams. The algal biomass was estimated from analysis of chlorophyll a. In Bere Stream the peak chlorophyll a cover occurred in April, while in the neighbouring streams, which have considerably lower nutrient levels, there was on peak. Assuming that 2% of a diatoms dry wt is chlorophyll a, then even in mid-April the biomass of epilithic algae amounted to no more than 15 g dry wt m Super(-2) of exposed gravel. Annual production was calculated to be > 15 times greater than biomass. The estimation of net primary production is always difficult for benthic floras and comparisons are especially difficult when different methods are used. But these figures contrast sharply with those for Ranunculus (water crowfoot) which has a ratio of annual production to maximal seasonal biomass of 1:16. The accumulation of algal biomass is apparently being prevented. Some organic matter may be excreted; some algae will be washed off the bed of the stream by current and grazing by herbivorous invertebrates will also tend to prevent algal accumulation.

Item Type: Book Section
Title: The production of algae growing on gravel in a chalk-stream
Personal Creator/Author:
CreatorsEmail
Marker, A.F.H.
Title of Book: Forty-fourth annual report for the year ended 31st March 1976
Refereed: No
Series Name: Annual Report, Freshwater Biological Association, Ambleside
Date: 1976
Publisher: Freshwater Biological Association
Place of Publication: Ambleside, UK
Issuing Agency: Freshwater Biological Association
Uncontrolled Keywords: Phytoplankton; Algae; England; Dorset; Annual report
Subjects: Biology
Ecology
Environment
Item ID: 5160
Depositing User: Mrs Christine Davey
Date Deposited: 10 May 2011 17:19
Last Modified: 29 Sep 2011 15:19
URI: http://aquaticcommons.org/id/eprint/5160

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