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Aspects of nitrogen fixation in Lough Neagh. I. Acetylene reduction and the frequency of Aphanizomenon flos‐aquae heterocysts
Author(s) -
RIDDOLLS ANTHEA
Publication year - 1985
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1985.tb00201.x
Subject(s) - aphanizomenon , heterocyst , nitrogenase , nitrogen fixation , acetylene , cyanobacteria , nitrogen , botany , biology , environmental chemistry , chemistry , anabaena , bacteria , genetics , organic chemistry
SUMMARY.1 An investigation was made of the relationships between rates of nitrogen fixation (acetylene reduction), Aphanizomenon flosaquae heterocysts, NO 3 ‐N concentration and other environmental factors which occurred in Lough Neagh between 1969 and 1972. 2 The maxima of cells differentiated as heterocysts (approximately 5% (1970), and approximately 7% (1971 and 1972) occurred when NO 3 ‐N concentration was very low or undetectable. 3 Acetylene reduction was detectable between 16 May and 8 September 1972 but was not measured in the other years. Rates were greatest in the euphotic zone and it appeared that the nitrogenase activity was closely linked to a light dependent system. 4 Areal rates of acetylene reduction were highly correlated with Aphanizomenon heterocyst concentration ( r =0.92). There was some indication that a release of phosphorus from the sediments might have stimulated Aphanizomenon nitrogen fixation on one occasion at the end of a calm period. Results show that the most likely conditions for the development of large crops of heterocystous species in Lough Neagh include a scarcity of NO 3 ‐N and a plentiful supply of phosphorus.