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Effects of concentrating phytoplankton on the acetylene‐reduction assay for nitrogenase activity
Author(s) -
LEONARDSON LARS
Publication year - 1983
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.1365-2427.1983.tb00676.x
Subject(s) - nitrogenase , phytoplankton , algae , heterocyst , environmental chemistry , plankton , photorespiration , biology , photosynthesis , nitrogen fixation , cyanobacteria , botany , ecology , chemistry , nutrient , bacteria , genetics
SUMMARY.1 The consequences of concentrating freshwater phytoplankton communities prior to measurement of nitrogenase activity using the acetylene‐reduction assay were investigated. 2 Retention of heterocystous blue‐green algae by 10 and 45 öm plankton nets was usually much less than 100% and the percent retention differed among blue‐green algal species and varied for the same species both on different sampling dates and in different lakes. Retention of heterocyst numbers and helerocyst volume during concentration differed from that of total cell volume of heterocystous blue‐green algae. 3 Effects of concentration on specific nitrogcnase activity varied among the lakes studied. In Lake Bysjön activity decreased on all sampling occasions, in Lake Trummen there was no apparent effect, and in Lake Vaxjosjon both results were found. 4 Effects on nitrogenase activity of mechanical disturbance during concentration and of increased pH. reduced carbon availability. light inhibition and subsaturation. photorespiration and oxygen supersaturation in concentrated samples are discussed. Interactions between these factors are suggested to explain the varying responses in the three lakes. 5 It is concluded that phytoplankton should not be concentrated in the acetylene‐reduction assay for nitrogenase activity, since both volumetric and cell concentration factors are inadequate and effects of concentration on specific nitrogenase activity are not predictable.