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Carbon and nitrogen dynamics in a maritime Antarctic stream
Author(s) -
DAVEY MARTIN C.
Publication year - 1993
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.1365-2427.1993.tb00812.x
Subject(s) - nitrogen , nutrient , perennial plant , environmental science , algal mat , nitrogen fixation , algae , cyanobacteria , carbon fibers , ecology , environmental chemistry , biology , chemistry , organic chemistry , composite number , bacteria , composite material , genetics , materials science
SUMMARY1 The carbon and nitrogen dynamics in a maritime Antarctic lake outflow stream were investigated. The stream and the algal communities could be split into two zones: a semi‐aquatic margin consisting of a perennial cyanobacteria/diatom mat and a flowing channel with a similar perennial mat that was overgrown by annual filamentous chlorophytes during the course of the summer. 2 Neither algal community was limited by nutrient availability. Major nutrients were always available in the stream water. There were slight differences in the atomic ratios of the mats, the N:P ratios in the channel mat being lower than those in the marginal mat. However, both these and the total dissolved N:P ratio in the stream water were all close to those that indicate a balanced supply. 3 There was no net carbon or nitrogen accumulation by the marginal mat suggesting that uptake processes were balanced by loss processes. 4 Maximum rates of carbon fixation (0.1–0.5mgCg −1 dry weight h −1 ) were similar to those of other perennial Antarctic algal mats. Productivity appeared to be limited by physical factors, but the effects of irradiance and temperature could not be separated. 5 There were no heterocystous cyanobacteria in the mat communities and rates of atmospheric nitrogen fixation were very low (0–10ngNmg −1 mat Nh −1 ). Fixation accounted for only 0.3% of the nitrogen accumulation of the channel mats, but was higher in the marginal mat where uptake of other sources of nitrogen was also low. 6 Nitrogen accumulation by the channel mat averaged 0.34gNm −2 day −1 . Only 0.05gNm −2 day −1 was accounted for by the uptake of dissolved inorganic nitrogen (nitrate plus ammonium). The major (80%) source of nitrogen appeared to be dissolved organic nitrogen. Recycling of nitrogen within the stream ecosystem may also be important.