Carbon and nitrogen dynamics in a maritime Antarctic stream

• Published in: Freshwater Biology
• Main Author: DAVEY, MARTIN C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1993
• Subjects: Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/j.1365-2427.1993.tb00812.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2427.1993.tb00812.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.1993.tb00812.x

SUMMARY 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. 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. There was no net carbon or nitrogen accumulation by the marginal mat suggesting that uptake processes were balanced by loss processes. 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. 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. 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.