Nit-rogen fixing blue-green algae as pioneer plants on Surtsey 1968-1 973 BY

• Main Author: G. Helmiit Schwaue
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Surtsey; Rogen
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.546.3303; http://www.surtsey.is/SRS_publ/1974-VII/1974_VII_2_04.pdf

Nitrogel1 is the most critical litniting major nut-trierlt in the terrestrial area of Surtsey ( H e n-rikssorl Pc H e n r i k s s o n 1974). If the water supply is sufficient, nitrogen undoubtedly limits the developrnent oil the algal vegetation. This finding is, among other tthings, supported by several hundred enrichment cultures which were kept in our laboratory during the study period. T h e cultures were set up on N-poor media, and were compared with controls containing slxffi-cient N, in which, the typical substrate types of Surtsey (lava, tephra of different grain sizes, fine fractions of windblown dust ancl sediments scoured out by precipitation) were tested in vary-ing quantities added to the nutrient medium. T h e resulting nurnber of species and the total production in all cases increased with the N-content of the medium, at least up to concen-trations of about 30 mg N (as NO:!) per 1000 rnl. Under these conditions, biological N-fixation is of great importance both in soil formation and in ecogenesis. I t has been apparent since 1968 that cornpared with nitrogen compounds, all other mineral nutrients are present in plentiful supply- some trace elements in toxic excess. T h e Cyanophyta,, a~nong which many are nitro-gen fixers, were collected and propagated in N-cleficient enrick~ment c~xlt~lres. T h e results of this work are only summarised here under the!leading of N-Eixing species sirice the processing of all the data will require more time. At the place of collection, sterile plates and nutrient solutions were illoculated with sub-strate samples. Other sarnples of the same sub-strate were also taken to the laboratory in I'liin and cultivated ill different media and under different conditions of light and temperature. T h e collectiolls 011 the island rvere made during 7 visits: