Temperature requirements of growth and temperature tolerance of macroalgae endemic to the Antarctic Region

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Abstract
Temperature requirements for growth and upper temperature tolerance were determined in 6 brown algal and 1 red algal species endemic to the Antarctic region. In microthalli of Himantothallus grandifolius, Phaeurus antarcticus, Desmarestia anceps and in a ligulate member of Desmarestia (Desmarestiales) growth was possible from 0.degree. C up to between 10 and 15.degree. C, and maximum survival temperatures were between 13 and 16.degree. C. Desmarestialean macrothalli grew optimally between 0 and 5.degree. C (next temperature tested; 10.degree. C) and exhibited upper survival temperatures of 11 to 13.degree. C. The upper survival temperature of microthalli of Elachista antarctica (Chordariales) was 18.degree. C. Ascoseira mirabilis (Ascoseirales) grew 0 up to 10.degree. C and survived 11.degree. C. Palmaria decipiens (Palmariales) grew 0 up to 10.degree. C (next temperature tested: 15.degree. C) and maximum survival temperature was 16 to 17.degree. C. All considered algae are stenotherm cold water species. Their northern distribution is determined by the winter temperature, just low enough [.ltoreq. 5 (or 10) .degree.C], to allow sufficient growth of the most temperature-sensitive stage in the life cycles of the studied species. Temperature tolerance does not limit algal distribution.