Summer biomass of a population of Phyllophora antarctica (Phyllophoraceae, Rhodophyta) from Antarctica

Abstract

Results of a study on summer biomass in aninfralittoral population of Phyllophora antarctica A.et E. S. Gepp from Terra Nova Bay (Ross Sea,Antarctica) are reported. The population studied grewat depths of 5 to 12 m. The highest value of biomass(1548 wet g m⁻²) was found at the end of January at6 m depth. Data showed that biomass depended mainly onthe presence or absence of large heavy specimens, eventhough these were always few in number. Moreover, thevery high number of specimens in weight classes 1 (upto 0.03 wet g) and 2 (> 0.03 to 0.06 wet g) recordedfrom December to January showed a relevant productionof new thalli in that period; the decrease of thetotal number of thalli from 8832 counted on 30December to 4384 counted on 10 February, showed someself-thinning in the population; the occurrence ofnumerous thalli belonging to weight classes 3 (>0.06 to 0.125 wet g), 4 (> 0.125 to 0.25 wet g) and5 (> 0.25 to 0.5 wet g) just at the end of December,allows to conclude that P. antarctica continues togrow, although at low rate, during the period ofwinter darkness. Finally, both the low number ofthalli of weight classes 6 (> 0.5 to 1 wet g) and 7(> 1 to 2 wet g) and the absence of thalli of theweight class 8 (> 2 wet g), recorded at the end ofDecember, indicate that most of specimens reachingduring the winter such weight classes (due to theirability to dark growth), died before summer.