© 1991 by The Society for Integrative and Comparative Biology
Ecological Studies of Seaweeds in McMurdo Sound, Antarctica1
Herbarium, University of California Berkeley, California 94720
Institute of Marine Sciences and Biology Board of Studies, University of California Santa Cruz, California 95064
Three species of benthic marine macroalgae comprise the chief components of the seaweed flora of McMurdo Sound, Antarctica. Quantitative studies at Cape Evans demonstrate a depth-related distribution pattern, with Iridaea cordata (Turner) Bory in shallow water, Phyllophora antarctica A. and E. S. Gepp abundant and fertile at intermediate depths, and Leptophytum coulmanicum (Foslie) Adey dominant below 20 m. The vertical distribution of species is correlated with irradiance levels. At sites with thinner annual sea ice and less snow accumulation (e.g., Cape Evans, Cape Royds, and Granite Harbor), vertical distributions are shifted downward relative to those at sites that remain covered most of the year with thick or snow-covered fast ice (e.g., Cape Armitage and New Harbor). Disturbance caused by ice scour and anchor ice probably determines the upper limit of algal distribution; herbivory is apparently absent.
There is a disproportionate representation of cystocarpic female gametophytes in populations of I. cordata and P. antarctica. Perennation via persistent basal crusts and apogamic recycling of gametophytes are suggested as factors structuring phase distribution. Although the overall size of I. cordata blades is greater (and cystocarpic plants more abundant) at Cape Royds than at Cape Evans, cystocarpic blades are similar in minimum size at both sites, indicating a threshhold size or age for the onset of reproduction in this species.