DISTRIBUTION AND SALINITY ADAPTATIONS OF BANGIA ATROPURPUREA (RHODOPHYTA), A PUTATIVE MIGRANT INTO THE LAURENTIAN GREAT LAKES1

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Abstract
In a survey of the distribution of Bangia atropurpurea (Roth) Ag. along the north and east shorelines of the Laurentian Great Lakes, it was observed that this species was concentrated in the lower lakes. Asexual reproduction by monospore formation was the only form of reproduction in these populations. First generation germlings derived from these spores grew in a wide range of salinities from 1 to 26‰, but the rate was inversely proportional to salinity. In addition, acclimation of parent plants to freshwater or marine media prior to sporulation affected growth rates of first generation germlings placed into a series of salinities. By the second and third generation, germlings with a lineage of seawater showed a preference for the higher salinities, 19 and 26‰ Plants collected in Lake Ontario exhibited no decline in photosynthetic rate as salinity was raised by 13‰ for 15 min. At 26‰ the rate was reduced by half and thylakoids were disrupted in the region of the pyrenoid. On the other hand, third generation plants with a history of seawater attained maximum photosynthetic rates at 26‰ and contained a normal thylakoid organization. Three chromosomes were observed in these plants, which agrees with some of the previous findings for marine Bangia. Origins and taxonomic status of Bangia growing In the Great Lakes are discussed in light of these findings.

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