| Filamentous algal endophytes are common in many species of chemically defended macroalgae along the western Antarctic Peninsula. Effects of filamentous algal endophytes in macroalgal hosts are unknown, but may be detrimental to host due to competition for light and nutrients or pathogenic effects. Growth of three species of red Antarctic macroalgae were examined in situ under varying loads of endophyte infection. The experiment occurred at the end of the Austral summer and lasted approximately six to nine weeks until population senescence was imminent. Growth was measured through change in mass, change in surface area, growth rate, relative growth rate and surface area corrected growth rate, and survivorship were scored throughout the experiment. High infection was correlated to decreased growth and survival in Gymnogongrus turquetii and Trematocarpus antarcticus. The relationship between hosts and their endophytes is best described as innocuous in Myriogramme mangini. Deterioration of the hosts' thalli and decreased growth rates may be natural this late in the Austral summer, however effects of increased infection are still apparent. Endophyte infection significantly increased in all species throughout the experiment as did fecundity in tetrasporic M. mangini. All endophytes in this study were fully pigmented green and brown filamentous algae, most of which were never found growing host free, some of which may be obligate endophytes. |
