The role of secondary metabolites in an Antarctic ecosystem

     Secondary metabolites are produced by a variety of plants and animals.  The roles in the ecosystem and the mechanisms of action for these compounds are not always well understood.  In this preliminary study, our objectives were to identify and document the effects of secondary metabolites in nascent freshwater lake ecosystems of Antarctica.  These lake systems have developed over the past forty to fifty years and remain unfrozen for most of the year.  They are populated by cyanobacterial mats which produce large amounts of secondary metabolites.  In addition, several lichen species are located around the lakes, adding metabolites indirectly via run-off and directly through the physical deposition of lichens in the lakes.  Our hypotheses were that extracts from the mats and (+)-usnic acid from the lichens were limiting and controlling the population of invertebrates that live in the lake systems.  Our results determined that only high concentrations of cyanobacterial extracts (67 & 100 ppm) affected the copepod populations.  (+)-Usnic acid caused high mortality at all concentrations except 0.1 ppm, therefore indicating a role in these lake ecosystems.  From our results we believe that this compound inhibits respiration.  As primary succession continues in this ecosystem, chemical ecology appears to play an important role in ecosystem development.