Gloeotrichia echinulata blooms in an oligotrophic lake: helpful insights from eutrophic lakes

Nuisance algal blooms are widely reported from eutrophic and hypereutrophic systems, but are relatively rare in oligotrophic systems. Recently, the cyanobacterium Gloeotrichia echinulata has begun blooming in oligotrophic to mesotrophic lakes in the northeastern USA. We explored whether existing knowledge about G. echinulata, derived from eutrophic systems, would be useful in predicting the recruitment dynamics of G. echinulata in an oligotrophic lake in central New Hampshire, USA. Our results indicate that, as in eutrophic lakes, there was a seasonal peak in both recruitment and surface abundance, with colonies recruiting from shallow (2 m) but not deep ( 5 m) sediments. Recruitment provided approximately 20–45% of the colonies to the 2005 G. echinulata surface bloom, within the range reported for eutrophic lakes. Thus, we conclude that observations of G. echinulata in eutrophic systems may be useful in predicting G. echinulata recruitment dynamics in oligotrophic lakes. Moreover, recruitment from the sediments appears to be an important mechanism that allows G. echinulata to bloom in lowas well as high-nutrient lakes. This benthic-pelagic coupling may, over time, result in an important transfer of nutrients in such oligotrophic lakes.