Plankton is an important constituent of aquatic ecosystems, dominated in freshwater ecosystems by diverse groups of bacterioplankton, phytoplankton, and zooplankton. The Plankton Ecology Group (PEG) has made noteworthy headway in understanding ecosystem dynamics through a series of formal PEG meetings (a brief update can be found in Lürling 2013). The most recent PEG Workshop was hosted by the National Autonomous University of Mexico, 12–18 February 2012 (Lürling et al. 2012), organized under the auspices of SIL. The meeting was attended by 125 participants from 9 countries, the majority (>60%) of whom were young, enthusiastic students from various post-graduate programs in Mexico. The PEG working group chairman, Dr. Miquel Lürling, in his introduction to the workshop highlighted the salient contributions of PEG to general ecological plankton theory. The first plenary lecture during this meeting was delivered by the president of SIL, Dr. Brian Moss, followed by regular contributions, both oral and poster. Following the workshop, it was decided to publish selected lectures in the SIL journal, Inland Waters (IW). An editorial committee formed to assist with the peer review process selected 9 manuscripts for publication in a special PEG issue of Inland Waters. The contributions in this issue represent a wide range of planktonic organisms, including toxic cyanobacteria, and the physical and chemical conditions under which the organisms occur. Some authors discuss the role of competition, predation, or both in freshwater ecosystems.