Temporal changes in essential fatty acid availability in different food sources in the littoral macrophyte zone

In littoral environments, different food resources are available for zooplankters. In addition to seston, species may feed on biofilms growing on sediments, plants (epiphyton), and at the air–water interface (neuston). However, despite a growing interest in these different biofilms, little is known about their food quality for microcrustaceans. In a field study, we measured changes in the food quality over time in terms of the essential fatty acid (EFA) content of different potential food sources for littoral consumers. The food quality of seston, neuston, and epiphyton growing on three different aquatic macrophytes were assessed. Our results showed that there is an important seasonal variability within each food source. However, in the system studied, epiphytic biofilms, especially those of Ludwigia and Callitriche offered the highest food quality, in terms of EFA content, throughout the year. As the highest EFA concentrations in each food source were found consecutively, high concentrations of these physiologically important compounds are maintained in the system throughout the year. Therefore, greater diversity of food resources could affect ecosystem productivity.