Variation in basal production sources supporting fish trophic guilds in the channel and floodplain ponds of the Rupununi River, Guyana, during dry season isolation

This is the authors' abstract. We don't add key points for this paper.

Most tropical rivers have a seasonal flood pulse that connects channel and floodplain habitats and facilitates entrance of allochthonous resources into the aquatic food web. Dry season isolation of floodplain habitats should result in greater spatial variation in production sources supporting aquatic food webs and greater input of autochthonous sources. We performed stable isotope analysis on tissue samples from fishes and basal production sources from the channel and three floodplain ponds of the Rupununi River, Guyana, to estimate assimilation of material originating from basal sources by five trophic guilds. Seston was the principal source assimilated by fish trophic guilds at each location, with the only exceptions being invertivores and piscivores inhabiting the river channel. Terrestrial plants were estimated to be the most important basal source supporting piscivores, possibly reflecting a time lag for basal source materials to pass several steps up food chains. Between-pond variation in proportions of basal resources assimilated by guilds was associated with differences in water depth and density of aquatic macrophytes. Findings further support the importance of autochthonous production sources for aquatic food webs of tropical rivers during the dry season and the role of floodplain heterogeneity in creating spatial variation in food web dynamics.