Food web structure in a tropical stream ecosystem

Abstract

This study investigated the structure and properties of a tropical stream food web in a small spatial scale, characterizing its planktonic, epiphytic and benthic compartments. The study was carried out in the Potreirinho Creek, a second-order stream located in the south-east of Brazil. Some attributes of the three subwebs and of the conglomerate food web, composed by the trophic links of the three compartments plus the fish species, were determined. Among compartments, the food webs showed considerable variation in structure. The epiphytic food web was consistently more complex than the planktonic and benthic webs. The values of number of species, number of links and maximum food chain length were significantly higher in the epiphytic compartment than in the other two. Otherwise, the connectance was significantly lower in epiphyton. The significant differences of most food web parameters were determined by the increase in the number of trophic species, represented mainly by basal and intermediate species. High species richness, detritus-based system and high degree of omnivory characterized the stream food web studied. The aquatic macrophytes probably provide a substratum more stable and structurally complex than the sediment. We suggest that the greater species richness and trophic complexity in the epiphytic subweb might be due to the higher degree of habitat complexity supported by macrophyte substrate. Despite differences observed in the structure of the three subwebs, they are highly connected by trophic interactions, mainly by fishes. The high degree of fish omnivory associated with their movements at different spatial scales suggests that these animals have a significant role in the food web dynamic of Potreirinho Creek. This interface between macrophytes and the interconnections resultant from fish foraging, diluted the compartmentalization of the Potreirinho food web.

The structure of food webs along river networks

“…However, it is important to note that if we had included more highly resolved meiofaunal and macrofaunal taxa the connectance of the river food webs would likely have been even lower. For example, a recent highly resolved tropical stream food web in Brazil which included all food web compartments including fishes had an overall connectance of 0.05 (Motta and Uieda 2005). The distribution of taxa between top, intermediate, and basal levels in the river food webs were more similar to lake and pond webs that have higher proportions of intermediate species than other stream webs.…”

Estructura trófica de los invertebrados acuáticos asociados a Egeria densa (Planch. 1849) en el lago de Tota (Boyacá-Colombia)

“…Esta variable tiende a disminuir cuando la meiofauna es incluida, sugiriendo una compensación entre la integridad y la resolución taxonómica (Thompson et al, 2012) y cuando la riqueza de especies es alta (Murtaugh y Kollath, 1997;Montoya y Sole, 2003). Sin embargo, cuando el detritus es incluido como trofoespecie basal en las redes tróficas, la conectancia tiende a aumentar (Pimm et al, 1991), este valor tambien puede ser atribuido a la presencia de E. densa, ya que, provee un sustrato estable y estructuralmente más complejo que el sedimento y el plancton (Motta y Uieda, 2005).…”

Influence of a waterfall over richness and similarity in adjoining pools of an Atlantic Rainforest stream

“…However, the main sources of Schmid-Araya's compilation were studies performed in temperate environments. On the other hand, Motta and Uieda (2005), working on a tropical stream, found a 112 species richness that includes meiofaunal groups (Protozoans and accounted for more than 60% of the total variation of samples. The first axis separated the samples taken from upstream pool of those taken from downstream pool, while the second axis separated samples by substrate grain size.…”