Carbon sources of fish in an Amazonian floodplain lake

Abstract

In a tropical floodplain lake in central Amazon (L. Camaleao), we investigated seasonal shifts in primary carbon sources for commercially important fish species over an hydrological cycle. Carbon and nitrogen stable isotope and stomach content analyses were conducted to investigate the feeding preferences of six species with different feeding habits: Cichla monoculus (piscivorous species), Schizodon fasciatus (herbivorous), Prochilodus nigricans (detritivorous), and the omnivorous species Triportheus angulatus, Colossoma macropomum and Mylossoma duriventre. Stomach content and isotopic analyses exhibited a high seasonal variation for four out of the six species. The dominant food items were fruits and seeds, plant material, zooplankton and aquatic and terrestrial insects. Over the hydrological cycle, C-3 plants were the major carbon source for all fish species. In addition, seston and aquatic C-4 macrophytes were very important carbon sources for most species. Our findings underpin the complex trophic linkages between floodplain lakes and the aquatic terrestrial transition zone as postulated by the Flood Pulse Concept

Temporal variation of energy sources in a floodplain lake fish community

“…Terrestrial carbon from the riparian zone was the most important primary production that supported fish biomass in the spring, while it gave minor contributions in summer (Figures 3 and 4). Our results are similar to those presented by studies done on tropical (Wantzen et al 2002;Oliveira et al 2006) and temperate (Zeug and Winemiller 2008;Roach et al 2009) floodplain habitats. As low-water conditions result in contraction of aquatic habitats, newly expanded floodplain habitats provide an immediate influx of allochthonous detritus and invertebrates.…”

“…The inter-relationship between aquatic and terrestrial environments transports a great variety of food sources to the water column, strongly influencing consumer-resource interactions (Winemiller 2005;Oliveira et al 2006;Zeug and Winemiller 2008). Terrestrial carbon from the riparian zone was the most important primary production that supported fish biomass in the spring, while it gave minor contributions in summer (Figures 3 and 4).…”

“…Many chemical and biological factors are affected by seasonal water level fluctuation, and potential energy sources for aquatic food webs may differ between low-and high-water periods (Wantzen et al 2002;Oliveira et al 2006;Zeug and Winemiller 2008;Shoup and Wahl 2009;Wang, Yu, Li et al 2011a). Available food sources for fish may be limited and less varied during low-water periods, although flooding during high-water periods can bring fish in contact with a greater abundance and diversity of food sources, such as terrestrial plants (Wantzen et al 2002;Junk and Wantzen 2004;Zeug and Winemiller 2008;Roach et al 2009).…”

“…The subsequent development of mixing models also provides opportunities to quantitatively trace the contribution of multiple food sources entering the food web (Post 2002;Phillips and Gregg 2003;Newsome et al 2007). Investigations on multiple stable isotopes ( 13 C and 15 N) have successfully determined feeding relationships and energy flows in floodplain rivers and lakes (Wantzen et al 2002;Oliveira et al 2006;Herwig et al 2007;Zeug and Winemiller 2008;Roach et al 2009). For example, studies on floodplain rivers have demonstrated that terrestrial materials combined with algae production comprise an important energy source apart from macrophytes or phytoplankton (Herwig et al 2004(Herwig et al , 2007.…”

“…Stable isotope studies in tropical and temperate floodplain lakes show significant variations in the energy sources of fish as water level varies (Wantzen et al 2002;Reid et al 2008). In addition, C3 plants are the major carbon source for all fish species in the Amazonian floodplain (Oliveira et al 2006). There are few studies on food web dynamics of floodplain lakes in China.…”