Effect of temperature on nutrient cycling associated to the elemental relationship of a stream shredder and its food resource.

CALAPEZ, A.; DÍAZ VILLANUEVA, V.; CANHOTO, C.; ALBARIÑO, R.J.

Huelva, Espana

Congreso; IV Congreso Ibérico de Limnología; 2008

Universidad de Huelva

Metabolic rates increase with temperature, regulating the rates at which material resources are taken up from the environment, used for biological structure and function, and excreted back into the environment. In this regard, global warming may affect stoichiometric relationships and nutrient cycling by accelerating biological rates of organisms that face strong elemental imbalances with their food resources. Although organism metabolic rates will increase as result of a higher temperature, we hypothesized that no change in the elemental composition of its body (C:N:P) would occur. In contrast, N and P recycling (excretion and egestion rates) of those organisms are expected to increase with temperature but their responses may vary with contrasting food resources. With this purpose, the stream shredder Sericostoma vittatum was fed on three different single leaf diets: Alnus glutinosa, Quercus robur and Eucalyptus globulus, at 15º or 20º C, for 10 days. We measured larval consumption, egestion, excretion and respiration rates at each temperature X diet treatments, and analysed P and N content in food resource, consumer body, faeces and soluble wastes to estimate and compare C:N:P ratios of those ecological compartments. Consumer stoichiometry was strict in larvae among resources but not between temperatures (C:N body ratios were lower at 20º C). Temperature increased respiration and N cycling, but its effects on excretion and egestion rates changed with leaf species. In Q. robur and E. globulus diets, temperature increased N excretion while in A. glutinosa it increased N egestion. Results indicate that temperature may alter the quantity and quality of the metabolic end-products of detritus feeders but this effect may depend on food resource nature.