Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

Abstract

The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and foodchain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types.ecological efficiency ͉ ecological stoichiometry ͉ fish ͉ zooplankton ͉ phytoplankton

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

“…Stoichiometric arguments based on light and nutrient levels indicate that while increases in light at low irradiance levels may increase phytoplankton biomass and thus zooplankton growth, high light levels may reduce the nutritional quality of phytoplankton for higher trophic levels (Urabe and Sterner 1996;Dickman et al 2008). Two important consequences of this are that more transparent lakes have lower food quality (higher carbon : phosphorus [C : P]) in the surface waters (Sterner et al 1997) and that the food in the DCM is likely to be of higher nutritional quality than that in the surface waters (Rothhaupt 1991).…”

Roles of phosphorus and ultraviolet radiation in the strength of phytoplankton‐zooplankton coupling in a Mediterranean high mountain lake

“…Durant et al (2005) showed that food resources and consumer levels also determine the strength of PZC. Other characteristics that have been identified to qualitatively affect the strength of PZC include food quality (Dickman et al 2008), phytoplankton taxonomic composition (Auer et al 2004), zooplankton diversity (McCann et al 1998), alternative food resources such as microphytobenthos or microbial communities (Rautio and Vincent 2006), and zooplankton predators (Hessen et al 2006;Dickman et al 2008). All of these might be influenced by global stressors.…”

The effects of the psychiatric drug carbamazepine on freshwater invertebrate communities and ecosystem dynamics

“…Aquatic invertebrates, particularity those that bioturbate sediments, alter the flux of nutrients into water , Palmer et al 2000. Changes in nutrient concentrations may lead to changes in the efficiency of energy transfer through food chains (Dickman et al 2008). Additionally, changes in nutrient concentrations may influence other ecosystem functions such as primary production and decomposition, as identified in this study ( Palmer et al 2000).…”