Aquatic Food Web Structure and the Flow of Carbon

Abstract

Abstract Carbon cycling is a cornerstone concept of ecosystem ecology, which has implications for climate change, ecosystem health, and human activities. This review investigates pathways of carbon within freshwater ecosystems, the role of terrestrial carbon in food webs, and the effects of food web structure on C emissions. Carbon may co-limit primary production even in waters super-saturated with CO2. Allochthonous carbon-subsidies make most lakes and rivers net heterotrophic; however, the use of carbon-subsidies by the food web (FW) may be limited by low nutritional quality of terrestrial C-compounds and the inability of bacteria to synthesise polyunsaturated fatty acids (PUFA), which are essential for metazoan growth. Bacterivorous nanoflagellates which can synthesise PUFA are likely to create a channel connecting allochthonous C with metazoan production in some water bodies. Published studies suggest that FW structure may affect: carbon fluxes in and out of lake ecosystems; carbon accumulation and di...