Allochthonous organic carbon can subsidize consumers in aquatic systems, but this subsidy may only be significant in relatively small systems with high organic matter loading. We tested the importance of allochthonous carbon to consumers in a relatively large (258,000 m 2 ) clear‐water lake by adding H 13 CO 3 daily for 56 d. Dissolved inorganic carbon (DIC) was substantially enriched in 13 C by the addition, but it was also v...

In many small aquatic ecosystems, watershed loading of organic C exceeds autochthonous primary production. Although this allochthonous organic C has long been thought of as refractory, multiple lines of evidence indicate that substantial portions are respired in the receiving aquatic ecosystem. To what extent does this terrestrial C support secondary production of invertebrates and fish? Do current models adequately trace the...

Net ecosystem production (NEP) is the difference between gross primary production (GPP) and community respiration (R). We estimated in situ NEP using three independent approaches (net CO 2 gas flux, net O 2 gas flux, and continuous diel O 2 measurements) over a 4–7 yr period in a series of small lakes in which food webs were manipulated and nutrient loadings were experimentally varied. In the absence of manipulation, these lak...

Wildlife refuges are sites of dense aggregations of wintering waterfowl. Refuge managers are concerned about local water‐quality effects and the amount of birdborne nutrient load that might cause eutrophication in roosting ponds and(or) be exported to downstream systems. We initiated this research effort to test the hypothesis that daily feeding migrations by geese represented a significant source of nutrients to wetland syste...

Both harvest rates and food web interactions may be altered through use of different gill net mesh sizes in the fisheries of Lake Victoria, East Africa. Thus, conservation of the native ichthyofauna is intimately linked to patterns of exploitation in the fisheries. We used bioenergetics modeling to estimate the harvest rates of introduced Nile perch (Lates cf. niloticus) and changes in their predation rates on other important...

Phytoplankton biomass and production in lakes tend to be increased by phosphorus input and decreased by grazing or high levels of colored, dissolved organic carbon (DOC). We estimated and compared the effects of these three factors by using data from three lakes that were manipulated during 1991–1995, and data from a reference lake. Multivariate probability distributions of chlorophyll or primary production, as predicted by P...

Piscivorous fish play an important role in regulating lake food web structure. However, most ultimately piscivorous fish pass through a period of planktivory before becoming piscivorous. In 1993 and 1994, two large cohorts of young‐of‐the‐year largemouth bass ( Micropterus salmoides ) were recorded in Paul Lake, Michigan. The 1993 and 1994 cohorts were the largest recorded in data extending back to 1984 and occurred during a p...