title: Unimodal response of fish yield to dissolved organic carbon.
abstract: Here, we demonstrate a contrasting effect of terrestrial coloured dissolved organic material on the secondary production of boreal nutrient poor lakes. Using fish yield from standardised brown trout gill-net catches as a proxy, we show a unimodal response of lake secondary productivity to dissolved organic carbon (DOC). This suggests a trade-off between positive and negative effects, where the initial increase may hinge upon several factors such as energy subsidising, screening of UV-radiation or P and N load being associated with organic carbon. The subsequent decline in production with further increase in DOC is likely associated with light limitations of primary production. We also show that shallow lakes switch from positive to negative effects at higher carbon loads than deeper lakes. These results underpin the major role of organic carbon for structuring productivity of boreal lake ecosystems.
authors.affiliation: Norwegian Institute for Nature Research, P.O. 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Anders G
authors.initials: AG
authors.lastname: Finstad
authors.forename: Ingeborg P
authors.initials: IP
authors.lastname: Helland
authors.forename: Ola
authors.initials: O
authors.lastname: Ugedal
authors.forename: Trygve
authors.initials: T
authors.lastname: Hesthagen
authors.forename: Dag O
authors.initials: DO
authors.lastname: Hessen
mesh_terms: D000818:Animals; D018533:Biomass; D057486:Carbon Cycle; D005399:Fishes; D060106:Lakes; D009930:Organic Chemicals; D010944:Plants
chemical_list: D009930:Organic Chemicals
keywords: Brown trout; DOC; Salmo trutta; light; limiting factors; production