title: Community structure influences species' abundance along environmental gradients.
abstract: Species' response to abiotic environmental variation can be influenced by local community structure and interspecific interactions, particularly in restricted habitats such as islands and lakes. In temperate lakes, future increase in water temperature and run-off of terrestrial (allochthonous) dissolved organic carbon (DOC) are predicted to alter community composition and the overall ecosystem productivity. However, little is known about how the present community structure and abiotic environmental variation interact to affect the abundance of native fish populations. We used a space-for-time approach to study how local community structure interact with lake morphometric and climatic characteristics (i.e. temperature and catchment productivity) to affect brown trout (Salmo trutta L.) yield in 283 Norwegian lakes located in different biogeographical regions. Brown trout yield (based on data from standardized survey gill net fishing; g 100 m(-2) gill net night(-1)) was generally lower in lakes where other fish species were present than in lakes with brown trout only. The yield showed an overall negative relationship with increasing temperature and a positive relationship with lake shoreline complexity. Brown trout yield was also negatively correlated with DOC load (measured using Normalized Difference Vegetation Index as a proxy) and lake size and depth (measured using terrain slope as a proxy), but only in lakes where other fish species were present. The observed negative response of brown trout yield to increasing DOC load and proportion of the pelagic open-water area is likely due to restricted (littoral) niche availability and competitive dominance of more pelagic fishes such as Arctic charr (Salvelinus alpinus (L.)). Our study highlights that, through competitive interactions, the local community structure can influence the response of a species' abundance to variation in abiotic conditions. Changes in biomass and niche use of top predators (such as the brown trout), associated with predicted changes in direct and indirect climatic factors, may have further influences on the structure and function of temperate lake ecosystems.
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Antti P
authors.initials: AP
authors.lastname: Eloranta
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Ingeborg P
authors.initials: IP
authors.lastname: Helland
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Odd T
authors.initials: OT
authors.lastname: Sandlund
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Trygve
authors.initials: T
authors.lastname: Hesthagen
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: Ola
authors.initials: O
authors.lastname: Ugedal
authors.affiliation: Norwegian Institute for Nature Research (NINA), P.O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.|Department of Natural History, NTNU University Museum, Erling Skakkes gate 47A, NO-7013, Trondheim, Norway.
authors.forename: Anders G
authors.initials: AG
authors.lastname: Finstad
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology; D044822:Biodiversity; D005398:Fisheries; D060106:Lakes; D008954:Models, Biological; D009664:Norway; D011156:Population Density; D014337:Trout / Q000502:physiology*
keywords: biogeography; catchment characteristics; climate change; habitat structure; lake morphometry; light condition; resource competition; secondary production