Spatial and temporal variance in fatty acid and stable isotope signatures across trophic levels in large river systems

River Research and Applications
By: , and 

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Abstract

Fatty acid and stable isotope signatures allow researchers to better understand food webs, food sources, and trophic relationships. Research in marine and lentic systems has indicated that the variance of these biomarkers can exhibit substantial differences across spatial and temporal scales, but this type of analysis has not been completed for large river systems. Our objectives were to evaluate variance structures for fatty acids and stable isotopes (i.e. δ13C and δ15N) of seston, threeridge mussels, hydropsychid caddisflies, gizzard shad, and bluegill across spatial scales (10s-100s km) in large rivers of the Upper Mississippi River Basin, USA that were sampled annually for two years, and to evaluate the implications of this variance on the design and interpretation of trophic studies. The highest variance for both isotopes was present at the largest spatial scale for all taxa (except seston δ15N) indicating that these isotopic signatures are responding to factors at a larger geographic level rather than being influenced by local-scale alterations. Conversely, the highest variance for fatty acids was present at the smallest spatial scale (i.e. among individuals) for all taxa except caddisflies, indicating that the physiological and metabolic processes that influence fatty acid profiles can differ substantially between individuals at a given site. Our results highlight the need to consider the spatial partitioning of variance during sample design and analysis, as some taxa may not be suitable to assess ecological questions at larger spatial scales.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spatial and temporal variance in fatty acid and stable isotope signatures across trophic levels in large river systems
Series title River Research and Applications
DOI 10.1002/rra.3295
Volume 34
Issue 7
Year Published 2018
Language English
Publisher John Wiley & Sons Ltd.
Contributing office(s) Upper Midwest Environmental Sciences Center
Description 10 p.
First page 834
Last page 843