Marine Biology

, Volume 142, Issue 6, pp 1131–1140 | Cite as

Environmental correlates of large-scale spatial variation in the δ15N of marine animals

  • S. JenningsEmail author
  • K. J. Warr


Nitrogen stable isotopes can be used to estimate the trophic position of consumers in food webs. However, the nitrogen stable isotope ratios (δ15N) of primary producers at the base of food webs are highly variable and must be accounted for in these estimates. To assess spatial variation in the δ15N of primary producers, we measured the δ15N of phytoplankton-feeding bivalve molluscs (queen scallops Aequipecten opercularis) at sites in the north-east Atlantic (Irish Sea, English Channel, North Sea). Queen scallops are good monitors of spatial patterns in the δ15N of phytoplankton because their slow rate of tissue turnover integrates variability in the δ15N of their diet. A significant proportion of spatial variation in δ15N was statistically explained by widely recorded environmental variables such as salinity, depth and temperature. Accordingly, we developed a linear model to predict and map large-scale spatial patterns in scallop δ15N from the environmental variables. We used the model, in conjunction with new data on the spatial variation in δ15N of two predatory fishes, to show that 51% and 77% of spatial variance in dab Limanda limanda and whiting Merlangius merlangus δ15N, and hence apparent trophic level, could be attributed to differences in δ15N at the base of the food chain. Since temperature and salinity are correlated with base δ15N, and since gradients in these physical variables are particularly pronounced in coastal areas and close to estuaries, spatial comparisons of trophic position are easily biased if fine-scale information on base δ15N is not available. Conversely, in offshore regions, where temperature and salinity show little variation over large areas, variations in base δ15N and the associated bias will be less.


Phytoplankton Trophic Position Isotope Ratio Mass Spectrometry Shell Height Beam Trawl 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank Anne Bruce and Rowan White for conducting the stable isotope analysis, Jon Barry and Mike Nicholson for statistical advice and analyses, Tracy Dinmore and the officers and crew of R.V. "Corystes" and R.V. "Cirolana" for help with sampling, Keith Weston, Ruth Parker and Dave Mills for useful information on phytoplankton ecology and the referees for useful comments that helped to clarify the text. We thank CEFAS (DP166) and the DEFRA MF07 'Impacts of fishing' programme (MF0731) for funding this research.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Centre for Environment, Fisheries and Aquaculture ScienceLowestoft LaboratoryLowestoftUK

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