MEPS 454:119-133 (2012)  -  DOI:

Phenological trends and trophic mismatch across multiple levels of a North Sea pelagic food web

Sarah Burthe1,*, Francis Daunt1, Adam Butler2, David A. Elston3, Morten Frederiksen1,4, David Johns5, Mark Newell1, Stephen J. Thackeray6, Sarah Wanless1

1Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK
2Biomathematics and Statistics Scotland, The Kings Buildings, Edinburgh EH9 3JZ, UK
3Biomathematics and Statistics Scotland, Craigiebuckler, Aberdeen AB15 8QH, UK
4Dept. of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
5Sir Alister Hardy Foundation for Ocean Science, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
6Centre for Ecology & Hydrology, Lancaster Environment Centre, Bailrigg, Lancaster LA1 4AP, UK

ABSTRACT: Differential phenological responses to climate among species are predicted to disrupt trophic interactions, but datasets to evaluate this are scarce. We compared phenological trends for species from 4 levels of a North Sea food web over 24 yr when sea surface temperature (SST) increased significantly. We found little consistency in phenological trends between adjacent trophic levels, no significant relationships with SST, and no significant pairwise correlations between predator and prey phenologies, suggesting that trophic mismatching is occurring. Finer resolution data on timing of peak energy demand (mid-chick-rearing) for 5 seabird species at a major North Sea colony were compared to modelled daily changes in length of 0-group (young of the year) lesser sandeels Ammodytes marinus. The date at which sandeels reached a given threshold length became significantly later during the study. Although the phenology of all the species except shags also became later, these changes were insufficient to keep pace with sandeel length, and thus mean length (and energy value) of 0-group sandeels at mid-chick-rearing showed net declines. The magnitude of declines in energy value varied among the seabirds, being more marked in species showing no phenological response (shag, 4.80 kJ) and in later breeding species feeding on larger sandeels (kittiwake, 2.46 kJ) where, due to the relationship between sandeel length and energy value being non-linear, small reductions in length result in relatively large reductions in energy. However, despite the decline in energy value of 0-group sandeels during chick-rearing, there was no evidence of any adverse effect on breeding success for any of the seabird species. Trophic mismatch appears to be prevalent within the North Sea pelagic food web, suggesting that ecosystem functioning may be disrupted.

KEY WORDS:Timing of breeding · Climate change · Prey size · Ammodytes marinus · Winter NAO · Long-term studies · Zooplankton · Phytoplankton

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Cite this article as: Burthe S, Daunt F, Butler A, Elston DA and others (2012) Phenological trends and trophic mismatch across multiple levels of a North Sea pelagic food web. Mar Ecol Prog Ser 454:119-133.

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