Get access

Spatial variability of the plankton trophic interaction in the North Sea: a new feature after the early 1970s

Authors

  • Marcos Llope,

    Corresponding author
    1. Sir Alister Hardy Foundation for Ocean Science (SAHFOS), The Laboratory, Plymouth, UK
    Current affiliation:
    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Oslo, Norway
    • Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Oslo, Norway
    Search for more papers by this author
  • Priscilla Licandro,

    1. Sir Alister Hardy Foundation for Ocean Science (SAHFOS), The Laboratory, Plymouth, UK
    Search for more papers by this author
  • Kung-Sik Chan,

    1. Department of Statistics and Actuarial Science, University of Iowa, Iowa City, IA, USA
    Search for more papers by this author
  • Nils Chr. Stenseth

    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Oslo, Norway
    2. Flødevigen Marine Research Station, Institute of Marine Research, His, Norway
    Search for more papers by this author

Correspondence: Present address: Marcos Llope, Instituto Español de Oceanografía, Centro Oceanográfico de Cádiz, Puerto Pesquero, Muelle de Levante s/n, PO Box 2609, E-11006 Cádiz, Andalucía, Spain, tel. + 34 956294189, fax + 34 956294232, e-mail: marcos.llope@cd.ieo.es

Abstract

Traditionally, marine ecosystem structure was thought to be bottom-up controlled. In recent years, a number of studies have highlighted the importance of top-down regulation. Evidence is accumulating that the type of trophic forcing varies temporally and spatially, and an integrated view – considering the interplay of both types of control – is emerging. Correlations between time series spanning several decades of the abundances of adjacent trophic levels are conventionally used to assess the type of control: bottom-up if positive or top-down if this is negative. This approach implies averaging periods which might show time-varying dynamics and therefore can hide part of this temporal variability. Using spatially referenced plankton information extracted from the Continuous Plankton Recorder, this study addresses the potential dynamic character of the trophic structure at the planktonic level in the North Sea by assessing its variation over both temporal and spatial scales. Our results show that until the early-1970s a bottom-up control characterized the base of the food web across the whole North Sea, with diatoms having a positive and homogeneous effect on zooplankton filter-feeders. Afterwards, different regional trophic dynamics were observed, in particular a negative relationship between total phytoplankton and zooplankton was detected off the west coast of Norway and the Skagerrak as opposed to a positive one in the southern reaches. Our results suggest that after the early 1970s diatoms remained the main food source for zooplankton filter-feeders east of Orkney–Shetland and off Scotland, while in the east, from the Norwegian Trench to the German Bight, filter-feeders were mainly sustained by dinoflagellates.

Get access to the full text of this article

Ancillary