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Marine Ecology Progress Series

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MEPS 498:73-84 (2014)  -  DOI:

Interactions among density, climate, and food web effects determine long-term life cycle dynamics of a key copepod

Saskia A. Otto1,2,*, Georgs Kornilovs3, Marcos Llope4, Christian Möllmann2

1Stockholm Resilience Centre, Stockholm University, Kräftriket 2b, 10691 Stockholm, Sweden
2Institute for Hydrobiology and Fisheries Science, Center for Earth System Research and Sustainability (CEN), KlimaCampus, University of Hamburg, Grosse Elbstrasse 133, 22767 Hamburg, Germany
3Department of Fish Resources Research, Institute of Food Safety, Animal Health and Environment, Daugavgrivas str. 8,
1048 Riga, Latvia
4Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Cádiz, Puerto Pesquero, Muelle de Levante s/n, PO Box 2609, 11006 Cádiz, Andalucía, Spain
*‑Corresponding author:

ABSTRACT: Increasing pressure on animal populations through climate change and anthropogenic exploitation fuel the need to understand complex life cycle dynamics of key ecosystem species and their responses to external factors. Here, we provide a novel, integrative study on the long-term population dynamics of Pseudocalanus acuspes, a key species in the Baltic Sea, explicitly considering its distinct life-history stages, and testing for linear, non-linear, and non-additive climate and food web effects. Based on a unique data set of stage-specific abundance covering almost 5 decades of sampling (1960 to 2008, with 1408 samples), we use generalized additive modeling (GAM) and its respective non-additive threshold (TGAM) formulation to test for (1) density effects on subsequent life-history stages within the internal life cycle, (2) the effect of exogenous bottom-up (i.e. hydro-climatic) and top-down (i.e. predation) pressures, and (3) changes between bottom-up and top-down regulation. We show that linear density effects are always present, explaining a high proportion of interannual variability, while effects of external pressures are non-linear or non-additive and strongly stage- and season-specific. In general, younger stages of P. acuspes are more affected by atmospheric winter conditions and water temperature, whereas older stages are influenced by conditions of deepwater salinity and predation pressure. These bottom-up processes, however, are not necessarily stable, and can depend on the level of top-down predation pressure. Our study demonstrates the complex and non-stationary interplay between internal and external factors regulating long-term animal population dynamics.

KEY WORDS: Life cycle dynamics · Climate change · Internal and external effects · Generalized additive modeling · Top-down vs. bottom-up control · Non-additive effects · Zooplankton

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Cite this article as: Otto SA, Kornilovs G, Llope M, Möllmann C (2014) Interactions among density, climate, and food web effects determine long-term life cycle dynamics of a key copepod. Mar Ecol Prog Ser 498:73-84.

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