title: Disentangling the mechanisms behind climate effects on zooplankton.
abstract: Understanding how climate influences ecosystems is complicated by the many correlated and interrelated impacting factors. Here we quantify climate effects on Calanus finmarchicus in the northeastern Norwegian Sea and southwestern Barents Sea. By combining oceanographic drift models and statistical analyses of field data from 1959 to 1993 and investigating effects across trophic levels, we are able to elucidate pathways by which climate influences zooplankton. The results show that both chlorophyll biomass in spring and C. finmarchicus biomass in summer relate positively to a combination of shallow mixed layer depth and increased wind in spring, suggesting that C. finmarchicus biomass in summer is influenced by bottom-up effects of food availability. Furthermore, spatially resolved C. finmarchicus biomass in summer is linked to favorable transport from warmer, core areas to the south. However, increased mean temperature in spring does not lead to increased C. finmarchicus biomass in summer. Rather, spring biomass is generally higher, but population growth from spring to summer is lower, after a warm compared with a cold spring. Our study illustrates how improved understanding of climate effects can be obtained when different datasets and different methods are combined in a unified approach.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, 0316 Oslo, Norway; n.c.stenseth@ibv.uio.no l.c.stige@ibv.uio.no k.o.kvile@ibv.uio.no.
authors.forename: Kristina Ø
authors.initials: KØ
authors.lastname: Kvile
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, 0316 Oslo, Norway;
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Langangen
authors.affiliation: Laboratory of Trophology, Knipovich Polar Research Institute of Marine Fisheries and Oceanography, 183763 Murmansk, Russia.
authors.forename: Irina
authors.initials: I
authors.lastname: Prokopchuk
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, 0316 Oslo, Norway; n.c.stenseth@ibv.uio.no l.c.stige@ibv.uio.no k.o.kvile@ibv.uio.no.
authors.forename: Nils C
authors.initials: NC
authors.lastname: Stenseth
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, 0316 Oslo, Norway; n.c.stenseth@ibv.uio.no l.c.stige@ibv.uio.no k.o.kvile@ibv.uio.no.
authors.forename: Leif C
authors.initials: LC
authors.lastname: Stige
mesh_terms: D000818:Animals; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D002980:Climate; D017753:Ecosystem; D015048:Zooplankton / Q000254:growth & development* / Q000378:metabolism
chemical_list: D002734:Chlorophyll
keywords: Calanus finmarchicus; bottom-up control; climate; ecosystem dynamics; zooplankton
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