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A fundamental question in plankton ecology is to understand the mechanisms that govern community structure and the effect of changing environments on interactions across trophic levels. Here, we develop a novel trait-based approach for multi-trophic level analysis of observational data from the southern California Current ecosystem, spanning a range of organisms from bacteria to macrozooplankton. We focus on activity traits that are realized differently across trophic levels: for unicellular organisms we consider resource acquisition strategy and motility, for more complex organisms we characterize foraging mode, and for all we use size as a master trait. These traits affect interactions across the trophic levels by balancing feeding success and predatory risk, and their expression is closely linked to the physical environment. We examine how the environment shapes ecosystem interactions by comparing contrasting provinces of the region: from nutrient-limited open ocean to the upwelling-dominated coast. The open ocean protist community is dominated by motile, mixo- and heterotrophic cells, while larger, non-motile, autotrophic cells dominate in the coastal provinces. The contribution of small passive feeders to the zooplankton community increases in the upwelling region due to increased efficiency of prey capture in the more turbulent environment. The larger passive feeders exhibit an inverse pattern, possibly reflecting the contrast in the predation pressure posed by fish. We discuss the shifts in the size distribution and resulting food web interactions, and the implications these may bring for the ecosystem functioning.


Kenitz, K. M., DTU Aqua, Denmark,

Andersen, K. H., DTU Aqua, Denmark

Visser, A. W., DTU Aqua, Denmark

Ohman, M. D., Scripps Institution of Oceanography, USA

Landry, M. R., Scripps Institution of Oceanography, USA

Kiørboe, T., DTU Aqua, Denmark


Oral presentation

Session #:006
Date: 02/27/2017
Time: 15:00
Location: 313 A

Presentation is given by student: No