Evaluation of functional trait diversity for marine zooplankton communities in the Northeast subarctic Pacific Ocean

Functional trait diversity relates variation in the structure of biological communities to function and ecosystem processes. Zooplankton occupy a central position in marine food webs, modulating energy availability to higher trophic levels, while themselves affected by environmental variation. The use of traits with functional diversity potentially enables a more mechanistic understanding of variation and regulation of zooplankton communities than is possible with taxonomic diversity alone. Traits for 42 zooplankton species from the northeast subarctic Pacific were assembled from the literature and applied to a 16-year time series from the oceanographic Line P. We assembled traits on body size, ontogeny, habitat and feeding behaviours. Six major functional groupings were identified via a trait-based cluster dendrogram. Several functional diversity indices were also calculated, and compared with analogous taxonomic diversity indices. Analogue diversity indices were significantly correlated. Both types of diversity indices revealed some year-specific "anomalies" which were associated with broad-scale oceanographic and climatic regime shifts. We propose that the functional diversity approach may represent an additional ecological tool with which we can gain further understanding of zooplankton function and trophic linkages in a changing ocean, in part because functional traits are often based on easily measured morphological characters.