Winter zooplankton dynamics in the English Channel and southern North Sea: trends and drivers from 1991 to 2013

Winter has long been regarded as a period of minor importance in marine zooplankton ecology with static, low concentrations and growth rates of organisms. Yet, there is growing evidence that winter conditions influence spring bloom strength. With rising water temperatures, growing importance of fish larvae survival during winter and the lack of data to parameterize ecosystem models for this period, research focus shifted on winter zooplankton ecology. To enable looking into past changes in winter zooplankton ecology, we established a new winter zooplankton time series based on samples collected in the eastern English Channel and southern North Sea by the International Herring Larvae Survey since 1988. Four areas of the study region were identified containing different congregations of zooplankton. Overall, zooplankton size decreased while total zooplankton abundance increased, reaching its maximum in 2011. Zooplankton abundance dynamics were mainly related to temperature, chlorophyll a concentration and North Atlantic Oscillation index. Depth and Atlantic water inflow strongly influenced zooplankton size. Increased chlorophyll a concentration and high abundances of small copepods indicated bottom-up controlled secondary production since 2010 and a possible winter bloom in 2011. Based on the analysed parameters, no relation between herring larvae abundance and zooplankton or environmental drivers was determined.

Transcriptomics and metatranscriptomics in zooplankton: wave of the future?

Molecular tools have changed the understanding of zooplankton biodiversity, speciation, adaptation, population genetics and global patterns of connectivity. However, the molecular resources needed to capitalize on these advances continue to be limited in comparison with those available for other eukaryotic plankton. This deficiency could be addressed through an Ocean Zooplankton Open ‘Omics Project (Ocean ZOOP) that would generate de novo assembled transcriptomes for hundreds of metazoan plankton species. A collection of comparable reference transcriptomes would generate a new framework for ecological and physiological studies. Defining species niches, identifying optimal habitats, assessing adaptive capacity and predicting changes in phenology are just a few examples of how such a resource could transform studies on zooplankton ecology.