Marine ecosystems, climate and phenology: introduction

Mid to high-latitude marine ecosystems are characterized by strong intra-seasonal variability in productivity across multiple trophic levels. It is understood that climate variability, as well as projected climate change, is likely to cause substantial changes in the timing of key seasonal events, such as the spring phytoplankton bloom, dates of diapause for zooplankton, or nesting dates in seabirds. However, it is not well known how changes in timing across multiple trophic levels will impact predator-prey relationships. Several mechanistic hypotheses have been put forth to explain changes in fish production in relation to phenological variability of prey, including Cushing’s (1990; Adv Mar Biol 26:249–293) ‘match-mismatch’ hypothesis, yet there have been few tests of these ideas relative to ongoing oceanographic change. In this Theme Section, we present 9 papers that relate ocean climate variability and climate change to timing of key events for zooplankton, fish, and seabirds from northern hemisphere marine ecosystems. They cover phenological variability and consequences of timing changes for species of the California Current, Gulf of Alaska, NE Atlantic Ocean, Arctic Ocean and northern Japan Sea, all cold-water ecosystems, and highlight the importance of phenology as a key response variable, as well as the complexity of ecological relationships to be impacted by marine climate change. Multi-trophic level changes in phenology of species abundance and productivity are likely to have important consequences to marine ecosystem structure and function.