New publication: Whale Migration and climate change

"Timing of migratory baleen whales at the Azores in relation to the North Atlantic spring bloom" is the title of the new publication in Marine Ecology Progress Series of Fleur Visser and colleagues describing how baleen whales use the waters around the Azores as a drive through snack bar when migrating north towards their summer feeding grounds.

Four years of whale observations collected from the Island of Pico, Azores, were matched with satellite data on ocean chlorophyll concentration, an indicator for phytoplankton abundance. The results showed that each year, the whales timed their visit to these waters perfectly. It takes northern krill, a favourite prey of baleen whales, about 13-15 weeks to mature, feeding on the phytoplankton. Arriving 13-16 weeks after the start of the plankton bloom, the whales presence coincides with the moment the main dinner is being served: mature northern krill. Generally, whales were thought to fast during their northward migration. But observations of feeding whales remaining up to 17 days in these waters, showed this old fasting idea was not correct. In fact, whales use these waters to snack and gain energy on their long migration north.

The islands of the Azores are located just north of the North Atlantic Subtropical Gyre (NASG), which consists of low nutrient waters resulting from permanent stratification. Climate change models predict a northerly expansion of the NASG as a result of rising sea water temperatures. Incorporation of the Azores in the expanding zone of the NASG would suppress the spring bloom, thereby strongly reducing the productivity of the Azorean waters, which eventually might result in the loss of a foraging area at the early stages of spring migration.