Overarching questions that remain unanswered include: what genetic forms of pelagic Sargassum are involved, and what is the cause and geographic source of these accumulations? And as "ecosystem engineers" how do mass accumulations of Sargassum impact the microbial food web that dominates the open ocean, as well as coastal ecosystems where it strands?

The RV Pelagia "Sargassum" Cruise PE-455 aims to address these questions. In a series of blogs scientists and students share their research, findings and experiences. 

A view of our vessel from inside the "Great Sargassum Belt". Concentrations of this brown macroalga are so high that they can be detected using satellite images from space. Photo: Erik Zettler