Marine plankton, despite their tiny size, are crucial for the functioning of marine food webs. It is not just about one organism eating another; when this happens, it helps release the nutrients accumulated within living matter, making them available again for microalgae. Plankton are present in freshwater and in all the seas and oceans on the planet. Moreover, they are responsible for supporting life on Earth and has provided us (on geological timescales) with a significant portion of the oxygen we breathe. In just a small spoonful of seawater, we can find around fifty million viruses, five million bacteria, hundreds of thousands of small unicellular flagellates, thousands of microscopic algae, five heterotrophic ciliates or dinoflagellates, and, with some luck, a small crustacean like copepods. This book aims to bridge the gap between scientific research and the general public, offering a captivating exploration of the fascinating world of marine plankton. Through engaging narratives and visually compelling illustrations, readers will gain insights into the importance of plankton in marine ecosystems, their diverse forms, and the crucial role they play in maintaining our planet's health.

Albert Calbet is a marine researcher working at the Institute of Marine Sciences, CSIC (Barcelona, Spain), specialized in the ecology and ecophysiology of micro- and mesozooplankton. He has made significant contributions to the field, particularly in understanding the role of microzooplankton in marine food webs. Albert completed his Ph.D. in Marine Sciences in 1997 at the Institute of Marine Sciences (ICM), CSIC, after which he pursued postdoctoral research at the University of Hawaii at Manoa. He has held various positions at ICM, including Deputy Director. Albert has published over 120 peer-reviewed articles, authored books and book chapters, and actively participated in scientific conferences worldwide. He has been involved in teaching and mentoring students at the Ph.D., Master, and undergraduate levels. Albert's research has been supported by prestigious institutions, and he has served as a reviewer for funding agencies and on the editorial boards of scientific journals. Committed to science outreach, he manages several Web pages and engages with the public through social media, outreach articles, and books.