Viruses are the most abundant biological entities on Earth, with an estimated 4 × 10³⁰ particles globally (1). Given that more than 70% of the planet is covered by oceans, it is unsurprising that seawater contains staggering viral loads (2). Within this immense diversity, double-stranded DNA viruses of the phylum Nucleocytoviricota, which includes many lineages of “giant viruses,” are among the most abundant in the ocean (3, 4). Among the Nucleocytoviricota, prasinoviruses play a particularly central role in surface waters by infecting members of the Mamiellophyceae, a ubiquitous class of unicellular green algae that are among the most widespread marine primary producers (5). Marine phytoplankton are fundamental to global biogeochemical cycles, contributing nearly half of Earth’s primary production. Prasinoviruses represent a substantial fraction of the marine eukaryotic virome (6). By regulating their algal hosts, they influence population dynamics, shape community composition, drive nutrient cycling, and affect carbon export to the deep sea, with outcomes depending on host interactions and ecosystem context (7, 8). Despite their ecological significance, prasinoviruses remain relatively understudied when compared to other abundant oceanic viruses, such as cyanophages.

The genomes analyzed here represent the first viruses from the tropical North Pacific that infect the abundant phytoplankton order Mamiellales. Comparing isolates from the same location demonstrates h...

The Trump Administration has vowed to dissolve the center that provides critical extreme weather and climate data for our nation.