How does the unicellular plankton reproduce

Modelled gamete fusion numbers in planktonic Foraminifera

Reproductive biology is integral to evolutionary processes in organisms, yet gaining detailed insights poses major challenges. Planktonic Foraminifera are globally distributed marine protists and important contributors to the global carbon cycle with distinct biodiversity patterns. Knowledge on their life cycle remains incomplete, yet the production of flagellated gametes implies a sexual mode of reproduction. In the open ocean, this would rely on sufficient gamete encounters to maintain viable populations, which is problematic for protist plankton with low population densities. We applied dynamic modelling with parameters based on prior observations to verify if random gamete encounters are sufficient for maintaining viable populations. Temporal and spatial synchronization of gamete release seems inevitable to that end, and planktonic Foraminifera seemingly optimized their individual reproductive success at the expense of gene flow. This may explain their high degree of diversity and contributes to our understanding of plankton ecology and evolution.