Encounter rates of elongated phytoplankton in turbulence

Phytoplankton come in a variety of shapes, however, elongated morphologies dominate. While aspect ratios above 5 are quite common for individual cells, chain-forming species can exhibit aspect ratios greater than 100. How cell shape affects encounter rates between phytoplankton in mild turbulence has been an open question. In this contribution, we present results from direct numerical simulations of elongated phytoplankton cells in turbulence, showing that encounters between elongated cells are significantly enhanced compared to spherical cells. Consequently, the timescales of marine snow formation are smaller for elongated cells than for spherical cells, which offers a potential explanation for the rapid clearance times of many phytoplankton blooms.