How do water currents transfer pollen in submerged marine members of Hydrocharitaceae?

In submerged marine members of the Hydrocharitaceae family, pollination is achieved through a specialized process adapted to an underwater environment. Because these plants are dioecious and remain permanently submersed, they cannot rely on surface-based mechanisms like those found in many freshwater species.1

Instead, the pollen released from staminate flowers adheres in chains, effectively functioning as a single, elongated pollen grain. These chains are suspended in the water column and are transported by water currents. This elongated structure is a significant evolutionary adaptation, as it is much more likely to make contact with a stigma than an individual, smaller grain would be. Successful pollination occurs when one of these drifting pollen chains comes into contact with a stigma.1