Kelp release huge numbers of zoospores into the sea. Each must find a suitable surface and attach before it can grow into the next stage of the kelp life cycle. Until now, we knew surprisingly little about how swimming shapes this make-or-break moment.
In our new University of Sussex study, I filmed zoospores from three kelp species under a microscope and used computer tracking to follow them. Some swam quickly and purposefully. Others moved slowly, spun in circles or barely moved. I then compared their movement with how successfully they settled (attached to surface to establish new growth).
The result was striking: samples with a higher proportion of swimming zoospores settled much more successfully. The most mobile groups were predicted to achieve around three times as much settlement as the least mobile groups. Fast, directed swimmers also had the greatest chance of encountering a surface.
This matters for Sussex because kelp recovery depends not only on adult kelp surviving, but also on the next generation successfully attaching and growing. Zoospore swimming could provide an early, sensitive way to test whether pollution, suspended sediment, warming or other pressures are making recovery harder—before damage becomes visible in adult kelp.
By examining zoospore motility, we are investigating how environmental pressures affect the earliest stages of kelp recruitment. The next step is to apply this approach to real coastal conditions to help identify where these tiny beginnings have the best chance to thrive.
By guest author, Marianne Glascott, Doctoral Researcher at the University of Sussex