Cross‐depth connectivity shows that deep kelps may act as refugia by reseeding climate‐vulnerable shallow beds

Refugia are habitats where species can survive or retreat to during environmental disturbances. One key assumption of that constitute refugia is they may assist in the persistence impacted populations through provision reproductive propagules. This “reseeding” hypothesis assumes demographic connectivity exists between and habitats. We tested this for kelp Ecklonia radiata, a temperate marine foundation dominant coast Australia. Our study site was Western Australia, system deep considered act as their shallow counterparts, yet, which estimations population have overlooked propagule dispersal across depth. Here, we simulated ocean circulation conditions three-dimensional oceanographic model propagules by incorporating physical properties zoospores within model. The trajectories were tracked analyzed identify probability settlement domain study. Measurements fecundity depth obtained region, used estimate zoospore densities. show E. radiata capacity supply reefs. results released at deeper beds (40 m depth) transported reefs (<20 densities sufficient drive fertilization. Analysis particle exchange among depths also indicates mid-depth (~25 important “stepping stones” cross-depth connectivity, enhancing shallowest deepest locations, especially when different separated tens kilometers. after an disturbance, persistent kelps sourcing reseeding reefs, provided adequate recruitment growth. demonstrates exchange, habitat-building living areas undamaged biophysical disturbances reseed aid recovery if regrowth, ensure persistence.