Kelp gametophytes in changing oceans

Kelp forests are ecologically diverse habitats that provide vast ecosystem goods and services, but are threatened by climate and anthropogenic stressors. Laminarian kelps have an alternating biphasic life cycle, and while there is a growing understanding of climate impacts on the macroscopic diploid sporophyte, impacts on the microscopic haploid gametophyte stage are just emerging. There exists a strong history of gametophyte literature on single species and environmental factors, but only recently studies have increasingly examined multiple climate stressors, species and populations. We synthesize studies on kelp gametophytes, building upon our understanding of their responses to environmental conditions and subsequent vulnerabil-ity in changing oceans. Kelp gametophytes have a broad tolerance to environmental conditions predicted to change with climate change, including temperature and irradiance, but large variation exists among species and populations. Key processes such as gametogenesis and early sporophyte development consistently appear more sensitive to environmental conditions than vegetative growth and may present bottlenecks to ongoing kelp persistence. Indirect effects of climate change negatively affect kelp gametophytes through competition, grazing and sedimentation. Modern genomic techniques are paving the way to transition research into field settings that include both sporophyte and gametophyte stages. Unravelling the response of gametophytes to changing environmental conditions is beginning to provide an understanding of overall kelp forest persistence and enables proactive conservation and management initiatives in changing oceans