Kelp forests are ecologically diverse habitats that provide vast ecosystem goods and services but are in decline due to a range of anthropogenic stressors. Ocean warming is driving the transition of kelp forests to alternative states like urchin barrens and algal turfs, resulting in dramatic declines in biodiversity. To mitigate such profound ecosystem changes, a full understanding of the kelp life cycle is necessary. Kelps have an alternating biphasic life cycle, and while there is growing understanding of the mechanisms driving change in the macroscopic sporophyte stage, impacts on the microscopic gametophyte stage remain a knowledge gap. Ecological interactions of gametophytes with grazers are largely unstudied but may be critical in the reversal from barren states to kelp forests. We show that several micro-grazers can negatively impact gametophyte persistence but facilitate their reproduction. Warming appears not to change the impact of these herbivores on gametophytes but does hamper gametophyte recovery from grazing. These findings show the complexity of ecological interactions with kelp microscopic stages and beg further research on the ecological functioning of kelp gametophytes under climate change.