The cold-temperate kelp species Alaria esculenta, Saccharina latissima and Laminaria digitata co-occur at the same depth at a variety of locations. Due to their heteromorphic life cycle a large part of their development is only microscopically visible. We investigated the impact of sedimentation, temperature and light (as abiotic factors) and interspecific competition and grazing (as biotic factors) on early developmental stages in multi-factorial approaches. The germination success, speed of gametogenesis and survival of juvenile sporophytes were followed in laboratory and field experiments. Although germination is mostly an autonomous process it was negatively affected by unfavourable abiotic conditions, especially high sediment load. Speed of gametogenesis was temperature dependent with species-specific optima. The recruitment success of young sporophytes was dependent on all interacting abiotic factors which also influenced the resource competition between the different species. For example, juvenile A. esculenta sporophytes overgrew L. digitata at 5 °C, while they had no competitive chance at 15 °C. High sediment loads were most detrimental for sporophyte survival, but interestingly, moderate grazing could decrease the negative impact of intermediate sediment loads. It became evident that many factors influence the outcome of recruitment in kelps and that changing temperature or increased sedimentation lead to a species-specific reaction which may influence the outcome of competition and thereby community structure. More field experiments are required to get ecologically relevant data because survival rates in the field were much lower compared to controlled laboratory conditions despite density control of spores in comparative experiments.