This study aims to compare the performance and reproductive success of early life stages of A. esculenta and L. digitata from Kongsfjorden, Spitsbergen under simulated Arctic environmental conditions. Two experiments were performed. Firstly, gametophytes were exposed to Arctic winter conditions and then transferred to recovery spring conditions. During winter conditions the gametophytes from both species hampered their growth and despite the lower survival rate of L. digitata, the capacity to recover and become reproductive was greater than in A. esculenta. A multifactorial experiment was also performed to investigate the parental kelp canopy shading effect and the influence of current and projected Arctic summer temperatures and nutrient levels in the gametophyte survival, reproduction, and recruitment success. A. esculenta had a greater survival and reproductive success than L. digitata, except under very dense canopy conditions. Greater reproductive success was observed for both species under simulated intermediate canopy and high nutrient levels. Predicted summer temperatures of 9°C lead to a negative effect on reproduction, particularly in A. esculenta. Moreover, parental kelp canopy shading was important for L. digitata reproductive success. Kelp communities can be shaped by seasonality and natural shading, and climate change could shift recruitment patterns.
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