Looks can be deceiving: contrasting temperature characteristics of two morphologically similar kelp species co-occurring in the Arctic

Abstract Two morphologically similar digitate kelp species, Laminaria digitata and Hedophyllum nigripes , co-occur along a shallow sublittoral depth gradient in the Arctic but, contrast to L. very few ecophysiological data exist for H. . We investigated growth, survival, photosynthetic characteristics carbon:nitrogen ratios of juvenile sporophytes, recruitment survival gametophytes genetically verified isolates both species temperature gradients (0–25 °C) over 14 days. survived 23–24 °C, while sporophytes 21–22 °C. had lower affinities. Gametophytes 19–21 18 Male were more heat-tolerant than female species. The pronounced cold adaption compared also became apparent different sporophyte growth optima ( : 15 °C; 10 gametogenesis 5–15 0–10 °C). Higher suggest an adaptation nutrient poor conditions. overall performance possibly restricts Arctic–Sub-Arctic regions, behaved similarly cold-temperate populations. Our that future increase seawater temperatures may hamper success favour environments.