Continuous photoperiod of the Artic summer stimulates the photosynthetic response of some marine macrophytes

• Published in: Aquatic Botany
• Main Authors: Sanz-Martín, Marina, Hendriks, Iris E., Carstensen, Jacob, Marbà, Núria, Krause-Jensen, Dorte, Sejr, Mikael K., Duarte, Carlos M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Carbon dioxide; Continuous photoperiod; Electron transport rate; Macrophytes; Subarctic; Arctic; Greenland; Climate change; Sea ice
• Online Access: https://pure.au.dk/portal/da/publications/continuous-photoperiod-of-the-artic-summer-stimulates-the-photosynthetic-response-of-some-marine-macrophytes(ddb5445a-e73d-435d-9851-043f05303e33).html; https://doi.org/10.1016/j.aquabot.2019.06.005; http://www.scopus.com/inward/record.url?scp=85068108653&partnerID=8YFLogxK

Subarctic macrophytes are predicted to expand in the Arctic as a result of on-going global climate change. This will expose them to 24 h of light during the Arctic summer while pCO 2 levels are predicted to rise globally. Here, we tested the photosynthetic activity of two brown macroalgae (Ascophyllum nodosum, Fucus vesiculosus) and one seagrass (Zostera marina) from subarctic Greenland, measuring their relative maximum electron transport rate (rETR max ), photosynthetic efficiency (α) and saturating irradiance (I k ) after 3 days of incubation at different photoperiods (12:12 h, 15:09 h, 18:06 h, 21:03 h and 24:00 h, light:dark) with ambient values of pCO 2 (200 ppm, characteristic of current subarctic surface waters) and increased pCO 2 (400 and 1000 ppm). The photosynthetic parameters rETR max and I k increased significantly with longer photoperiods and increased, however insignificantly, with increased pCO 2 . Responses differed between species. A. nodosum and Z. marina showed the highest increase of rETR max and I k from 12 h to 24 h while the increase of F. vesiculosus was smaller. Our results suggest that as subarctic macrophytes expand in the Arctic in response to retracting sea ice, the long summer days will stimulate the productivity of the species tested here, while the effect of high-CO 2 environment needs further research.