Photosynthetic response of Arctic kelp zoospores exposed to radiation and thermal stress

Abstract

Zoospores of Arctic kelp species, Alaria esculenta, Laminaria digitata and Saccharina latissima were exposed to different temperature (2 • C to 19 • C) and radiation (photosynthetically active radiation (PAR = P), PAR + UV-A (PA), and PAR + UV-A + UV-B (PAB)) conditions in the laboratory. Species-specific responses to the combined effect of light and temperature stress showed sensitivity in the order S. latissima > L. digitata > A. esculenta. The optimum temperature range for photosynthesis in different Arctic kelp species' zoospores was between 7-13 • C, temperatures higher than in the natural environment. Short-term response to increasing temperature was non-lethal while moderate temperature increase had an ameliorating effect on the overall biological effect of UVR; where the lowest photoinhibition was observed at 13 • C under PAB and higher photosynthetic recovery was observed in UVR-pre-exposed zoospores at 7-13 • C compared to 2 • C. Above the temperature optima, continued cultivation under high temperature had a negative impact on the recovery of photoinhibition. The higher capacity for non-photochemical quenching (NPQ) in A. esculenta and L. digitata helped to regulate and protect photosynthesis under light and temperature stress compared to S. latissima. The investigated Arctic kelp species may be able to locally survive under the influence of UVR at a certain range of temperature increase but the southernmost distribution range of the species may shift to higher latitudes; although natural selection may result in genotypes adapted to stressful environment.

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…Arctic kelps' spore photosynthesis and gametophyte growth rate have a high temperature affinity between 12 and 13 • C (Roleda, 2009(Roleda, , 2016; this temperature is 7-8 • C higher than the in situ summer water temperature (5-6 • C) in Kongsfjorden (Svalbard) (Hanelt et al, 2001;Svendsen et al, 2002). Moreover, the germination rate was also enhanced when summer mean temperature was increased by 4-5 • C (Zacher et al, 2016).…”

Short-term effects of increasing CO2, nitrate and temperature on three Mediterranean macroalgae: biochemical composition

“…Moreover, studies on the effect of global climate changes on aquatic organisms have mostly been conducted with 1 or 2 variables, and interactions between multiple factors have scarcely been studied (Franklin & Foster 1997, Gordillo et al 2001, Bischof et al 2006a, Häder et al 2007). For example, the effect of increased UVR, temperature and CO 2 on photosynthetic metabolism, nutrient incorporation and growth has been studied in algae from Medi terranean and Atlantic waters off the southern Iberian Peninsula (reviewed in Häder & Figueroa 1997, Figueroa & Gómez 2001, but also in algae from the North Sea (Hanelt et al 1997b) and the Arctic region (Hanelt et al 1997a, Hanelt 1998, Roleda 2009). Investigations have been conducted in the field (in situ) and in experimentally controlled conditions under solar radiation (outdoor) and under artificial conditions (indoor).…”

Seaweeds and Their Communities in Polar Regions

“…Moreover, the temperature optima for photosynthesis in the few tested Antarctic species are well below values determined in temperate species . Likewise, the optimum temperature for photosynthesis in zoospores of Alaria esculenta, Laminaria digitata, and Saccharina latissima from Arctic Spitsbergen is with 7-13 C relatively low (Roleda 2009). In contrast, the optima for respiration are clearly located at higher temperatures.…”