Photosynthesis, carbon uptake and antioxidant defence in two coexisting filamentous green algae under different stress conditions

Abstract

The physiological basis for ecological processes is in many cases little understood. The purpose of this work was to link 3 important physiological processes in algae -photosynthesis, carbon uptake and antioxidant defence -to life form. The organisms used were the morphologically similar filamentous green algal species Cladophora glomerata and Ulva procera, which seemingly occupy the same niche when they co-occur in dense belts in the upper littoral zone of the brackish Baltic Sea in summer. Their life strategies are different: the annual C. glomerata usually stays attached throughout summer, while the ephemeral U. procera can appear and disappear from the same site from week to week. The algae were growing in the field under exactly the same conditions (mixed stands) and were immediately used in experiments at a field station. Fundamental ecophysiological differences were found between the 2 species. (1) Higher photosynthetic activity was detected in U. procera. (2) More shade-adaptations were found in U. procera, and more sun-adaptations in C. glomerata. (3) C. glomerata uses a proton pump for HCO 3 -transport, and carbon uptake does not depend on periplasmic carbonic anhydrase. This is an advantage in dense algal belts with longer periods of carbon limitation. (4) C. glomerata invests more in carotenoid protection against oxidative stress, including high carotenoid/chlorophyll ratios and a functional violaxanthin xanthophyll cycle. (5) U. procera was more sensitive to oxidative stress created by UV-B radiation than C. glomerata, which correlates with a more effective intracellular (carotenoid and enzymatic) defence against oxidative stress in C. glomerata. (6) H 2 O 2 in the seawater medium had a negative effect on photosynthesis in C. glomerata, but not in U. procera. This suggests that a high release of H 2 O 2 by U. procera under oxidative stress may damage C. glomerata. While the ecophysiological traits of C. glomerata seem to be directed toward persistence, those of U. procera seem to be more engaged with large but short-term gains. This is in accordance with their different life strategies.

Effects of temperature and irradiance on photosynthesis and growth of a green-tide-forming species (Ulva linza) in the Yellow Sea

“…The productivity and light availability of the ESV individuals of U. linza were higher than those of the LSV individuals over a wide range of irradiance and temperature conditions after 7-d acclimation, although nutrient-poor seawater from the Yellow Sea was used for the experiments. Photosynthetic parameter (P B max and α) values of ESV individuals were higher than those of previous published values for U. linza, but LSV individuals had similar or lower values (Table 1) (Arnold and Murray 1980;Coutinho and Zingmark 1987;Merceron et al 2007;Choo et al 2005). High productivity and light availability of ESV individuals are possible mechanisms for proliferating algal abundance, even if nutrients are limited.…”

“…Error bars=SD status (Gordillo et al 2002;Choi et al 2010). The C:N ratio of ESV individuals was relatively lower than that of ulvoid macroalgae reported (Choo et al 2005;Nelson et al 2008;Choi et al 2010) and increased significantly after long-term acclimation to various irradiance and temperature levels because tissue nitrogen utilization efficiency was high in ESV tissues. Even under nutrient-poor condition in the open ocean, ESV individuals can still grow because they have high nitrogen reserves in their tissue based on C:N and N:P ratio.…”

Physiological, biochemical, and ultrastructural responses of the green macroalga Urospora penicilliformis from Arctic Spitsbergen to UV radiation

“…An increase in pigment content (carotenoids) in the presence of UV-B indicates an efficient protective pigment mechanism in Ulva rigida C. Agardh (Altamirano et al 2000). Similarly, in Cladophora glomerata (Linnaeus) Kützing defense against UVR-induced oxidative stress is enabled through carotenoid protection including high carotenoids/chlorophyll ratio and a functional xanthophyll cycle (Choo et al 2005). In comparison to the field control, lutein and neoxanthin of Urospora (this study) increased slightly, but only as a response to the lab conditions, because this increase also occurred in the PAR-only sample.…”

Antioxidant response of the seagrass Posidonia oceanica when epiphytized by the invasive macroalgae Lophocladia lallemandii

“…It has been evidenced that algae produce higher concentrations of defensive compounds in areas subject to high herbivore pressure (Paul and Fenical, 1986). Aside from the synthesis of defensive metabolites, the production of ROS has been shown to have a significant contribution towards the survival of algae against pathogens (Bouarab et al, 2001;Küpper et al, 2002), It has been suggested that the release of H 2 O 2 may act as a chemical defence against herbivores and epiphytes or as an allochemical in direct competition with other algal species (Choo et al, 2005). Collen and Pedersen (1994) also reported the role of H 2 O 2 in the formation of volatile halogenated defensive compounds.…”