Increased CO2 modifies the carbon balance and the photosynthetic yield of two common Arctic brown seaweeds: Desmarestia aculeata and Alaria esculenta

Abstract

Ocean acidification affects with special intensity Arctic ecosystems, being marine photosynthetic organisms a primary target, although the consequences of this process in the carbon fluxes of Arctic algae are still unknown. The alteration of the cellular carbon balance due to physiological acclimation to an increased CO 2 concentration (1300 ppm) in the common Arctic brown seaweeds Desmarestia aculeata and Alaria esculenta from Kongsfjorden (Svalbard) was analysed. Growth rate of D. aculeata was negatively affected by CO 2 enrichment, while A. esculenta was positively affected, as a result of a different reorganization of the cellular carbon budget in both species. Desmarestia aculeata showed increased respiration, enhanced accumulation of storage biomolecules and elevated release of dissolved organic carbon, whereas A. esculenta showed decreased respiration and lower accumulation of storage biomolecules. Gross photosynthesis (measured both as O 2 evolution and 14 C fixation) was not affected in any of them, suggesting that photosynthesis was already saturated at normal CO 2 conditions and did not participate in the acclimation response. However, electron transport rate changed in both species in opposite directions, indicating different energy requirements between treatments and species specificity. High CO 2 levels also affected the N-metabolism, and 13 C isotopic discrimination values from algal tissue pointed to a deactivation of carbon concentrating mechanisms. Since increased CO 2 has the potential to modify physiological mechanisms in different ways in the species studied, it is expected that this may lead to changes in the Arctic seaweed community, which may propagate to the rest of the food web.

Responses of macroalgae to CO2 enrichment cannot be inferred solely from their inorganic carbon uptake strategy

“…As with growth rates and net photosynthesis, mixed results were reported for δ 13 C in the current literature (Table ). For example, an increased growth rate was combined with decreased δ 13 C in Lomentaria australis (current study), whereas growth rates and δ 13 C simultaneously decreased in Desmarestia aculeata (Iñiguez et al, ). This shows that it is important to measure physiological processes and parameters (e.g., net photosynthetic rates, C:N ratios, and δ 13 C) in addition to measuring the response (i.e., growth), if we are to understand how the response to CO 2 enrichment is regulated.…”

“…References: [1] Ho and Carpenter (); [2] Sarker, Bartsch, Olischläger, Gutow, and Wiencke (); [3] Israel and Hophy (); [4] Gao et al (); [5] Lignell and Pedersén (); [6] García‐Sánchez et al (); [7] Rivers and Peckol (); [8] Chen, Zou, Zhu, and Yang (); [9] Xu, Zou, and Gao (); [10] Liu, Zou, and Yang (); [11] Zou and Gao (); [12] Kang, Kambey, Shen, Yang, and Chung (); [13] Kim et al (); [14] Suárez‐Álvarez, Gómez‐Pinchetti, and García‐Reina (); [15] Bender‐Champ, Diaz‐Pulido, and Dove (); [16] Kübler et al (); [17] Olischläger and Wiencke (); [18] Nunes et al (); [19] Sebök, Herppich, and Hanelt (); [20] Gordillo, Carmona, Viñegla, Wiencke, and Jiménez (); [21] Kram et al (); [22] Israel, Katz, Dubinsky, Merrill, and Friedlander (); [23] Liu and Zou (); [24] Xu, Chen, et al (); [25] Mercado, Javier, Gordillo, Xavier Niell, and Figueroa (); [26] Gao et al (); [27] de Paula Silva, Paul, Nys, and Mata (); [28] Reidenbach et al (); [29] Kang and Chung (); [30] Kang and Kim (); [31] Liu and Zou (); [32] Gao et al (); [33] Xu and Gao (); [34] Li, Xu, and He (); [35] Li, Zhong, Zheng, Zhuo, and Xu (); [36] Björk, Haglund, Ramazanov, and Pedersén (); [37] Gordillo, Niell, and Figueroa (); [38] Rautenberger et al (); [39] Gordillo, Figueroa, and Niell (); [40] Iñiguez et al (); [41] Gordillo et al (); [42] Iñiguez, Heinrich, Harms, and Gordillo (); [43] Gutow et al (); [44] Kawamitsu and Boyer (); [45] Ober and Thornber (); [46] Mensch et al (); [47] Iñiguez et al, (); [48] Fernández et al (); [49] Swanson and Fox (); [50] Thom (); [51] Kang and Chung (); [52] Olischläger, Iñiguez, Koch, Wiencke, and Gordillo (); [53] Zou (); [54] Zo...…”

Ecosystem Kongsfjorden: new views after more than a decade of research

“…At the first sight, one might think that enhanced supply of CO 2 should lead to an elevation of photosynthetic rates. However, this was not the case, as described by Iñiguez et al (2015), who showed no significant effect of CO 2 , neither on gross photosynthesis nor on the light saturation parameter (E k ; Gordillo et al 2016). Other processes were affected, however, such as respiration, release of dissolved organic carbon (DOC) and accumulation of storage carbohydrates and lipids.…”

“…As a result, growth was stimulated in three of six species. The growth rate decreased in one species, but was not affected in the other two species (Iñiguez et al 2015;Gordillo et al 2016). Elevated temperature combined with elevated CO 2 level influenced photosynthetic performance in a speciesspecific way.…”

Large-scale seaweed cultivation diverges water and sediment microbial communities in the coast of Nan'ao Island, South China Sea

“…Anthropological activity has caused a decline in pH of seawater, termed ocean acidification, which has effected on microbial community diversity and microbe-driven biogeochemical cycling Witt et al, 2011). Because seaweed has high rates of CO 2 fixation through photosynthesis (Gao and McKinley, 1994;Iñiguez et al, 2015;Muraoka, 2004), the pH in seaweed surrounding water is higher than other natural sea area (Suzuki et al, 2015). In addition, the pattern and concentration of nutrients have direct influence on microbial metabolism such as respiration and growth in marine ecosystems (Stelzer et al, 2003;Zeigler Allen et al, 2012).…”