CCm performance in Arctic and Antarctic seaweeds in a warming and acidifying marine environment

Presentación oral al congresoOcean acidification and warming are affecting with special intensity the polar coastal ecosystems. The Arctic kelps Saccharina latissima and Laminaria solidungula from Kongsfjorden (Svalbard) were cultured at 4 and 9 ºC in combination with current (390 ppm, CC) and increased (1200 ppm, HC) levels of atmospheric CO2. The Antarctic endemic Desmarestia anceps and D. menziesii were cultured at 2 and 7 ºC, and also at CC and HC.For all these species ∂13C values suggested an absence of deactivation of carbon concentrating mechanisms at increased CO2 levels. The lack of inhibition of CCM at high CO2 shown by ∂13C values seems to be a common pattern in polar species, but it is not related to responses in photosynthesis and growth. Growth of both Arctic species were largely unaffected by increased CO2 conditions, regardless the temperature. In contrast, the Antarctic species were favored by high CO2, specially at the highest temperature. External carbonic anhydrase (eCA) was responsible for about 50% to 80% of the photosynthetic O2 evolution in all the species, according to inhibition assays using DBS. CO2 promoted a decrease in eCA contribution to O2 evolution in the Antarctic species but not in the Arctic ones. The addition of EZ did not promote further inhibition in any species, indicating a low relevance of internal CA, although a concomitant inhibition of eCA may mask this contribution if no other mechanism of active transport was operating. Our latest results of the gene expression of D. anceps reveal that there is a low response to CO2. The relevance of this resilience to CO2 in polar environments will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Elevated CO₂ alleviates high PAR and UV stress in the unicellular Chlorophyte Dunaliella tertiolecta

The effects of increased CO2 and irradiance on the physiological performance of the chlorophyte Dunaliella tertiolecta were studied at different PAR and UVR (UVA+UVB) irradiances, simulating the solar radiation at different depths, under present (390 ppmv, LC) and predicted CO2 levels (1000 ppmv, HC). Cell stress after UVR-exposure was mostly attenuated under HC levels, as evidenced by a decrease in reactive oxygen species accumulation. DNA damage showed a 42-fold increase in cyclobutane-pyrimidine dimers formation under the highest irradiance in LC with respect to the lowest irradiance. Photolyase gene expression was upregulated under HC resulting in a drastic decrease in CPDs accumulation to only 25% with respect to LC. However, the expression of genes related to the replacement of photosynthetic apparatus proteins (PsbA and LHCII) were downregulated at HC compared to LC. Proliferating cell nuclear antigen (PCNA) accumulation was always higher in HC and the accumulation pattern indicated its involvement in DNA repair or growth depending on the irradiance doses. Our results suggest that marine unicellular chlorophytes might possibly become more resilient to UVR exposure under future CO2 regimes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Warming modifies the seasonal photophysiology and productivity of Arctic macroalgae

Warming is affecting Kongsfjorden ecosystem with special intensity due to the influence of oceanic currents altered by Global Change. The effects of this stressor on the ecophysiology of Arctic seaweeds have been widely investigated, but mostly restricted to summer. However, Arctic coastal ecosystems experience strong seasonal changes in environmental light conditions from 24-hours of darkness in winter to 24-hours of light in summer, which likely alter the photosynthetic performance of macroalgae. In order to understand how increasing temperature will affect Kongsfjorden ecosystem dynamics it is crucial to analyze the effect of seasonal photoperiod on the responses of Arctic seaweeds to warming. Thus, we carried out experiments in September (fall equinox), March (spring equinox) and August (24h of light) to compare the photophysiological responses of common seaweed species of Kongsfjorden after acclimation to continuous light and 12:12 light:darkness at 4ºC, as well as the responses to increased temperature (8ºC) at the corresponding seasonal photoperiod. Due to 24-hours light stress in summer, macroalgae generally showed reduced photosynthetic capacity when compared to the equinoxes. Additionally, higher photoinhibition along with higher respiration rates were induced when seaweeds were exposed to continuous light in the equinoxes, whereas macroalgae exposed to 12:12 light/dark cycles in summer showed no changes in the photosynthetic capacities and respiratory rates. The increase in temperature frequently enhanced 14CO2 fixation and respiration rates, while growth rates were mostly unaltered, but season-specific and species-specific effects were observed. These results are highly valuable for constructing primary productivity models of the macrophytobenthos for the whole fjord, which can serve to make accurate predictions of productivity and ecosystem functioning in near-future scenarios.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Seasonal variation in the biochemical composition of Arctic macroalgae: Effect of warming and photoperiod

The effect of temperature and photoperiod along the year on the composition of 5 macroalgal species representative of the sublittoral system of Kongsfjorden was studied in laboratory conditions. These species were the ochrophytes Saccharina latissima and Alaria esculenta, the rhodophytes Phycodrys rubens and Ptilota gunneri, and the chlorophyte Monostroma aff. arcticum (only present from summer to early autumn). Three different seasons were compared: early March, early August and late September. Two temperatures were tested (4 and 8°C) as well as continuous irradiation (CL - simulating summer) and 12:12 h light:dark photoperiod (simulating equinoxes). Total carbon was not affected by warming or photoperiod, except in S. latissima in autumn under CL and 4°C, being 40% higher than with photoperiod. Nitrogen content generally increased by photoperiod, the highest being found in 12:12 L/D in all seasons. Carbohydrates were maximal in CL conditions in all species, indicating that their synthesis is light-stimulated, mainly in the equinoxes. In general, warming did not induce significant changes in carbohydrate content. Lipid content was affected by photoperiod only in brown algae. In S. latissima lipids presented maximum values in CL in the autumn equinox, while in A. esculenta was under photoperiod in summer. Protein content did not change with warming or photoperiod in three out of the five species, and only in S. latissima and P. gunneri proteins were higher in CL than under photoperiod in the autumn equinox. In summary, the results indicate that only isolated changes in the composition of these representative macrophytes may be expected under warming conditions in near-future scenarios, while a general increase in carbon, carbohydrates and proteins under CL was observed mainly in the autumn equinox. The relation of this increase with light utilisation performance will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto MACROARTES, CGL2015-67014-R

Effects of increased co2 in the carbon budget and the photosynthetic yield of the arctic seaweeds alaria esculenta and desmarestia aculeata

The physiological acclimation to increased pCO2 (1300 ppm) of two common Arctic seaweeds from Kongsfjord (Svalbard) was analysed under laboratory conditions after 7 days of incubation. Growth rate changed in both species as a result of a reorganization of the carbon budget of the cell. Since increased CO2 have the potential to modify physiological mechanisms in different ways for each species, it is expected that it may lead to changes at the seaweeds community level that could alter the whole food web.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Study of radiactivity on Arctic marine seaweed from Kongsfjorden (Svalbard)

Levels of natural and anthropogenic radionuclides have been determined in six brown and red seaweed species from Arctic coasts (Kongsfjorden, Spitsbergen, Svalbard Islands) in order to characterize the radioactivity in this ecosystem. Samples were collected in September 2014, August 2017 and July 2019. Levels of 7Be, 40K, 208Tl, 210Pb, 226Ra and 228Ra were measured by high-resolution gamma spectrometry. While anthropogenic radionuclides (1 4 C and 1 2 9 I) were determined by low-energy accelerator mass spectrometry (LEAMS). The activities of 129I are two orders of magnitude higher than those found in algae collected on the Spanish Atlantic Coast and presents more variability than the 14C results, indicating their different affinity to this element depending on the species. Radionuclide tracers discharged from Sellafield and La Hague are transported into the Arctic Ocean where they circulate at different depth levels, marking water of Atlantic origin (Karcher et al., 2012).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Proyecto CGL2015/67014

Interactive effects of ocean acidification and elevated temperature on seaweed physiology

Archivo en PDF de la presentación realizada en el citado congresoInteractive effects of ocean acidification and elevated temperature on seaweed physiology Francisco J. L. Gordillo Departamento de Ecologia, Universidad de Malaga, Spain Seaweeds are the major primary producers of the Arctic coastal ecosystems. A significant part of the food web, both aquatic and terrestrial depend on the biomass production of these organisms. Temperature is a well known abiotic factor determining biogeographic distribution of seaweeds, but little is known on how the increase in CO₂ may modify the response of seaweeds to increased temperature. Our group aims to elucidate the mecanisms involved in the acclimation to the new environmental scenario the seaweeds are facing. Metabolic processes such as inorganic carbon utilisation have been revealed as acting in a different way in Arctic seaweeds than in their cold-temperate counterparts. In non-polar species, one of the major enzymes involved in inorganic carbon acquisition, the external carbonic anhydrase (eCA) is known to be repressed under high CO₂. However, Arctic seaweeds show high values of eCA activity and seem to be little affected by CO₂, so that eCA might have evolutively changed as part of the adaptation to low temperature. Other processes involved in the carbon balance of the organisms are photosynthesis and organic carbon release to the external medium. The release of organic carbon acts as a regulatory mechanism for internal C:N balance, so that differences in inorganic carbon utilisation (acquisition and photosynthesis) may lead to a different proportion of primary production lost as organic C. As a consequence, the acclimation of seaweeds to changing CO₂ and temperature would change the C balance of the thalli, so affecting the biogeochemical cycle of C. These responses are highly species-specific, with species taking advantage of the new scenario and others suffering an adverse effect. Changes in both the C balance and species dominance/composition may propagate to other trophic levels, potentially changing the whole ecosystem.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Polar seaweeds facing a climate change

En este trabajo se aporta información sobre la aclimatación de las macroalgas polares a las condiciones cambiantes en su ambiente natural derivadasd del cambio climático.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Seasonal changes in photosynthesis and biochemical composition in Arctic macroalgae undergoing a climatic transition

Seasonal physiology of the algal community in Kongsfjorden sublittoral ecosystem is expected to be affected by Global Climate Change. We characterized the photosynthetic performance (by means of chlorophyll a fluorescence, O2 evolution and 14C fixation) and biochemical composition (pigments, soluble carbohydrates and proteins, lipids and total C and N) of five common macroalgae of Kongsfjorden, from early autumn 2016 to late summer 2017. The studied species were Saccharina latissima and Alaria esculenta (ochrophytes), Phycodrys rubens and Ptilota gunneri (rhodophytes), and Monostroma aff. arcticum (chlorophyte, not present in March). Fluorescence results endorse the previously reported higher values of maximum quantum yield (Fv/Fm) and electron transport rates (ETRmax) in brown and green species than in red ones. In addition, a decrease in ETRmax and lower saturation irradiances in brown and green algae in summer suggest more sensitivity to continuous irradiation than in red ones. Photosynthetic parameters calculated from O2 measurements show that brown species have a better photosynthetic performance in March in response to increasing irradiance, while red and green species did in September. In general, 14C fixation was higher in September, except for A. esculenta (in March). The loss of photosynthetic capacity in summer could be attributed to a decrease in pigment concentration, except for M. arcticum. Composition also varied: in summer, under continuous illumination, brown and green species accumulated more soluble carbohydrates, while rhodophytes did in early autumn. In most species lipids had minimum values in March and proteins did not show a clear temporal pattern. In general, high N content in March and high C content in August reveal a seasonal pattern in elemental composition, related to nutrient and light availability along the year. Seasonal responses are species-specific and likely related to their particular adaptive features to the Arctic environment.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech