Nathalie Korbee

Macroalgal responses to ocean acidification depend on nutrient and light levels

Ocean acidification may benefit algae that are able to capitalise on increased carbon availability for photosynthesis but is expected to have adverse effects on calcified algae through dissolution. Shifts in dominance between primary producers will have knock-on effects on marine ecosystems and will likely vary regionally, depending on factors such as irradiance (light vs shade) and nutrient levels (oligotrophic vs eutrophic). Thus experiments are needed to evaluate interactive effects of combined stressors in the field. In this study, we investigated the physiological responses of macroalgae near a CO2 seep in oligotrophic waters off Vulcano (Italy). The algae were incubated in situ at 0.2 m depth using a combination of three mean CO2 levels (500, 700-800 and 1200 µatm CO2), two light levels (100 and 70% of surface irradiance) and two nutrient levels of N, P, and K (enriched vs non-enriched treatments) in the non-calcified macroalga Cystoseira compressa (Phaeophyceae, Fucales) and calcified Padina pavonica (Phaeophyceae, Dictyotales). A suite of biochemical assays and in vivo chlorophyll a fluorescence parameters showed that elevated CO2 levels benefitted both of these algae, although their responses varied depending on light and nutrient availability. In C. compressa, elevated CO2 treatments resulted in higher carbon content and antioxidant activity in shaded conditions both with and without nutrient enrichment - they had more Chla, phenolic and fucoxanthin with nutrient enrichment and higher quantum yield (Fv/Fm) and photosynthetic efficiency (αETR) without nutrient enrichment. In P. pavonica, elevated CO2 treatments had higher carbon content, Fv/Fm, αETR, and Chla regardless of nutrient levels - they had higher concentrations of phenolic compounds in nutrient enriched, fully-lit conditions and more antioxidants in shaded, nutrient enriched conditions. Nitrogen content increased significantly in fertilised treatments, confirming that these algae were nutrient

Acumulación de aminoácidos tipo micosporina (MAAs): biosíntesis, fotocontrol y funciones ecofisiológicas

Los efectos nocivos que inducen la radiacion UV en organismos acuaticos pueden ser aminorados a traves de varios mecanismos de fotoproteccion entre los que se encuentran la acumulacion de sustancias que absorben radiacion UV (fotoprotectores) y activacion de sistemas antioxidantes. Entre los fotoprotectores descritos se encuentran los aminoacidos tipo micosporina (MAAs). En esta revision se enfatiza sobre la capacidad fotoprotectora y antioxidante de estas sustancias. La funcion fotoprotectora de los MAAs puede deducirse de las caracteristicas fotofisicas de estos compuestos. Es sabido que actuan como pantalla pasiva disipando termicamente la energia UV absorbida. La acumulacion de MAAs se induce tanto por radiacion UV (UV-A y UV-B) como por luz azul dentro de la banda de la radiacion activa fotosintetica (PAR). Por otro lado, hay algunas referencias que indican otras funciones fisiologicas de los MAAs, incluyendo la actividad antioxidante, la regulacion osmotica y la reproductora. Siendo los MAAs sustancias nitrogenadas, recientemente se ha comenzado a estudiar la influencia de la disponibilidad de nitrogeno en la acumulacion de estos, en combinacion con UV y/o alta irradiancia de PAR. El amonio se moviliza hacia los MAAs relativamente rapido, por lo que se ha propuesto tambien a los MAAs como reservorio de nitrogeno

Effects of short-term irradiation on photoinhibition and accumulation of mycosporine-like amino acids in sun and shade species of the red algal genus Porphyra

The effect of irradiance (40 and 840 micromol photons m(-2) s(-1)) of short-term (48 h) irradiation on photosynthetic activity (estimated as oxygen evolution and as chlorophyll fluorescence), specific absorption and fluorescence excitation spectra, photosynthetic pigment accumulation (chlorophyll a and biliproteins) and UV-absorbing compounds (mycosporine-like amino acids, MAAs) was investigated in sun and shade species of the red algal genus Porphyra collected in Trondheimsfjord (Norway). In the sun type, high irradiance exposure (840 micromol photons m(-2) s(-1)) did not alter the Chl a concentration, however, exposure to a lower irradiance (40 micromol photons m(-2) s(-1)) for 48 h significantly increased the chlorophyll concentration. The content of MAAs was significantly higher in the suntype than in the shade type algae. Porphyra-334 is the main MAA in this species followed by shinorine. The total content of MAAs significantly (P<0.05) increased in the sun type after 48 h exposure to both high and low irradiances. However, in the shade type, porphyra-334 significantly decreased (P<0.05) after both high and low irradiance exposure. Photosynthetic activity (as oxygen evolution) and the optimal quantum yield (F(v)/F(m)), as an indicator of photoinhibition, decreased under low and high irradiance in the shade type algae and no full recovery was observed when the algae were transferred to very low irradiation. The sun type algae presented a higher capacity of acclimation to increased irradiance than the shade type algae. This high acclimation of sun type algae to short term high irradiance exposure (48 h) is explained by the higher thermal dissipation. This was estimated as the ratio of nonphotochemical quenching related to the light dose (q(N):dose) and by the accumulation of MAAs.

Effect of nutrient supply on photosynthesis and pigmentation to short-term stress (UV radiation) in Gracilaria conferta (Rhodophyta).

The effects of increased photosynthetic active radiation (PAR), UV radiation (UVR), and nutrient supply on photosynthetic activity, pigment content, C:N ratio and biomass yield were studied in tank cultivated Gracilaria conferta (Rhodophyta). Electron transport rate (ETR) and biliprotein content were higher under high nutrient supply (HNS), obtained from fishpond effluents, compared to low nutrient supply (LNS), in contrast to mycosporine-like amino acids (MAAs) dynamic. The high MAA content in LNS-algae could be explained by higher UVR penetration in the thallus and by the competition for the use of nutrients with other processes. Effective quantum yield decreased after short-term exposure to high irradiance whereas full recovery in shade was produced only under slightly heat shock. UVA radiation provoked an additional decrease in photosynthesis under high water temperature. UVB radiation reversed UVAs negative effect mainly with HNS. Results support that nutrient-sufficiency help G. conferta to resist environmental changes as short-term temperature increase.

Physiological response and photoacclimation capacity of Caulerpa prolifera (Forsskål) J.V. Lamouroux and Cymodocea nodosa (Ucria) Ascherson meadows in the Mar Menor lagoon (SE Spain)

The macroalga Caulerpa prolifera colonized the Mar Menor coastal lagoon after the enlargement of the main inlet in 1972, coexisting now with the previous Cymodocea nodosa meadows. The physiological response and the photoacclimation capacity of both species were studied. For this purpose in vivo chlorophyll a fluorescence, photoprotective mechanisms and oxidative stress were measured in both species in summer 2010 and exposure-recovery experiments were conducted to determine the acclimation capacity of both species. The results suggest that C. prolifera behaves as a shade-adapted species with a low photoprotective capacity, light being one of the main factors governing its distribution in the lagoon. The high photosynthetic capacity and lack of photoinhibition found in C. nodosa suggest that this species is highly photoprotected. It also possesses a high concentration of lutein and a high de-epoxidation degree, related to a much higher NPQ(max) value.

Characterization of Grateloupia lanceola (Halymeniales, Rhodophyta), an obscure foliose Grateloupia from the Iberian Peninsula, based on morphology, comparative sequence analysis and mycosporine-like amino acid composition

Foliose Grateloupia species are among the most commonly reported introduced species of red algae in European waters. Unequivocal identification at species level, however, has proven exceedingly difficult owing to a relatively low number of clear-cut diagnostic characters and considerable morphological plasticity. Because of their morphological similarity many of these species were placed in synonymy by subsequent generations of phycologists. In the present paper we demonstrate that Gratelopia lanceola, a native European species, is distinct from G. turuturu, a western Pacific alga introduced in European waters. These conclusions are based on comparative gene sequences (rbcL and LSU rDNA) as well as morphology and mycosporine-like amino acid (MAA) signatures. Even though support was largely lacking from rbcL and the combined analysis, G. lanceola was clearly separated from G. turuturu as well as other foliose species. These data, together with earlier accounts on genuine G. doryphora and G. schizophylla, indicate that foliose Grateloupia species display a clear geographic structuring, which has only become obscured by the recent introduction of morphologically similar species (pseudo-cryptic species) along Atlantic coasts and in the Mediterranean Sea. Grateloupia lanceola also showed a different MAA composition when compared with G. turuturu, regardless of spatial-temporal influences. The concentrations were about 3 mg g−1 DW and about 5 mg g−1 DW in G. turuturu and G. lanceola, respectively. The main MAA in Grateloupia lanceola was porphyra-334, which represented almost 100% of these compounds. Only some traces (<1%) of shinorine and palythine were found in this species. On the other hand, the dominant MAA in G. turuturu was shinorine, which represented approximately 92% of the total MAA content; palythine contributed about 7.5% while traces of asterina-330 were also found.

Interactive Effects of UV Radiation and Nutrients on Ecophysiology: Vulnerability and Adaptation to Climate Change

The IV Report of the Intergovernmental Panel of Climate Change (IPCC, 2007a, b) has concluded that the warming of the Earth is unequivocal as is now evident from observations of the increasing global air and ocean temperatures, the reduction of ice and snow in polar region and high mountains, and rising global average sea level. It is crucial to know the vulnerability and the ecosystem capacity of adaptation to climate change. Most of the studies are being conducted in land ecosystems and oceanic waters; meanwhile, it is necessary for a greater research effort in coastal waters, lakes, and lagoons. The IV-IPCC report defines the adaptation capacity as the capability of a system to adapt or adjust to climate change (including the climate variability and the climate extremes) to take the advantages of the opportunities or to carry the consequences. On the other hand, the vulnerability of the systems is the grade in which the systems are not capable of carrying the adverse effects of climate change. The vulnerability is a function of character, magnitude, and change rate of climate change, and also of the submitted environmental variations, the sensitivity, and capacity of adaptation of the ecosystems.

Interactive Effect of UVR and Phosphorus on the Coastal Phytoplankton Community of the Western Mediterranean Sea: Unravelling Eco-Physiological Mechanisms.

Some of the most important effects of global change on coastal marine systems include increasing nutrient inputs and higher levels of ultraviolet radiation (UVR, 280–400 nm), which could affect primary producers, a key trophic link to the functioning of marine food webs. However, interactive effects of both factors on the phytoplankton community have not been assessed for the Mediterranean Sea. An in situ factorial experiment, with two levels of ultraviolet solar radiation (UVR+PAR vs. PAR) and nutrients (control vs. P-enriched), was performed to evaluate single and UVR×P effects on metabolic, enzymatic, stoichiometric and structural phytoplanktonic variables. While most phytoplankton variables were not affected by UVR, dissolved phosphatase (APAEX) and algal P content increased in the presence of UVR, which was interpreted as an acclimation mechanism of algae to oligotrophic marine waters. Synergistic UVR×P interactive effects were positive on photosynthetic variables (i.e., maximal electron transport rate, ETRmax), but negative on primary production and phytoplankton biomass because the pulse of P unmasked the inhibitory effect of UVR. This unmasking effect might be related to greater photodamage caused by an excess of electron flux after a P pulse (higher ETRmax) without an efficient release of carbon as the mechanism to dissipate the reducing power of photosynthetic electron transport.

Short-term effects of solar UV radiation and NO3- supply on the accumulation of mycosporine-like amino acids in Pyropia columbina (Bangiales, Rhodophyta) under spring ozone depletion in the sub-Antarctic region, Chile

Abstract Short-term variations of mycosporine-like amino acids (MAAs) in Pyropia columbina (Montage) W.A. Nelson exposed to nitrate (NO3-) enrichment under different outdoor light treatments during the spring ozone depletion of 2008 in Punta Arenas (Chile) were investigated. Segments of P. columbina thalli were cultivated under three treatments of solar radiation without or with NO3- supply (0.38 mmol l-1): PAR (P), PAR+UVA (PA), and PAR+UVA+UVB (PAB). Samples were taken at 8:00 h (initial value), 9:30, 12:30, 15:30, and 18:00 h on November 8 and at 9:00 h on November 9 (recovery period). A complex dynamic of MAAs affected by light quality and NO3- supply was observed. During the light period, the highest content of MAAs was reached under PAB and NO3- enrichment, whereas MAAs increased during the recovery period in P and PAB with no NO3- supply. Five MAAs were identified: porphyra-334, shinorine, asterina-330, palythine, and mycosporine-glycine. The hourly accumulation of each MAA varied mainly according to the time of exposure and NO3- supply. In general, the percentage of porphrya-334 increased, whereas the other MAAs decreased during the exposure period. These results suggest that MAA content in P. columbina varied in the short-term (hours) and the changes were related to the solar irradiance received and NO3- availability.

Biofiltration of fishpond effluents and accumulation of N-compounds (phycobiliproteins and mycosporine-like amino acids) versus C-compounds (polysaccharides) in Hydropuntia cornea (Rhodophyta)

The biofiltration capacity, biomass-yield and accumulation of N- and C-compounds of Hydropuntia cornea were analyzed. Algae were grown in different conditions for 28 d: outdoor and indoor, with or without fishpond effluents. N-uptake efficiency of these effluents was higher than 95% after 7 d both outdoors and indoors. N-enriched conditions reduced the extent of photoinhibition and increased the maximal quantum yield in H. cornea. The biomass-yield was higher in outdoor grown-algae after 7 d and decreased independently of the treatment after 28 d. N, acid polysaccharide (AP) and mycosporine-like amino acid (MAA)-yields decreased throughout the experiment in all conditions. The highest MAA-yield was observed in fishpond effluent outdoor-grown algae, indicating a positive effect of increased radiation on MAA accumulation. However, APs were higher under N-depleted conditions. The use of MAAs as UV-screening and antioxidants, and the use of AP as immunostimulants are discussed.