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Short-term effects of pCO2 (700–380 ppm; High carbon (HC) and Low carbon (LC), respectively) and nitrate content (50–5 µM; High nitrogen (HN) and Low nitrogen (LN), respectively on photosynthesis were investigated in Ulva rigida (Chlorophyta) under solar radiation (in-situ) and in the laboratory under artificial light (ex-situ). After six days of incubation at ambient temperature (AT), algae were subjected to a 4 °C temperature increase (AT+4 °C) for 3 d. Both in-situ and ex-situ maximal electron transport rate (ETRmax) and in situ gross photosynthesis (GP), measured by O2 evolution, presented highest values under HCHN, and lowest under HCLN, across all measuring systems. Maximal quantum yield (Fv/Fm), and ETRmax of photosystem (PS) II [ETR(II)max] and PSI [ETR(I)max], decreased under HCLN at AT+4 °C. Ex situ ETR was higher than in situ ETR. At noon, Fv/Fm decreased (indicating photoinhibition), whereas ETR(II)max and maximal non-photochemical quenching (NPQmax) increased. ETR(II)max decreased under AT+ 4 °C in contrast to Fv/Fm, photosynthetic efficiency (α ETR) and saturated irradiance (EK). Thus, U. rigida exhibited a decrease in photosynthesis under acidification, changing LN, and AT+4 °C. These results emphasize the importance of studying the interaction between environmental parameters using in-situ versus ex-situ conditions, when aiming to evaluate the impact of global change on marine macroalgae.

Three macroalgal species belonging to Chlorophyta (Ulva rigida), Rhodophyta (Ellisolandia elongata) and Phaeophyceae (Heterokontophyta; Cystoseira tamariscifolia), natu- rally growing at the same shore level and representing 3 morpho-functional groups, were exposed to short-term changes in temperature under different carbon and nitrogen regimes. Experiments were conducted in outdoor tanks at 4 combinations of carbon and nitrogen levels under reduced solar radiation. In vivo chl a fluorescence parameters and pigment contents were monitored to assess diurnal physiological responses and potential for recovery. Strong fluctuations in chl a flu- orescence parameters, but not in chl a content, were observed in response to diurnal variation in solar radiation and light climate within the tanks; sensitivity varied between algal species and, in some cases, depended on the carbon and nitrogen regime. Nitrogen uptake was similarly high in U. rigida and E. elongata and lowest in C. tamariscifolia. In U. rigida and E. elongata, chl a con- centrations decreased after high-carbon treatments. Effective photosystem II quantum efficiency was reduced in all species at noon, and lowest in C. tamariscifolia. The results highlight the com- plexity of physiological short-term acclimations which were most likely linked to biochemical changes at the cellular level. Long-term experiments are required in future for more comprehen- sive investigation of the observed interactive effects of the different environmental parameters.

The presence and activation of mitogen-activated protein kinase (MAPK)-like pro- teins in 3 macroalgae with different morphology and phylogeny (Ulva rigida, Ellisolandia elon- gata and Cystoseira tamariscifolia) were studied during the experimental workshop of the Inter- national Group on Aquatic Productivity. Macroalgae were exposed in the short term (days) to different carbon and nitrogen levels and raised temperature (+4°C over ambient conditions) in mesocosms under controlled conditions mimicking current and future ocean acidification. Three MAPK-like proteins of 40, 42 and 44 kDa similar to mammalian p38 kinase (p38), stress-activated protein kinase/c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) were detected, and their phosphorylation occurred both under low- and high-carbon as well as under low- and high-nitrogen conditions (LC, HC, LN, HN, respectively). Moreover, increased temperature led to differential responses of the MAPKs in these species. In U. rigida, p38 phos- phorylation initiated the acclimation to temperature stress in LC, while this role was mainly played by JNK in HC during the first 24 h. In E. elongata, p38 was primarily activated in LCLN and in HC treatment. In C. tamariscifolia, JNK was mainly activated in LN during the first 24 h, while both p38 and JNK were activated in HC, but only after 24 h at elevated temperature. U. rigida was the only species in which ERK phosphorylation increased at increased temperature. These results suggest that both E. elongata and C. tamariscifolia are close to the upper limit of their temperature range at the temperatures tested in this work, and that Ulvales could have physiological advan- tages in Medi terranean systems in a scenario of future CO2-enrichment with high nitrogen loads.

The possible protective role against ultraviolet (UV) radiation of the sheathing leaves that wrap the young flowers of Ruppia drepanensis and Althenia orientalis was assessed. The effects of UV radiation on the viability of their pollen grains and those of R. maritima were also analysed. The absorption of the sheathing leaves of R. depranensis for visible and UV wavelengths was analysed using a spectrophotometer. Pollen grains of these species were exposed at different times to darkness, only photosynthetic active radiation (PAR), PAR+ultraviolet-A radiation (PAR+UV-A) and PAR+UVA+ ultraviolet-B radiation (PAR+UV-A+UV-B), and pollen viability was estimated by means of fluorescein diacetate test. The sheathing leaves presented a maximum absorbance at approximately 320 nm. On the other hand, the highest loss of pollen viability was produced in the presence of UV-B, especially in the case of A. orientalis. Nevertheless, viability of pollen was more affected by UV-A radiation in both Ruppia species than in A. orientalis. The effect of UV-B radiation was higher in the species with underwater pollination than in species with surface water pollination or combined surface -underwater pollination. Ecological implications are discussed.

The relationship between O(2)-based gross photosynthesis (GP) and in vivo chlorophyll fluorescence of Photosystem II-based electron transport rate (ETR) as well as the relationship between effective quantum yield of fluorescence (Phi(PSII)) and quantum yield of oxygen evolution (Phi(O_2)) were examined in the green algae Ulva rotundata and Ulva olivascens and the red alga Porphyra leucosticta collected from the field and incubated for 3 days at 100 mumol m(-2) s(-1) in nutrient enriched seawater. Maximal GP was twice as high in Ulva species than that measured in P. leucosticta. In all species ETR was saturated at much higher irradiance than GP. The initial slope of ETR versus absorbed irradiance was higher than that of GP versus absorbed irradiance. Only under absorbed irradiances below saturation or at values of GP

The effects of solar radiation and solar radiation deprived of ultraviolet radiation (λ

Short-term effects of increasing pCO(2); 380 ppm (LC) vs. 700 ppm (HC); at different nitrogen levels; 5 mu M nitrate (LN) vs. 50 mu M (HN); on the contents of protein, mycosporine-like amino acids (MAAs), phenolic compounds and total fatty acids, antioxidant activity, calcification and C: N ratios were analyzed in 3 eulittoral Mediterranean macroalgae with different bio-optical characteristics and carbon assimilation efficiencies: Cystoseira tamariscifolia (Heterokontophyta), Ulva rigida (Chlorophyta) and Ellisolandia elongata (Rhodophyta). After acclimation to different pCO(2) and nitrogen conditions for 6 d, the algae were subjected to a 4 degrees C temperature increase for 3 d. Increasing temperature and pCO(2) produced alterations in the biochemical composition of the 3 macroalgae. Short-term variations of protein levels were observed in U. rigida, with clearly decreased values in the HCLN treatment. In C. tamariscifolia, protein decreased after the temperature increase but only under LC. The interaction of temperature and N affected phenolic compounds only in U. rigida and the content of MAAs in E. elongata. The functional patterns of the 3 macroalgae in response to the pCO(2), nitrogen and temperature regimes may be explained in terms of their bio-optical characteristics and antioxidant activity. The vulnerability and acclimation of the 3 species to the expected variations of climate change factors are discussed.

A Monitoring-PAM fluorometer with high temporal resolution (every 5 min) was used to assess the effects on photosynthesis in Ulva rigida (Chlorophyta) during exposure to 2 different CO2 conditions: current ('LC', 390 ppm), and the predicted level for the year 2100 ('HC', 700 ppm) in a crossed combination with 2 different daily pulsed nitrate concentrations ('LN', 5 mu M and 'HN', 50 mu M) and 2 temperature regimes (ambient and ambient +4 degrees C). Effective quantum yield (Delta F/F-m') in the afternoon was lower under HCLN conditions than under the other treatments. The decrease in Delta F/F-m' from noon to the afternoon was significantly lower under +4 degrees C compared to ambient temperature. Maximal quantum yield (F-v/F-m) decreased during the night with a transient increase 1 to 3 h after sunset, whereas a transient increase in Delta F/F-m' was observed after sunrise. These transient increases have been related to activation/ deactivation of the electron transport rate and the relaxation of non-photochemical quenching. Relative electron transport rate was higher under the LC and +4 degrees C treatment, but the differences were not significant due to high variability in daily irradiances. Redundancy analysis on the data matrix for the light periods indicates that photosynthetically active radiation through the day is the main variable determining the physiological responses. The effects of nutrient levels (mainly carbon) and experimental increase of temperature were low but significant. During the night, the effect of nutrient availability is of special importance with an opposite effect of nitrogen compared to carbon increase. The application of the Monitoring-PAM to evaluate the effects of environmental conditions by simulating climate change variations under outdoor-controlled, semi-controlled conditions is discussed.

Aquatic macrophyte biomass, diaspore bank distribution and their relationship to spatial variability of depth, nutrients (nitrite, nitrate, ammonium and soluble reactive phosphorus) as well as sediment granulometry in an athalassohaline lake have been studied during one wet hydrological year. The results indicate that species growing in the lake show different spatial distribution patterns throughout the lake. Indirect gradient analysis (canonical analysis) results showed a first axis defined as a function of Ulva flexuosa Wulfen biomass which is, in turn, positively correlated with interstitial ammonium and Soluble Reactive Phosphorus (SRP). The second axis was mainly established due to Lamprothamnium papulosum (Wallr.) J. Groves biomass which correlated positively to depth and negatively to interstitial ammonium and SRP. These results revealed a NESW eutrophic gradient allowing the U. Flexuosa biomass proliferation. This phenomenon could increase the shadow effect over the rest of the macrophytes inhabiting this shallow lake. Moreover, the eutrophic harmful effect on the macrophyte physiology and over the diaspore bank could have important consequences in the survival of such important populations. The results reported in this study show the need for studies as the base to select sampling points for monitoring this wetland.La distribución de la biomasa de los macrófitos acuáticos y de su banco de semillas y oogonios ha sido investigada en relación a la profundidad, los nutrientes (nitrito, nitrato, amonio y fósforo soluble reactivo) y la granulometría del sedimento durante un año hidrológico húmedo. Los resultados muestran patrones de distribución diferentes en las distintas especies. Los resultados del análisis canónico basado en análisis de gradiente indirecto muestran un primer eje definido en función de la biomasa de U. Flexuosa, Wulfen que, a su vez, está positivamente correlacionada con el amonio intersticial y el fosfato soluble. El segundo eje se establecía principalmente en función de la biomasa de Lamprothamnium papulosum (Wallr.) J. Groves, que a su vez estaba positivamente relacionada con la profundidad y negativamente correlacionada con el amonio intersticial y el fosfato soluble. Estos resultados ponen de manifiesto un gradiente NE-SW de eutrofización que induce la proliferación de U. Flexuosa, lo que podría contribuir a aumentar el efecto de sombreo sobre el resto de los macrófitos de la laguna. Además la eutrofización puede ejercer un efecto negativo tanto en la fisiología de los macrófitos como sobre el banco de diásporas poniendo en riesgo la supervivencia de estas poblaciones. Los resultados obtenidos en el presente estudio resaltan la necesidad de disponer de estudios de base para seleccionar los puntos de muestreo necesarios para monitorizar este tipo de humedales.

We have studied the plasticity of the photosynthetic apparatus in the endangered aquatic macrophyte Althenia orientalis to the gradient of light availability within its meadow canopy. We determined diurnal change in situ irradiance, light quality, in vivo chlorophyll a fluorescence, ex situ oxygen evolution rates, respiration rate and pigment concentration. The levels of photosynthetic photon flux density (PFD) and ultraviolet radiation (UVR) and the red/far-red ratio decreased with depth within the canopies of A. orientalis. Apical leaves had a greater decrease of the maximal quantum yield (F v/F m) in the morning and a faster recovery rate in the afternoon than those in the basal ones. The relative electron transport rate (ETRr) was not saturated at any time of the day, even in the apical leaves that received the highest light. The maximum light-saturated rate of gross photosynthesis (GPmax) took place in apical leaves around noon. The chlorophyll a/b ratio values were higher, and the chlorophyll/carotenoid ratio values lower, in apical leaves than basal ones. The highest concentrations in total carotenoids were reached in the apical leaves around noon. A. orientalis has a high capacity to acclimatize to the changes in the light environment, both in quality and quantity, presenting sun and shade leaves in the same stem through the vertical gradient in the canopy.

In vivo chlorophyll fluorescence measured by pulse amplitude modulated (PAM) fluorometry was used as an indicator of photosynthetic activity in tank-cultivated red algae wGracilaria cornea and Asparagopsis armata (tetrasporophyte phase, previously known as Falkenbergia rufolanosa)x using effluent seawater from sea bream fishponds (Sparus aurata). Optimal quantum yield of indoorgrown G. cornea did not change during the period analysed (2 months). In contrast, optimal quantum yield decreased drastically in algae transferred from indoor to outdoor conditions. Maximal electron transport rate increased and photosynthetic pigments decreased in algae growing outdoors, indicating an acclimation to high irradiance. After 16 days, chlorophyll fluorescence decreased drastically and recovered partially when algae were transferred again from outdoor to indoor conditions. Falkenbergia rufolanosa was grown at three different biomass densities (4, 6 and 8 g l -1 ). The effects of three consecutive air compressor failure events on the photosynthetic activity were followed. An apparent degradation of the physiological conditions of the algae (resulting in their bleaching) was observed, concomitant with a strong decrease in the optimal quantum yield. This decrease was higher at algal biomass densities of 4gl -1 than at 6 or 8 g l-1. Three days after transfer to optimal conditions, i.e., normal aeration conditions, optimal quantum yield reached values around 0.50–0.55, close to the values before stress conditions. The results revealed that the use of chlorophyll fluorescence is a powerful means to rapidly detect different stress situations in integrated cultivation of seaweeds using fishpond effluents. In particular, the optimal quantum yield of algae can be monitored regularly as an early warning of the physiological stress in cultures.