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Biochemical compositions and photosynthetic characteristics of three naturally cohabitated macroalgae, Ulva fasciata, Sargassum hemiphyllum and Grateloupia livida, were comparably explored in the field conditions in Daya Bay, northern South China Sea, as well as their responses to temperature rise. Chlorophyll a (Chl a) and carotenoids contents of U. fasciata were 1.00 ± 0.15 and 0.57 ± 0.08 mg g-1 in fresh weight (FW), being about one- and two-fold higher than that of S. hemiphyllum and G. livida; and the carbohydrate content was 20.3 ± 0.07 mg g-1 FW, being about three- and one-fold higher, respectively. Throughout the day, the maximal photochemical quantum yield (FV/FM) of Photosystem II (PS II) of these three macroalgae species decreased from morning to noon, then increased to dusk and kept steady at nighttime. Consistently, the rapid light curve-derived light utilization efficiency (α) and maximum relative electron transfer rate (rETRmax) were lower at noon than that at morning- or night-time. The FV/FM of U. fasciata (varying from 0.78 to 0.32) was 38% higher than that of G. livida throughout the day, and that of S. hemiphyllum was intermediate. The superoxide dismutase (SOD) and catalase (CAT) activities in U. fasciata were lower than that in S. hemiphyllum and G. livida. Moreover, the rises in temperature species-specifically mediated the damage (k) caused by stressful high light and the corresponding repair (r) to photosynthetic apparatus, making the r/k ratio increase with the rising temperature in U. fasciata, unchanged in S. hemiphyllum but decreased in G. livida. Our results indicate that U. fasciata may compete with S. hemiphyllum or G. livida and dominate the macroalgae community under aggravatedly warming future in the Daya Bay.

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Little attention has been given to the combined effects of elevated atmospheric CO2-induced ocean acidification (OA) and heavy metal pollution on marine macroalgae at the young stage. This study investigated the mutual effects of copper (Cu) and elevated CO2 on the young sporophytes of brown macroalgae Sargassum fusiforme. A matrix of four copper concentrations, 0, 0.025, 0.075 and 0.15 mg‧L-1, and two levels of CO2 (ambient CO2: 400 µatm; elevated CO2: 1,000 µatm) were used. High concentration of copper exposure greatly depressed photosynthesis and growth of the young sporophytes of S. fusiforme by reducing the apparent photosynthetic efficiency (ɑ), maximum net photosynthetic oxygen evolution rate (Pmax), maximum photochemical quantum yield (Fv/Fm) and pigments content (Chl a and Car). While elevated CO2 alone had obscure impact on this alga. However, the inhibition of Cu stress on Fv/Fm was weakened by elevated CO2, which also decreased the light compensation point (Ic). Meanwhile, the Cu2+-induced ascent in the dark respiration rate (Rd) and superoxide dismutase (SOD) activity was mitigated under the growth with elevated CO2, suggesting an alleviated oxidative stress. Overall, we propose that, under CO2 enrichment condition, the young sporophytes of S. fusiforme may increase photosynthesis efficiency and synthesize less enzymatic antioxidants in face of increasing Cu stress.

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In this study, we examined the effects of increased temperature (15, 20 and 25 °C) and different light levels (50, 200 µmol photons m-2 s-1) on two widely distributed diatoms, namely Phaeodactylum tricornutum and Thalassiosira weissflogii. Results showed that increasing light level counteracted the negative effects of high temperature on photosynthesis in both species, suggesting an antagonistic interaction between light and temperature. Contrary to the above results, light limitation diminished the temperature-sensitivity of carbonic anhydrase activity in two diatoms. We also observed species-specific responses of biomass, where increased temperature significantly decreased the biomass of P. tricornutum at both low and high light levels but showed no effects on T. weissflogii. Our study demonstrated that light can alter the physiological responses of diatoms to temperature but also revealed interspecific variations. We predict that in the future ocean with shallower upper mixed layer, T. weissflogii may be more competitive than P. tricornutum.

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We investigated how elevated CO2 affects the responses of Gracilariopsis lemaneiformis and Ulva lactuca to NH4+ enrichments. All algae were incubated under four nutritional conditions (zero addition, 100, 500, and 2500 µM NH4+), and two CO2 levels (390 ppm and 1000 ppm). The growth, photosynthesis, and soluble protein contents of both species increased under the eutrophication condition (100 µM NH4+). However, the growth and carotenoid contents of the two species declined when NH4+ concentration increased. Under the super eutrophication condition (2500 µM NH4+), all indexes measured in G. lemaneiformis were suppressed, while the growth and photosynthesis in U. lactuca changed indistinctively, both compared with the control. Moreover, under the super eutrophication condition, elevated CO2 reduced the suppression in the growth of G. lemaneiformis, but decreased the growth of U. lactuca. Nonetheless, G. lemaneiformis displayed much lower growth rates than U. lactuca under the super eutrophication and elevated CO2 condition.

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Diatoms are experiencing striking fluctuations in seawater carbonate chemistry in the natural marine environment, especially in coastal seawaters. Here, we show that the diatoms Thalassiosira weissflogii and Phaeodactylum tricornutum, which utilize different carbon acquisition mechanisms, respond differently to short-term changes in seawater carbonate chemistry. Our results showed that T. weissflogii showed significantly higher photosynthetic oxygen evolution rates than that of P. tricornutum at low levels of CO2 or HCO3-. This suggests that T. weissflogii had higher affinities for CO2 or HCO3- when their concentrations were not sufficient to support saturated growth and photosynthesis. While the activity of Rubisco in P. tricornutum positively correlated with carbonic anhydrases (CA), we observed negative relationship between Rubisco and CA activity in the diatom T. weissflogii. These contrasting physiological responses of diatoms with varied carbon acquisition mechanisms indicate different abilities to cope up with abrupt changes in seawater carbonate chemistry. We propose that the ability to respond to varying carbonate chemistry may act as one determinant of the diatom distributions and phytoplankton community structures.

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A high removal rate (>99.7%) of combined arsenite (As(III)) and Cd (Cd(II)) in low concentration (1000 µg/L) from contaminated water was achieved by a calcined MgZnFe-CO3 layered double hydroxide (CMZF) adsorbent. Batch control studies and a series of spectroscopy detection technologies were employed to investigate the removal mechanism and interactions between As(III) and Cd(II) on the interface of water/CMZF. Synergistic adsorption and photooxidation occurred based on the systematical kinetic and isotherm studies. The enhanced removal of As(III) was achieved by the photooxidation, formation of ternary As(III)Cd(II) surface complexes and enhanced hydrogen bond. Meanwhile, oxidative formed negative charged As(V) could reduce the electrostatic repulsion force between Cd(II) cations and play a role as anion bridging, consequently resulted in a stronger attraction between CMZF and Cd(II). Combined with the verdicts of relevant characterizations such as XRD, XPS and EPR, it was assumed that the deep co-removal mechanism could be attributed to the coupling of various processes including intercalation, complexation, photooxidation of As(III) and precipitation of CdCO3. Moreover, the successful removal of As(III) and Cd(II) from real water matrix qualified the CMZF a potentially attractive adsorbent for both As(III) and Cd(II) deep treatment in practical engineering.

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Intertidal macroalgae suffer different environmental conditions and mat densities during growing period. In the present study, Ulva lactuca Linnaeus were collected from high, intermediate, and low tidal zones at Nan'ao Island, China. These algal photosynthetic pigments and photosynthesis behaviors with different mat densities were measured. The aim is to examine how the physiological responses and acclimation match the representative tidal distribution and algal mat density. The photosynthetic pigment (chlorophyll a and carotenoid) contents and irradiance-saturated maximum photosynthetic rates (Pmax) were greater in low zone-grown U. lactuca compared with the algae grown at high and intermediate zones. Under low algal mat density, the Pmax, apparent photosynthetic efficiency (α), and dark respiration rate (Rd) of U. lactuca grown at low zone were increased, whereas the irradiance saturation points (Ik) were decreased, compared with the algae grown at higher zone. However, the Pmax of high and intermediate zone-grown U. lactuca at high algal mat density were greater than at low density. Moreover, the pH compensation point of low zone-grown thalli (9.98) was lower than the higher zone-grown thalli (more than 10.15); however, the chlorophyll fluorescence parameters (reflect photosynthetic system activity) of the thalli collected from the three different zones were similar. Therefore, we proposed that the effects of varied densities on the photosynthetic rates of these three tidal zone-grown U. lactuca thalli were different, which might be related with different capacity of HCO3- utilization of macroalgae at their zonations.

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The frequent outbreaks of cyanobacteria bloom are often accompanied by the generation and release of reduced phosphorus species (e.g., phosphine), which raises interesting questions regarding their potential algae-related effects. To clarify the physiological and biochemical responses of cyanobacteria to phosphine, Microcystis aeruginosa was treated with different concentrations of phosphine. Net photosynthetic rate, total antioxidant capacity (T-AOC), catalase (CAT) activity, and the concentrations of chlorophyll a, carotenoid and total protein were investigated and scanning electron microscopy (SEM) was conducted to elucidate the physiological and biochemical responses of M. aeruginosa to phosphine. The results showed that phosphine was beneficial to the growth of algal cells after M. aeruginosa acclimatized to the treatment of phosphine, and treatment with 2.48 × 10-2 mg/L phosphine had a greater positive effect on the growth and reproduction of M. aeruginosa than 7.51 × 10-3 mg/L phosphine, in which most algal cells were smooth and flat on day 16. Treatment with the high concentration of phosphine (7.51 × 10-2 mg/L) for 16 d reduced T-AOC, CAT activity, net photosynthetic rate, and the concentrations of chlorophyll a, carotenoid and total protein of M. aeruginosa to the minimums, resulting in the lysis and death of M. aeruginosa cells, which indicates phosphine has a toxic effect on the growth of algal cells. However, the high concentration of phosphine (7.51 × 10-2 mg/L) had a greater positive effect on the growth of M. aeruginosa cells than the lower two (7.51 × 10-3 mg/L and 2.48 × 10-2 mg/L) from 3 d to 12 d. Our findings provide insight into how phosphine potentially affects the growth of M. aeruginosa cells and the important roles of elevated phosphine on the outbreak of cyanobacteria bloom.

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Cadmium is one of the major heavy metal pollutions in coastal waters, and it is well known that cadmium at trace concentration is toxic to macroalgae. Change in marine carbonate system and ocean acidification caused by elevated atmospheric CO2 also alter physiological characteristics of macroalgae. However, less research is focused on the combined impacts of elevated CO2 and cadmium pollution on the growth and physiology in macroalgae. In this study, the maricultivated macroalga Pyropia haitanensis (Rhodophyta) was cultured at three levels of Cd2+ (control, 4 and 12 mg L-1) and two concentrations of CO2, the ambient CO2 (AC, 410 ppm) and elevated CO2 (HC, 1100 ppm). The results showed that 12 mg L-1 Cd2+ significantly suppressed the relative growth rate and superoxide dismutase activity in AC-grown P. haitanensis, while such inhibition extents by Cd2+ were alleviated in HC-grown algae. Cd2+ had no effects on efficiency of electron transport (α) and maximum electron transport rate (ETRmax), but α was increased by elevated CO2. Cd2+ dramatically suppressed the maximum net photosynthesis oxygen evolution rate (NPRm) and the minimum saturation irradiance (Ik) when the algal thalli were grown at AC, while such suppression of NPRm by Cd2+ was much decreased when the thalli were grown at HC. Collectively, our results suggested that elevated CO2 would alleviate Cd2+ toxicity on P. haitanensis.

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Physiological metabolisms of seaweeds usually suffered climate changes in the field. Gracilariopsis lemaneiformis and Ulva lactuca, collected from Nan'ao Island, Shantou, China, were cultured under ambient and elevated CO2 supply (390 and 800 µl L-1), with low and high temperatures (15 °C and 25 °C) for 2 weeks, aiming to compare the difference of the main physiological metabolism between two seaweed species in response to the elevated CO2 and high temperature. At 15 °C, the pH reduction in the culture medium caused by elevated CO2 was larger in G. lemaneiformis than in U. lactuca. At 25 °C, elevated CO2 significantly increased photosynthetic rates (Pn or Pg) and maintained constant respiratory rates (Rd) in G. lemaneiformis. However, for 25 °C-grown U. lactuca, the increment of CO2 did not enhance the Pn (Pg) rates but rapidly decreased the Rd rates itself. With the higher Rd/Pg ratios in G. lemaneiformis than U. lactuca, the warming thereby promoted more allocation of photosynthetic products to respiratory consumption in G. lemaneiformis. Both Pg and Rd rates exhibited lower temperature acclimation in two seaweeds. In addition, elevated CO2 markedly increased the relative growth rate (RGR) and phycobiliprotein (PB) contents at 25 °C, but exhibited no enhancement of chlorophyll a (Chl a), carotenoids (Car), soluble carbohydrate (SC), and soluble protein (SP) contents in G. lemaneiformis, with the reduction of SC when temperature increased only. We suggested that climate changes were probably a more benefit to U. lactuca than to G. lemaneiformis, inherently justifying the metabolism during G. lemaneiformis maricultivation.

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The branches and mass of Gracilaria lemaneiformis increase with growth season, and the thalli sink to deeper depths with increasing biomass density during maricultivation. The changing depth and algal mat density may affect the physiology of the algae. In the present study, the photosynthetic behaviors regarding different biomass densities in G. lemaneiformis thalli collected from different stocking depths were determined, to examine how photosynthesis of this farmed alga was affected by the growth depths and algal mat densities. Our results showed that the chlorophyll a (Chl a), carotenoids (Car), phycoerythrin (PE) contents, and irradiance-saturated maximum photosynthetic rates (P max) of the deeper layer-grown algae were significantly increased relative to the surface layer-grown algae. The P max, apparent photosynthetic efficiency (α) and dark respiration rate (R d) of G. lemaneiformis thalli, were reduced, whereas the irradiance saturation points (I k) were increased, with the increasing algal mat density. We proposed that appropriate measures are needed to trade off the stocking depth and biomass density, in an effort to maintain a relative high photosynthetic productivity during G. lemaneiformis maricultivation.

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Ocean acidification caused by rising CO2 is predicted to increase the concentrations of dissolved species of Fe(II) and Fe(III), leading to the enhanced photosynthetic carbon sequestration in some algal species. In this study, the carbon and nitrogen metabolism in responses to increased iron availability under two CO2 levels (390 µL L-1 and 1000 µL L-1), were investigated in the maricultivated macroalga Pyropia haitanensis (Rhodophyta). The results showed that, elevated CO2 increased soluble carbonhydrate (SC) contents, resulting from enhanced photosynthesis and photosynthetic pigment synthesis in this algae, but declined its soluble protein (SP) contents, resulting in increased ratio of SC/SP. This enhanced photosynthesis performance and carbon accumulation was more significant under iron enrichment condition in seawater, with higher iron uptake rate at high CO2 level. As a key essential biogenic element for algae, Fe-replete functionally contributed to P. haitanensis photosynthesis. Increased SC fundamentally provided carbon skeletons for nitrogen assimilation. The significant increase of carbon and nitrogen assimilation finally contributed to enhanced growth in this alga. This was also intuitively reflected by respiration that provided energy for cellular metabolism and algal growth. We propose that, in the predicted scenario of rising atmospheric CO2, P. haitanensis is capable to adjust its physiology by increasing its carbon and nitrogen metabolism to acclimate the acidified seawater, at the background of global climate change and simultaneously increased iron concentration due to decreased pH levels.

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The key step to realize metal recovery from bioleaching solutions is the recovery of copper from bioleaching lixivium of waste printed circuit boards in high-grade form. The influences of cathode material, current density, initial pH and initial copper ion concentration on the efficiency and energy consumption of copper recovery from artificial bioleaching lixivium under condition of constant current were investigated using an electro-deposition approach. The results showed that the larger specific surface area of the cathode material (carbon felt) led to the higher copper recovery efficiency (the recovery efficiencies of the anode and the cathode chambers were 96.56% and 99.25%, respectively) and the smaller the total and unit mass product energy consumption (the total and unit mass product energy consumptions were 0.022 kW x h and 15.71 kW x h x kg(-1), respectively). The copper recovery efficiency and energy consumption increased with the increase of current density. When the current density was 155.56 mA x cm(-2), the highest copper recovery efficiencies in the anode and cathode chambers reached 98.51% and 99.37%, respectively. Accordingly, the highest total and unit mass product energy consumptions were 0.037 kW x h and 24.34 kW x h x kg(-1), respectively. The copper recovery efficiency was also significantly affected by the initial copper ion concentration. The increase of the initial copper ion concentration would lead to faster decrease of copper ion concentration, higher total energy consumption, and lower unit mass product consumption. However, the initial pH had no significant effect on the copper recovery efficiency. Under the optimal conditions (carbon felt for cathode materials, current density of 111.11 mA x cm(-2), initial pH of 2.0, and initial copper ion concentration of 10 g x L(-1)), the copper recovery efficiencies of the anode and cathode chambers were 96.75% and 99.35%, and the total and unit mass product energy consumptions were 0.021 kW x h and 14.61 kW x h x kg(-1), respectively. The deposited copper on the cathode material was fascicularly distributed and no oxygen was detected.

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The red seaweed Gracilariopsis is an important crop extensively cultivated in China for high-quality raw agar. In the cultivation site at Nanao Island, Shantou, China, G. lemaneiformis experiences high variability in environmental conditions like seawater temperature. In this study, G. lemaneiformis was cultured at 12, 19, or 26°C for 3 weeks, to examine its photosynthetic acclimation to changing temperature. Growth rates were highest in G. lemaneiformis thalli grown at 19°C, and were reduced with either decreased or increased temperature. The irradiance-saturated rate of photosynthesis (Pmax ) decreased with decreasing temperature, but increased significantly with prolonged cultivation at lower temperatures, indicating the potential for photosynthesis acclimation to lower temperature. Moreover, Pmax increased with increasing temperature (~30 µmol O2  · g(-1) FW · h(-1) at 12°C to 70 µmol O2  · g(-1) FW · h(-1) at 26°C). The irradiance compensation point for photosynthesis (Ic ) decreased significantly with increasing temperature (28 µmol photons · m(-2)  · s(-1) at high temperature vs. 38 µmol photons · m(-2)  · s(-1) at low temperature). Both the photosynthetic light- and carbon-use efficiencies increased with increasing growth or temperatures (from 12°C to 26°C). The results suggested that the thermal acclimation of photosynthetic performance of G. lemaneiformis would have important ecophysiological implications in sea cultivation for improving photosynthesis at low temperature and maintaining high standing biomass during summer. Ongoing climate change (increasing atmospheric CO2 and global warming) may enhance biomass production in G. lemaneiformis mariculture through the improved photosynthetic performances in response to increasing temperature.

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The responses of respiration and photosynthesis to temperature fluctuations in marine macroalgae have the potential to significantly affect coastal carbon fluxes and sequestration. In this study, the marine red macroalga Gracilaria lemaneiformis was cultured at three different temperatures (12, 19, and 26°C) and at high- and low-nitrogen (N) availability, to investigate the acclimation potential of respiration and photosynthesis to temperature change. Measurements of respiratory and photosynthetic rates were made at five temperatures (7°C-33°C). An instantaneous change in temperature resulted in a change in the rates of respiration and photosynthesis, and the temperature sensitivities (i.e., the Q10 value) for both the metabolic processes were lower in 26°C-grown algae than 12°C- or 19°C-grown algae. Both respiration and photosynthesis acclimated to long-term changes in temperature, irrespective of the N availability under which the algae were grown; respiration displayed strong acclimation, whereas photosynthesis only exhibited a partial acclimation response to changing growth temperatures. The ratio of respiration to gross photosynthesis was higher in 12°C-grown algae, but displayed little difference between the algae grown at 19°C and 26°C. We propose that it is unlikely that respiration in G. lemaneiformis would increase significantly with global warming, although photosynthesis would increase at moderately elevated temperatures.

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The photosynthetic oxygen evolution characteristics were examined in both vegetative (blade) and sexual reproductive (receptacle) tissues of Sargassum henslowianum (Fucales, Phaeophyta) from the Shenao bay of Nanao Island, China, to establish the mechanism of photosynthetic acquisition of inorganic carbon (Ci) in this species. In natural seawater (pH 8.1, ca. 2.2 mM Ci), irradiance-saturated net photosynthetic rate (NPR) was greater by 25.3% in blade than receptacle, whereas dark respiratory rate (DR) was 2-fold higher in receptacle than blade. NPR at pH 8.1 was nearly saturated with the 2.2 mM Ci for both blade and receptacle. However, the values of the half-saturation constant for Ci were sharply increased at pH 9.0. NPR was significantly affected, but DR was remained unchanged, with the variation of the pH values in seawater. The data from the final pH value derived from the pH-drift experiments and the comparison between the measured and theoretically estimated photosynthetic rates suggested that both blade and receptacle were capable of acquiring HCO(3)(-) in seawater. The inhibitors experiments showed that a HCO(3)(-) dehydration mechanism mediated by external carbonic anhydrase activity occurred in both the blade and receptacle tissues of S. henslowianum. The proton buffer TRIS had no inhibitory effect on NPR at normal pH value in natural seawater (pH 8.1), but it significantly depressed NPR at pH 9.0. This suggested that proton transport occurred at the outside of the plasma membrane facilitated the operation of the carbon acquisition at pH 9.0. It was proposed that the strategy of photosynthetic carbon acquisition at higher pH would prevent the alga from the damage of over-excitation and photoinhibition in case of sunshine and calm water. We concluded that the blade and receptacle tissues of S. henslowianum have similar mechanism of acquisition of exogenous Ci from seawater to drive photosynthesis; yet they are differentiated more or less with the photosynthetic properties.

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The short-term and long-term effects of elevated CO2 on photosynthesis and respiration were examined in cultures of the marine brown macroalga Hizikia fusiformis (Harv.) Okamura grown under ambient (375 µL · L(-1) ) and elevated (700 µL · L(-1) ) CO2 concentrations and at low and high N availability. Short-term exposure to CO2 enrichment stimulated photosynthesis, and this stimulation was maintained with prolonged growth at elevated CO2 , regardless of the N levels in culture, indicating no down-regulation of photosynthesis with prolonged growth at elevated CO2 . However, the photosynthetic rate of low-N-grown H. fusiformis was more responsive to CO2 enrichment than that of high-N-grown algae. Elevation of CO2 concentration increased the value of K1/2 (Ci) (the half-saturation constant) for photosynthesis, whereas high N supply lowered it. Neither short-term nor long-term CO2 enrichment had inhibitory effects on respiration rate, irrespective of the N supply, under which the algae were grown. Under high-N growth, the Q10 value of respiration was higher in the elevated-CO2 -grown algae than the ambient-CO2 -grown algae. Either short- or long-term exposure to CO2 enrichment decreased respiration as a proportion of gross photosynthesis (Pg) in low-N-grown H. fusiformis. It was proposed that in a future world of higher atmospheric CO2 concentration and simultaneous coastal eutrophication, the respiratory carbon flux would be more sensitive to changing temperature.

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Gracilaria lemaneiformis was exposed to 0, 25, 50, 100, 250 and 500 microg x L(-1) of Cu2+ to study its physiological responses to Cu2+ stress. When the Cu2+ concentration was > or = 50 microg x L(-1), the relative growth rate (RGR) of G. lemaneiformis decreased significantly, and the optimal quantum yield (Fv/Fm), the maximum relative electron transfer rate (rETRmax), and the relative electron transfer efficiency (alpha) exhibited the same variation trend, compared with the control. With the increase of Cu2+ concentration, the maximum net photosynthetic rate (Pmax) and light saturation point (LSP) decreased significantly, light compensation point (LCP) had a significant increase, while chlorophyll a, carotenoid, and phycobiliprotein contents decreased after an initial increase. When the Cu2+ concentration reached 500 microg x L(-1), the chlorophyll a, carotenoid, and phycobiliprotein contents decreased significantly. It was suggested that G. lemaneiformis could tolerate low concentration Cu2+ stress, but its physiological activities were inhibited markedly when exposed to > or =50 microg x L(-1) of Cu2+.

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Marine photosynthesis drives the oceanic biological CO(2) pump to absorb CO(2) from the atmosphere, which sinks more than one third of the industry-originated CO(2) into the ocean. The increasing atmospheric CO(2) and subsequent rise of pCO(2) in seawater, which alters the carbonate system and related chemical reactions and results in lower pH and higher HCO(3) (-) concentration, affect photosynthetic CO(2) fixation processes of phytoplanktonic and macroalgal species in direct and/or indirect ways. Although many unicellular and multicellular species can operate CO(2)-concentrating mechanisms (CCMs) to utilize the large HCO(3) (-) pool in seawater, enriched CO(2) up to several times the present atmospheric level has been shown to enhance photosynthesis and growth of both phytoplanktonic and macro-species that have less capacity of CCMs. Even for species that operate active CCMs and those whose photosynthesis is not limited by CO(2) in seawater, increased CO(2) levels can down-regulate their CCMs and therefore enhance their growth under light-limiting conditions (at higher CO(2) levels, less light energy is required to drive CCM). Altered physiological performances under high-CO(2) conditions may cause genetic alteration in view of adaptation over long time scale. Marine algae may adapt to a high CO(2) oceanic environment so that the evolved communities in future are likely to be genetically different from the contemporary communities. However, most of the previous studies have been carried out under indoor conditions without considering the acidifying effects on seawater by increased CO(2) and other interacting environmental factors, and little has been documented so far to explain how physiology of marine primary producers performs in a high-CO(2) and low-pH ocean.

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Gamete release is an essential event in artificial seeding of the economic brown seaweed, Hizikia fusiforme. Mass egg release occurred in the dark, with few eggs being discharged in the light. Release of eggs was elicited with eight practical salinity units (one PSU identical with 1 g sea salts l(-1)) and was inhibited by salinity levels >32 PSU. Egg release was optimal at 23 degrees C, and was decreased by 72% in agitated seawater compared to unstirred seawater. Inhibitors of photosynthesis and ions channels suppressed egg release, indicating that this process was physiologically associated with photosynthetic activity and ion transport.

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