DARK CARBON FIXATION STUDIES ON THE INTERTIDAL MACROALGA ASCOPHYLLUM NODOSUM (PHAEOPHYTA) 1

The characteristics of dark carbon fixation by Ascophyllum nodosum were investigated. In longitudinal profile the maximum rates of dark and light dependent fixation are found at the apex. The use of Michaelis-Menten kinetics did not suitably describe the relationship between the uptake rate in the dark and the total inorganic carbon concentration. Dark fixation was saturated at a total inorganic carbon concentration [TIC] of 2.5 mM. The use of the Hill-Whittingham equation to describe the uptake curve indicates that the process is diffusion limited. Comparisons of dark fixation at high (8.0) and low (5.2) pH suggest that bicarbonate ions are used as a source of inorganic carbon. The transfer of ¹⁴C, fixed in the dark, from the ethanol soluble to the insoluble fraction was relatively slow irrespective of the light treatment during the chase period. Ascophyllum nodosum displays a small diel fluctuation in the pH of aqueous extracts and titratable acidity similar to that displayed by CAM plants. The significance of dark fixation to the overall carbon budget is discussed.     

Isolation and characterization of mutants of two diazotrophic cyanobacteria tolerant to high concentrations of inorganic carbon

Diazotrophic heterocystous cyanobacteria Nostoc calcicola and Anabaena sp. ARM 629 were investigated for their ability to grow in presence of sodium bicarbonate (NaHCO3) or carbon dioxide (CO2) under cultural conditions. Maximum growth was observed in 75 mM NaHCO3 and 5% CO2 in N. calcicola and Anabaena ARM 629, respectively. Although their growth rate declined, N. calcicola and Anabaena sp. could tolerate upto 250 mM NaHCO3 and 20% CO2, respectively. N-methyl-N'-nitro N nitrosoguanidine induced mutants of these cyanobacteria were isolated which showed growth upto 1 M NaHCO3 (N. calcicola) or 50% CO2 (Anabaena sp.) in comparison to their wild types. The mutants also showed cross-resistance to either of the inorganic carbon compounds, which was not observed for wild type. It was concluded that mutants were altered in multiple properties enabling them to grow at elevated levels of inorganic carbon compounds.     

Growth limitation of three Arctic sea ice algal species: effects of salinity, pH, and inorganic carbon availability

The effect of salinity, pH, and dissolved inorganic carbon (TCO₂) on growth and survival of three Arctic sea ice algal species, two diatoms (Fragilariopsis nana and Fragilariopsis sp.), and one species of chlorophyte (Chlamydomonas sp.) was assessed in controlled laboratory experiments. Our results suggest that the chlorophyte and the two diatoms have different tolerance to fluctuations in salinity and pH. The two species of diatoms exhibited maximum growth rates at a salinity of 33, and growth rates at a salinity of 100 were reduced by 50% compared to at a salinity of 33. Growth ceased at a salinity of 150. The chlorophyte species was more sensitive to high salinities than the two diatom species. Growth rate of the chlorophyte was greatly reduced already at a salinity of 50 and it could not grow at salinities above 100. At salinity 33 and constant TCO₂ concentration, all species exhibited maximal growth rate at pH 8.0 and/or 8.5. The two diatom species stopped growing at pH > 9.5, while the chlorophyte species still was able to grow at a rate which was 1/3 of its maximum growth rate at pH 10. Thus, Chlamydomonas sp. was able to grow at high pH levels in the succession experiment and therefore outcompeted the two diatom species. Complementary experiments indicated that growth was mainly limited by pH, while inorganic carbon limitation only played an important role at very high pH levels and low TCO₂ concentrations.     

Nutrient limitation of phytoplankton in a naturally acidic lake (Lake Caviahue, Argentina)

As a result of a low pH, the inorganic carbon of acidic lakes is present as CO₂ at air-equilibrium concentration and is substantially lower than the inorganic carbon concentration in higher-pH waters with bicarbonate. This situation is quite common in artificially acidified lakes and where inorganic carbon is considered the limiting factor in phytoplankton growth. Apart from low inorganic carbon content, Lake Caviahue in Argentina has low nitrogen and high phosphorus content. The aim of this work was to assess the importance of inorganic carbon, phosphorus, and nitrogen, relating data on lake nutrients to phytoplankton species requirements. Lake samples taken in the 2004–2006 period did not show any particular trend in the vertical distribution of the water column of ammonium, inorganic carbon, and phosphorus with reference to either seasonality or depth. A decrease of some 15% in the lake’s phosphorus concentration was observed over the same period. Although the total phytoplankton biomass in Lake Caviahue was similar throughout the period, a seasonal variation was observed. Lab bioassays were carried out with solutions of bicarbonates, ammonium, nitrates, and phosphate. We worked with three species separately, namely, two chlorophytes, Keratococcus rhaphidioides and Watanabea sp.; and one euglenophyte, Euglena mutabilis. Answers to specific nutrient requirements differed for each algal species: both chlorophytes prefer ammonium or nitrates added on their own, whereas the euglenophyte registered a higher growth rate with the joint addition of ammonium and phosphorus. Even when the limiting nutrient(s) for phytoplankton yield and rate varied between species, we observed a tendency for nitrogen limitation in Lake Caviahue.     

CO2对转基因鱼腥藻生长的影响

为了进一步探索转基因鱼腥藻高密度培养的方法,在小型气升式反应器中研究了CO2对转基因鱼腥藻7120培养的影响。结果发现转基因鱼腥藻培养过程中通入5％ CO2能促进藻细胞生长,12d生物量提高7．44％,由于光照限制,不能大幅提高15d收获生物量,但生长周期能缩短近20％;而高浓度(10％)的CO2抑制转基因鱼腥藻的生长。CO2是通过调节pH值和影响碳源利用来影响藻细胞生长的,合适浓度的CO2有利于转基因鱼腥藻的培养。     

Modelling microalgal activity as a function of inorganic carbon concentration: accounting for the impact of pH on the bicarbonate system

The aim of this study is to develop a generic model that can predict algal photosynthetic activity as a function of total inorganic carbon and pH, which will assist in the design and operation of algal culture systems. This is important as the availability of inorganic carbon plays a critical role in algal growth and product accumulation, and in practice, pH is not constant in an algal culture. Hence, such a model will assist in predicting and understanding carbon limitation in algae growth and product accumulation systems. The model builds on published work on inorganic carbon uptake in natural algal systems and extends it to systematically account for wide pH and total inorganic carbon ranges. This study develops and validates a simple model which integrates a summative carbon dioxide and bicarbonate Monod kinetic relationship with inorganic carbon equilibrium chemistry. This is the first time that the algal photosynthetic oxygen production rate has been described as a function of both total inorganic carbon and pH. The model was tested against published and experimental data over an extended pH and total inorganic carbon range. Kinetic parameters estimated by the model match those presented in the literature. The Chlorella alga tested in the experiments showed little affinity for bicarbonate which agrees with previous observations for this alga.     

Circadian rhythm and fast responses to blue light of photosynthesis in Ectocarpus (Phaeophyta,Ectocarpales)

Photosynthesis of Ectocarpus siliculosus (Dillwyn) Lyngb. under continuous saturating red irradiation follows a circadian rhythm. Blue-light pulses rapidly stimulate photosynthesis with high effectiveness in the troughs of this rhythm but the effectiveness of such pulses is much lower at its peaks. In an attempt to understand how blue light and the rhythm affected photosynthesis, the effects of inorganic carbon on photosynthetic light saturation curves were studied under different irradiation conditions. The circadian rhythm of photosynthesis was apparent only at irradiances which were not limiting for photosynthesis. The same was found for blue-light-stimulated photosynthesis, although stimulation was observed also under very low red-light irradiances after a period of adaptation, provided that the inorganic-carbon concentration was not in excess. Double-reciprocal plots of light-saturated photosynthetic rates versus the concentration of total inorganic carbon (up to 10 mM total inorganic carbon) were linear and had a common constant for half-saturation (3.6 mM at pH 8) at both the troughs and the peaks of the rhythm and before and after blue-light pulses. Only at very low carbon concentrations was a clear deviation found from these lines for photosynthesis at the rhythm maxima (red and blue light), which indicated that the strong carbon limitation specifically affected photosynthesis at the peak phases of the rhythm. Very high inorganic carbon concentrations (20 mM) in the medium diminished the responses to blue light, although they did not fully abolish them. The kinetics of the stimulation indicate that the rate of photosynthesis is affected by two blue-light-dependent components with different time courses of induction and decay. The faster component seemed to be at least partially suppressed at red-light irradiances which were not saturating for photosynthesis. Lowering the pH of the medium had the same effects as an increase of the carbon concentration to levels of approx. 10 mM. This indicates that Ectocarpus takes up free CO₂ only and not bicarbonate, although additional physiological mechanisms may enhance the availability of CO₂.Abbreviation TIC total inorganic carbon     

The utilization of bicarbonate ions by the macroalga Ascophyllum nodosum (L.) Le Jolis

Abstract A comparison of some of the methods used to determine whether aquatic plants have the ability to utilize bicarbonate ions as a source of inorganic carbon for photosynthesis has been applied to the intertidal macroalga Ascophyllum nodosum. These include: observing photosynthesis at a high pH (below the alga's CO₂ compensation point), pH compensation point determinations, comparing the photosynthetic characteristics at low pH (5.20) and at high pH (7.95), estimating the maximal rates at which CO₂ can diffuse through the unstirred layer and the rate at which CO₂ can be produced from bicarbonate dehydration in the unstirred layer. All indicated that Ascophyllum nodosum can use bicarbonate ions for photosynthesis, though some were not always consistent. Calculating the total inorganic carbon concentration from pH measurements and acidification CO₂ determinations revealed that the assumption that the alkalinity remains constant during pH drift experiments is not always valid.     

Measurement of respiratory CO2 production of roots in an aquatic medium

Changes in pH, total alkalinity and O₂ concentration were followed in an aquatic medium with excised wheat roots (Tritkum aestivum L.). Concentrations of total inorganic carbon and free CO₂ were calculated from total alkalinity and pH according to carbonate equilibria. The total inorganic carbon was estimated by flow-injection infra-red gas analysis. Total alkalinity increased in the root medium during incubation. Respiratory CO₂ production was estimated best from the increase in total inorganic carbon measured with an infra-red gas analyser.     

Biochemical responses and photosynthetic performance of Gracilaria sp. (Rhodophyta) from Cádiz,Spain, cultured under different inorganic carbon and nitrogen levels

Photosynthetic acclimation and the interactions between carbon (C) and nitrogen (N) metabolism have been studied in the red macroalga Gracilaria sp. from Cádiz, Spain, cultured under different inorganic C and N levels. The use of chemostats and buffered medium allowed continuous restoration of the alkaline reserve and constancy of pH during the experiments. The N:C ratios and phycobiliprotein, chlorophyll a and soluble protein contents decreased when Gracilaria sp. was grown at low N levels. Algae grown in a high inorganic C concentration (5% CO₂) displayed a higher soluble carbohydrate concentration and maximum photosynthesis rates but a lower photosynthesic affinity for inorganic C, and lower phycobiliprotein and Rubisco contents, than those cultured at low inorganic C levels (air CO₂). The inorganic C enrichment also affected the N uptake and assimilation in Gracilaria sp., causing a decrease in the N uptake rate even under conditions of N sufficiency. These results reflect the significant influence of the inorganic C growth regime on N assimilation in Gracilaria sp.     

Photosynthetic kinetics determine the outcome of competition for dissolved inorganic carbon by freshwater microalgae: implications for acidified lakes

Summary Photosynthetic kinetics with respect to dissolved inorganic carbon were used to predict the outcome of competition for DIC between the green alga Selenastrum minutum and the cyanobacterium Synechococcus leopoliensis at pH 6.2, 7.5, and 10. Based on measured values of the maximum rate of photosynthesis, the half-saturation value of photosynthesis with respect to DIC (K ₁ ^2/DIC ), and the DIC compensation point, it was predicted that S. leopoliensis would lower the steady-state DIC concentration below the DIC compensation point of S. minutum. This should result in competitive displacement of the green alga at a rate equivalent to the chemostat dilution rate. This prediction was validated by carrying out competition experiments over the range of pH. These results suggest that the low levels of DIC in air-equilibrated acidified lakes may be an important rate-limiting resource and hence affect phytoplankton community structure. Furthermore, the low levels of DIC in these systems may be below the DIC compensation point for some species, thereby precluding their growth at acid pH solely as a function of DIC limitation. The potential importance of DIC in shaping phytoplankton community structure in acidified systems is discussed.Abbreviations growth rate - _max maximum growth rate - K concentration of dissolved inorganic carbon required to maintain half-maximal rate of growth - K ₁ ^2/DIC concentration of dissolved inorganic carbon required to maintain half-maximal photosynthesis - DIC dissolved inorganic carbon - P _max maximum rate of photosynthesis - R ^* substrate concentration required for an organism to maintain a growth rate equal to the mortality rate - DIC compensation point (DIC) concentration where gross photosynthesis equals respiration - i.e. net photosynthesis equals zero     

INORGANIC CARBON TRANSPORT IN RELATION TO CULTURE AGE AND INORGANIC CARBON CONCENTRATION IN A HIGH-CALCIFYING STRAIN OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1

The relationships among inorganic carbon transport, bicarbonate availability, intracellular pH, and culture age were investigated in high-calcifying cultures of Emiliania huxleyi (Lohmann) Hay & Mohler. Measurement of inorganic carbon transport by the silicone-oil centrifugation technique demonstrated that gadolinium, a potential Ca²⁺ channel inhibitor, blocked intracellular inorganic carbon uptake and photosynthetic ¹⁴CO₂₊ fixation in exponential-phase cells. In stationary-phase cells, the intracellular inorganic carbon concentration was unaffected by gadolinium. Gadolinium was also used to investigate the link between bicarbonate and Ca²⁺ transport in high-calcifying cells of E. huxleyi. Bicarbonate availability had significant and rapid effects on pH_i in exponential- but not in stationary-phase cells. 4′, 4′-Diisothiocyanostilbene-2,2′-disulfonic acid did not block bicarbonate uptake from the external medium by exponential-phase cells. Inorganic carbon utilization by exponential- and stationary-phase cells of Emiliania huxleyi was investigated using a pH drift technique in a closed system. Light-dependent alkalization of the medium by stationary-phase cells resulted in a final pH of 10.1 and was inhibited by dextran-bound sulphonamide, an inhibitor of external carbonic anhydrase. Exponential-phase cells did not generate a pH drift. Overall, the results suggest that for high-calcifying cultures of E. huxleyi the predominant pathway of inorganic carbon utilization differs in exponential and stationary phase cells of the same culture.     

Photosynthetic inorganic carbon uptake and accumulation in two marine diatoms

Some physiological characteristics of photosynthetic inorganic carbon uptake have been examined in the marine diatoms Phaeodactylum tricornutum and Cyclotella sp. Both species demonstrated a high affinity for inorganic carbon in photosynthesis at pH7.5, having K_1/2(CO₂) in the range 1.0 to 4.0mmol m^?3 and O_2? and temperature-insensitive CO₂ compensation concentrations in the range 10.8 to 17.6 cm³ m^?3. Intracellular accumulation of inorganic carbon was found to occur in the light; at an external pH of 7.5 the concentration in P. tricornutum was twice, and that in Cyclotella 3.5 times, the concentration in the suspending medium. Carbonic anhydrase (CA) was detected in intact Cyclotella cells but not in P. tricornutum, although internal CA was detected in both species. The rates of photosynthesis at pH 8.0 of P. tricornutum cells and Cyclotella cells treated with 0.1 mol m^?3 acetazolamide, a CA inhibitor, were 1.5- to 5-fold the rate of CO₂ supply, indicating that both species have the capacity to take up HCO₃^? as a source of substrate for photosynthesis. No Na⁺ dependence for HCO₃^? could be detected in either species. These results indicate that these two marine diatoms have the capacity to accumulate inorganic carbon in the light as a consequence, in part, of the active uptake of bicarbonate.     

Microalgal bacterial floc properties are improved by a balanced inorganic/organic carbon ratio

Microalgal bacterial floc (MaB‐floc) reactors have been suggested as a more sustainable secondary wastewater treatment. We investigated whether MaB‐flocs could be used as tertiary treatment. Tertiary influent has a high inorganic/organic carbon ratio, depending on the efficiency of the secondary treatment. In this study, the effect of this inorganic/organic carbon ratio on the MaB‐flocs performance was determined, using three sequencing batch photobioreactors. The MaB‐flocs were fed with synthetic wastewater containing 84, 42, and 0 mg L⁻¹ C‐KHCO₃ supplemented with 0, 42, 84 mg L⁻¹ C‐sucrose, respectively, representing inorganic versus organic carbon. Bicarbonate significantly decreased the autotrophic index of the MaB‐flocs and resulted in poorly settling flocs. Moreover, sole bicarbonate addition led to a high pH of 9.5 and significant lower nitrogen removal efficiencies. Sucrose without bicarbonate resulted in good settling MaB‐flocs, high nitrogen removal efficiencies and neutral pH levels. Despite the lower chlorophyll a content of the biomass and the lower in situ oxygen concentration, 92–96% of the soluble COD‐sucrose was removed. This study shows that the inorganic/organic carbon ratio of the wastewater is of major importance and that organic carbon is requisite to guarantee a good performance of the MaB‐flocs for wastewater treatment. Biotechnol. Bioeng. 2011; 108:549–558. © 2010 Wiley Periodicals, Inc.     

Measurement of carbon dioxide compensation points of freshwater algae

A technique is described for the measurement of total dissolved inorganic carbon by acid release as CO₂ followed by its conversion to methane and detection by flame ionization in a modified gas chromatograph. This method was used to determine the dissolved inorganic carbon concentration reached at compensation point when algae were allowed to photosynthesize in a closed system in a buffer at known pH, and the CO₂ compensation point was calculated from this concentration. The CO₂ compensation points of 16 freshwater algae were measured at acid and alkaline pH in air-saturated medium: at acid pH the CO₂ compensation points ranged from 4.8 to 41.5 microliters per liter while at alkaline pH they ranged from 0.2 to 7.2 microliters per liter. Removal of O₂ from the medium caused a slight lowering of compensation point at acid pH but had little effect at alkaline pH. These low, O₂-insensitive compensation points are characteristic of C₄ plants. It is suggested that these low CO₂ compensation points are maintained by an active bicarbonate uptake by algae especially at alkaline pH.     

Chondrus crispus (Gigartinaceae,Rhodophyta) tank cultivation: optimizing carbon input by a fixed pH and use of a salt water well

The injection of exogenous carbon into intensively cultivated algal tanks is necessary to insure a maximum growth rate by stabilizing the dissolved inorganic carbon (DIC) pool, but represents the major part of the cultivation cost (ca. 73%). This study was conducted in paddle-wheel tanks ranging in size from 260 m² to 1000 m². Additional carbon was provided by carbon dioxide mixed into the incoming sea water through a tubular reactor. Production vs pH was analysed on 120 growth measurements covering two years of continuous cultivation. Whereas production peaked at pH 8.0–8.2, the economic optimum for pH regulation was in the range 8.4–8.5, where CO₂ injection was greatly reduced (–29%) for only a slight decrease in production (–4%). Expressed as a function of pH level, the specific carbon injection (g c gdw^–1 of Chondrus produced) showed an inverse exponential relationship, whereas gross photoconversion ratio (gdw mol photons^–1) varied according to a second degree equation with a low amplitude. The photoconversion ratio was not improved when the culture was maintained at a DIC concentration higher than the natural equilibrium (0.64 ± 0.11 gdw mol photons^–1 at 2.35 mM and 0.65 ± 0.15 gdw mol photons^–1 at 3.19 MM).A complementary source of carbon was found in underground salt water with a high and stable DIC concentration (10.15 ± 0.25 mmole Cl^–1). The mixing of the well water with natural sea water allowed another economy of CO₂ (–20% at pH 8.5) and nutrients (–12%), the total unitary cost of production being cut by about 17%.     

The interactive effects of light and inorganic carbon on aquatic plant growth

Submerged aquatic macrophytes grow across a wide, often coupled, range of light and inorganic carbon availabilities, and each single factor influences photosynthesis and acclimation. Here we examine the interactive effects of light and inorganic carbon on the growth of Elodea canadensis and Callitriche cophocarpa. The plants were grown in the laboratory at a range of light intensities (0–108 μmol m⁻²s⁻¹) and four inorganic carbon regimes in a crossed factorial design. Plant growth rates, measured over 3–4 weeks of incubation, increased in response to increasing light intensity and inorganic carbon availability, and significant interactive effects were observed. The light-use efficiency for growth at low light increased 2-fold for Callitriche and 6-fold for Elodea between the lowest and highest inorganic carbon concentrations applied. Also, the growth rate at the highest light intensity increased with inorganic carbon availability, but the relative increase was smaller than at low light. Both species acclimated to the light and carbon regime such that the chlorophyll content declined at low and high light intensities and the initial slopes of the photosynthetic CO₂ and HCO₃⁻ response curves declined at high levels of CO₂. Callitriche responded less markedly than Elodea to changing inorganic carbon availability during growth, and the initial slope of the photosynthetic HCO₃⁻ response curve, in particular, was greatly reduced (>90%) in Elodea by high CO₂. It is suggested that the coupled responses of aquatic macrophytes to light and inorganic carbon influence their ability to develop dense stands at high light in shallow water and to extend to greater depths in waters rich in inorganic carbon.     

A protein involved in co-ordinated regulation of inorganic carbon and glucose metabolism in the facultative photoautotrophic cyanobacteriumSynechocystis PCC6803

The involvement of a gene ofSynechocystis PCC6803,icfG, in the co-ordinated regulation of inorganic carbon and glucose metabolism, was established. TheicfG gene codes for a 72 kDa protein, which shows no homology with those registered in data libraries. Expression oficfG required glucose, the actual inducer probably being glucose-6-phosphate, and was independent of light and of the external inorganic carbon concentration. Mutants carrying an inactivated copy oficfG were constructed. Their growth characteristics were identical to those of the wild type under all regimes except in limiting inorganic carbon with glucose being present either before or after the transfer to the limiting conditions. These conditions completely prevented growth, both in the light and in the dark. The inhibition could be relieved by several intermediates of the tricarboxylic acid cycle. Assays of various enzymic activities related to inorganic carbon uptake and to its assimilationvia either the Calvin cycle or phosphoenolpyruvate carboxylase did not reveal the level of action of IcfG. Possible models include a blockage of the assimilation of both carbon sources in the absence of IcfG, or the inhibition of Ci incorporation route(s) essential under limiting inorganic carbon conditions, even when glucose is present, and even in the dark.     

A study of the growth condition and solubilization of phosphate from hydroxyapatite byPantoea agglomerans

The growth conditions ofPantoea agglomerans, a phosphate solubilizing organism, were studied in our laboratory to determine the optimal conditions.Pantoea agglomerans showed the highest growth rate at 30°C, pH 7.0 and 2 vvm, after 50 h cultivation. A certain relationship between pH and phosphate concentration, was evident when the glucose concentration in the medium was changed. Increasing glucose concentration increased the pH buffer action of the broth. At glucose concentrations higher than the optimum concentration of 0.2 M, the cell growth was retarded.P. agglomerans consumed glucose as a substrate to produce organic acids which caused the pH decrease in the culture medium. The phosphate concentration in the medium was increased by the presence of the organic acids, which solubilized insoluble phosphates such as hydroxyapatite.     

蛋白核小球藻生长和无机碳利用对不同光照强度和CO2浓度的响应

为了探讨光照强度和CO₂浓度对蛋白核小球藻(Chlorella pyrenoidosa)生长、无机碳利用的复合效应, 丰富绿藻中无机碳浓缩机制的资料, 该文设置两种光照强度(40和120 µmol photons•m^-2•s^-1)和两种CO₂浓度(0.04%和0.16%)组合成4种条件, 比较了蛋白核小球藻生长、无机碳浓度、pH补偿点、光合放氧速率、碳酸酐酶(CA)活性和α-CA基因转录表达对这4种培养条件的响应。结果发现: 蛋白核小球藻在高光强高CO₂浓度组生长最快; 低光强高CO₂浓度组培养体系中总无机碳浓度为1163.3 µmol•L^-1, 显著高于其他3组; 高光强低CO₂浓度组藻的pH补偿点最高(9.8), 而低光强高CO₂浓度组藻的pH补偿点最低(8.6); 低光强高CO₂浓度组藻的最大光合速率(V_max)和最大光合速率一半时的无机碳浓度(K_0.5)最高, 分别是其他3组的1.28-1.91倍和1.61-2.00倍; 高光强低CO₂浓度组藻的胞外CA活性最高; 而低光强低CO₂浓度组藻的胞外α-CA基因表达量显著高于其他3组。以上结果表明低CO₂浓度可促进蛋白核小球藻的pH补偿点和无机碳亲和力的提高, 诱导胞外CA活性及α-CA基因的表达; 该藻主要以HCO₃^-为无机碳源, 其对无机碳的利用受光照的调节。