Cell cycles and proliferation patterns in Haematococcus pluvialis

Most studies on Haematococcus pluvialis have been focused on cell growth and astaxanthin accumulation;far less attention has been paid to cell cycles and proliferation patterns.The purpose of this study was to clarify cell cycles and proliferation patterns in H.pluvialis microscopically using a camera and video recorder system.The complicated life history of H.pluvial i s can be divided into two stages:the motile stage and the non-motile stage.All the cells can be classifi ed into forms as follows:motile cell,nonmotile cell,zoospore and aplanospore.The main cell proliferation,both in the motile phase and non-motile phase in H.pluvialis,is by asexual reproduction.Under normal growth conditions,a motile cell usually produces two,sometimes four,and exceptionally eight zoospores.Under unfavorable conditions,the motile cell loses its fl agella and transforms into a non-motile cell,and the non-motile cell usually produces 2,4 or 8 aplanospores,and occasionally 20–32 aplanospores,which further develop into non-motile cells.Under suitable conditions,the non-motile cell is also able to release zoospores.The larger non-motile cells produce more than 16 zoospores,and the smaller ones produce 4 or 8 zoospores.Vegetative reproduction is by direct cell division in the motile phase and by occasional cell budding in the non-motile phase.There is,as yet,no convincing direct evidence for sexual reproduction.     

Corrosion behavior of anodic oxidized TiO<Subscript>2</Subscript> film in seawater

TiO₂ films were formed on metallic titanium substrates by the anodic oxidation method in H₂SO₄ solution under the 80V D.C.. Phase component and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Water contact angles on titanium oxide film surface were measured under both dark and sunlight illumination conditions. Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry impedance spectrum (EIS) and polarization curves. The result showed that the TiO₂ film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on its surface. The average water contact angle of the film was 116.4° in dark, in contrast to an angle of 42.7° under the UV illumination for 2 hours, which demonstrates good hydrophobic property. The anti-corrosion behavior of the TiO₂ film was declining with the extended immersion time. Under dark conditions, however, the hydrophobic TiO₂ film retarded the water infiltrating into the substrate. The impedance changed slowly and the corrosion current density was 2 orders of magnitude lower than that with the film illuminated by sunlight. All of those mentioned above indicate that the TiO₂ film possesses much better performance under dark condition, and it can be applied as an engineering material under dark seawater environment.     

Effects of iron electrovalence and species on growth and astaxanthin production of Haematococcus pluvialis

To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe²⁺-EDTA and Fe³⁺-EDTA) and species (Fe-EDTA, Fe(OH)_x^32x and FeC₆H₅O₇) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe³⁺-EDTA, Fe²⁺-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell) was obtained under conditions of 18 μmol/L Fe²⁺-EDTA, despite the lower cell density (2.3×10⁵ cell/ml) in such condition. Fe³⁺-EDTA is more effective than Fe²⁺-EDTA in improving the cell growth. Especially, the maximal steady-state cell density, 2.9×10⁵ cell/ml was obtained at 18 μmol/L Fe³⁺-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)_x^32x, FeC₆H₅O₇) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC₆H₅O₇ performed the best. Under the condition of a higher concentration (36 μmol/L) of FeC₆H₅O₇, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC₆H₅O₇, Fe(OH)_x^32x and EDTA-Fe. Supported by Xiamen Scientific and Technologic Projects (No. 3052Z20031086), Xiamen University Alumni Association Foundation in Singapore, and the First National College Students Innovative Experimental Project     

Antioxidative capacity and enzyme activity in Haematococcus pluvialis cells exposed to superoxide free radicals

The antioxidative capacity of astaxanthin and enzyme activity of reactive oxygen eliminating enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were studied in three cell types of Haematococcus pluvialis exposed to high concentrations of a superoxide anion radical (O₂⁻). The results show that defensive enzymes and astaxanthin-related mechanisms were both active in H. pluvialis during exposure to reactive oxygen species (ROS) such as O₂⁻. Astaxanthin reacted with ROS much faster than did the protective enzymes, and had the strongest antioxidative capacity to protect against lipid peroxidation. The defensive mechanisms varied significantly between the three cell types and were related to the level of astaxanthin that had accumulated in those cells. Astaxanthin-enriched red cells had the strongest antioxidative capacity, followed by brown cells, and astaxanthin-deficient green cells. Although there was no significant increase in expression of protective enzymes, the malondialdehyde (MDA) content in red cells was sustained at a low level because of the antioxidative effect of astaxanthin, which quenched O₂⁻ before the protective enzymes could act. In green cells, astaxanthin is very low or absent; therefore, scavenging of ROS is inevitably reliant on antioxidative enzymes. Accordingly, in green cells, these enzymes play the leading role in scavenging ROS, and the expression of these enzymes is rapidly increased to reduce excessive ROS. However, because ROS were constantly increased in this study, the enhance enzyme activity in the green cells was not able to repair the ROS damage, leading to elevated MDA content. Of the four defensive enzymes measured in astaxanthin-deficient green cells, SOD eliminates O₂⁻, POD eliminates H₂O₂, which is a by-product of SOD activity, and APX and CAT are then initiated to scavenge excessive ROS.     

Stability and changes in astaxanthin ester composition from Haematococcus pluvialis during storage

In this paper, we investigated the effects of temperature, oxygen, antioxidants, and corn germ oil on the stability of astaxanthin from Haematococcus pluvialis under different storage conditions, and changes in the composition of astaxanthin esters during storage using high performance liquid chromatography and spectrophotometry. Oxygen and high temperatures （22-25~C） significantly reduced the stability of astaxanthin esters. Corn germ oil and antioxidants （ascorbic acid and vitamin E） failed to protect astaxanthin from oxidation, and actually significantly increased the instability of astaxanthin. A change in the relative composition of astaxanthin esters was observed after 96 weeks of long-term storage. During storage, the relative amounts of free astaxanthin and astaxanthin monoesters declined, while the relative amount of astaxanthin diesters increased. Thus, the ratio of astaxanthin diester to monoester increased, and this ratio could be used to indicate if astaxanthin esters have been properly preserved. If the ratio is greater than 0.2, it suggests that the decrease in astaxanthin content could be higher than 20%. Our results show that storing algal powder from H. pluvialis or other natural astaxanthin products under vacuum and in the dark below 4~C is the most economical and applicable storage method for the large-scale production of astaxanthin from H. pluvialis. This storage method can produce an astaxanthin preservation rate of at least 80% after 96 weeks of storage.     

Emissions of biogenic sulfur gases (H<Subscript>2</Subscript>S,COS) from <Emphasis Type="Italic">Phragmites australis</Emphasis> coastal marsh in the Yellow River estuary of China

Emissions of biogenic sulfur gases (hydrogen sulfide (H₂S) and carbonyl sulfide (COS)) from Phragmites australis coastal marsh in the Yellow River estuary of China were determined during April to December in 2014 using static chamber-gas chromatography technique with monthly sampling. The results showed that the fluxes of H₂S and COS both had distinct seasonal and diurnal variations. The H₂S fluxes ranged from 0.09 μg/(m²·h) to 7.65 μg/(m²·h), and the COS fluxes ranged from–1.10 μg/(m²·h) to 3.32 μg/(m²·h). The mean fluxes of H₂S and COS from the P. australis coastal marsh were 2.28 μg/(m²·h), and 1.05 μg/(m²·h), respectively. The P. australis coastal marsh was the emission source of both H₂S and COS over the whole year. Fluxes of H₂S and COS were both higher in plant growing season than in the non-growing season. Temperature had a dramatic effect on the H₂S emission flux, while the correlations between COS flux and the environmental factors were not found during sampling periods. More in-depth and comprehensive research on other related factors, such as vegetation, sediment substrates, and tidal action is needed to discover and further understand the key factors and the release mechanism of sulfur gases.     

The antitumor effect of bromophenol derivatives <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">Leathesia nana</Emphasis> extract <Emphasis Type="Italic">in vivo</Emphasis>

To investigate the antitumor effect of bromophenol derivatives in vitro and Leathesia nana extract in vivo, six bromophenol derivatives 6-(2,3-dibromo-4,5-dihydroxybenzyl)-2,3-dibromo-4,5-dihydroxy benzyl methyl ether (1), (+)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroisobenzofuran (2), 3-bromo-4-(2,3-dibromo-4,5-dihydroxybenzyl)-5-methoxymethyl-pyrocatechol (3), 2,2′,3,3′-tetrabromo-4,4′,5,5′-tetrahydroxy-diphenylmethane (4), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (5), 2,2′,3-tribromo-3′,4,4′,5-tetrahydroxy-6′-ethyloxymethyldiphenylmethane (6) were isolated from brown alga Leathesia nana, and their cytotoxicity were tested by MTT assays in human cancer cell lines A549, BGC-823, MCF-7, B16-BL6, HT-1080, A2780, Bel7402 and HCT-8. Their inhibitory activity against protein tyrosine kinase (PTK) with over-expression of c-kit was analyzed also by ELISA. The antitumor activity of ethanolic extraction of Leathesia nana (EELN) was evaluated on S₁₈₀-bearing mice. All compounds showed very potent cytotoxicity against all of the eight cancer cell lines with IC₅₀ below 10 μg/mL. In PTK inhibition study, all bromophenol derivatives showed moderate inhibitory activity and compounds 2, 5 and 6 showed significant bioactivity with the inhibition ratio of 77.5%, 80.1% and 71.4%, respectively. Pharmacological studies reveal that EELN could inhibit the growth of Sarcoma 180 tumor and increase the indices of thymus and spleen to improve the immune system remarkably in vivo. Results indicated that the bromophenol derivatives and EELN can be used as potent antitumor agents for PTK over-expression of c-kit and considered in a new therapeutic strategy for treatment of cancer. Supported by the National High Technology Research and Development Program of China (863 Program, No. 2007AA09Z410) and Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-209)     

Distributions and Relationships of CO<Subscript>2</Subscript>, O<Subscript>2</Subscript>, and Dimethylsulfide in the Changjiang (Yangtze) Estuary and Its Adjacent Waters in Summer

The distributions and relationships of O₂, CO₂, and dimethylsulfide (DMS) in the Changjiang (Yangtze) Estuary and its adjacent waters were investigated in June 2014. In surface water, mean O₂ saturation level, partial pressure of CO₂ (pCO₂), and DMS concentrations (and ranges) were 110% (89%–167%), 374 μatm (91–640 μatm), and 8.53 nmol L^?1 (1.10–27.50 nmol L^?1), respectively. The sea-to-air fluxes (and ranges) of DMS and CO₂ were 8.24 μmol m^?2 d^?1 (0.26–62.77 μmol m^?2 d^?1), and ?4.7 mmol m^?2 d^?1 (?110.8-31.7 mmol m^?2 d^?1), respectively. Dissolved O₂ was oversaturated, DMS concentrations were relatively high, and this region served as a sink of atmospheric CO₂. The pCO₂ was significantly and negatively correlated with the O₂ saturation level, while the DMS concentration showed different positive relationships with the O₂ saturation level in different water masses. In vertical profiles, a hypoxic zone existed below 20 m at a longitude of 123°E. The stratification of temperature and salinity caused by the Taiwan Warm Current suppressed seawater exchange between upper and lower layers, resulting in the formation of a hypoxic zone. Oxidative decomposition of organic detritus carried by the Changjiang River Diluted Water (CRDW) consumed abundant O₂ and produced additional CO₂. The DMS concentrations decreased because of low phytoplankton biomass in the hypoxic zone. Strong correlations appeared between the O₂ saturation level, pCO₂ and DMS concentrations in vertical profiles. Our results strongly suggested that CRDW played an important role in the distributions and relationships of O₂, CO₂, and DMS.     

EFFECTS OF WATER TABLE AND NITROGEN ADDITION ON CO2 EMISSION FROM WETLAND SOIL

Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes. Water table and nutritious availability are significant impact factors to influence responses of CO₂ emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen status have been incubated to measure rates of CO₂ emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3 nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO₂ emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m²·h) and 307.89mg/(m²·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however, highest CO₂ emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might be important to influence the effect of water table on the CO₂ emission from the wetland soil. Nitrogen addition led to enhancing CO₂ emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious treatments, low CO₂ emissions at high water tables and high CO₂ emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table changes and nutritious imports would effect the CO₂ emission from wetland. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 90211003) and the Knowledge Innovation Program of Chinese Academy of Sciences (No. KACX3-SW-332) Biography: YANG Ji-song (1978-), male, a native of Chengwu of Shandong Province, Ph.D. candidate, specialized in environmental ecology and wetland biogeochemistry. E-mail: yangjisong@neigae.ac.cn     

Impacts of CO<Subscript>2</Subscript> enrichment on growth and photosynthesis in freshwater and marine diatoms

The physiological responses of Nitzschia palea Kvtzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 μl/L increased the dissolved inorganic carbon （D!C） and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher Ik values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO5 in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO5 and CO2. Although doubled CO2 level would enhance the biomass of N. patea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of IV. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.     

<Emphasis Type="Italic">p</Emphasis>CO<Subscript>2</Subscript> and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO2 （pCO2） was investigated in the Changjiang （Yangtze River） Estuary, Hangzhou Bay and their adjacent areas during a cruise in August 2004, China. The data show that pCO2 in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago. The pCO2 varied from 168 to 2 264 μatm, which fell in the low range compared with those of other estuaries in the world. The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m^-2 d^-1 in average of 24.4 ± 16.5 mmol m^-2 d^-1. Although the area studied was estimated only 2 × 10^4 km^2, it emitted （5.9 ± 4.0） × 10^3 tons of carbon to the atmosphere every day. The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.     

CHEMICAL WEATHERING PROCESSES AND ATMOSPHERIC CO2 CONSUMPTION OF HUANGHE RIVER AND CHANGJIANG RIVER BASINS

Rock weathering plays an important role in studying the long-term carbon cycles and global climatic change. According to the statistics analysis, the Huanghe (Yellow) River water chemistry was mainly controlled by evaporite and carbonate weathering, which were responsible for over 90% of total dissolved ions. As compared with the Huanghe River basin, dissolved load of the Changjiang (Yangtze) River was mainly originated from the carbonate dissolution. The chemical weathering rates were estimated to be 39.29t/(km²·a) and 61.58t/(km²·a) by deducting the HCO ₃ ⁻ derived from atmosphere in the Huanghe River and Changjiang River watersheds, respectively. The CO₂ consumption rates by rock weathering were calculated to be 120.84×10³mol/km² and 452.46×10³mol/km²annually in the two basins, respectively. The total CO₂ consumption of the two basins amounted to 918.51×10⁹mol/a, accounting for 3.83% of the world gross. In contrast to other world watersheds, the stronger evaporite reaction and infirm silicate weathering can explain such feature that CO₂ consumption rates were lower than a global average, suggesting that the sequential weathering may be go on in the two Chinese drainage basins. Foundation item: Under the auspices of Ministry of Science and Technology Project of China (No. G1999043075) Biography: LI Jing-ying (1974-), female, a native of Xinye of Henan Province, Ph.D., associate professor, specialized in environmental geochemistry. E-mail: wxxljy2001@public.qd.sd.cn     

Variation in Rubisco and other photosynthetic parameters in the life cycle of Haematococcus pluvialis

Cells of Haematococcus pluvialis Flot. et Will were collected in four different growth phases. We quantified the initial and total enzyme activity of ribulose-1,5-bisphosphate carboxylase (Rubisco) in crude extracts, and the relative expression of large-subunit ribulose-1,5-bisphosphate caboxylase / oxygenase (rbcL) mRNA. We measured the ratio of photosynthetic rate to respiration rate (P/R), maximal effective quantum yield of photosystem II (Fv/Fm), electron transport rate (ETR), actual photochemical efficiency of PSII in the light (ΦPSII), and non-photochemical quenching (NPQ). Green vegetative cells were found to be in the most active state, with a relatively higher P/R ratio. These cells also displayed the lowest NPQ and the highest Fv/Fm, ETR, and ΦPSII, indicating the most effective PSII. However, both Rubisco activity and rbcL mRNA expression were the lowest measured. In orange resting cysts with relatively lower P/R and NPQ, Rubisco activity and rbcL expression reached a peak, while Fv/Fm, ETR, and ΦPSII were the lowest measured. Taking into account the methods of astaxanthin induction used in industry, we suggest that Rubisco may participate in astaxanthin accumulation in H. pluvialis. A continuous and sufficient supply of a carbon source such as CO2 may therefore aid the large scale production of astaxanthin.     

Spatial Distributions and Potential Sources of Long Chain (C<Subscript>30</Subscript>, C<Subscript>32</Subscript> 1,15-) Alkyl Diols in Surface Sediments from Eastern China Marginal Seas

Long chain alkyl diols have shown important potential for the reconstruction of sea surface temperature, productivities and upwelling conditions in marine or lacustrine environments. However, little is known about the distribution and sources of the diols in eastern China marginal seas (CMS), which are areas of important organic carbon sink. Here the contents of C₃₀ and C₃₂ 1,15-diols were analyzed in 181 surface sediments from eastern CMS. The similar distribution pattern and strong linear correlation between C₃₀ and C₃₂ diols indicated that they had similar biological source, with a dominance of C₃₀ diol. Their contents ranged from 7–2726 ng g^?1 for C₃₀ diol and 5–669 ng g^?1 for C₃₂ diol, and both showed higher values mainly in the mud area of the Yellow Sea, while the TOC normalized contents showed a more obvious seaward increasing trend. The similar distribution pattern and significant positive correlation between diols and the other marine biomarkers (brassicasterol, dinosterol, C₃₇ alkenones) indicated C₃₀ and C₃₂ diols in eastern CMS were mainly from marine algae. This conclusion was also supported by principal component analysis (PCA). Our results also showed that sediment diol contents were generally related to marine productivity, suggesting that diols could be applied for marine productivity reconstruction in eastern CMS.     

Assessment and comparison of <Emphasis Type="Italic">in vitro</Emphasis> immunoregulatory activity of three astaxanthin stereoisomers

In recent years, the immune-modulatory role of all-trans astaxanthin from different pigment sources has been studied. It was reported that all-trans astaxanthin might exist as three stereoisomers, and the composition of all-trans stereoisomers in natural materials differs from that of synthetic products. However, the different biological effects of various all-trans stereoisomers still remain unclear. In the present study, we evaluated the bioactivity of three astaxanthin stereoisomers, (3S,3’S)-trans-, (3R,3’R)-trans-and meso-trans-astaxanthin, in regulating cell-mediated immune response using mice lymphocytes and peritoneal exudates cells (PECs) systems. After the treatment with three astaxanthin stereoisomers (20 μmol L^?1), the lymphocyte proliferation capacity, neutral red phagocytosis of PECs and natural killer (NK) cell cytotoxic activity were comparatively assessed. The results showed that all three astaxanthin stereoisomers significantly promoted lymphocyte proliferation, phagocytic capacity of PECs, and cytotoxic activity of NK cells. Moreover, the (3S,3’S)-trans-astaxanthin exhibited a much higher response than others.     

Effects of salinity fluctuation amplitudes on growth, osmolarity, Na＋-K＋-ATPase activity and Hsp70 of juvenile Chinese shrimp Fenneropenaeus chinensis Osbeck

The effects of various salinity fluctuation amplitudes (2, 4, 6 and 8) on the growth, osmolarity, Na⁺-K⁺-ATPase activity and Hsp70 of juvenile Fenneropenaeus chinensis cultured in seawater with a salinity of 20 were studied. The results show that weight gain in the salinity fluctuation treatments was better than that in control; in particular, the weight gain of treatments S4 and S0, at 231.8% and 196.3%, respectively, was significantly different (P<0.05). The hemolymph osmolarity of treatments S0, S2, S4, S6 and S8 was 635.4, 630.8, 623.6, 614.4 and 600.3 mOsm/kg, respectively, and decreased with increasing salinity fluctuation amplitude. The level of Na⁺-K⁺-ATPase activity in gills of F. chinensis was higher than that in hepatopancreas, but there were no significant differences among all treatments, either in gills or hepatopancreas (P>0.05). The relative level of Hsp70 in treatment S4 was 48.4% and 40.4% higher than control in muscle and eyestalks, respectively, with the highest values being recorded under a salinity fluctuation amplitude of 4.     

Molecular identification and culture observation on <Emphasis Type="Italic">Acrochaete leptochaete</Emphasis> (Chaetophoraceae,Chlorophyta) from China

Acrochaete leptochaete (Huber) Nielsen (Chaetophoraceae, Chlorophyta) was isolated from the macroalgae Chaetomorpha collected from intertidal pools in Rongcheng, Shandong, China. 18S rDNA combined with ITS regions were used to ascertain the morphological identification of the isolated material. Based on the unialgal culture, asexual reproduction and growth characteristics of A. leptochaete were investigated over wide ranges of temperature and irradiance. Results revealed that asexual reproduction of A. leptochaete could be realized by biflagellate zoospores. The zoospores germinated directly to give self- replicating generations. Zoospore germination was bipolar. A temperature range from 13-21°C and a lower irradiance of 36 μmol/(m2·s) were most favorable for the growth of A. leptochaete. Thallus organization, an important taxonomic criterion for the genus Acrochaete, was affected markedly by temperature and irradiance. Our results extend the knowledge about the species’ general biology and its morphological plasticity. For classification and identification of a simple microphytic algae like A. leptochaete, which are traditionally placed in the class Chaetophoraceae, we propose that molecular tools associated with culture observations are applied.     

Effects of elevated seawater pCO<Subscript>2</Subscript> on early development of scallop <Emphasis Type="Italic">Argopecten irradias</Emphasis> (Lamarck, 1819)

To investigate the effects of elevated seawater pCO₂ on the early developmental stages of marine benthic calcifying organisms, we exposed the eggs and larvae of Argopecten irradias, an important bivalve species in Chinese aquaculture, in seawater equilibrated with CO₂-enriched (1000 ppm) gas mixtures. We demonstrated that elevated seawater pCO₂ significantly interfered with fertilization and larval development and resulted in an increased aberration rate. Fertilization in the treatment (pH 7.6) was 74.3% ± 3.8%, which was 9.7% lower than that in the control (pH 8.3) (84.0% ±3.0%). Hatching success decreased by 23.7%, and aberration rate increased by 30.3% under acidic condition. Larvae in acidified seawater still developed a shell during the post-embryonic phase. However, the shell length and height in the treatment were smaller than those in the control. The development of embryos differed significantly at 12 h after fertilization between the two experimental groups. Embryos developed slower in acidified seawater. Nearly half of the embryos in the control developed into D-shaped larvae at 48 h after fertilization, which were considerably more than those in the treatment (11.7%). Results suggest that future ocean acidification (OA) would cause detrimental effects on the early development of A. irradias.     

Effects of ocean acidification driven by elevated CO<Subscript>2</Subscript> on larval shell growth and abnormal rates of the venerid clam, <Emphasis Type="Italic">Mactra veneriformis</Emphasis>

The venerid clam (Mactra veneriformis Reeve 1854) is one of the main cultured bivalve species in intertidal and shallow subtidal ecosystems along the west coast of Korea. To understand the effects of ocean acidification on the early life stages of Korean clams, we investigated shell growth and abnormality rates and types in the D-shaped, umbonate veliger, and pediveliger stages of the venerid clam M. veneriformis during exposure to elevated seawater pCO₂. In particular, we examined abnormal types of larval shell morphology categorized as shell deformations, shell distortions, and shell fissures. Specimens were incubated in seawater equilibrated with bubbled CO₂-enriched air at (400±25)×10^-6 (ambient control), (800±25)×10^-6 (high pCO₂), or (1 200±28)×10^-6 (extremely high pCO₂), the atmospheric CO₂ concentrations predicted for the years 2014, 2084, and 2154 (70-year intervals; two human generations), respectively, in the Representative Concentration Pathway (RCP) 8.5 scenario. The mean shell lengths of larvae were significantly decreased in the high and extremely high pCO₂ groups compared with the ambient control groups. Furthermore, under high and extremely high pCO₂ conditions, the cultures exhibited significantly increased abundances of abnormal larvae and increased severity of abnormalities compared with the ambient control. In the umbonate veliger stage of the experimental larvae, the most common abnormalities were shell deformations, distortions, and fissures; on the other hand, convex hinges and mantle protuberances were absent. These results suggest that elevated CO₂ exerts an additional burden on the health of M. veneriformis larvae by impairing early development.