Aspects of 14CO2-fixation by endosymbiotic rhodoplasts in the marine opisthobranchiate Hermaea bifida

When the marine opisthobranchiate slug Hermaea bifida Mont. is incubated in a H¹⁴CO ₃ ^- -seawater medium in the light, a considerable net gain of ¹⁴C-assimilates is observed. Electron microscopic control provided evidence that this ¹⁴C-fixation is due to photosynthesis by chloroplasts (=rhodoplasts) endosymbiotic in the cells of the digestive gland of the slug. After thin-layer chromatographic analysis various ¹⁴C-labelled photosynthates could be traced. The assimilate pattern of the rhodoplasts is compared with that of the marine red alga Griffithsia flosculosa (Ellis) Batt., from which the plastids are acquired by feeding. The nutritional relationship of this endosymbiosis is discussed, with emphasis on the occurrence of functional chloroplast endosymbioses among the eolidiform species of the Sacoglossa.     

Autoradiographic investigation of uptake and storage of exogenous sperm by the ovary of the compound ascidian Diplosoma listerianum

The movement of radiolabelled non-self sperm within the female reproductive tract of cultured specimens of the hermaphroditic ascidian Diplosoma listerianum Milne Edwards was investigated by light-microscope autoradiography. Passage of male gametes up the oviduct (fertilization canal) to the ovary was demonstrated for sperm known unequivocally to be of external (non-self) origin. The lumen of the ovary was directly confirmed as a site of long-term storage of sperm, as had previously been suggested from circumstantial evidence. The ovary had a branching structure. Sperm entered blind diverticula leading from the main lumen of the ovary, and persisted there adjacent to the oocyte at the end of each of these side-branches. This arrangement included the association of stored sperm with very small, immature oocytes. An investigation of the time-course of sperm uptake showed that exogenous sperm did not enter the oviducts of recipient ramets for some time (>3 h) after they were initially available, with first presence of sperm noted in the distal half of the duct at 9 h and greatest recorded uptake at 27 h. Sperm had reached the ovary 6.6 h after the first observation of their occurrence in the distal part of the oviduct. Uptake declined steeply between 27 and 46.8 h of continual exposure to sperm released by a single genetic source, and remained low at 81 h. The significance of these observations for the mating pattern of D. listerianum is discussed.     

Uptake of L-valine and other amino acids by the polychaete Nereis virens

For valine uptake by the polychaete Nereis virens Sars, the kinetic constants were: V _max=355 nmol g^-1 fresh weight h^-1, K _m=20 M. Leucine and some other amino acids acted as partial inhibitors of valine uptake. Valine uptake rate was 78% higher at 21.5 S than at 14 S. The major portion of valine absorbed by the polychaete could be extracted as free valine, with 6.5 to 15.6% being respired, and 3.6 to 9.5% incorporated into proteins. Calculations indicate that 7 to 12% of the metabolism of N. virens may be sustained by uptake of glycine and aspartic acid from natural concentrations. It is suggested that uptake of amino acids by this worm is important in the nitrogen cycling of marine sediments.     

Elimination of Pentachlorobiphenyls by Nereis virens (Polychaeta) in the Laboratory and the Marine Environment

Fifty sandworms, Nereis virens, were maintained in a closed aquarium system with continuous charcoal filtration at 12°C and 27.6‰ S. They were dosed orally for 10 consecutive days with a mixture of three pentachlorobiphenyls: 35 ng 2,4,6,2',4'-pentachloro[U-¹⁴C]biphenyl, 106 ng 2,4,5,2',5'-pentachlorobiphenyl, and 106 ng 2,3,4,2',5'-pentachlorobiphenyl per g of Nereis virens per day. At the end of the dosing period the accumulated compounds were measured in 5 worms, the remaining 45 specimens were divided into three groups for determining the PCB elimination under different conditions for 14 to 26 weeks: in the laboratory with feeding, in the laboratory without feeding, and in a cage moored in the Weser estuary.

The accumulation percentages for these PCB compounds were 41, 26 and 4% respectively. Times for the initial 50% decrease t_e50 were 4.4, 2.8 and 1.9 weeks respectively, and appeared the same in all three experimental groups. However, in the laboratory experiments the metabolites of the ¹⁴C-labelled compound amounted to ∼60%, compared to the field experiment with ∼30%. This extended the t_e50 for ¹⁴C activity (metabolites included) to ∼9 weeks in the laboratory experiments.     

CO2 fixation and translocation in benthic marine algae. III. Rates and ecological significance of translocation in Laminaria hyperborea and L. saccharina

Translocation of ¹⁴C-labelled assimilates in Laminaria hyperborea and L. saccharina is strictly basipetal within the thallus. The lowermost 20 cm of the frond accumulates 71% (L. hyperborea) or 63% (L. saccharina) of the basipetallymoving translocate after a period of 96 h from initial feeding with NaH¹⁴CO₃. Whereas translocation was found to occur at all seasons in L. saccharina, which grows throughout the year, no translocation of newly synthesized photosynthate occurred in L. hyperborea in October, when no frond enlargement takes place, nor in January, when the new fond occurs as a tiny outgrowth. In L. hyperborea, organic material, assimilated by the old frond during the period of rapid growth, is exported at the rate of 0.5 mg C · dm^-2 · h^-1. In L. saccharina, 14 to 18 cm frond length are necessary for an elongation rate of the growing zone, situated in lowermost 10 cm of the frond, of 1 cm per week. The significance of translocation in the two Laminaria species is demonstrated by comparison of export rates with growth rates measured in situ and in the laboratory.Dedicated to Professor Dr. Otto Stocker on his 85th birthday.     

Maintenance of coelomic fluid pH in sea urchins exposed to elevated CO2: the role of body cavity epithelia and stereom dissolution

Experimental ocean acidification leads to a shift in resource allocation and to an increased [HCO₃ ^?] within the perivisceral coelomic fluid (PCF) in the Baltic green sea urchin Strongylocentrotus droebachiensis. We investigated putative mechanisms of this pH compensation reaction by evaluating epithelial barrier function and the magnitude of skeleton (stereom) dissolution. In addition, we measured ossicle growth and skeletal stability. Ussing chamber measurements revealed that the intestine formed a barrier for HCO₃ ^? and was selective for cation diffusion. In contrast, the peritoneal epithelium was leaky and only formed a barrier for macromolecules. The ossicles of 6 week high CO₂-acclimatised sea urchins revealed minor carbonate dissolution, reduced growth but unchanged stability. On the other hand, spines dissolved more severely and were more fragile following acclimatisation to high CO₂. Our results indicate that epithelia lining the PCF space contribute to its acid–base regulation. The intestine prevents HCO₃ ^? diffusion and thus buffer leakage. In contrast, the leaky peritoneal epithelium allows buffer generation via carbonate dissolution from the surrounding skeletal ossicles. Long-term extracellular acid–base balance must be mediated by active processes, as sea urchins can maintain relatively high extracellular [HCO₃ ^?]. The intestinal epithelia are good candidate tissues for this active net import of HCO₃ ^? into the PCF. Spines appear to be more vulnerable to ocean acidification which might significantly impact resistance to predation pressure and thus influence fitness of this keystone species.     

Effect of two TiO2 nanoparticles on the growth of unicellular green algae using the OECD 201 test guideline: influence of the exposure system

This work aimed at assessing the influence of different exposure systems to perform the commonly used OECD 201 freshwater algal growth inhibition test in the context of nanoparticles hazard assessment. Two distinct TiO₂ nanoparticles were considered and three different exposure systems were investigated: Erlenmeyers flasks and 24-well microplates (both using an orbital shake system), and an alternative system using cylindrical vials and magnetic stirring. All three systems are in accordance with the OECD 201 test guideline recommendations. We concluded that the exposure systems applied to achieve the test can substantially affect the ecotoxicological results and the subsequent calculated ECx. The selected systems influenced both the interaction between algal cells and TiO₂ nanoparticles as well as the growth inhibition recorded. Disparities in ecotoxicity relative to the TiO₂ nanoparticles tested were also observed and are finally discussed.     

三江源区植被固定CO2释放O2功能评价

植被在固定CO2释放O2和大气与陆地生态系统碳循环中起着十分重要的作用,是区域和全球环境变化的主要反馈和调节系统,具有重要的生态功能,体现出生态服务价值。根据三江源区多次科考调查及相关资料,计算各种植被类型的净初级生长量,进而根据光合作用方程式、造林成本法、碳税法和工业制氧法估算其固定CO2和释放O2的物质量及其价值量。结果表明:三江源区植被年净初级生长量为8.67×107t·a-1,固定CO21.41×108t·a-1,释放O21.04×108t·a-1。根据造林成本法和碳税法估算出三江源区植被固定CO2的价值为2.8926×1010元·a-1。利用造林成本法和工业制氧法估算出释放O2的价值为3.9157×1010元·a-1。三江源区植被固定CO2释放O2物质量和价值量中,草甸贡献率最高,其次是落叶灌丛、沼泽和草原。本研究对地处青藏高原腹地、生态系统脆弱且空气稀薄的江河源区的生态系统结构和功能的研究具有重要意义。     

Dark CO2 uptake by the diatom Chaetoceros simplex in response to nitrogen pulsing

In a continuing investigation of dark CO₂ uptake by nitrogen-limited cultures of the marine diatom Chaetoceros simplex (Bbsm), we expanded on several of our earlier conclusions regarding the potential application of this physiological response for measuring the degree and type of nitrogen limitation in phytoplankton populations. First, the duration over which the maximal enhancement of dark ¹⁴CO₂ uptake was sustained after NH ₄ ⁺ enrichment was a function both of the concentration of added NH ₄ ⁺ and the standing crop of phytoplankton nitrogen — in effect, the total N demand. Second, pulsing with NH ₄ ⁺ for a given degree of N-limitation always produced the same level of enhanced dark CO₂ uptake regardless of whether the cultures were preconditioned with oxidized or reduced nitrogen. In contrast, urea pulsing led to reduced dark CO₂ uptake, but the effect was most pronounced in cells grown on NO ₃ ^– . And third, the assay could be used to distinguish readily between no, moderate, and severe N limitation. The degree of severe N limitation was quantitatively correlated with the degree of enhanced dark CO₂ uptake, but this relationship was not so clear in the region of moderate N limitation. The main advantage of the assay is that it is a relatively simple and effective alternative to more complicated techniques for gauging the degree and form of N limitation in phytoplankton. Further evaluation will be required, both in the laboratory and field, before the assay can be calibrated for quantitative use.Contribution No. 5982 from the Woods Hole Oceanographic Institution     

Cadmium accumulation by green algae Cladophora glomerata (L.) Kutz. (Chlorophyta) in presence of Nile tilapia Oreochromis niloticus (L.)

Accumulation of metals by aquatic organisms is mostly affected by other biological components in environments. In this study, cadmium (Cd) accumulation in green algae, Cladophora glomerata (L.) Kutz., exposed to 0.1 and 1.0 mg L^?1 of Cd for 15 and 30 days was examined in laboratory conditions in the presence of Nile tilapia Oreochromis niloticus (L.). The green algae C. glomerata accumulated Cd concentrations as 690 ± 70 and 3430 ± 470 mg kg^?1 on day 15, and 1130 ± 180 and 6830 ± 1540 mg kg^?1 on day 30. There were significant increases (p < 0.05) in metal accumulation by green algae as the exposure time and metal concentration increased. The results also indicated that the presence of Nile tilapia in the medium led to a significant Cd accumulation in the green algae compared to control (p < 0.05).     

Night metabolism of recent photosynthate by sea ice algae in the high Arctic

Changes in intracellular distribution of recent (labelled) photosynthate during light-dark incubations were consistent with overnight consumption of low molecular weight compounds and carbohydrate, but continued protein synthesis, in sea ice algae from Resolute Passage, Canada, during April and May, 1986. Synthesis of labelled protein at night varied with preceding light availability but was always less than 30% of the daytime rate. Comparisons of labelled photosynthate dynamics against oxygen consumption and net changes of particulate matter composition and concentration showed that soluble polysaccharide was not the only major metabolic substrate, and that much of the carbon lost overnight was not recent, labelled photosynthate. Total net lipid synthesis was greatly underestimated by labelled photosynthate allocation. However, overnight consumption of the labelled lipid was directly proportional to photon flux density in the preceding light period, suggesting a short-term energy storage function for the small labelled portion of the total lipid pool. Arctic ice algae appear to incorporate only limited amounts of recent photosynthate into their large lipid pools even over a full 24 h photoperiod.     

Production of biodiesel from macroalgae by supercritical CO2 extraction and thermochemical liquefaction

We compare two different techniques for the extraction of biodiesel from macroalgae: the thermochemical liquefaction and the extraction using supercritical carbon dioxide (sc-CO₂). The first allows to use wet material, while sc-CO₂ requires dry material and uses moderate temperature and pressure so that it can be useful for the extraction of thermolabile compounds which may decompose at the temperature at which thermal methos are carried out. In both cases the extracted oil was characterized quantitatively and qualitatively. The novelty of the work is that in the literature the use of macroalgae for the production of biodiesel has not so far been described, while they are used mainly as food or other purposes.     

Sexual reproduction in the compound ascidian Diplosoma listerianum (Tunicata). I. Metamorphosis,storage and phagocytosis of sperm in female duct

In the colonial ascidian Diplosoma listerianum (collected in the Lagoon of Venice in 1986 and 1991), ovulating eggs detach themselves from the ovary wall and segregate in the tunic without exposure to seawater. With the aim of finding evidence of the pathway followed by spermatozoa to approach the oocyte, histological and ultrastructural observations were made. The results showed that the hollow ovary elongates in a fertilization canal which flanks the sperm duct and opens externally, next to the anus. Intercellular extended tight junctions isolate the lumen of this canal from the blood. Sperm were found in the fertilization canal, both free and in intracellular vacuoles of wandering cells (phagocytes). These sperm showed differences in comparison to those from the sperm duct, which are possible signs of a sperm reaction. The main modifications were shown by the dense groove, a narrow invagination of the plasmalemma bound to the nuclear envelope by dense material. In non-modified sperm, the groove runs spirally all along the head, while in those in the fertilization canal, it coils in the anterior half of the head, pressing back the long mitochondrion and endoplasmic tubules. These modifications were interpreted to be result of the release of the dense groove, considered to be a sort of stretched, contractile spring. The presence of sperm in the fertilization canal and particularly in phagocytes is discussed in relation to the capacity for exogenous sperm storage by zooids and to the necessity of waste clearance in order for successive waves of fresh sperm to be able to move towards fully grown oocytes. The origin of the female fertilization canal, the role of its tight junctions, and the complex sperm morphology are discussed as adaptations to internal fertilization in D. listerianum.     

A causal investigation on the determinants of CO2 in China

ABSTRACT

This article examines the causal relationship among carbon dioxide emissions, energy consumption, per capita economic growth, and international trade using temporal econometric models with serial data for the period 1980–2017 in China. In the Armax model all regressors are significant in having influenced the dependent CO2 variable. Subsequently, unidirectional causalities are identified from energy consumption and from commercial opening to carbon dioxide emissions, from commercial opening to energy consumption, from carbon dioxide emissions to per capita economic growth and from economic growth to commercial opening. These results show that, over time, more energy consumption in China results in more carbon dioxide emissions so there will be more environment pollution.     

投饵养鱼对潘家口水库藻类生长影响的围隔试验研究

设置投饵、投饵单养花鲢（Aristichthisnobilis）、投饵单养鲤鱼（Cyprinuscarpio）、投饵混养花鲢和鲤鱼以及空白对照5个围隔及水库背景水体,研究投饵养鱼对潘家口水库浮游藻类生长和群落结构的影响。结果发现,试验期间水库水体和空白对照围隔中总藻平均密度分别为2.60×10^6L^-1和3.38×10^6L^-1,均以蓝藻和绿藻为主且基本保持稳定状态;投饵能有效促进藻类生长,只投饵围隔中总藻平均密度达到1.17×10^8L^-1,藻种组成向单一鱼腥藻（Anabaena）方向演替;养殖花鲢抑制藻的生长,参照只投饵围隔,抑制率接近80%,绿藻占据极大优势,其中栅藻（Scenedesmussp）、芒锥藻（Errerellabornhemiensisconr）和空星藻（Coelastrumsp）成为优势藻种;投饵养殖鲤鱼也能有效降低藻生物量,总藻平均密度为4.07×10^7L^-1,绿藻占总藻的比例由27%增加到95%,其中空星藻和小球藻（ChlorellavulgarisBeij）为优势藻种;投饵混养花鲢和鲤鱼围隔中总藻密度稍高于单养花鲢和鲤鱼围隔,为4.37×10^7L^-1,栅藻和鱼腥藻为优势藻种。     

Oxygen and carbon dioxide exchange in the polychaete Nereis virens: influence of ventilation activity and starvation

The influence of ventilation activity and starvation on O₂ uptake and CO₂ production in the polychaete Nereis virens Sars was investigated during September 1986 using worms collected on intertidal flats outside the Nærå Strand estuary, Denmark. The activity level, measured as ventilation rate, , was linearly related to active O₂ uptake, , for worms inhabiting artificial burrows (i.e. tubes) in the laboratory. at 16°C was two and four times the extrapolated standard O₂ uptake ( =0) when was 100 and 500 ml g^-1 h^-1, respectively. The use of tubes had no significant effect on N. viren's temporal ventilation pattern, D_v, compared to natural burrows in sediment. The ventilation rate, , however, was 2 to 3 times higher in tubes than in burrows. Starvation affected both ventilation and gas exchange. increased slightly during the first six days remaining constant thereafter. D_v, on the othe hand, decreased during the first six days followed by a gradual increase to Day 20. The observed decrease in D_v (%) from Day 0 to 1 was attributed to insufficient acclimation of the worms. The time integrated ventilation rate, × D_v, increased gradually throughout the 20 d starvation period. and declined rapidly during the first days of starvation. After 10 d the gas exchange reached steady levels at about 50% of the initial rate. The observed decrease in metabolic rate during starvation was explained by a rapid initial reduction in specific dynamic action (SDA) followed by a gradual exhaustion of readily available metabolic reserves, e.g. glycogen and lipids.     

Photoperiodic control of growth and segment proliferation by Nereis (Neanthes) virens in relation to state of maturity and season

The effects of two fixed photoperiodic regimes on the rate of somatic growth and segment proliferation in the semelparous polychaete Nereis (Neanthes) virens Sars has been investigated. The two photoperiods (16 h light:8 h dark and 8 h light:16 h dark, hereafter LD 16:8 and LD 8:16) were close to the extremes experienced naturally by N. (N.) virens in the course of a year. The experiments were carried out during the ambient winter and all worms (including four-setiger larvae raised out of season) showed elevated feeding, growth and enhanced segment-proliferation rates when reared under LD 16:8, compared to worms reared under LD 8:16. The rate of replacement of lost segments after caudal ablation was also higher under LD 16:8. The number of segments present when the segment proliferation rate had fallen to zero was higher in individuals grown from birth under LD 16:8 compared to those grown under LD 8:16. Feeding activity showed a degree of spontaneous recovery under LD 8:16 from January onwards, but remained lower than under LD 16:8. This difference continued into the following spring, and was not attributable to differences in sexual maturity. We conclude that the rate of feeding in N. (N.) virens and other indicators of somatic growth rate such as rates of caudal regeneration and segment proliferation are directly influenced by the photoperiod, but that the seasonal cycle of growth also includes a circa-annual component modifying the response to static photoperiods according to the time of year. Received: 20 October 1998 / Accepted: 4 February 1999     

Sexual reproduction in the compound ascidian Diplosoma listerianum (Tunicata). II. Sperm penetration through ovary wall and evidence of internal fertilization

Diplosoma listerianum differs from most ascidians in that, at ovulation, eggs are emitted at the bottom of the ovary and segregated into the tunic, so that fertilization occurs far from seawater. A fertilization canal, a hollow extension of the ovary, conducts sperm towards the egg. In the present paper, ultrastructural evidence is reported on the morphological relationship between the ovary, egg envelopes and oocyte and on the mechanism by which sperm-egg interaction is established. In the ovary, the very complex sperm, equipped with a spiral dense groove, undergo metamorphosis as the first step in a sperm reaction and then pass through the ovary epithelium insinuating themselves between the intercellular junctions which appear to be mouldable, although able to maintain the egg-ovary barrier. Sperm then reach the vitelline coat, where a further step in the sperm reaction occurs. Before the egg abandons the ovary, the sperm head is incorporated into the oocyte by a process recalling phagocytosis, with the formation of an engulfing pocket. Sperm-egg contact and incorporation in D. listerianum occur in a way, never previously reported for other ascidians, in which fusion of plasma membranes takes place immediately after sperm-egg contact. Unlike other cytoplasmic components, the dense groove persists until the sperm enters the egg. It gives a corkscrew-like configuration to the sperm head and allows close adhesion to cell membranes, facilitating sperm movement. Expulsion of numerous cortical granules and features of a cortical reaction were observed in the egg penetrated by the sperm. The mode of internal fertilization of this species in comparison with that of other tunicates and phylogenetic aspects are discussed. Ripe colonies of D. listerianum collected in the Lagoon of Venice, Italy in 1986 and 1991 and colonies reared on glass in aquaria were used for our investigations.     

Effect of elevated CO2 on coarse-root biomass in Florida scrub detected by ground-penetrating radar

Growth and distribution of coarse roots in time and space represent a gap in our understanding of belowground ecology. Large roots may play a critical role in carbon sequestration belowground. Using ground-penetrating radar (GPR), we quantified coarse-root biomass from an open-top chamber experiment in a scrub-oak ecosystem at Kennedy Space Center, Florida, USA. GPR propagates electromagnetic waves directly into the soil and reflects a portion of the energy when a buried object is contacted. In our study, we utilized a 1500 MHz antenna to establish correlations between GPR signals and root biomass. A significant relationship was found between GPR signal reflectance and biomass (R2 = 0.68). This correlation was applied to multiple GPR scans taken from each open-top chamber (elevated and ambient CO2). Our results showed that plots receiving elevated CO2 had significantly (P = 0.049) greater coarse-root biomass compared to ambient plots, suggesting that coarse roots may play a large role in carbon sequestration in scrub-oak ecosystems. This nondestructive method holds much promise for rapid and repeatable quantification of coarse roots, which are currently the most elusive aspect of long-term belowground studies.