Uptake Of Algae Research Articles

Conserved cobalamin acquisition protein 1 is essential for vitamin B12 uptake in both Chlamydomonas and Phaeodactylum.

Microalgae play an essential role in global net primary productivity and global biogeochemical cycling. Despite their phototrophic lifestyle, over half of algal species depend for growth on acquiring an external supply of the corrinoid vitamin B12 (cobalamin), a micronutrient produced only by a subset of prokaryotic organisms. Previous studies have identified protein components involved in vitamin B12 uptake in bacterial species and humans. However, little is known about its uptake in algae. Here, we demonstrate the essential role of a protein, cobalamin acquisition protein 1 (CBA1), in B12 uptake in Phaeodactylum tricornutum using CRISPR-Cas9 to generate targeted knockouts and in Chlamydomonas reinhardtii by insertional mutagenesis. In both cases, CBA1 knockout lines could not take up exogenous vitamin B12. Complementation of the C. reinhardtii mutants with the wild-type CBA1 gene restored B12 uptake, and regulation of CBA1 expression via a riboswitch element enabled control of the phenotype. When visualized by confocal microscopy, a YFP-fusion with C. reinhardtii CBA1 showed association with membranes. Bioinformatics analysis found that CBA1-like sequences are present in all major eukaryotic phyla. In algal taxa, the majority that encoded CBA1 also had genes for B12-dependent enzymes, suggesting CBA1 plays a conserved role. Our results thus provide insight into the molecular basis of algal B12 acquisition, a process that likely underpins many interactions in aquatic microbial communities.

Reducing Cement Plant Emissions via Algae Cultivation and Anaerobic Digestion

Concrete is an essential aspect of modern infrastructure, and is a much-preferred construction material as it is a highly resistant and requires low maintenance. Concrete is produced through the creation of a paste comprised of cement and water that is mixed with aggregates such as sand and gravel. However, the concrete industry is one of the largest consumers of natural resources globally, and the emissions associated with its production are very high. Cement, one of the primary constituents of concrete, emits 0.93 pounds of CO2 for every pound produced. Thus, concrete production is a major source of CO2 emissions and accounts for approximately 8% of global carbon emissions. As the global demand for concrete continues to increase, it is evident that efforts must be made to reduce emissions associated with its production to mitigate climate change. This research proposes that the cultivation of algae can be integrated into the process of cement production so as to reduce the emissions associated with concrete. Algae uptake CO2 through photosynthesis, having a CO2 bio-fixation efficiency of 10-50 times higher than terrestrial plants. Algae have the ability to capture 1.8 kg of CO2 per kilogram of algal biomass. Therefore, we hypothesize that, through the integration of algae cultivation and cement production, CO2 can be effectively recycled through a closed-loop system. Algal biomass can be cultivated using the CO2 emitted from cement flue gas. The cultivated algae can be harvested and used to produce methane gas (CH4) via anaerobic digestion, which can in turn be used to power the cement plant, which will in turn produce more CO2 to be captured through further algal cultivation.

Decreasing arsenic accumulation but promoting arsenate biotransformation in Microcystis aeruginosa regulated by nano-Fe2O3.

Iron oxide nanoparticles (nano-Fe2O3) widely distribute in waters with low toxicity to aquatic organisms. But it is unclear for nano-Fe2O3 to affect the fate of coexisting arsenic (As) with its bioaccumulation and biotransformation. In this study, we thus mainly investigated arsenate (As(V)) toxicity, uptake kinetics, biotransformation and subcellular distribution in Microcystis aeruginosa influenced by nano-Fe2O3. The results showed that M. aeruginosa was more sensitive to As(V) associated with nano-Fe2O3. Due to the exaggerated increase of efflux rate constants of As compared with the uptake rate constants in algal cells affected by different levels of nano-Fe2O3, the As(V) bioconcentration factor decreased with nano-Fe2O3 increasing correspondingly, indicating that As bioaccumulation was diminished by nano-Fe2O3. The decreased As accumulation in M. aeruginosa could be supported by the evidential As(V) sequestration through high adsorption of nano-Fe2O3, which resulted in decreasing free As level for algae uptake in media. Meanwhile, As subcellular distribution was adjusted by nano-Fe2O3 with decreasing in cell walls and rising in cytoplasmic organelles compared with nano-Fe2O3 free. As(V) reduction and methylation were enhanced with increasing nano-Fe2O3, stimulating by its sensitivity to the interaction of nano-Fe2O3 and As(V) as well as the rising level of As in cytoplasmic organelles of this algae. It is confirmed by the higher relative gene expression levels of arsC and arsM in elevated nano-Fe2O3. Accordingly, it is highlighted to be deserved more attention that the changing behavior of As(V) by nano-Fe2O3 that reduce As bioaccumulation and accelerate its biotransformation in algae in As contaminated water.

Animal Feed from Microalgae Grown on Biogas Digestate as Sustainable Alternative to Imported Soybean Meal

This work investigates microalgae’s potential to reduce North-Western Europe environmental burden from excess nitrogen polluting groundwater and provide an environmental replacement for current animal feed. Algae uptake nutrients from nutrient-rich digestate from biogas plants and turn them into high-value feedstock, which can substitute soybean meal imported from overseas and avoid deforestation of rainforests. Life cycle assessments were conducted based on novel and original data from engineers in academia and industry, acquired through pilot-scale research facilities in the UK, France, and Belgium. The findings of this study highlight the environmental impacts of three different technologies with varying scales of production. Mixotrophic algal feed production shows higher productivities and fewer energy demands than the phototrophic systems. Still, the process is less favourable due to higher impacts on human health and ecosystems than imported soybean meal, whereas the impact on resources is more negligible. Sensitive analysis indicates that further technological development, increased productivities, and renewable energy use can improve the environmental competitiveness of algal feedstock. Since this process is a promising solution for making feedstock out of excess nutrients and having an alternative source for imported soybean meal with a comparable, efforts to realize these improvements and successfully upscaling algal feedstock production in combination with biogas plants are justified and can improve the environmental footprint of algal biomass production.

Second-Generation Phosphorus: Recovery from Wastes towards the Sustainability of Production Chains

Phosphorus (P) is essential for life and has a fundamental role in industry and the world food production system. The present work describes different technologies adopted for what is called the second-generation P recovery framework, that encompass the P obtained from residues and wastes. The second-generation P has a high potential to substitute the first-generation P comprising that originally mined from rock phosphates for agricultural production. Several physical, chemical, and biological processes are available for use in second-generation P recovery. They include both concentrating and recovery technologies: (1) chemical extraction using magnesium and calcium precipitating compounds yielding struvite, newberyite and calcium phosphates; (2) thermal treatments like combustion, hydrothermal carbonization, and pyrolysis; (3) nanofiltration and ion exchange methods; (4) electrochemical processes; and (5) biological processes such as composting, algae uptake, and phosphate accumulating microorganisms (PAOs). However, the best technology to use depends on the characteristic of the waste, the purpose of the process, the cost, and the availability of land. The exhaustion of deposits (economic problem) and the accumulation of P (environmental problem) are the main drivers to incentivize the P’s recovery from various wastes. Besides promoting the resource’s safety, the recovery of P introduces the residues as raw materials, closing the productive systems loop and reducing their environmental damage.

Competition Among Trivalent Elements (Al, Eu, Fe, Gd, Nd, Tm, and Y) for Uptake in Algae and Applicability of the Biotic Ligand Model.

Rare earth elements (REE) are essential in many new technologies. While anthropogenic dispersion of REE into the environment are expected in the future, their biogeochemical fate and interactions at biological interfaces are still largely unexplored. Due to their chemical nature (generally trivalent and hard metals), REE can potentially compete among themselves or with other ubiquitous trivalent metals for uptake sites at the surface of aquatic organisms. In the current study, the bioavailability and uptake of gadolinium (Gd) was assessed in the green alga, Chlamydomonas reinhardtii, while in the presence of various trivalent elements (Al, Eu, Fe, Nd, Tm, and Y). In the absence of competitors, Gd uptake was well described by a Michaelis-Menten equation with an affinity constant (KGd) of 107.1 and a maximum internalization flux (Jmax) of 1.95 ± 0.09 × 10-2amolµm-2min-1. Neither Al(III) nor Fe(III) had notable effects on Gd uptake in the conditions tested; however, Gd uptake was reduced with increasing concentrations of other REE. These had binding constants with uptake sites very similar to that of Gd (KNd, Y, Tm, Eu = 107.0). Our results suggest that the different REE likely share common transport sites and that the biotic ligand model (BLM) can be used to predict their uptake.

Algae (Raphidocelis subcapitata) mitigate combined toxicity of microplastic and lead on Ceriodaphnia dubia

They not only directly impact aquatic organisms, but also indirectly impact these organisms by interacting with background toxins in the environment. Moreover, under realistic environmental conditions, algae, a natural food for aquatic organisms, may alter the toxicity pattern related to MPs. In this research, we first examined the toxicity of MPs alone, and their effect on the toxicity of lead (Pb) on Ceriodaphnia dubia (C. dubia), a model aquatic organism for toxicity survey. Then, we investigated the effect of algae on the combined toxicity of MPs and Pb. We observed that, MPs significantly increased Pb toxicity, which was related to the increase in soluble Pb concentration and the intake of Pb-loaded MPs, both of which increased the accumulation of Pb in C. dubia. The presence of algae mitigated the combined toxicity of MPs and Pb, although algae alone increased Pb accumulation. Therefore, the toxicity mitigation through algae uptake came from mechanisms other than Pb accumulation, which will need further investigation.

Free ammonia is the primary stress factor rather than total ammonium to Chlorella sorokiniana in simulated sludge fermentation liquor

Microalgal growth was inhibited in high-strength ammonium wastewater, but the actual stress factor and their physiological responses remain to be elucidated. In this study, compared to either the total ammonium or pH alone, free ammonia (FA) concentration clearly exhibited negative correlation with the growth of Chlorella sorokiniana cultivated in the simulated sludge fermentation liquor (SFL), which could be well described by an exponential decay model, indicating of the primary stress factor. Subsequently, six concentrations of FA were selected for further investigation and samples were monitored for: 1) growth and ammonium removal; 2) changes in photosynthetic system; 3) changes in reactive oxygen species (ROS) and soluble extracellular polymeric substances (S-EPS); as well as 4) biomass biochemical composition. Both the growth performance and photosynthetic parameters Fv/Fm and YII negatively correlated with FA concentrations. The highest biomass production was observed at the lowest initial FA concentration (2.06 mg/L) and almost no growth was observed in the highest FA concentration (110.97 mg/L).Ammonium nitrogen was removed by algae uptake and evaporation. Cell stress was indicated by significantly increased production of ROS (2.53–12.92 FI/1010cells) and secretion of S-EPS (144.13–160.86 mg/g DW). High FA concentrations induced the accumulation of cellular carbohydrates and palmitic acid. The stress responses to FA observed provide a guide in strategies for microalgal adaptation and growth in high-strength ammonium wastewater.

Toxicokinetic modeling of octylphenol bioconcentration in Chlorella vulgaris and its trophic transfer to Daphnia magna.

Bioconcentration of 4-tert-Octylphenol (OP) in freshwater algae Chlorella vulgaris was investigated by considering the effects of algal growth and exudate excretion. The OP uptake in algae was approximately 113mgkg-1 after 24h, and the uptake rate constant was estimated as 2.4×104Lkg-1 d-1. The OP sorption onto exudates reduced OP bioavailability to C. vulgaris to 11% after 24h, with a sorption coefficient of 9.7×103Lkg-1. The elimination of OP by algae growth (0.80 d-1) was dominant over real elimination (0.60 d-1). The calculated bioconcentration factor of OP in C. vulgaris following uptake and elimination rate constants was 4.0×104Lkg-1. Further, bioaccumulation of OP in Daphnia magna was investigated by considering both aqueous and dietary (C. vulgaris) exposures. Uptake and elimination rates of OP via water were 1.6×104Lkg-1 d-1 and 0.95 d-1, respectively, while ingestion rate and assimilation efficiency via diet were 0.41 d-1 and 58%, respectively. The OP accumulation in D. magna predominantly occurred via water (63%) relative to diet (37%), resulting in a bioaccumulation factor of 2.7×104Lkg-1. The estimated trophic transfer factor was 0.25, suggesting that OP biomagnification was unlikely in the C. vulgaris-D. magna trophic relationship.

Marine macroalgae as a dietary source of genoprotection in gilthead seabream (Sparus aurata) against endogenous and exogenous challenges

DNA integrity and stability are essential to organisms' health and survival. However, it has been neglected in what concerns to fish farming, disregarding the potential impact of endogenous/ exogenous factors. As marine macroalgae constitute a source of natural compounds with a large spectrum of biological activities, this study, situated in the interface of nutritional-genetic research and development of algae practical applications, aimed to evaluate the genoprotective properties of a macroalgae-enriched diet (total percentage of 5%, incorporating equal percentages of Ulva rigida, Gracilaria gracilis and Fucus vesiculosus) in gilthead seabream (Sparus aurata). Protection was assessed in relation to a basal genome integrity and against an exogenous genotoxic challenge (cyclophosphamide; CP). Fish were reared for 30 days with the supplemented diet, being then injected with CP and sampled at days 3 and 10 post-injection (p.i.). To evaluate whether the favorable effects remain after the end of supplementation, a fish subgroup previously fed with algae-enriched diet was submitted to a diet reversion at day 3 p.i., being thereafter fed with the standard diet. Genetic damage was evaluated through the erythrocytic nuclear abnormalities (ENA) and comet assays and complemented by the assessment of the antioxidant system. Results pointed out that algae-enriched feed exhibits anti-genotoxic properties, mostly expressed in relation to the exogenous pressure, manifest in relation to DNA strand breaks and chromosomal lesions, also reducing oxidative DNA damage. Nonetheless, blood antioxidants were only punctually altered by the supplemented diet (e.g. catalase and glutathione-S-transferase). Analyzing the effect persistence, it was perceived that 7 days without algae uptake was enough to partially reduce the protection efficacy. Overall, these findings are promising towards the benefits of macroalgae inclusion in fish diet, and thus, to invigorate mariculture activity and the commercial use of algae, also providing new insights on the DNA protection mechanisms.

Exposure to crude oil micro-droplets causes reduced food uptake in copepods associated with alteration in their metabolic profiles

Acute oil spills and produced water discharges may cause exposure of filter-feeding pelagic organisms to micron-sized dispersed oil droplets. The dissolved oil components are expected to be the main driver for oil dispersion toxicity; however, very few studies have investigated the specific contribution of oil droplets to toxicity. In the present work, the contribution of oil micro-droplet toxicity in dispersions was isolated by comparing exposures to oil dispersions (water soluble fraction with droplets) to concurrent exposure to filtered dispersions (water-soluble fractions without droplets). Physical (coloration) and behavioral (feeding activity) as well as molecular (metabolite profiling) responses to oil exposures in the copepod Calanus finmarchicus were studied. At high dispersion concentrations (4.1–5.6mg oil/L), copepods displayed carapace discoloration and reduced swimming activity. Reduced feeding activity, measured as algae uptake, gut filling and fecal pellet production, was evident also for lower concentrations (0.08mg oil/L). Alterations in metabolic profiles were also observed following exposure to oil dispersions. The pattern of responses were similar between two comparable experiments with different oil types, suggesting responses to be non-oil type specific. Furthermore, oil micro-droplets appear to contribute to some of the observed effects triggering a starvation-type response, manifested as a reduction in metabolite (homarine, acetylcholine, creatine and lactate) concentrations in copepods. Our work clearly displays a relationship between crude oil micro-droplet exposure and reduced uptake of algae in copepods.

Evidence for the retention of two evolutionary distinct plastids in dinoflagellates with diatom endosymbionts.

Dinoflagellates harboring diatom endosymbionts (termed “dinotoms”) have undergone a process often referred to as “tertiary endosymbiosis”—the uptake of algae containing secondary plastids and integration of those plastids into the new host. In contrast to other tertiary plastids, and most secondary plastids, the endosymbiont of dinotoms is distinctly less reduced, retaining a number of cellular features, such as their nucleus and mitochondria and others, in addition to their plastid. This has resulted in redundancy between host and endosymbiont, at least between some mitochondrial and cytosolic metabolism, where this has been investigated. The question of plastidial redundancy is particularly interesting as the fate of the host dinoflagellate plastid is unclear. The host cytosol possesses an eyespot that has been postulated to be a remnant of the ancestral peridinin plastid, but this has not been tested, nor has its possible retention of plastid functions. To investigate this possibility, we searched for plastid-associated pathways and functions in transcriptomic data sets from three dinotom species. We show that the dinoflagellate host has indeed retained genes for plastid-associated pathways and that these genes encode targeting peptides similar to those of other dinoflagellate plastid-targeted proteins. Moreover, we also identified one gene encoding an essential component of the dinoflagellate plastid protein import machinery, altogether suggesting the presence of a functioning plastid import system in the host, and by extension a relict plastid. The presence of the same plastid-associated pathways in the endosymbiont also extends the known functional redundancy in dinotoms, further confirming the unusual state of plastid integration in this group of dinoflagellates.

Insights into intrathalline genetic diversity of the cosmopolitan lichen symbiotic green alga Trebouxia decolorans Ahmadjian using microsatellite markers

Trebouxia decolorans is a widespread and common symbiotic green alga that is found in association with different species of lichen-forming fungi. By applying T. decolorans-specific microsatellite markers, we investigated the within-thallus diversity of T. decolorans in thalli of Xanthoria parietina and Anaptychia ciliaris. We found several algal strains in most of the thalli of both hosts. High genetic differentiation among thalli suggests that algal diversity is generated de novo via mutation in both fungal hosts. Rarefied allelic richness of the algae was higher in thalli of X. parietina. Our results indicate that in X. parietina intrathalline algal diversity is additionally created by environmental uptake of algae either at the start of the symbiotic association or during the lifetime of the thallus. This study indicates that promiscuous host-symbiont associations in lichen symbioses with Trebouxia spp. may be more common than currently recognized.

Metal accumulation and oxidative stress responses in Ulva spp. in the presence of nocturnal pulses of metals from sediment: A field transplantation experiment under eutrophic conditions

In aquatic systems under eutrophic conditions, remobilization of metals from sediment to the overlying water may occur. Consequently, adaptive responses of local organisms could result from the accumulation of metals intermittently released from the sediment. In summer 2007, a field transplantation experiment was performed in the Óbidos lagoon (Portugal) with Ulva spp. comprising three short-term exposures (between 15:30–23:30; 23:30–07:30; 07:30–15:30) during a 24-h period. In each period, Ulva spp. was collected at a reference site located in the lower lagoon (LL) and transplanted to a eutrophic site located at the Barrosa branch (BB), characterized by moderate metal contamination. For comparison purposes, macroalgae samples were simultaneously exposed at LL under the same conditions. Both sites were surveyed in short-time scales (2–4 h) for the analysis of the variability of physical–chemical parameters in the water and metal levels in suspended particulate matter. The ratios to Al of particulate Mn, Fe, Cu and Pb increased during the period of lower water oxygenation at the eutrophic site, reaching 751 × 10−4, 0.67, 12 × 10−4, 9.9 × 10−4, respectively, confirming the release of metals from the sediment to water during the night. At the reference site, dissolved oxygen oscillated around 100%, Mn/Al ratios were considerably lower (81 × 10−4–301 × 10−4) compared to BB (234 × 10−4–790 × 10−4), and no increases of metal/Al ratios were found during the night. In general, algae uptake of Mn, Cu, Fe, Pb and Cd was significantly higher at the eutrophic site compared to the reference site. The results confirmed the potential of Ulva spp. as bioindicator of metal contamination and its capability to respond within short periods. An induction of SOD, an inhibition of CAT and the increase of LPO were recorded in Ulva spp. exposed at BB (between 23:30 and 7:30) probably as a response to the higher incorporation of Mn, Fe and Pb in combination with the lack of dissolved oxygen in the water. Current findings emphasize the importance of assessing, in eutrophic systems, the relationship between the variability of chemical conditions and its repercussions on autochthonous organisms over day–night cycles.

Effect of Nanoparticles in Top Consumers

We characterise how commercially manufactured polystyrene nanoparticles affect the behaviour of and metabolism in fish. The nanoparticles were fed to the fish through an aquatic food chain from uptake in algae, through zooplankton to fish. This design model mimics natural systems, as nanoparticles released into an aquatic environment will associate with organic and inorganic materials before reaching top consumers. At feeding times the fish were filmed and the behaviour of the fish fed with nanoparticles was compared to a control group. We recorded significant differences in behaviour between the control and the test group. Fish exposed to nanoparticles through the food chain had lower activity and required longer time to feed. Immediately after feeding the activity was high in both groups but declined more rapidly in the group fed with nanoparticles even if there was plenty of food left. The distance between the fish was smaller for nano-fed fish during feeding, indicating a disrupted hunting behaviour. Changes in the metabolome in organs were evaluated by NMR spectroscopy, where we saw a significant difference in muscle and liver. The main differences in muscle metabolites were increased level of lysine and inosine/adenosine. In liver samples we saw an increased level of ethanol. Moreover, morphological differences were observed in the brain and the muscles in the nanoparticle-fed fish. Our results show that polystyrene nanoparticles have severe effects both on behaviour and metabolism of fish. Future studies will include investigations on particle distribution and on the fate of nanoparticles released into the aquatic environment through the sewage system.

Experiments on the operation of a combined aquaculture-algae system

A combined aquaculture-algae system was developed for the purification and reuse of effluent water from intensive fish production in a combination of a high-rate algal pond and extensive fishpond. The integrated system was operated as a closed system, thus the water demand was reduced through the recirculation of the treated water. The pilot-scale experimental system consisted of three different compartments: tanks for intensive fish production, an algal pond where the excess nutrients are removed by algae uptake and a fishpond where the produced algae biomass was consumed by fish. The objective of this study was to describe and evaluate the nutrient transformation efficiency of the combined system through the analysis of the organic carbon, nitrogen and phosphorus budgets.

Effects of oxygen on the release and distribution of phosphorus in the sediments under the light condition

Effects of oxygen on the release and distribution of phosphorus (P) in the sediments in the presence of light were investigated, using sediment cores and overlying water from Lake Taihu, in China. The results show that P can be released from sediments to the overlying water in both anoxic and aerobic conditions. But more P was released in the anoxic condition. The transformation of P between various fractions in the sediments was observed during the release experiments. Concentrations of Ca-bound P and organic P in the sediments decreased in both conditions, but Fe/Al-bound P increased in the aerobic condition. The decrease of total P and P fractions in the sediments is consistent with the accumulative increase in quantity (AIQ) of total P (TP) in the overlying water, but is contrary with the AIQ of dissolved inorganic P. This is due to the uptake of algae by the dissolved inorganic P. Total nitrogen in the sediments in the anoxic condition was lower than that in the aerobic condition, and pH in the overlying water increased in the anoxic condition.

MACROALGAL (FUCUS VESICULOSUS) δ15N VALUES TRACE DECREASE IN SEWAGE INFLUENCE

Nutrient discharges from sewage treatment plants can contribute significantly to coastal and estuarine eutrophication. To counter anthropogenic nitrogen (N) loads in a Baltic Sea coastal embayment, improved (∼85%) N removal was implemented in a tertiary sewage‐treatment plant. This study used nitrogen stable‐isotope ratios (δ15N) in attached brown macroalgae, Fucus vesiculosus, to map the change in the spatial extent of the influence of sewage‐derived N. Elevated N content and δ15N values (δ15N = 8–9‰) suggest that sewage N was still traceable in algal tissues despite enhanced N removal from the effluent. However, the δ15N values decreased significantly with distance and approached background levels within 10–12 km of the outfall. Compared to a survey conducted in 1989, prior to enhanced N removal in the sewage treatment plant, macroalgae were 2.5–6‰ lower in δ15N values within 24 km from the outfall, demonstrating a decline in the importance of sewage‐derived nutrients to macroalgae, particularly in the inner reaches of the bay. Beyond 25 km from the outfall, δ15N values were at background levels (δ15N = 4‰). Two‐source mixing models estimate that the percentage sewage contribution to total algal N uptake in algae near the outfall was ∼40% in 1989 and ∼12% in 1999. Similarly, temporal variation in individual plants estimate that the percentage sewage N contribution to algae within 1 km from the outfall declined from >40% in the mid‐1990s to ∼20% in 2002. Nutrient budget calculations showed that F. vesiculosus is not an effective sink for N, assimilating only ∼3% of total annual N loads entering the bay.

Several Key Parameters of Dynamics of Phosphorus Uptake Involved with Competition for Resources of <i>Microcystis aerugionosa</i> in Lake Taihu

对从太湖分离的铜绿微囊藻(Microcystis aerugionosa)进行了不同氮磷比对生长影响的实验, 以探索蓝藻生长优势形成的基础.实验结果虽然在一定程度上符合氮磷摩尔比低于29蓝藻将会占据优势的理论, 但发现只在较低的营养水平时比较吻合.同时进行了不同磷营养条件下磷营养摄取与生长的实验, 为太湖富营养化研究中应用的水质模型提供所需的参数值.微囊藻生长的磷半饱和常数K_s=16.21μM、磷摄取的半饱和常数K_m=17.66μM、藻细胞最小的磷份额K=4.36μg/mg(dw);微囊藻在实验条件下的过度储磷系数Q₀/Q_max=0.14;测定了磷饥饿和磷丰富时细胞最大的摄磷速率分别为1.66μg/(L·mg·h)和0.06μg/(L·mg·h).可见初始细胞内磷份额较低的藻细胞对磷的吸收速率要比胞内磷份额较高的藻细胞高.;The experiment investigated the relationship of growth characters and phosphorus uptake of Microsystems aerugionosa from Lake Taihu under laboratory conditions.With phosphate and nitrate in oligotrophic level, the growth rate of the alga supported the N-P rule while in hyper-eutrophic level did not.It is concluded from this study that the N: P rule does not apply to the conditions which P and N were enough.Growth of algae was strongly affected by phosphorus availability.The half saturation constant of P uptake of algae K_m was 17.66μM and P half saturation constant for algae growth K_s was16.21 μM.The P subsistence quota of algae K=4.36μg/mg(dw).As affected by the initial cellular P quota, the P uptake rates were different.Maximum uptake rate for algae when P is deficient (V_max, d) was 1.66μg/(L·mg·h) and sufficient maximum P uptake rate (V_max, s) was 0.06μg/(L·mg·h).P luxury storage coefficient Q₀/Q_max=0.14.

Relating the Speciation of Cd, Cu, and Pb in Two Connecticut Rivers with Their Uptake in Algae

Metal complexation characteristics (conditional stability constants and available ligand concentration) were measured with differential pulse anodic stripping voltammetry (DPASV) for the trace metals cadmium, copper, and lead in two Connecticut rivers. These parameters permit calculation of the free ion concentration [M2+ (H2O)n] for each metal. Parallel experiments in waters from the same rivers were conducted to measure metal uptake in a representative freshwater diatom (Stephanodiscus hantzschii) and chlorophyte (Chlorella vulgaris). For copper the results of the uptake experiments are consistent with calculated speciation based on the measured DOM complexation characteristics, supporting the belief that voltammetry can provide valid information about metal bioavailability. Although uptake of lead did not closely follow speciation predictions, an inverse relationship between uptake and the concentration of available ligands in each river existed, similar to that of copper.