Brackish Medium Research Articles

Proto-dolomite spherulites with heterogeneous interior precipitated in brackish water cultivation of freshwater cyanobacterium Leptolyngbya boryana

Primary dolomite is believed to be formed through cyanobacterial calcification, yet the details and mechanisms of this process are not fully understood. In this study, a freshwater filamentous cyanobacterium, Leptolyngbya boryana, was cultured and domesticated in artificial freshwater and brackish solutions with various Mg/Ca ratios. The hydrochemistry, the extracellular polymeric substance (EPS) composition, and precipitate mineralogy in the medium were monitored. The results showed that the L. boryana induced proto-dolomite precipitation in brackish medium with salinity of 1.5 % and Mg/Ca ratio of 5. The proto-dolomite in this study has a “double spherical” appearance and a hollow core, which may have originally been filled by the complex composed of EPS and amorphous CaMg carbonate. With regard to elemental composition, the cyanobacterially-induced proto-dolomite is rich in calcium inside and magnesium-rich on the surface, and cyanobacterial organic matter is sealed inside the particles during spherulite growth. In this study, the accelerators for Mg2+ to enter the carbonate lattice mainly include extracellular acidic amino acids and polysaccharides. The changes of these promoters among different cultures were related to the growth state of cyanobacteria under salinity stress. The polysaccharides concentration has a significant increasing in the dolomite-precipitating medium, indicating that it may be the main promoter of proto-dolomite precipitation and significantly increases the amount of Mg2+ precipitation. At the meantime, the amount of precipitated Ca2+ was suppressed by increasing salinity and Mg2+, thus leading to the precipitation of proto-dolomite in this shifting process. This study can potentially provide a reference for explaining the dolomite (proto-dolomite) precipitation in aerobic brackish environment where cyanobacteria thrive.

A kinetic characterization of the gill V(H+)-ATPase from two hololimnetic populations of the Amazon River shrimp Macrobrachium amazonicum.

This investigation examines the kinetic characteristics and effect of acclimation to a brackish medium (21 ‰S) on gill V(H+)-ATPase activity in two hololimnetic populations of M. amazonicum. We also investigate the cellular immunolocalization of the enzyme. Immunofluorescence findings demonstrate that the V(H+)-ATPase c-subunit is distributed in the apical pillar cells of shrimps in fresh water but is absent after acclimation to 21 ‰S for 10 days. V(H+)-ATPase activity from the Tietê River population is ≈50% greater than the Grande River population, comparable to a wild population from the Santa Elisa Reservoir, but is 2-fold less than in cultivated shrimps. V(H+)-ATPase activity in the Tietê and the Grande River shrimps is abolished after 21 ‰S acclimation. The apparent affinities of the V(H+)-ATPase for ATP (0.27 ± 0.04 and 0.16 ± 0.03 mmol L-1, respectively) and Mg2+ (0.28 ± 0.05 and 0.14 ± 0.02 mmol L-1, respectively) are similar in both populations. The absence of V(H+)-ATPase activity in salinity-acclimated shrimps and its apical distribution in shrimps in fresh water underpins the importance of the crustacean V(H+)-ATPase for ion uptake in fresh water.

Study on Sedimentary Environment Elements and Sedimentary Model of Lacustrine Shale in E1f2 Member, Gaoyou Depression, Subei Basin

Although the potential of lake facies shale oil and gas resources is enormous, the lithology is complex, heterogeneous, and obviously controlled by a sedimentary environment. By integrating cores, thin sections, X-ray diffraction analysis, trace elements, organic geochemical indexes, and paleontological data, this work studies sedimentary environment elements and sedimentary model of shale in the E1f2 member, Gaoyou Depression, Subei Basin. The shale in the E1f2 member is completely shore lacustrine deposits forming into the hot dry climate of tropical central and south Asia. The lake basin extended continuously, with brackish water, strong reduction, and medium water stratification. The transgression resulted in the rapid rise of water, salinity, reducibility, and water stratification. As the climate becomes wetter, the E1f2 water level, salinity, reduction, and stratification decrease. The shale in E1f2 members is characterized by sedimentary zones, which are divided into muddy water desalination deposit in the flooded zone, clear water salinization deposit in the transition zone, and still water salinization deposited in the clear water zone. Under palaeotopography settings of E1f2 members, combining characteristics of vertical stratification and the plane zone of the lake, an integrated sedimentary model of lacustrine shale in a flat platform has been established under climate and transgression control. The plane area of the lake could be divided into the slow slope zone, sub-depression zone, processes zone, deep slope zone, and deep depression zone, corresponding roughly to the sedimentary zones of the flooded zone, transition zone, and clear water zone. Moreover, the oil shale enriched in low-lying parts of the paleotopography is mainly deposited at the end of muddy water areas and clear water areas.

Simulation of geoelectrical responses of structures buried in freshwater and brackish water environments

Marine geoelectrical simulation offers the opportunity to predict matrix type, interstitial fluid and geometry of buried structures. In this research, simulation of geoelectrical responses over buried structures in freshwater and brackish water environments were tested. A model tank made of acrylic and housed within an iron frame was built for the experiment. The tank was filled with water and sieved sediment having grain sizes ≤1.18 mm, corresponding to very coarse sand to colloid. Four models were designed namely freshwater static model (FSM), brackish water static model (BSM), freshwater model with buried structures (FMBS), and brackish water model with buried structures (BMBS). A bamboo pipe, metal pipe and granite block were buried in the FMBS and BMBS. Physico-chemical parameters of the water which includes temperature (22.74 – 26.06 °C), salinity (0.07 – 15.72 psu), conductivity (153 – 25,420 μS/cm and resistivity (5.6 x 103 – 6.6 x 103 Ω-cm) were measured. Dipole-dipole array using inter-electrode separation (a) of 5 cm and 1≤n≤5 was adopted. Resistivity measurements obtained were processed and inverted using non-linear least-square optimization technique. We present obtained results as contoured 2D resistivity structures. FSM and FMBS were characterized by relatively high resistivity values compared with the BSM and BMBS. The buried materials were effectively resolved in the freshwater models, compared to the brackish water model due to higher contrast in resistivity between the material and saturating fluid. The bamboo pipe was not effectively delineated in the brackish water medium, as a result of the low resistivity contrast which exists between the medium and the material. Zones with high compaction are characterized by high resistivity values, while concealed channel structures were characterized by low compaction. Estimated depth were exact for the freshwater models but was over estimated by `∼12.5% in the brackish water models. Marine electrical resistivity method shows great potential in mapping structures buried in medium with high contrasting resistivity values, and sedimentary structures with varying degree ofcompaction.

Australian Strains of Botryococcus braunii Examined for Potential Hydrocarbon and Carotenoid Pigment Production and the Effect of Brackish Water

The green alga Botryococcus braunii produces abundant hydrocarbons, in the form of drop-in biodiesel, which promoted interest in the species as a renewable fuel. However, despite the observation of dense populations in the wild, Botryococcus grows very slowly in culture, severely limiting its potential for development as a bioresource. Undertaking a biodiscovery program, we found new strains of Botryococcus in locations ranging from tropical to temperate Australia and from both fresh and brackish waters. As part of the ecophysiological characterisation of this new biodiversity, lipid and pigment compositions were studied for six new strains from six different locations. The strains were inoculated in either freshwater or brackish (salinity of 4)-based medium and maintained over 150 days. The growth of cultures was studied continuously, while lipid and pigment composition were analysed at final harvest on day 150. No significant differences in growth rate between fresh and brackish media were observed. Some strains were more tolerable of brackish conditions than others with a link between salinity tolerance and original location. The use of lower salinity (4 ppt) had a minimal effect on lipid composition, with only two of the six strains showing a different hydrocarbon profile in comparison to the other strains; pigment composition showed only minor variations for fresh and brackish water cultures, although the concentrations varied significantly with the freshwater cultures containing higher pigment concentrations.

Improving the Energy Balance of Hydrocarbon Production Using an Inclined Solid–Liquid Separator with a Wedge-Wire Screen and Easy Hydrocarbon Recovery from Botryococcus braunii

The green colonial microalga Botryococcus braunii produces large amounts of hydrocarbons and has attracted attention as a potential source of biofuel. When this freshwater microalga is cultured in a brackish medium, the hydrocarbon recovery rate increases; furthermore, the colony size becomes large. In this study, the effects of such changes on the energy balance of harvesting and hydrocarbon recovery were studied via filtrate experiments on an inclined separator and extraction from a concentrated slurry. The inclined separator was effective for harvesting large-colony-forming algae. The water content on the wire screen of slit sizes larger than 150 µm was <80% and a separation rate of >85% could be achieved. The input energy of the harvesting using the brackish medium with this separator was ≈44% of that using the freshwater medium with vacuum filtration, while the input energy of the hydrocarbon recovery using the brackish medium was ≈88% of that using the freshwater medium with pre-heating before n-hexane extraction. Furthermore, the energy profit ratio of the process in the brackish medium was 2.92, which was ≈1.2 times higher than that in the freshwater medium. This study demonstrated that filtration techniques and hydrocarbon recovery from B. braunii with a low energy input through culture in a brackish medium are viable.

EVALUATION OF GROWTH IN ATLANTIC WHITE SHRIMP LITOPENAEUS SETIFERUS (LINNAEUS, 1767) JUVENILES, USING BIOFLOC AS A FOOD SOURCE IN A CONTROLLED ENVIRONMENT

Biofloc is a new system, little known or applied in Mexico, that offers a high level of sustainability for aquaculture due to its great versatility in terms of nutrient recycling, which enables savings in feed costs and a significant reduction in water exchange. With the objective of evaluating the results of the use of Biofloc in aquaculture, a simulation of an aquaculture facility using Biofloc culture techniques was conducted under controlled laboratory conditions. The use of a combination of shrimp feed and refined sugar as a carbon source enabled the development of floccules, not only enabling the identification of those high-performing organisms and their development in the medium, but also facilitating shrimp capture in order to evaluate growth during each treatment. The treatments were undertaken in two different culture media, one in brackish water and the other in seawater, in which the length and weight of the animals was measured, with their behavior during the bioassay also recorded. It was found that the brackish medium enabled better shrimp development than the seawater medium, provided that the parameters and material in suspension are kept at stable levels, with the former medium providing shrimp an environment rich in food and free of pathogens.

The surface structure of Botryococcus braunii colony prevents the entry of extraction solvents into the colony interior

The green colonial microalga Botryococcus braunii (race B) has attracted considerable attention because it is known to produce many hydrocarbons. The hydrocarbons are present in the extracellular matrix that connects the cells located in the interior of a B. braunii colony; however, the surface of each colony is covered with a retaining wall and a fibrillar colony sheath. This unique colony structure is thought to be associated with hydrocarbon storage and known to affect the extractability of hydrocarbons by using an organic solvent. In this study, we investigated the relation between hydrocarbon extractability and changes in the colony surface structure after two distinct treatments: culture of the algae in brackish medium or thermal pretreatment of the algae before solvent extraction. Both the treatments improved hydrocarbon extractability when non-polar solvents such as n-hexane were used. Thermal pretreatment inhibited the formation of fibrils on the surface of algal colonies, as revealed by rapid-freezing and freeze-substitution electron microscopy. However, when the alga was cultured in brackish medium, the fibrils on the surface shortened and became less dense. Thus, the fibrillar colony sheath that mainly consisted of saccharic components prevented the entry of organic solvents into the colony interior, and thus hydrocarbon extraction.

Re-cultivation of Neochloris oleoabundans in exhausted autotrophic and mixotrophic media: the potential role of polyamines and free fatty acids.

Neochloris oleoabundans (Chlorophyta) is widely considered one of the most promising microalgae for biotechnological applications. However, the large-scale production of microalgae requires large amounts of water. In this perspective, the possibility of using exhausted growth media for the re-cultivation of N. oleoabundans was investigated in order to simultaneously make the cultivation more economically feasible and environmentally sustainable. Experiments were performed by testing the following media: autotrophic exhausted medium (E+) and mixotrophic exhausted medium after cultivation with glucose (EG+) of N. oleoabundans cells grown in a 20-L photobioreactor (PBR). Both exhausted media were replenished with the same amounts of nitrate and phosphate as the control brackish medium (C). Growth kinetics, nitrate and phosphate consumption, photosynthetic pigments content, photosynthetic efficiency, cell morphology, and lipid production were evaluated. Moreover, the free fatty acid (FFA) composition of exhausted media and the polyamine (PA) concentrations of both algae and media were analyzed in order to test if some molecules, released into the medium, could influence algal growth and metabolism. Results showed that N. oleoabundans can efficiently grow in both exhausted media, if appropriately replenished with the main nutrients (E+ and EG+), especially in E+ and to the same extent as in C medium. Growth promotion of N. oleoabundans was attributed to PAs and alteration of the photosynthetic apparatus to FFAs. Taken together, results show that recycling growth medium is a suitable solution to obtain good N. oleoabundans biomass concentrations, while providing a more sustainable ecological impact on water resources.

Cryptic diversity in the euryhaline red alga Caloglossa ogasawaraensis (Delesseriaceae, Ceramiales)

:Caloglossa ogasawaraensis is one of the most widespread species of its genus, having been reported from marine to freshwater habitats in tropical to temperate regions of both hemispheres. Because little phenotypic variation has been reported for this species, we investigated genetic, physiological, and/or morphological variations in 18 strains of C. ogasawaraensis isolated from 14 countries. The combined data of plastid-encoded ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) gene and its spacer, nuclear-encoded large subunit (LSU) rDNA, and mitochondrion-encoded cox spacer region suggested that this species is divided into three groups; Group I contains Australian, Melanesian, and Micronesian strains; Group II includes strains from western Pacific coasts, Micronesia, and Madagascar; and Group III consists eastern Pacific–Atlantic and Malaysian strains. Considering wide distribution range and close genetic similarity within the groups, a long-distance dispersal event does not seem to be rare in this species. Growth of the strains was compared between brackish (salinity = 8) and seawater (salinity = 32) media; most Group I strains grew well in both brackish and seawater media; whereas, all the Group II strains showed better growth in the brackish medium. Morphological analyses of the strains incubated under the same conditions revealed that the Group III strains had wider rhizoids than the other strains. However, this feature was highly variable and easily affected by environmental and algal conditions. Although such morphological and physiological variations suggest speciation of the three phylogenetic groups, more clear-cut features are required to describe them as distinct morpho-species.

Growth, morphology and photosynthetic responses of Neochloris oleoabundans during cultivation in a mixotrophic brackish medium and subsequent starvation

The green microalga Neochloris oleoabundans is able to grow in both low and high salinity media and is largely studied for its capability to accumulate lipids under starvation. Moreover, N. oleoabundans is a mixotrophic alga, and then organic carbon addition can promote its growth. This research aims to study the morpho-physiological aspects, with a particular attention on the photosynthetic response, both during mixotrophic growth and starvation in brackish media, more sustainable than freshwater cultivation. In the first step, the alga was cultivated mixotrophically in a brackish medium added with an apple waste product; in the second one, cells were starved also to verify lipid induction. Results indicate that growth is highly promoted during the first week of mixotrophic cultivation, while photosynthetic pigments and lipids are over-produced during the following three weeks of cultivation. In parallel, in mixotrophic cultures the maximum PSII quantum yield was enhanced during the exponential phase of growth. Interesting changes affected the mixotrophic cultures with respect to the partitioning of absorbed light energy. Starvation of both 7-day-grown mixotrophic and autotrophic cultures caused growth inhibition, pigments and photosynthesis downshifting, and concomitantly promoted evident lipid synthesis.

Growth and lipid synthesis promotion in mixotrophic Neochloris oleoabundans (Chlorophyta) cultivated with glucose

In the recent years, the studies concerning the cultivation of Neochloris oleoabundans for biofuel purposes have increased, in relation to its capability to accumulate lipids when grown under nutrient starvation. Unfortunately, this cultivation mode does not allow to reach high biomass densities, which are required to improve the feasibility of the process. Increasing knowledge of the microalgal physiology is necessary to obtain new useful information for the improvement of culture performance in the perspective of large-scale cultivation. In this work, the mixotrophic cultivation of N. oleoabundans in a brackish medium added with different glucose concentrations has been tested under shaking, with the aim of stimulating growth alongside lipid accumulation inside cells. Cell morphology, glucose consumption, photosynthetic pigment content and photosynthetic efficiency were also investigated. Among all tested glucose concentrations (0-30 g L(-1)), it was observed that 2.5 g L(-1) was the optimal concentration, allowing to obtain the best compromise between glucose supplement, biomass production and lipid accumulation. Growth was highly enhanced in mixotrophic cultures, linked to the release of cells from sporocysts. A unique feature characterising mixotrophy in N. oleoabundans was the promotion of the maximum quantum yield of Photosystem II. Moreover, when mixotrophic cells entered the stationary phase, high lipid accumulation was induced. This study shows that the addition of glucose to N. oleoabundans remarkably increases the production of biomass enriched in lipids and represents an advancement for the cultivation of this microalga for applied purposes.

Radial transport of salt and water in roots of the common reed (Phragmites australis Trin. ex Steudel)

To understand the root function in salt tolerance, radial salt and water transport were studied using reed plants growing in brackish habitat water with an osmotic pressure (πM ) of 0.63 MPa. Roots bathed in this medium exuded a xylem sap with NaCl as the major osmolyte and did so even at higher salt concentration (πM up to 1.3 MPa). Exudation was stopped after a small increase of πM (0.26 MPa) using polyethylene glycol 600 as osmolyte. The endodermis of fine lateral roots was found to be the main barrier to radial solute diffusion on an apoplastic path. Apoplastic salt transfer was proven by rapid replacement of stelar Na(+) by Li(+) in an isomolar LiCl medium. Water fluxes did not exert a true solvent drag on NaCl. Xylem sap concentrations of NaCl in basal internodes of transpiring culms were more than five times higher than in medial and upper ones. It was concluded that the radial NaCl flux was mainly diffusion through the apoplast, and radial water transport, because of the resistance of the cell wall matrix to convective mass flow, was confined to the symplast. Radial salt permeation in roots reduced the water stress exerted by the brackish medium.

Salinity promotes growth of freshwater Neochloris oleoabundans UTEX 1185 (Sphaeropleales, Chlorophyta): morphophysiological aspects

Baldisserotto C., Ferroni L., Giovanardi M., Boccaletti L., Pantaleoni L. and Pancaldi S. 2012. Salinity promotes growth of freshwater Neochloris oleoabundans UTEX 1185 (Sphaeropleales, Chlorophyta): morphophysiological aspects. Phycologia 51: 700–710. DOI: 10.2216/11-099.1Neochloris oleoabundans was described as a freshwater unicellular green microalga; however, some literature suggested that it was an edaphic and halotolerant alga. Neochloris oleoabundans was studied so far for its high lipid content, especially under nitrogen starvation, for possible industrial applications. Information on the morphophysiological characteristics of the alga and its photosynthetic apparatus in different culture conditions still remained incomplete. In the present work, its growth was compared using low-salinity and brackish media with increasing nitrogen supply. The morphophysiological aspects, with a special attention on its photosynthetic apparatus, were analysed through light and transmission electron microscopy, photosynthetic pigment quantification, PSII maximum quantum yield measurements and evaluations of the chlorophyll-protein assembly state. In contrast to what has been reported in previous work on the positive effect of nitrate on N. oleobundans growth, we found negative or negligible effects in our samples cultivated in low-salinity or brackish media, respectively. Brackish conditions induced a better growth of the alga, which showed some morphological variations (cell volume enlargement, cell wall thickening, increased stromatic starch and polyphosphate grains). Furthermore, brackish cultured algae were characterized by a strong increase in cellular chlorophylls and carotenoids. Fluorimetric analyses pointed to the absence of disturbance to the photosynthetic apparatus and to a higher photosynthetic efficiency in brackish cultured samples with respect to controls in the low-salinity medium, indicating a somehow better photosynthetic performance. Interestingly, the behaviour of the F680/F685+694 ratio pointed to a possible positive correlation between nitrogen supply and PSII core stability. On the whole, morphological, biochemical and biophysical results confirmed the higher acclimatized growth of N. oleoabundans in brackish media, which seem more suitable for algal growth than low-salinity ones.

Selection of Arthrospira platensis strains with productivity in brackish water with high boron levels for commercial production in the Lluta Valley

Adaptation and selection of Arthrospira platensis strains, for cultivation in brackish water with excess boron (B) in the Lluta Valley can become an interesting alternative that would allow to extend these cultures to areas that possess the environmental conditions, but that lack the fresh water needed to do it. Strains TX98 and P88 were evaluated in laboratory conditions with three different media of brackish water and with the white medium, the Zarrouk modified medium (MZM). The growing media with brackish water with a B concentration present in the Lluta River of 20 mgL -1 (B20) and medium with 30 mgL -1 (B30), and 10 mg L -1 of B (B10). The effect of the different media on the growing parameters with a culture temperature of 25 ± 1ºC in the three treatments, strains TX98 and P88 triplicate, Arthrospira platensis , showed tolerance. It was statistically determined that in the growth, the two strains, the three treatments and in the interrelation of both there were significant differences (p -1 (dry weight) in brackish water with medium B20. Therefore, the highest rate of specific growth (μmax) was obtained with the TX98 strain grown in the brackish medium B30 and the lowest duplication time (0.597 days). Cells grown in brackish water with B had a slightly biochemically modified composition with the white, in relation to the protein content, in the cases in which there are differences in the B content, specifically B30 treatment. For the culture with brackish water from the Lluta River, the TX98 strain is recommended with 10 mg of B using a laboratory to pilot scale.

High DON bioavailability in boreal streams during a spring flood

Riverine inputs of nitrogen is an important factor that controls productivity of coastal marine waters. Dissolved organic nitrogen (DON) comprises most of the N in boreal rivers. During spring floods, DON flux may exceed the baseflow flux by several orders of magnitude. However, little is known about the biological availability of spring flood DON and, thus, its potential effect on coastal productivity.We have investigated the dynamics of DON bioavailability and chemical composition during a spring flood in two streams in northern Sweden. Potential bioavailability was determined by employing bacterial regrowth bioassays with brackish medium and a coastal bacterial inoculum. In addition, concentrations of urea and amino acids and the proportion of D‐isomers in total dissolved amino acids were analyzed because a high proportion of D‐isomers is suggested to indicate old and refractory organic material.During the flood, potential DON bioavailability increased from 19–28% at baseflow to 55–45% during peak flow in the two streams, while DON concentration remained relatively constant. At the end of the flood, bioavailability returned to the baseflow values. Potential DON bioavailability was positively correlated with the concentration of dissolved combined amino acids and the proportion of L‐enantiomers of amino acids. However, only 5–18% of DON was identified as urea and free and combined amino acids, suggesting that bacteria also utilized other DON compounds. Our results imply that a major portion of the annual export of labile nitrogen occurred during a few weeks of spring flood.

Implications of salinity fluctuation for growth and nitrogen metabolism of the marine diatom Ditylum brightwellii in comparison with Skeletonema costatum

In 1987 effects of salinity fluctuations on growth of Ditylum brightwellii (West) Grunow, isolated from the Eastern Scheldt estuary (SW Netherlands) in 1981, were studied. D. brightwellii was grown in a 12 h light: dark cycle at constant salinity in brackish media. Ammonium-limited cultures were subjected to a salinity fluctuation. By decreasing the salinity to 4.8‰ photosynthesis and cell division were inhibited; cells were deformed. Protein and carbohydrate contents increased slightly, dark respiration was stimulated and cellular levels of glucose decreased at low salinity; this indicated a possible role of sugars in osmoregulation. Ammonium was accumulated in cultures, amino acids may have been stored; the role of the vacuole as a storage compartment was discussed. Both the ammonium uptake capacity and the affinity for ammonium decreased. Nitrogen limitation was relieved in the transient state. [With the activity of the nitrogen assimilation enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT) being uninhibited by lower salinity.] Recovery from hypo-osmotic stress during a salinity increase was initiated by stimulated photosynthesis; chlorophyll a increased, but persistant contractions of cytoplasm (with chloroplasts) may have delayed cell growth. The glutamate dehydrogenase (GDH) activity decreased further whereas the cellular level of alanine increased in the presence of large ammonium pools; this may indicate a temporary activity of ADH (alanine dehydrogenase). Skeletonema costatum (Greville) Cleve, recovered faster from hypoosmotic stress than did D. brightwellii. Due to an osmotic shock from 13.6 to 7.1‰ S both species excreted amino acids and glucose; S. costatum accumulated more glucose, D. brightwellii accumulated more amino acids. S. costatum may with the competition for nitrogen in waters with an unstable salinity; it will replace D. brightwellii.