Effects of salinity and food on growth and survival rate of mangrove snail (\(\textit{Nerita balteata}\) Reeve, 1885) at the spat larvae stage

Mangrove snail (Nerita balteata) belongs to gastropoda species distributed in the coastal intertidal and offshore islands of Quang Ninh province. Although the artificial seeds production of this species have been successful but still having a bottle neck as a low survival rate in the process by veliger larvae are transformed into spat larvae stage. Experiments were conducted to determine effects of salinity and food on growth rate and survival rate of mangrove snail in the stage of spat larvae in Quang Ninh province. The results showed that the optimal salinity for growth and developtment of spat larvae was 25‰ that resulted in a absoluted growth rate of 16.5 ± 2.19 µm/day and survival rate of 26.5 ± 0.57% and significantly higher compared to other treatments. The diet of benthic microalgae (Navicula sp.) combined with formulated feed (AP0 and Frippak) were most suitable for the growth and development of mangrove snail at the spat larvae stage with absoluted growth rate of 25,7 ± 1,28 µm/day; Whereas the survival rate of larvae of 32,3 ± 2,52% was significantly higher than those in the other treatments.

Effect of water salinity on survival and osmotic level of larval (Zoea Stage) of mud crabs Scylla tranquebarica

Mud crab of the genus Scylla are considered one of the most sought-after seafood today. This crab species has high quality and delicious aging growth rate and encourage expansion in the aquaculture sector especially in Southeast Asian Countries. However, salinity changes will cause changes in organisms osmotic pressure, and every aquatic biota has an optimal salinity range for survival. The study focuses on evaluating the effect of water salinity on the survival and osmotic levels of the purple mud crab, larvae of Scylla tranquebarica at the zoea stage. The LC50 assessment was performed in 10 different level of water salinity (0; 5; 10; 15; 20; 25; 30; 35, 40, and 50 ppt). Each treatment involved 20 ind./L of newly hatched crabs and being observed for 24 h in 10 different water salinity using 1 L volume glass container. The number of crab’s mortality were taken for each salinity regime. Larval behavior monitored during experiment. Meanwhile, the measurement of osmotic level was carried out at the salinity of 25, 30, and 35 ppt. The result shows that mud crab larvae exhibit any tolerance on the low salinity ranged from 0-10 ppt and the salinity of > 40 ppt. On the other hand, mud crab larvae were still able to survive at the salinity ranged from 20-40 ppt for more than 24 hours. The trend of the osmotic level of mud crab to survive is by hypo osmotic to iso osmotic.

Synergistic Effect of Nanofluids and Surfactants on Heavy Oil Recovery and Oil-Wet Calcite Wettability

In recent years, unconventional oils have shown a huge potential for exploitation. Abundant reserves of carbonate asphalt rocks with a high oil content have been found; however, heavy oil and carbonate minerals have a high interaction force, which makes oil-solid separation difficult when using traditional methods. Although previous studies have used nanofluids or surfactant alone to enhance oil recovery, the minerals were sandstones. For carbonate asphalt rocks, there is little research on the synergistic effect of nanofluids and surfactants on heavy oil recovery by hot-water-based extraction. In this study, we used nanofluids and surfactants to enhance oil recovery from carbonate asphalt rocks synergistically based on the HWBE process. In order to explore the synergistic mechanism, the alterations of wettability due to the use of nanofluids and surfactants were studied. Nanofluids alone could render the oil-wet calcite surface hydrophilic, and the resulting increase in hydrophilicity of calcite surfaces treated with different nanofluids followed the order of SiO2 > MgO > TiO2 > ZrO2 > γ-Al2O3. The concentration, salinity, and temperature of nanofluids influenced the oil-wet calcite wettability, and for SiO2 nanofluids, the optimal nanofluid concentration was 0.2 wt%; the optimal salinity was 3 wt%; and the contact angle decreased as the temperature increased. Furthermore, the use of surfactants alone made the oil-wet calcite surface more hydrophilic, according to the following order: sophorolipid (45.9°) > CTAB (49°) > rhamnolipid (53.4°) > TX-100 (58.4°) > SDS (67.5°). The elemental analysis along with AFM and SEM characterization showed that nanoparticles were adsorbed onto the mineral surface, resulting in greater hydrophilicity of the oil-wet calcite surface, and the roughness was related to the wettability. Surfactant molecules could aid in the release of heavy oil from the calcite surface, which exposes the uncovered calcite surface to its surroundings; additionally, some surfactants adsorbed onto the oil-wet calcite surface, and the combined role made the oil-wet calcite surface hydrophilic. In conclusion, the study showed that hybrid nanofluids showed a better effect on wettability alteration, and the use of nanofluids and surfactants together resulted in synergistic alteration of oil-wet calcite surface wettability.

Oil emulsion characteristics as significance in efficiency forecast of oil-displacing formulations based on surfactants

Enhanced oil recovery in mature fields can be implemented using chemical flooding with the addition of surfactants using surfactant-polymer (SP) or alkaline-surfactant-polymer (ASP) flooding. Chemical flooding design is implemented taking into account reservoir conditions and composition of reservoir fluids. The surfactant in the oil-displacing formulation allows changing the rock wettability, reducing the interfacial tension, increasing the capillary number, and forming an oil emulsion, which provides a significant increase in the efficiency of oil displacement. The article is devoted with a comprehensive study of the formed emulsion phase as a stage of laboratory selection of surfactant for SP or ASP composition. In this work, the influence of aqueous phase salinity level and the surfactant concentration in the displacing solution on the characteristics of the resulting emulsion was studied. It was shown that, according to the characteristics of the emulsion, it is possible to determine the area of optimal salinity and the range of surfactant concentrations that provide increased oil displacement. The data received show the possibility of predicting the area of effectiveness of ASP and SP formulations based on the characteristics of the resulting emulsion.

Osmolyte Signatures for the Protection of Aspergillus sydowii Cells under Halophilic Conditions and Osmotic Shock

Aspergillus sydowii is a moderate halophile fungus extensively studied for its biotechnological potential and halophile responses, which has also been reported as a coral reef pathogen. In a recent publication, the transcriptomic analysis of this fungus, when growing on wheat straw, showed that genes related to cell wall modification and cation transporters were upregulated under hypersaline conditions but not under 0.5 M NaCl, the optimal salinity for growth in this strain. This led us to study osmolyte accumulation as a mechanism to withstand moderate salinity. In this work, we show that A. sydowii accumulates trehalose, arabitol, mannitol, and glycerol with different temporal dynamics, which depend on whether the fungus is exposed to hypo- or hyperosmotic stress. The transcripts coding for enzymes responsible for polyalcohol synthesis were regulated in a stress-dependent manner. Interestingly, A. sydowii contains three homologs (Hog1, Hog2 and MpkC) of the Hog1 MAPK, the master regulator of hyperosmotic stress response in S. cerevisiae and other fungi. We show a differential regulation of these MAPKs under different salinity conditions, including sustained basal Hog1/Hog2 phosphorylation levels in the absence of NaCl or in the presence of 2.0 M NaCl, in contrast to what is observed in S. cerevisiae. These findings indicate that halophilic fungi such as A. sydowii utilize different osmoadaptation mechanisms to hypersaline conditions.

Effect of Different Salinity Levels on Population Dynamics and Growth of the Cyclopoid Copepod Oithona nana

Copepods are one of the most abundant and diverse live food sources for mesopelagic and bathypelagic fishes and crustaceans. They could contribute to the overlap of the transition period from live feed to an artificial weaning diet in marine larvae production. However, the culture conditions still need optimization to provide sufficient production to cover the increasing demand for marine hatcheries. Therefore, the present study investigated the effects of different salinity levels (5, 10, 15, 20, 25, and 30 ppt) on the population growth, growth rate, and population composition (males, females, copepodite, and nauplii ratio) of the marine copepod, Oithona nana. The experiment continued for 15 days, under laboratory-controlled conditions of temperature (27 ± 1 °C), pH (7.7 ± 0.15), and continuous gentle aeration in 30 L glass aquaria. The copepod culture aquaria were supplemented with a mixture of soybean and yeast (0.5 g 10−6 individual−1 24-h−1) as a feed source. The highest significant population growth and population growth rate of O. nana were achieved with a salinity level of 20 ppt. Regarding population composition, O. nana cultured at the salinity level of 20 ppt recorded the highest significant percentages of copepodite and nauplii. The results concluded that copepod, O. nana, is capable of withstanding abrupt changes in the salinity, but there are limits to their tolerance, with an optimal salinity level of 20 ppt. This salinity level achieved the highest population growth and the highest percentages of copepodite and nauplii of marine Copepoda, O. nana.

Early Study on Embryogenesis O.woworae at Different Salinities

Oryzias woworae is an endemic fish of Sulawesi. This endemic fish naturally had faced endangered illegal and unlawful capture, therefore it is needed to be protected and conserved by a cultivation system. This research aims to provide basic information related to the cultivation of O. woworae to know the optimum salinity of hatching media and its influence on the hatchability of eggs and the length of time hatching O. woworae. This research was conducted using experimental methods and presented descriptively. The treatment used in this study is 0 ppt, 2-4 pt, 6-8 ppt, 10-12 ppt. The results showed that O. woworae eggs can hatch in salinity 0 ppt until 10-12 ppt and the best salinity for the length of hatching time is treatment of 2-4 ppt which is 7th day 14 hours 20 minutes. Treatment 0 ppt, 2-4 ppt and 6-8 ppt can reach 100%. This can be concluded that the optimum salinity of the hatching rate of Oryzias woworae until 6-8 ppt, but in treatment 10-12 ppt hatchability only gets 80% as some embryos become shrinking. Hatchability per day shows the treatment of 2-4 ppt is the best treatment, on the 7th day as much as 40% and on the 8th day as much as 40%. The optimal salinity for hatching O. woworae eggs is 2-4 ppt treatment, salinity that can expedite the length of hatching time and produce hatching rate by 100%.

Photoinhibition and β-Carotene Production From Dunaliella sp. Isolated From Salt Pans of Goa

The microalgae Dunaliella is a commercially viable species and well known for its extreme environmental tolerance and β-carotene production under stressful conditions. We examined the effect of salinity and light intensity on the growth and β-carotene production, respectively, in two different species of Dunaliella: Dunaliella. sp. and D. salina, isolated from the salt pans of Goa. Both the species were cultured in growth media with different salinity levels to establish the optimum salinity favouring maximum cell growth. Thereafter, the cells were cultured under optimum NaCl concentration, exposed to a range of light intensity and monitored for β-carotene production. The two species, identified based on their molecular characteristics, displayed a significant difference in growth and β-carotene production. Both D. salina and D. sp achieved a maximum cell density of 11.82×106 cells/ml and 18.76×106 cells/ml at 0.75 M and 0.5 M salinity, respectively. D. salina accumulated a large amount of total carotenoid (36.95 pg. cell-1) when cultured at 0.75 M salinity and exposed to high light intensity (1000 µmol m− 2 S− 1). In contrast, the carotenoid content per cell was low in Dunaliella sp. (3.07 pg. cell-1) when cultured under optimal salinity (0.5M) and high light intensity, indicating photoinhibition. We found that different Dunaliella species exhibit different photo-physiological properties that need further evaluation to identify the right candidate for industrial applications.