Fresh Sea Research Articles

Comparison of metabolite profiles and cytotoxicity of the black sea cucumber (Holothuria atra) dried with different drying techniques

Holothuria atra is a species of sea cucumber that could be a source of cytotoxic compounds. The present work aimed to determine the effect of different drying techniques on the profile of metabolites and cytotoxicity of sea cucumber extracts. Sea cucumbers were dried in the sun for 3 d, and then oven-dried at a temperature of 40, 50, and 60°C for 24 h. Fresh sea cucumbers without drying served as a control. The dried and fresh sea cucumbers were extracted by maceration for 12 h using ethanol. The metabolite profiling was performed using Fourier-transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC) analyses, whereas the cytotoxicity was assayed by MTT method using the human breast ductal carcinoma cells (T47D). Analyses of FTIR and HPLC showed that the bioactive compounds of the ethanol extract were relatively stable during drying. This was in line with its cytotoxicity against T47D cells, which did not show significant differences between treatments. Based on these results, it was concluded that drying by sun or oven did not damage the bioactive compounds in the ethanolic extract of sea cucumber.

Aerosols in Northern Morocco-2: Chemical Characterization and PMF Source Apportionment of Ambient PM2.5

Insufficient data on the chemical composition of PM2.5 and its emission sources in the southwestern (SW) Mediterranean area has been identified. Ambient PM2.5 samples were collected in an urban area of Tetouan city, northern Morocco. Chemical mass closure calculations and positive matrix factorization were performed for the comprehensive dataset of PM2.5 chemical analyses. Mass closure improved when multipliers (1.2 and 0.23, respectively) were used for the conversion of organic carbon (OC) and calcium ion (Ca2+) into particulate organic matter (POM) and mineral dust masses, respectively. The mass closure model performed well in this SW Mediterranean region, with a significant correlation (r2 = 0.97) obtained between gravimetrically measured and chemically determined PM2.5 mass. The one-year average concentration of PM2.5 was 17.96 μg/m3, and the major chemical components were POM (34%), secondary inorganic aerosol (SIA) (28%), and black carbon (18%), while unidentified mass was 4%. The mass concentration and most of the chemical components of PM2.5 showed clear seasonal variations, with a summer-high and winter-low pattern for SIA, dust, and BC. In the winter months, POM was the dominant component. Source apportionment analysis revealed that PM2.5 emission sources, regarding their typical tracers, were ammonium sulfate (SO42−, NH4+, K+, NO3−), road traffic and biomass burning emissions (OC, BC), fresh sea salt (Cl−, K+, NO3−), aged sea salt (Mg2+, Na+, Ca2+), and oxalate-rich (oxalate, NO3−) factors. Further, it is hoped that these findings help to improve the scientific understanding of SW Mediterranean aerosols.

Analisis Pendapatan Usaha Ikan Asin di Kelurahan Sumber Jaya Kecamatan Kampung Melayu Kota Bengkulu

This study aims to find out how much income from salted fish business in Sumber Jaya Village, Kampung Melayu District, Bengkulu City. This type of research is descriptive research. The subjects in this study were 21 salted fish business people in Sumber Jaya Village, Kampung Melayu District, Bengkulu City. Data collection techniques using observation, interviews and documentation. Data analysis techniques using data processing, data analysis, interpretation of the results of the analysis. The results of this study found that the capital used in the salted fish business is own capital. The raw materials for this business are fresh sea fish and salt. The production costs in the salted fish business include the cost of production facilities, equipment depreciation costs, labor costs and other costs. The income of salted fish business in Sumber Jaya Village, Kampung Melayu Subdistrict, Bengkulu City in 1 month is the smallest, namely Rp. 3,619,304 and the largest is Rp. 5,707,304. The average income of salted fish business is RP 4,663,304..

Absorption and Sinking Speed of Artocarpus Stems Rope (Artocarpus sp.) and Carex Grass Rope (Carex sp.) in Freshwater and Seawater

Artocarpus stems (Artocarpus sp.) and Carex grass (Carex sp.) have not been applied to fishing gear materials. The fibers produced made into a rope, where this rope is used to absorption and sinking speed test in fresh water and sea water.The absorption of Artocarpus stems rope was 320.30% and 282,60% in fresh water and sea water. Meanwhile for sinking speed have a 5,78 cm/s and 5,08 cm/s for fresh water and sea water. For the Carex grass rope, the absorption in fresh water and sea water was 287,67% and 218,02%. Sinking speed value 2,97 cm/s and 2,67 cm/s for fresh water and sea water. The value of absorption and sinking speed in fresh water is higher than in sea water for both types of rope

Role of Macrophytes: A Review

Macrophytes are large aquatic plants belonging to taxonomically diverse groups. They are adapted morphologically, anatomically and physiologically to grow in aquatic habitats of fresh water, brackish water or sea water. This review is based on the rigorous study of literature and papers based on work done on wetlands and macrophytes. Surveys show that macrophytes form an important component in the structure and functioning of an aquatic ecosystem. They play a vital role in the sustenance of life by providing habitat, food, fodder, fiber, green manure, medicines and other useful products. They act as a bioindicator, influence water quality, perform nutrient cycling and reduce shore erosion. The work concluded that knowledge of floral diversity in any aquatic habitat is essential as each and every plant has its role in food chain and they must be documented and conserved before they become extinct without being acknowledged. Researches must be undertaken to scientifically study and extract the important constituents from unknown flora by identifying them with the help of indigenous people so that it can be further flourished for the welfare of mankind. The aim of this paper is to review the diverse roles of macrophytes and to focus on the conservation of aquatic resources and the biodiversity within them, as they not only provide various ecosystem services but are important for the livelihood and ecological balance.

Characterization of flesh firmness and ease of separation in the fermentation of sea bass in terms of protein structure, texture, and muscle tissue structural changes

This study aims to investigate the reasons for the firmness of fish flesh and the easy separation of fish flesh after curing and fermentation processing of fermented sea bass (FSB) under pressure (approximately 0.02 kg/cm2). Herein, we analyzed fish texture, protein structure, and muscle tissue structure. Results suggest that from the RW (fresh sea bass) to the FS6 (sea bass spontaneously fermented at 6–8 °C for 6 day) processing stage, the increase in hardness and chewiness resulted in firm FSB flesh. The space between the FSB muscle fibers increased and holes appeared in the muscle fiber structure of the FSB. After curing and fermentation of FSB, the stable β-sheet content in the secondary structure of fish meat protein was reduced from 17.1 % to 0 % and converted to an unstable β-turn structure (increased from 36.5 % to 69.5 %). The decrease in the collagen content of the FSB flesh resulted in unstable fish tissue structure. In addition, the FSB myofibrils broke down. Pressure and curing dehydration play a key role in the firmness and easy separation of FSB meat. This study provides a reference for high-value utilization of fermented fish.

Identification and quantification of chemical reactions in a coastal aquifer to assess submarine groundwater discharge composition.

In coastal aquifers, two opposite but complementary processes occur: Seawater intrusion (SWI), which may salinize heavily exploited aquifers, and Submarine groundwater discharge (SGD) which transports oligo-elements to the sea. Aquifers are expected to be chemically reactive, both because they provide abundant surfaces to catalyze reactions and the mixing of very different Fresh Water (FW) and Sea Water (SW) promote numerous reactions. Characterizing and quantifying these reactions is essential to assess the quality and composition of both aquifer water, and SGD. Indeed, sampling SGD is difficult, so its composition is usually uncertain. We propose a reactive end-member mixing analysis (rEMMA) methodology based on principal component analysis (PCA) to (i) identify the sources of water and possible reactions occurring in the aquifer and (ii) quantify mixing ratios and the extent of chemical reactions. We applied rEMMA to the Argentona coastal aquifer located North of Barcelona that contains fluvial sediments of granitic origin and overlies weathered granite. The identification of end members (FW and SW) and the spatial distribution of their mixing ratios illustrate the application procedure. The extent of reactions and their spatial distribution allow us to distinguish reactions that occur as a result of mixing from those caused by sediment disequilibrium, which are relevant to recirculated saltwater SGD. The most important reaction is cation exchange, especially between Ca and Na, which promotes other reactions such as Gypsum and Fluorite precipitation. Iron and Manganese are mobilized in the SW portion but oxidized and precipitated in the mixing zone, so that Fe (up to 15 μEq/L) and Mn (up to 10 μEq/L) discharge is restricted to SW SGD. Nitrate is reduced in the mixing zone. The actual reaction amounts are site-specific, but the processes are not, which leads us to conjecture the importance of these reactions to understand the SGD discharge elsewhere.

Ultrasound assisted slightly acidic electrolyzed water treatment on the protein structure stability of vacuum‐packaged sea bass (Lateolabrax japonicas) during refrigerated storage

AbstractThis study evaluated the synergistic effects of ultrasound (US) and slightly acidic electrolyzed water (SAEW) treatment on the myofibril protein structure of vacuum‐packed sea bass (Lateolabrax japonicas) during refrigerated storage. Fresh sea bass fillets were treated with US, SAEW, US combined with SAEW treatment (US + SAEW), and sterile water (Control) for 10 min, respectively. Different indexes, such as hardness, myofibril fragmentation index (MFI), water activity (aw), and surface hydrophobicity, which also combined with protein characteristic (intrinsic fluorescence intensity) were analyzed. The results showed that the US treatment increased the MFI and surface hydrophobicity of sea bass. Compared with the control group, the bactericidal effect of US + SAEW treatment made the sample better water holding capacity, water activity, and higher fluorescence intensity. Differential scanning calorimetry spectrum results showed that samples treated by US had loose myofibrillary structure, which was convenient for SAEW to act more effectively. US + SAEW treatment retarded the degradation of protein. These results provided evidence that US + SAEW treatment could maintain the quality of fish.

Monitoring Fish Freshness in Real Time under Realistic Conditions through a Single Metal Oxide Gas Sensor.

The realization of an unobtrusive and effective technology able to track fish freshness in real time and inform on its edibility is highly demanded, but still unachieved. In the present paper, we address this issue through a single metal oxide gas sensor working in temperature modulation mode. The system can work without an external reference air source, which is an appealing feature for its possible integration in domestic refrigerators. Tests were carried out using fresh sea bream fillets as case study and working both inside the refrigerator and at room temperature. Parallel gas chromatography–mass spectrometry and microbiological characterization indicated the marked dependence of both the microbiological condition and the gas-phase composition from the individual sample and from the storage temperature. Despite such a large variability, which may be expected in real applications, the proposed system provided similar responses whenever the total bacterial population approached and exceeded the edibility threshold of 107 CFU/g.

Effects of freeze-drying and use of artificial seawater on phosphorus exchange isotherms in brackish water sediments

This study reports results on the estimated magnitude of changes in P sorption isotherms in clayey mud sediments when performed using (1) freeze-dried instead of fresh sediment samples and (2) artificial sea water (ASW) instead of ambient near-bottom water. The sediments used differed in their P sorption. For the isotherms, sediments were equilibrated for 48 h in solutions of varying P concentration whereafter the amount of P sorbed or desorbed was determined. We adjusted the modified Freundlich equation to the isotherm data and assessed differences in the isotherms between the treatments by comparing equilibrium P concentrations and P buffering capacities determined from the isotherm equation. Freeze-drying decreased the P sorption in all investigated sediments, but the magnitude of the changes varied depending on the properties of the sediments. The effect was minor in the sediment abundant in P sorption sites and low in easily exchangeable P, while it was clearer in the sediments originally high in P or low in sorption surfaces. ASW and ambient water produced similar isotherms suggesting that ASW is a suitable equilibrium solution in P exchange experiments with muddy clay sediments. This study enlightens the processes occurring in freeze-drying. The results highlight that when examining the effects of dissimilar treatments or experimental conditions on the P exchange isotherms the magnitude and significance of the observed changes should be evaluated in a proper context considering the precision of the method.Article highlightsThe effects of freeze-drying on P sorption isotherms are minor in sediments abundant in unoccupied sorption surfaces.Artificial sea water is a suitable background matrix for the P exchange isotherms.The precision of the method should be considered when comparing the effects of differing isotherm treatments.

Integrating experience with databases, bioinformatics, and wet lab exercises for students in an introductory genetics course.

Students often have no exposure to the incredible amount of genomic and proteomic data that is freely and easily accessible online. Becoming familiar with these resources, and seeing how they could be applied to a specific research question, is a prerequisite for students to apply them to their own scientific development. Many students have to "see it" and "do it" before they "get it." This paper describes a teaching laboratory for undergraduate Genetics students that combines exploration of several publicly available databases with some simple bioinformatic exercises and "'real" live experience in a wet lab exercise. The goal is to teach skills in applying genomic data to a real scientific question. In this exercise, students identify a target protein after exploring several protein and signal transduction databases, such as the Kyoto Encyclopedia of Genes and Genomes database. They then search for the encoding RNA in a newly available sea star mature egg transcriptome database and for the DNA in an existing sea star genome database. The students design primers against specific regions or domains in their target RNA and amplify these by reverse transcription PCR against RNA purified from fresh sea star eggs. The PCR reactions are analyzed by agarose gel electrophoresis. It is hoped that the combination of the computational biology exercises with the real lab work will excite the students and stimulate them to explore this exciting new biology further.

Seacat - Catalysts for Direct Seawater Electrolysis

With current technology, the direct electrolysis of seawater struggles with ACSFRs (active chlorine species formation reactions), including the ClER (chlorine evolution reaction), competing with the formation of gaseous oxygen on the anode side. The corrosive and poisonous chlorine compounds produced in the ClER pose a significant issue, essentially destroying the electrolyser in a short period of time. Since the purification of seawater requires both energy and increased investment and maintenance costs, today water electrolysis is often not economically feasible in regions with no fresh water access.This marks the starting point of this PhD project. The primary goal of this thesis is the development and demonstration of a catalyst suitable for direct electrolysis of seawater to hydrogen and oxygen, without the formation of Cl2.Nickel based layered double hydroxides (Ni-LDH) and oxyhydroxides (Ni-OOH), particularly when doped with other transition metals, have shown very high catalytic activity with respect to the OER. If sufficient current densities under practical conditions (1A/cm2, < 80 °C, stable for several thousand hours) below the thermodynamic onset potential of the ClER of around 1.7 V could be reached, an active suppression of the ClER is not necessarily needed.Initially, we investigate potential highly active mixed-metal LDH catalysts for the OER in sea water splitting, which are synthesized by a particularly simple, quick and efficient procedure proposed by Li et al. in 2020. Based on their work, we conduct a screening study of 36 unique compounds derived from abundantly available transition metals (Ni, Fe, Mn, Cr, Co, Cu, Zn, Al). The LDHs are coated onto a Ni foam substrate by a two-step dip coating process from metal nitrate solutions. In a first approach, we only consider compounds consisting of two transition metals with equal molar ratios. We then investigate their catalytic activity as well as the long term stability for up to 1000 hours in industrially relevant (60 – 80°C, 6M KOH) fresh water and sea water conditions, particularly regarding catalyst poisoning effects of the sea water constituents on the catalyst.We then give an outlook on the next step in the project, which will be to make use of the simple synthesis procedure by implementing it into an autonomous lab robot setup. The robot platform will comprise all steps of the experiment from synthesis over electrochemical testing, data analysis and machine learning based optimization. This way, we will showcase the potential of combining high-throughput screening with AI-assisted materials discovery. As a proof-of-concept, the robot will reproduce the initial screening study that was carried out manually. Subsequently, autonomous data analysis and synthesis optimization functionality will be implemented and the robot will run several iterations of closed-loop catalyst optimization experiments without human interaction.

Potential of feed supplements on morphometric and gonad weight of fish exposed to microplastics

Microplastic can highly accumulated in fresh water, sea water, sedimentary, and marine life species. Its tiny size and large quantity cause it to become ubiquitous and highly bioavailable in aquatic organism. The potential of probiotic supplement from lactic acid bacteria and Vitamin C has proven effective and beneficial in remedial process of living organisms that exposed to toxic materials in microplastic. This research wants to analyze the potential of feed supplement on morphometric and gonad weight of fish exposed to microplastics. Thirty six tilapias divided into two groups; one group given feed variant (commercial pellet, mixture of commercial pellet and probiotic, and mixture of commercial pellet and Vitamin C) and other group given microplastic concentrate variant (0; 0,1; 1; and 10 mg/L) for 15 days. The result shows changes in morphometry and the weight of fish gonad. A significant microplastic exposure reduce the size of tilapia’s morphometry (body size, standard size, head size, and body width), go nad’s weight, and tilapia’s weight. The addition of probiotics increased the morphometry of tilapia exposed to microplastics.This research will give useful informations for fish farmers in developing fish resources and fish farming.

Effect of Organic Acid Added Washing Solution on the Quality of Fresh Chilled Sea Bream (Sparus aurata)

Bu çalışmada ülkemizde ticari öneme sahip olan çipura balıklarının (Sparus aurata) yıkama suyuna eklenen farklı konsantrasyonlardaki (%2, 2+2, 4+4 ve 5+5) asetik asit ve sitrik asit solüsyonlarının +4 °C’de muhafaza sırasında çipura balıklarında meydana gelen mikrobiyolojik ve duyusal değişimler incelenmiştir. Araştırmanın sonuçlarına göre % 2’lik sitrik asit ilavesi ve asetik asit ilavesi 9-10 güne kadar raf ömrü sunmakta olduğunu göstermiştir. Sitrik ve asetik asitlerin birlikte ilavesi ise 12 güne kadar raf ömrünü uzatabilmektedir. Ancak organik asitlerin birlikte ilavesinde yüksek konsantrasyon (%5+5) örneklerin duyusal kalitesinde kayıplara sebep olduğunu göstermiştir. Bu kapsamda çipura balıklarının muhafazasında organik asitlerin birlikte ilavesi için konsantrasyonun % 2 ve 4 arasında olması ürünlerin duyusal kalitelerinin de korunması açısından önemli olduğu sonucuna varılmıştır.

Vitamin and mineral content of microalgae Phorpyridium and Chlorella and development prospects for food raw materials in Indonesia

Porphyridium cruentum is a product of the division of the genus Rhodophyta. It is a single cell that lives or colonizes freely in mucillago. The cells continuously secrete mucillago compounds, forming a capsule that envelops the cells. Mucillago is a sulfate polysaccharide that is soluble in water [1]. Microalgae Chlorella sp. are marine algae that can grow on fresh water and sea water media. This type of algae has a green pigment included in it class Chlorophyceae of the Chlorellaceae family. The goal of this study was to find out how much vitamin and mineral content there was in Phorpyridium and Chlorella cultivated on Conway media. The findings demonstrate that Phorpyridium has a higher vitamin E content than vitamins B1, B2, and B6. ie. 2,4 mg/100 g. Mineral analysis showed that Phorpyridium contained K minerals (45,7 mg/100g), Ca (201 g/100g), Mg (1090 mg/100g), Fe (38,2 mg/kg), Zn (3,45 mg/kg), Se (0,04 mg/kg), and P (2351 mg/kg).. Vitamin analysis of Chlorella show that vitamin B1 in Chlorella higher than Phorpyridium ie.( 3,71 mg/kg). Mineral analysis showed that Chlorella contained K minerals (714 mg/100g), Ca (331 g/100g), Mg (335 mg/100g), Fe (539 mg/kg), Zn (21,7 mg/kg), Se (0,22 mg/kg), and P (2982 mg/kg).

ANALISA PERPINDAHAN PANAS HEAT EXCHANGER MESIN INDUK (STUDI KASUS: KM. SUMBER MUTIARA)

Heat exchanger (HE) is a component of the main engine cooling system that plays a very important role in the process of changing the fluid temperature by exchanging the amount of heat with other fluids. The use of HE in the main engine cooling system should be considered in controlling after operation. HE performance can be analyzed using heat transfer analysis in the form of heat absorbed by HE (Q), LMTD and heat transfer coefficient (U). This study aims to analyze heat transfer in the form of calculations of absorbed heat, LMTD and heat transfer coefficient on the main engine HE KM Sumber Mutiara. This study measures the temperatures of fresh water and sea water entering and leaving the HE. In addition, measurement of water discharge and determination of the dimensions of the HE used for the main engine cooling system of KM Sumber Mutiara. This research shows that the highest heat value absorbed by HE (Q) is at RPM 1200 at 44.85 kJ/s, for the LMTD value at RPM 1000 at 45.69 oC and for the U value at RPM 1100 at 824 W/m2. oC. HE main engine KM Sumber Mutiara has not maximized its performance due to the fouling factor from sea water. The need for preventive maintenance and additional filters on the KM Sumber Mutiara Main Machine Heat Exchanger to increase the effectiveness of the HE.

Micro-spectroscopic and freezing characterization of ice-nucleating particles collected in the marine boundary layer in the eastern North Atlantic

Abstract. Formation of atmospheric ice plays a crucial role in the microphysical evolution of mixed-phase and cirrus clouds and thus climate. How aerosol particles impact ice crystal formation by acting as ice-nucleating particles (INPs) is a subject of intense research activities. To improve understanding of atmospheric INPs, we examined daytime and nighttime particles collected during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign conducted in summer 2017. Collected particles, representative of a remote marine environment, were investigated for their propensity to serve as INPs in the immersion freezing (IMF) and deposition ice nucleation (DIN) modes. The particle population was characterized by chemical imaging techniques such as computer-controlled scanning electron microscopy with energy-dispersive X-ray analysis (CCSEM/EDX) and scanning transmission X-ray microscopy with near-edge X-ray absorption fine-structure spectroscopy (STXM/NEXAFS). Four major particle-type classes were identified where internally mixed inorganic–organic particles make up the majority of the analyzed particles. Following ice nucleation experiments, individual INPs were identified and characterized by SEM/EDX. The identified INP types belong to the major particle-type classes consisting of fresh sea salt with organics or processed sea salt containing dust and sulfur with organics. Ice nucleation experiments show IMF events at temperatures as low as 231 K, including the subsaturated regime. DIN events were observed at lower temperatures of 210 to 231 K. IMF and DIN observations were analyzed with regard to activated INP fraction, ice-nucleation active site (INAS) densities, and a water activity-based immersion freezing model (ABIFM) yielding heterogeneous ice nucleation rate coefficients. Observed IMF and DIN events of ice formation and corresponding derived freezing rates demonstrate that the marine boundary layer aerosol particles can serve as INPs under typical mixed-phase and cirrus cloud conditions. The derived IMF and DIN parameterizations allow for implementation in cloud and climate models to evaluate predictive effects of atmospheric ice crystal formation.

Measurement report: Characterization and source apportionment of coarse particulate matter in Hong Kong: insights into the constituents of unidentified mass and source origins in a coastal city in southern China

Abstract. Coarse particulate matter (i.e. PM with an aerodynamic diameter between 2.5 and 10 µm – PM2.5 and PM10 – or PMcoarse) has been increasingly recognized for its importance in PM10 regulation because of its growing proportion in PM10 and the accumulative evidence for its adverse health impact. In this work, we present comprehensive PMcoarse speciation results obtained through a 1-year-long (January 2020–February 2021) joint PM10 and PM2.5 chemical speciation study in Hong Kong, a coastal and highly urbanized city in southern China. The annual average concentration of PMcoarse is 14.9 ± 8.6 µg m−3 (± standard deviation), accounting for 45 % of PM10 (32.9 ± 18.5 µg m−3). The measured chemical components explain ∼75 % of the PMcoarse mass. The unexplained part is contributed by unmeasured geological components and residue liquid water content, supported through analyses by positive matrix factorization (PMF) and the thermodynamic equilibrium model ISORROPIA II. The PMcoarse mass is apportioned to four sources resolved by PMF, namely soil dust/industrial and coal combustion, construction dust/copper-rich emissions, fresh sea salt, and an aged sea salt factor containing secondary inorganic aerosols (mostly nitrate). The PMcoarse concentration and source composition exhibit a distinct seasonal variation, a result mainly driven by the source areas the air masses have travelled through as revealed by back-trajectory analysis. In summer when the site is dominated by marine air mass, PMcoarse is the lowest (average = 8.1 µg m−3) and sea salt the largest contributor (47 %), followed by the two dust factors (36 % in total). In winter when the site receives air mass mainly from the northern continental region, PMcoarse concentration triples (24.8 µg m−3), with the two dust factors contributing three quarters of the aerosol mass. The potential dust source areas are mapped using the concentration-weighted trajectory technique, showing either the Greater Bay Area or the greater part of southern China as the origin of fugitive dust emissions leading to elevated ambient PMcoarse loadings in Hong Kong. This study, the first of this kind in our region, provides highly relevant guidance for other locations with similar monitoring needs. Additionally, the study findings point to the need for further research on the sources, transport, aerosol processes, and health effects of PMcoarse.

Multiscale and multifactor sea-groundwater interactions in southwestern Mauritania

Coastal aquifers in semi-arid zones are particularly exposed to environmental changes because of their low annual recharge and the increasing anthropogenic pressure. This is particularly the case in the Trarza phreatic aquifer (SW Mauritania), which is the uppermost northern part of the great Senegalese-Mauritanian sedimentary basin. The interactions between the Atlantic Ocean and the Tertiary-Quaternary aquifer have evolved considerably during the last millennia and these continuous changes concern the nature and location of processes at work, their intensity and their current consequences. In this vast region with a very flat topography, hydrodynamic and geochemical observations are still rare and currently allow only the main features of recent history to be reconstructed. The analysis of old and recent data reveals that eustatic variations and the annual flood of the Senegal River were in the past the most important factors of equilibrium between fresh water and sea water, even very far from the present coastline. Today, anthropization, in particular hydraulic developments and urbanisation, adds to the complexity of the system. At a more local scale, denser observations in the Nouakchott urban area or in the Diawling natural park provide a better understanding of current dynamics.

Development of edible composite film based on chitosan nanoparticles and their application in packaging of fresh red sea bream fillets

This research was conducted to assess the structure, mechanical, barrier and optical properties of three edible composite films based on chitosan nanoparticles. Films containing cinnamon-perilla essential oil (C-PEO) Pickering nanoemulsion had denser structure and better mechanical properties. In addition, films with anthocyanidins exhibited enhanced antioxidant activity. The results showed that both Pickering nanoemulsion and anthocyanidins could improve some properties of edible composite film based on chitosan nanoparticles. Finally, preservation experiments were carried out. Analysis of storage quality indices (sensory evaluation, microbiological analyses, pH, total volatile basic nitrogen, thiobarbituric acid values, color and texture) revealed the shelf life of fillets wrapped in three kinds of composite film was extended to 6–8 days. The preservation effect of plant essential oil compound anthocyanidin edible film for fillet was the best and anthocyanidins compound chitosan nanoparticles edible film was the best in appearance of protection. • Three novel chitosan nanoparticles films were prepared and characterized. • Physical properties of the film improved with adding Pickering nano-emulsion. • The effect of three kinds of edible film on the preservation of fresh fillets. • Composite film delayed lipid oxidation and proteolysis in fresh fillets.