Methylphosphonate Degradation and Salt-Tolerance Genes of Two Novel Halophilic Marivita Metagenome-Assembled Genomes from Unrestored Solar Salterns.

Aerobic bacteria that degrade methylphosphonates and produce methane as a byproduct have emerged as key players in marine carbon and phosphorus cycles. Here, we present two new draft genome sequences of the genus Marivita that were assembled from metagenomes from hypersaline former industrial salterns and compare them to five other Marivita reference genomes. Phylogenetic analyses suggest that both of these metagenome-assembled genomes (MAGs) represent new species in the genus. Average nucleotide identities to the closest taxon were <85%. The MAGs were assembled with SPAdes, binned with MetaBAT, and curated with scaffold extension and reassembly. Both genomes contained the phnCDEGHIJLMP suite of genes encoding the full C-P lyase pathway of methylphosphonate degradation and were significantly more abundant in two former industrial salterns than in nearby reference and restored wetlands, which have lower salinity levels and lower methane emissions than the salterns. These organisms contain a variety of compatible solute biosynthesis and transporter genes to cope with high salinity levels but harbor only slightly acidic proteomes (mean isoelectric point of 6.48).

Sources and fate of organic matter in a hypersaline lagoon: A study based on stable isotopes from the Pulicat lagoon, India.

Stable carbon (δ13C) and nitrogen (δ15N) isotopes of organic matter (OM) in bed sediments and suspended solids are thoroughly investigated in the Pulicat lagoon, India, in pre-South West (SW) monsoon (June 2018) and post-North East (NE) monsoon (March 2019) to understand the response of OM in salt stress conditions. A near absence of an external supply of water and intense evaporation, as suggested by higher hydrogen and oxygen isotope values (δD and δ18O) of the lagoon water, led to hypersaline conditions in the lagoon. Despite a long period of osmotic stress, a high OM concentration in suspended solids in post-NE monsoon suggests that autochthonous production is unaffected by salt stress conditions. Locally at different sites, the difference in δ13C (-4.9‰ to +1.4‰) and δ15N (-4.1‰ to +1.6‰) values of OM between suspended solids and bed sediments are higher in pre-SW monsoon compared to post-NE monsoon. The negative isotopic difference is caused by benthic respiration of OM and cation exchange with clay bound ammonium in bed sediments, whereas the positive difference is the result of cellulose decomposition in areas dominated by seagrasses. However, in post-NE monsoon, wind-induced re-suspension of bed sediments reduce the differences in δ13C (-2.3‰ to -0.1‰) and δ15N (-2.1‰ to +3‰) values. The source apportionments of δ15N values suggest inputs from sewage and fertilizers. Additionally, seagrass-detritus dislodged by fishing activities favors primary production. Overall, we suggest that the impact of the hypersaline conditions on in-situ productivity can be suppressed if wind activity and nutrient re-cycling are dominant. The present study is unique as it addresses the processes that operate in a hypersaline lagoon during the short-term failure of monsoon.

Validation of reference genes for quantitative real-time PCR in chemical exposed and at different age's brackish water flea Diaphanosoma celebensis.

Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), a primary approach for evaluating gene expression, requires an appropriate normalization strategy to confirm relative gene expression levels by comparison, and rule out variations that might occur in analytical procedures. The best option is to use a reference gene whose expression level is stable across various experimental conditions to compare the mRNA levels of a target gene. However, there is limited information on how the reference gene is differentially expressed at different ages (growth) in small invertebrates with notable changes such as molting. In this study, expression profiles of nine candidate reference genes from the brackish water flea, Diaphanosoma celebensis, were evaluated under diverse exposure to toxicants and according to growth. As a result, four different algorithms showed similar stabilities of genes for chemical exposures in the case of limited conditions using the same developmental stage (H2A was stable, whereas Act was fairly unstable in adults), while the results according to age showed a significantly different pattern in suite of candidate reference genes. This affected the results of genes EcRA and GST, which are involved in development and detoxification mechanisms, respectively. Our finding is the first step towards establishing a standardized real-time qRT-PCR analysis of this environmentally important invertebrate that has potential for aquatic ecotoxicology, particularly in estuarine environments.

Presence and biodistribution of perfluorooctanoic acid (PFOA) in Paracentrotus lividus highlight its potential application for environmental biomonitoring.

The first determination of presence and biodistribution of PFOA in ninety specimens of sea urchin Paracentrotus lividus from two differently contaminated sites along Palermo's coastline (Sicily) is reported. Analyses were performed on the sea urchins' coelomic fluids, coelomocytes, gonads or mixed organs, as well as on seawater and Posidonia oceanica leaves samples from the collection sites. PFOA concentration ranged between 1 and 13 ng/L in seawater and between 0 and 794 ng/g in P. oceanica. The analyses carried out on individuals of P. lividus from the least polluted site (A) showed PFOA median values equal to 0 in all the matrices (coelomic fluid, coelomocytes and gonads). Conversely, individuals collected from the most polluted site (B) showed median PFOA concentrations of 21 ng/g in coelomic fluid, 153 ng/g in coelomocytes, and 195 ng/g in gonads. Calculated bioconcentration factors of log10BCF > 3.7 confirmed the very bioaccumulative nature of PFOA. Significant correlations were found between the PFOA concentration of the coelomic fluid versus the total PFOA concentration of the entire sea urchin. PERMANOVA (p = 0.001) end Welch's t-test (p < 0.001) analyses showed a difference between specimens collected from the two sites highlighting the potential application of P. lividus as sentinel species for PFOA biomonitoring.

Phytoplankton of the Curonian Lagoon as a New Interesting Source for Bioactive Natural Products. Special Impact on Cyanobacterial Metabolites.

The bioprospecting of marine and brackish water systems has increased during the last decades. In this respect, microalgae, including cyanobacteria, and their metabolites are one of the most widely explored resources. Most of the bioactive compounds are isolated from ex situ cultures of microorganisms; however, analysis of field samples could also supply valuable information about the metabolic and biotechnological potential of microalgae communities. In this work, the activity of phytoplankton samples from the Curonian Lagoon was studied. The samples were active against antibiotic resistant clinical and environmental bacterial strains as well as against serine proteases and T47D human breast adenocarcinoma cells. No significant effect was found on Daphnia magna. In addition, using LC-MS/MS, we documented the diversity of metabolites present in field samples. A list of 117 detected cyanopeptides was presented. Cyanopeptolins constituted the largest class of cyanopeptides. As complex bloom samples were analyzed, no link between the observed activity and a specific sample component can be established. However, the results of the study showed a biotechnological potential of natural products from the Curonian Lagoon.

Effect of crevice morphology on SRB activity and steel corrosion under marine foulers.

Localized corrosion of submerged steel H-piles was detected in a Florida bridge spanning over a brackish river. Analysis of the water showed proliferation of sulfate reducing bacteria (SRB). The steel piles had coincident heavy marine growth that may support biofilms and biocorrosion. The objective of the research described here was to identify the role of the physical morphologies of macrofouling on SRB activity and the aggravation of microbiologically influences corrosion (MIC) of submerged steel bridge. Laboratory experiments were carried out in nutrient-rich environments inoculated with SRB, with both porous and laminate crevice conditions characteristic of soft and hard marine fouling. It was confirmed that SRB proliferation can occur within the crevice environments, but aeration levels under crevices with interaction with the bulk solution can affect SRB activity. Electrochemical impedance spectroscopy provided separation of environmental parameters and surface reaction parameters for the complicated systems relating to corrosion under the porous and laminate crevice geometries.

Long term salinity disrupts the hepatic function, intestinal health, and gills antioxidative status in Nile tilapia stressed with hypoxia.

In aquaculture, fish are stressed with several factors involved in impacting the growth rate and health status. Although Nile tilapia can resist brackish water conditions, hypoxia status may impair the health condition of fish. Nile tilapia were exposed to salinity water at 0, 10, and 20‰ for four weeks then the growth behavior was checked. The results showed meaningfully lowered growth rate, feed utilization, and survival rate when fish kept in 20‰ for four weeks. Then fish were subdivided into six groups (factorial design, 2 × 3) in normoxia (DO, 6 mg/L) and hypoxia (DO, 1 mg/L) conditions for 24 h. High salinity (10 and 20‰) combined with hypoxia stress-induced inflammatory features in the intestines, gills, and livers of fish. The activities of SOD, CAT, and GPX were increased in the intestines, gills, and livers of fish grown in 10 and 20‰ and exposed with hypoxia stress. Fish grown in 20‰ and stressed with hypoxia had the highest ALT, AST, and ALP levels (p < 0.05) among the groups. The highest transcription levels of Il-8, Il-1ß, Ifn-γ, Tnf-α, and Caspase-3 genes and the lowest level of Il-10 gene were observed in fish exposed with 20‰ and hypoxia. The outputs of Integrated Biomarker Response (IBR) showed marked differences between fish groups with varied values. The lowest IBR was observed in fish reared in fresh water and normoxia, while the highest IBR was seen in the group of fish reared in 20‰ and hypoxia conditions (p < 0.05). These results confirm that Nile tilapia can tolerate 10‰ in normoxia but 20‰ salinity combined with hypoxia results in oxidative stress, apoptosis, and inflammatory features in the intestines, gills, and livers. The obtained results indicate that hypoxia can affect the performances of Nile tilapia reared in brackish or high-water salinity leading to severe economic loss. Further future studies are required to understand the impact of different water salinities with hypoxia in the short term and long-term periods on the productivity of Nile tilapia.

Identification and response of cytochrome P450 genes in the brackish water flea Diaphanosoma celebensis after exposure to benzo[α]pyrene and heavy metals.

The cytochrome P450 (CYP) enzyme family is extensive; these enzymes participate in phase I enzyme metabolism and are involved in xenobiotic detoxification in all living organisms. Despite their significance in xenobiotic detoxification, little is known about the species-specific comparison of CYPs and their molecular responses in aquatic invertebrates. We identified 31 CYPs in the brackish water flea Diaphanosoma celebensis via thorough exploration of transcriptomic databases and measured the transcript profiles of 9 CYPs (within full sequences) in response to benzo[α]pyrene (B[α]P) and two heavy metals (cadmium [Cd] and copper [Cu]). Through phylogenetic analysis, the CYPs were separated and clustered into four clans: mitochondrial, CYP2, CYP3, and CYP4. The expression of 9 CYPs were differentially modulated (up- and/or downregulated) in response to B[α]P, Cd, and Cu. In particular, CYP370A15 was significantly upregulated in response to B[α]P, Cd, and Cu, suggesting that the identified CYPs are involved in xenobiotic detoxification and are useful as biomarkers in response to B[α]P, Cd, and Cu. This study aimed to comprehensively annotate cladoceran CYPs; our results will add to the existing knowledge on the potential roles of CYPs in xenobiotic detoxification in cladocerans.

Brackish water improves the taste quality in meat of adult male Eriocheir sinensis during the postharvest temporary rearing.

We investigated the effect of temporary rearing in brackish water on the taste quality in meat of crab cooked. The main salinity-responsive factors included 5'-nucleotides and free amino acids (FAAs) in crab meat that were identified using tri-step infrared spectroscopy. Compared to the fresh water group, the contents of 5'-adenosine monophosphate and 5'-inosine monophosphate in the brackish water group significantly increased in the 2nd week and decreased in the 6th week, respectively. The contribution ratio of umami FAAs increased from 8.1 to 13.5% in the 4th week in the brackish water group, showing maximum value of equivalent umami concentration. Moreover, Ca2+ and Cl- contents significantly increased in the 4th and 6th weeks, respectively (P < 0.05). Infrared spectroscopy was an effective method to identify the taste components. With respect to the taste quality, four weeks were determined as the best period for temporary rearing of the crab in brackish water.

Combined effects of heavy metals (Cd, As, and Pb): Comparative study using conceptual models and the antioxidant responses in the brackish water flea.

The combined effect of toxic inducers has emerged as a challenging topic, particularly due to their inconsistent impacts on the environment. Using toxic unit (TU) based on LC50 value, we investigated the 48 h acute toxicities of the following combinations: Cd + As, Cd + Pb, As + Pb, and Cd + As + Pb, and binary and ternary combined effects were interpreted using concentration addition (CA) and independent action (IA) model. The molecular effects of these combinations were further examined on the basis of gene expression (four GST and two SOD isoforms) and antioxidant enzymes activity (SOD and GST). The CA-predicted LC50 was similar to the observed results, indicating that the CA model is more applicable for evaluating the combined effects of the metal mixtures. Synergistic effects (ΣTULC50 < 0.8) were observed for the mixtures As + Pb and Cd + Pb, while additive effects (0.8 < ΣTULC50 < 1.2) were observed for the mixtures Cd + As + Pb and Cd + As. No antagonistic effects were observed in this study. Molecular biomarkers for oxidative stress caused by metals, as well as traditional endpoints such as lethality, have shown a clear response in assessing the toxicity of binary and ternary mixtures. This study opens up a new avenue for the use of biomarkers to assess the combined effects of metals in aquatic environments.

Modular Chitosan-Based Adsorbents for Tunable Uptake of Sulfate from Water.

The context of this study responds to the need for sorbent technology development to address the controlled removal of inorganic sulfate (SO42-) from saline water and the promising potential of chitosan as a carrier system for organosulfates in pharmaceutical and nutraceutical applications. This study aims to address the controlled removal of sulfate using chitosan as a sustainable biopolymer platform, where a modular synthetic approach was used for chitosan bead preparation that displays tunable sulfate uptake. The beads were prepared via phase-inversion synthesis, followed by cross-linking with glutaraldehyde, and impregnation of Ca2+ ions. The sulfate adsorption properties of the beads were studied at pH 5 and variable sulfate levels (50-1000 ppm), where beads with low cross-linking showed moderate sulfate uptake (35 mg/g), while cross-linked beads imbibed with Ca2+ had greater sulfate adsorption (140 mg/g). Bead stability, adsorption properties, and the point-of-zero charge (PZC) from 6.5 to 6.8 were found to depend on the cross-linking ratio and the presence of Ca2+. The beads were regenerated over multiple adsorption-desorption cycles to demonstrate the favorable uptake properties and bead stability. This study contributes to the development of chitosan-based adsorbent technology via a modular materials design strategy for the controlled removal of sulfate. The results of this study are relevant to diverse pharmaceutical and nutraceutical applications that range from the controlled removal of dextran sulfate from water to the controlled release of chondroitin sulfate.

Experimental evidence on the effects of temperature and salinity in morphological traits of the Microcystis aeruginosa complex.

Microcystis aeruginosa complex (MAC) encompasses noxious colonial bloom forming cyanobacteria. MAC representatives bloom in eutrophic freshwater and brackish ecosystems with stagnant water, were temperature and salinity are the main variables modulating their distribution, biomass and toxicity. Cell abundance and biovolume of MAC colonies define regulatory standards for public health. These variables depend upon colony size that in turn changes with environmental conditions. Here, we conducted two series of experiments to evaluate the response of MAC colonies morphological traits (length, volume, mucilage and number of cells) to temperature and salinity. In two series of experiments in the laboratory, we exposed natural MAC communities to three different temperatures (10, 21 and 30 °C) and four salinity levels (0, 5, 10 and 25 ppt) typically found in estuaries. We found that average colony length, volume and mucilage thickness did not change with temperature, but the cell-free space inside the colonies was smaller at the highest evaluated temperature (30 °C). Salinity fostered an increase in colony length, volume and mucilage thickness, while cell-free space diminished, resulting in higher cell density. The number of cells per colony was significantly related to colony size (length and volume) and both, temperature and salinity, affected the parameters of the relationships. Based on present results we propose statistical models to predict cell number per colony based on length and volume and accounting for the effect of salinity and temperature on these traits. This is applicable to ecological studies and to the monitoring of estuarine aquatic environments, by means of a fast and more accurate estimation of cell numbers to define MAC toxic populations early warning systems. A protocol is suggested for its application while the analysis of the interaction of temperature and salinity, as well as the variability in natural environments are objectives for future researches.

Preference for saline water of an amphidromous goby maintained during migration to upstream freshwater areas.

This study aimed to reveal the salinity preference of juveniles of an amphidromous goby, Sumi-ukigori Gymnogobius petschiliensis, while migrating to a freshwater area. Salinity choice experiments revealed that juveniles of this species significantly prefer brackish water (salinity 20) to freshwater (salinity 0) when acclimated to a salinity of 20 in advance. Additional experiments revealed no preference between brackish water and seawater (salinity 35). Since body size was not correlated with the strength of preference for brackish water, and adults of this species are also known to prefer brackish water at a salinity of 20 to freshwater, the preference for saline water may be consistent after migration to a freshwater area. Considering that juvenile G. petschiliensis would often migrate to freshwater areas just after entering streams, the migration should be against its salinity preference. This directly contrasts with other diadromous species, which prefer the salinity of destination areas during and after migration. Adult and juvenile G. petschiliensis may take advantage of high euryhalinity to choose habitats where such ecological costs, such as high predation risk and interspecific competition, are low (i.e., freshwater areas).

Lanthanum modified bentonite behaviour and efficiency in adsorbing phosphate in saline waters.

Lanthanum-modified bentonite (LMB, commercially called Phoslock®) has been widely applied in freshwater systems to manage eutrophication. Little is known, however, about its behaviour and efficiency in binding filterable reactive phosphorus (FRP) in saline environments. We assessed if LMB would adsorb phosphate over a range of salinities (0-32 ppth) comparing the behaviour in seawater salts and equivalent concentrations of NaCl. Lanthanum release from the bentonite matrix was measured and the La species prevailing in saline environments were evaluated through chemical equilibrium modelling. We demonstrated that LMB was able to adsorb FRP in all the salinities tested. Filterable lanthanum (FLa) concentrations were similarly low (<5 µgL-1) at all seawater salinities but considerably elevated, on occasion >2000 times greater in equivalent NaCl salinities. Mineralogical analysis indicates that La present in the clay interlayer was (partially) replaced by Na/Ca/Mg present in the seawater and a possible secondary P-reactive phase was formed, such as kozoite (LaCO3OH) or lanthanite (La2(CO3)3·8H2O) that may be physically dissociated from the LMB. Geochemical modelling also indicates that most FLa dissociated from LMB would be precipitated as a carbonate complex. In light of the identification of reactive intermediate phases, further studies including ecotoxicologial assays are required to assess any deleterious effects from the application of LMB to saline waters.

Comparative transcriptome profiling of selected osmotic regulatory proteins in the gill during seawater acclimation of chum salmon (Oncorhynchus keta) fry.

Salmonid fishes, chum salmon (Oncorhynchus keta) have the developed adaptive strategy to withstand wide salinity changes from the early life stage. This study investigated gene expression patterns of cell membrane proteins in the gill of chum salmon fry on the transcriptome level by tracking the salinity acclimation of the fish in changing environments ranging from freshwater (0 ppt) to brackish water (17.5 ppt) to seawater (35 ppt). Using GO analysis of DEGs, the known osmoregulatory genes and their functional groups such as ion transport, transmembrane transporter activity and metal ion binding were identified. The expression patterns of membrane protein genes, including pump-mediated protein (NKA, CFTR), carrier-mediated protein (NKCC, NHE3) and channel-mediated protein (AQP) were similar to those of other salmonid fishes in the smolt or adult stages. Based on the protein-protein interaction analysis between transmembrane proteins and other related genes, we identified osmotic-related genes expressed with salinity changes and analyzed their expression patterns. The findings of this study may facilitate the disentangling of the genetic basis of chum salmon and better able an understanding of the osmophysiology of the species.

Response of ammonia-oxidizing Bacteria and Archaea to long-term saline water irrigation in alluvial grey desert soils.

Soil nitrification via ammonia oxidation is a key ecosystem process in terrestrial environments, but little is known of how increasing irrigation of farmland soils with saline waters effects these processes. We investigated the effects of long-term irrigation with saline water on the abundances and community structures of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Irrigation with brackish or saline water increased soil salinity (EC1:5) and NH4-N compared to irrigation with freshwater, while NO3-N, potential nitrification rates (PNR) and amoA gene copy numbers of AOA and AOB decreased markedly under irrigation regimes with saline waters. Moreover, irrigation with brackish water lowered AOA/AOB ratios. PNR was positively correlated with AOA and AOB amoA gene copy numbers across treatments. Saline and brackish water irrigation significantly increased the diversity of AOA, as noted by Shannon index values, while saline water irrigation markedly reduced AOB diversity. In addition, irrigation with brackish or fresh waters resulted in higher proportions of unclassified taxa in the AOB communities. However, irrigation with saline water led to higher proportions of unclassified taxa in the AOA communities along with the Candidatus Nitrosocaldus genus, as compared to soils irrigated with freshwater. AOA community structures were closely associated with soil salinity, NO3-N, and pH, while AOB communities were only significantly associated with NO3-N and pH. These results suggest that salinity was the dominant factor affecting the growth of ammonia-oxidizing microorganisms and community structure. These results can provide a scientific basis for further exploring the response mechanism of ammonia-oxidizing microorganisms and their roles in nitrogen transformation in alluvial grey desert soils of arid areas.

An overview on the concentration of radioactive elements and physiochemical analysis of soil and water in Iraq.

In the last decade, radiation physics brought about a revolution in health science by improving scientific equipment and useful methodologies for measurement. Human beings are affected by ionizing radiations that radiate from radioactive elements. The quantity of radioactive elements is different inside and outside the earth's surface. Soil and water are exigencies of human lives which are contaminated by radioactive elements. These radioactive elements enter into the human body through drinking, eating and breathing. On reaching hazardous limits in the human body, these radioactive elements cause stomach cancer, lung cancer and leukemia. Measurement of radioactive elements in soil and water is helpful in monitoring the health issues caused by exposure to these elements. In Iraq, numerous studies about natural radioactivity, radon concentration and physiochemical parameters have been conducted by different researchers, of which most of the studies were conducted in Barsa, Nasirya, Najaf, Karbala, Baghdad, Balad, Kirkuk, Erbil, Mosul and Dohuk cities. This article aims to review and compile the studies conducted in these cities of Iraq from 2011 to 2019. In most articles, high-purity germanium (HPGe), RAD7 and CR-39 detectors are used for radioactivity and radon measurement. These cities are located in the low-high folded and Mesopotamian zones. From this study, it can be concluded that radon concentration in soil and water was greater in the Mesopotamian and lower in the low-high folded zones. Higher concentrations of natural radioactivity in water and soil were found in the low-high folded zone in Iraq. However, most of the conducted studies show that concentrations of radon and natural radioactivity are above the permissible limits recommended by the International Commission on Radiological Protection (ICRP) and World Health Organization (WHO). The values of physiochemical parameters were found to be greater in the Mesopotamian zone, but overall they are not above the permissible limits.

Potable-quality water recovery from primary effluent through a coupled algal-osmosis membrane system.

A coupled algal-osmosis membrane treatment system was studied for recovering potable-quality water from municipal primary effluent. The core components of the system included a mixotrophic algal process for removal of biochemical oxygen demand (BOD) and nutrients, followed by a hybrid forward osmosis (FO)-reverse osmosis (RO) system for separation of biomass from the algal effluent and production of potable-quality water. Field experiments demonstrated consistent performance of the algal system to meet surface discharge standards for BOD and nutrients within a fed-batch processing time of 2-3 days. The hybrid FO-RO system reached water productivity of 1.57 L/m2-h in FO using seawater as draw solution; and permeate flux of 3.50 L/m2-h in brackish water RO (BWRO) and 2.07 L/m2-h in seawater RO (SWRO) at 2068 KPa. The coupled algal-membrane system achieved complete removal of ammonia, fluoride, and phosphate; over 90% removal of calcium, sulfate, and organic carbon; and 86-89% removal of potassium and magnesium. Broadband characterization using high resolution mass spectrometry revealed extensive removal of organic compounds, particularly wastewater surfactants upon algal treatment. This study demonstrated long-term performance of the FO system at water recovery of 90% and with membrane cleaning by NaOH solution.

Health State, morphological characterization and biometric parameters in the mangrove crab Ucides cordatus Linnaeus, 1763 (Brachyura: Ocypodidae)

The crab Ucides cordatus is an important feature of mangroves in the North and Northeast of Brazil. In 2002 a large mortality was reported on this species in the Jaguaribe River Estuary. In order to investigate the possible causes specimens were collected monthly between May 2002 and December 2003 at five sites: Fortim (E1), Fortim (E2), Cumbe (E3) Aracati (E4) and Guajiru (E5). The mangrove structure and environmental parameters (salinity, pH, temperature and DO) were also evaluated. Water was collected for suspended solids analysis, BOD and nutrient levels. Salinity decreased in the rainy season, with no significant variation of pH and temperature. Dissolved oxygen levels had a mean of 5.7 mg L-1. Suspended solids increased at site E4, with BOD varying at E1 and E2 during the dry season. The same was observed at sites E1, E2 and E3 during the rainy season. Ammonia levels at E1 and E2 and phosphorus in all seasons, increased with rain events. Four lines of investigation were adopted: biometry, histology, hematology, and bioassay. There was no significant difference between animals in biometrics and histology showed no cellular alterations. However, hematology showed a significant difference between the E1 and E3 sites due to depletion in the number of hemocytes in E1, probably in response to environmental impacts. This can lead to poor immunity, leading to opportunistic pathogen infections such as viruses, bacteria and fungi. The bioassay showing no abnormal behavior or mortality. The structure the of mangrove was developed in all areas, except in E5 which served as a control site, with significant environmental stress with high levels of herbivorous growth (> 50%) and a salinity of around 50 ‰. It is believed that the mortality of the crabs was an occasional occurrence, probably due to toxin production by some fungal organism.

Investigating the contaminant transport of heavy metals in estuarine waters.

A three-dimensional contaminant transport model of heavy metal (copper) was coupled with the hydrodynamics and suspended sediment transport module to simulate the transport and distribution of heavy metal (copper) of the Danshui River estuarine system in northern Taiwan. The coupled model was validated with observational data including the water level, tidal current, salinity, suspended sediment concentration, and copper concentration. The model simulation results quantitatively reproduce the measurements. Furthermore, the validated model was employed to explore the influences of the freshwater discharge and suspended sediment on the distribution of copper concentrations in the tidal estuarine system. The results demonstrate that a high freshwater discharge results in a decreasing copper concentration, while a low freshwater discharge raises the copper concentration along the estuarine system. If the suspended sediment transport module was excluded in the model simulations, the predicted copper concentration underestimated the measured data. The distribution of copper concentrations without the suspended sediment transport module was lower than that with the suspended sediment transport module. The simulated results indicate that the freshwater discharge and suspended sediment play crucial roles in affecting the distribution of copper concentrations in the tidal estuarine system.