Добірка наукової літератури з теми "Hypersalinité"

Marine teleosts constantly lose water to their surrounding environment, a problem exacerbated in fish exposed to salinity higher than normal seawater. Some fish undergo hypersaline exposures in their natural environments, such as short- and long-term increases in salinity occurring in small tidal pools and other isolated basins, lakes, or entire estuaries. Regardless of the degree of hypersalinity in the ambient water, intestinal absorption of monovalent ions drives water uptake to compensate for water loss, concentrating impermeable MgSO4 in the lumen. This study considers the potential of luminal [MgSO4] to limit intestinal water absorption, and therefore osmoregulation, in hypersalinity. The overall tolerance and physiological response of toadfish ( Opsanus beta) to hypersalinity exposure were examined. In vivo, fish in hypersaline waters containing artificially low [MgSO4] displayed significantly lower osmolality in both plasma and intestinal fluids, and increased survival at 85 parts per thousand, indicating improved osmoregulatory ability than in fish exposed to hypersalinity with ionic ratios similar to naturally occurring ratios. Intestinal sac preparations revealed that in addition to the osmotic pressure difference across the epithelium, the luminal ionic composition influenced the absorption of Na+, Cl−, and water. Hypersalinity exposure increased urine flow rates in fish fitted with ureteral catheters regardless of ionic composition of the ambient seawater, but it had no effect on urine osmolality or pH. Overall, concentrated MgSO4 within the intestinal lumen, rather than renal or branchial factors, is the primary limitation for osmoregulation by toadfish in hypersaline environments.

Estuarine organisms are exposed to hypersaline conditions for prolonged periods during drought conditions and under severely restricted river flow resulting from freshwater abstraction and impoundments. Consequently, marine estuarine-dependent fish such as Rhabdosargus holubi may be subjected to extreme conditions, such as hypersalinity prevailing for long periods ( > 2 months). Hypersalinity may impact the energetic demands of fish due to osmoregulation leading to compromised growth. This study assessed the impact of high salinity on the growth and skeletal development of R. holubi juveniles. Skeletons of juveniles grown at different salinities in the wild and in aquaria were analysed for anomalies. The impact of hypersaline conditions on juvenile R. holubi growth was also determined in aquaria. Aquarium experiments indicated that hypersalinity of 50 did not significantly impact growth rates over two months. Overall, anomalies were rare and vertebral-related anomalies specifically did not differ significantly between salinities. However, fin rays were significantly impacted in fish growing at higher salinities in the wild. It was concluded that the strong osmoregulatory ability of R. holubi offers protection against hypersalinity affecting internal structures, but external structures may remain vulnerable. As such, from a locomotory standpoint, R. holubi may be vulnerable to long periods of exposure to hypersaline conditions.

Abstract This study aims to examine photophysiological and osmotic responses in seedlings of the seagrass Enhalus acoroides after exposure to different salinity levels. Seagrass seedlings were grown for 20 days in control (salinity 30), hyposaline (salinity 10 and 20) and hypersaline (salinity 40 and 50) conditions. The present study showed that both hypo- and hypersaline conditions affected the photophysiology of E. acoroides seedlings, reducing the maximum quantum yield of photosystem II (Fv/Fm) and total chlorophyll content. The photosynthetic system appeared to be more sensitive to hyposaline than to hypersaline conditions as shown by immediate declines in Fv/Fm and total chlorophyll content. Hyposaline conditions increased the water content in roots. The increase in tissue Na+ content induced by hypersalinity did not affect photosynthetic integrity and was more pronounced in leaves than in roots. It is concluded that the ionic homeostasis of E. acoroides seedlings is less affected by short-term hypersalinity than by hyposalinity. The K+/Na+ ratios in leaves with hypersalinity decreased by 20 days after treatment. Additionally, the photosynthetic efficiency (Fv/Fm and total chlorophyll content) is highly sensitive to salinity shifts and can be used as a marker for short-term acclimation to salinity stress in this seagrass species.

Strain ATCC 51466, a motile peanut Rhizobium sp., showed patterns of utilization of diverse carbon sources characteristic of fast growers. Bacteria had periplasmic neutral glucans with molecular weight close to 3000. When the extracellular concentration of NaCl was raised to 400 mM, the lag phase of the culture was prolonged about threefold and the generation time was increased almost twice. The changes in growth behavior of salt-stressed bacteria were accompanied by the full suppression of periplasmic oligoglucans and the accumulation of cellular trehalose. Almost identical changes in cell-associated oligoglucans were observed after exposing peanut Rhizobium sp. strain ATCC 10317 to hypersalinity. When the osmotic pressure of the medium was augmented by the addition of either 200 mM mannitol or 16% (w/v) polyethylene glycol, cells of strain ATCC 51466 contained decreased levels of oligoglucans and accumulated trehalose. On the other hand, the content of cellular trehalose increased throughout logarithmic and stationary phases of growth of strain ATCC 51466 in a medium supplemented with 400 mM NaCl. When bacterial cultures were shifted from hypersaline to basal media, oligoglucans were the only oligosaccharides detected. The addition of 10 mM proline to bacteria grown under hypersalinity led to a 50% decrease in the level of trehalose and to the accumulation of oligoglucans. The addition of 10 mM glycine betaine to bacteria grown under hypersalinity also produced accumulation of oligoglucans, but the level of trehalose did not decrease. The results presented here are consistent with a role for trehalose as a compatible solute in peanut Rhizobium ATCC 51466, and they suggest that exogenously added proline may act as a compatible solute in preference to trehalose.Key words: periplasmic glucans, trehalose, peanut Rhizobium, osmotic stress.

Self-sustaining populations of chinook salmon (Oncorhynchus tshawytscha) were established in New Zealand, from a common introduction group, near the turn of the 20th century. To investigate possible population divergence over this relatively short time scale we compared size, growth, and hypersalinity tolerance of families from two populations over their first year of rearing under shared conditions. Differences in initial fry mass were consistent with egg-size differences, but there was also evidence of genetic differences in early growth rates. Size differences between the populations decreased over time and rank correlations of mean family mass with initial egg and fry masses degraded over increasing intervals to nearly zero by the end of the year. Population effects on hypersalinity tolerance were not apparent after 4, 6, or 10 months of rearing (from yolk absorption), but family effects were suggested by ANOVAs and by the existence of groups of families with seemingly different relative seasonal optima for tolerance. Thus far, investigation of juvenile traits under common environmental conditions has shown less genetic divergence between the two New Zealand populations than is suggested by the range of differences found for phenotypic traits measured on wild adults in previous investigations.

Le loup Européen ou bar (Dicentrarchus labrax) effectue des migrations saisonnières vers des habitats où la salinité peut atteindre des niveaux dépassant les 50 ‰, notamment dans les lagunes Méditerranéennes. Nous avons comparé les réponses physiologiques à l’hyper salinité de deux lignées génétiques de D. labrax, en provenance d’Atlantique et de Méditerranée Ouest. Le rôle du rein et de l’intestin dans la réabsorption d’eau dépendante du transport de solutés ont été analysés. L’expression des récepteurs de l’arginine vasotocine et de l’isotocine (AVTR et ITR) a également été mesurée. Les analyses ont été réalisées deux semaines après un transfert de D. labrax soit en eau de mer (EM, 36 ‰), soit en eau hypersalée (EHS, 55 ‰). Une taille inférieure des glomérules rénaux a été mesurée en milieu hyper salé indiquant une limitation des pertes d'eau via l’urine en milieu hypersalé. Les niveaux protéiques et l’activité de l’ATPase Na+/K+ (NKA) étaient supérieurs en milieu hyper salé indiquant un transport actif accrue à cette salinité. L’aquaporine 1a (AQP1a) est exprimée dans certains tubules proximaux n’exprimant que très peu la NKA. De plus, les transcrits aqp1a et aqp1b sont moins exprimés en EHS qu’en EM suggérant un rôle limité de l’AQP1 dans la réabsorption d’eau couplée au transport ionique. Dans l’intestin postérieur, les niveaux de transcrits nka α1a, nkcc2, aqp8ab et aqp8aa étaient supérieurs en EHS qu’en EM ainsi que le niveau protéique AQP8ab. AQP8ab est localisé dans les enterocytes au niveau subapical, exprimant également le cotransporteur Na+/K+/2Cl- (NKCC2) apicalement, suggérant un lien fonctionnel entre l’absorption de Na+, Cl- et l’eau. Parmi les gènes paralogues AVTR, v1a2 est le plus abondant au niveau intestinal et il est surexprimé en EHS. Une comparaison intraspécifique a montré que la lignée Méditerranéenne présente une pression osmotique sanguine supérieure en EHS alors que la lignée Atlantique maintient sa pression osmotique constante. Des différences entre les lignées ont été montrées au niveau de l’intestin postérieur avec des activités NKA supérieures chez les loups Méditerranéens mais aussi une expression plus importante de plusieurs gènes chez les loups Méditerranéens, reflétant des différences adaptatives dans les mécanismes d’absorption d’eau entre les lignées de D. labrax
The European sea bass (Dicentrarchus labrax) migrates towards habitats where salinity can reach levels over 50 ‰, notably in Mediterranean lagoons. We compared physiological responses of Atlantic and West Mediterranean sea bass to hypersalinity. We focused on the role of the kidney and intestine in solute-driven water reabsorption. Intestinal arginine vasotocin and isotocin receptor (AVTR and ITR) expression were also analyzed. Fish were sampled following a two-week transfer from seawater (SW, 36 ‰) to either SW or hypersaline water (HW, 55 ‰). A decreased renal glomerulus size was measured in HW compared to SW indicating that sea bass minimize water loss through urine upon salinity increase. Renal relative protein amounts and activity of Na+/K+-ATPase (NKA) were significantly higher in fish exposed to hypersalinity regardless of their origin indicating increased ion transport. Renal aquaporin 1a (AQP1a) immunolabeling was mainly detected in proximal tubules that do not express NKA and aqp1a, aqp1b were downregulated in HW suggesting a limited role of AQP1 in solute-coupled water uptake at 55 ‰. In the posterior intestine, nka α1a, nkcc2, aqp8ab and aqp8aa mRNA expressions were higher in HW compared to SW as well as relative protein expression of AQP8ab. The sub-apical localization of AQP8ab and apical localization of Na+/K+, 2Cl- cotransporter (NKCC2) in enterocytes could indicate a functional link between Na+, Cl- and water uptake. Among AVTR paralogs, highest mRNA levels were recorded for v1a2 paralog which showed a higher expression in D. labrax intestine after transfer of fish to HW. Intraspecific comparisons showed that blood osmolality was unchanged in Atlantic sea bass following salinity transfer but was higher in Mediterranean sea bass in HW compared to SW. Differences between D. labrax lineages were observed in posterior intestines of fish maintained in SW regarding NKA activities and the expression of several genes invo lved in solute-coupled water uptake with significantly higher levels in Mediterranean sea bass, most likely reflecting adaptive differences in mechanism linked to ion-driven water reuptake within D. labrax lineages

Despite the increasing number of hypersaline discharges associated with desalination and, more recently, solute mining activities, there is little existing information relating to the effects such environmental disruptions may have on populations of commercially-important crustacean species. The present studies aim to redress this information-gap with novel investigations which have addressed some hypersalinity-induced behavioural and physiological responses of three crustacean species, the European lobster, Homarus gammarus (L), and two crab species, the brown crab, Cancer pagurus (L) and the velvet crab, Necora puber (L). All three species feature prominently in the East Yorkshire fisheries, and are found typically in full salinity seawater environments that show little salinity variability. The development of extensive gas storage caverns underground in East Yorkshire, UK, has led to the commencement of the discharge offshore of large volumes of hypersaline brine effluent into the local, normally salinity-stable habitat of the three test species The combined volume and concentration of this discharge has the potential to raise the salinity in the local environment and these studies have focused on the possible ecological and commercial implications of such changes. Each species was found to have a threshold value of hypersalinity above which halotaxic, preference behaviour was evoked (salinity 50 for H. gammarus and N. puber and salinity 45 for C. pagurus). The relationship between cardioventilatory activity and hypersalinity of H. gammarus and N. puber was examined under conditions when escape from the test salinity was prevented. Both showed a significantly decreased mean scaphognathite beat rate beyond a critical salinity value (salinity of 50 and 45 for H. gammarus and N. puber respectively). These salinities are consistent with the onset of the preference behaviour of these species. The heart rate of H. gammarus is also negatively related to increased salinity. These significant reductions in cardioventilation resulted in increased mortalities at salinities > 50–55. Significant changes to haemolymph pH and levels of haemolymph protein, haemocyanin, glucose and ammonia also occurred when test H. gammarus and N. puber were given sufficient time to acclimate to a test salinity. These changes made were typical of those under hypoxia in these and other decapod species and are consistent with the observed changes to the cardioventilatory behaviour. These findings prompt the novel hypothesis that hypersaline exposure beyond limits, which vary inter-specifically, elicits a switch to anaerobic respiration, even when the animals are in a fully-oxygenated medium. Results showed that when exposed to hypersaline conditions, H. gammarus was a weak iono-regulator, with the haemolymph ionic concentration increasing directly with that of the external medium whilst remaining slightly hypo-ionic to it. Late-postmoult H. gammarus were found to be less tolerant of hypersalinity than intermoult ones and, even when the carapace was approaching full hardness, were intolerant of salinities > 40. Contrastingly, C. pagurus with 96h LC50 at a salinity of 55.5 was the most tolerant of the three species tested. The lack of significant haemolymph change in this species suggests a strong degree of osmo- and iono- regulation. Under hypersaline exposure N. puber regulated haemolymph variables within the range of salinity 35–50. Higher salinities were found to require a more protracted acclimation period. The combined effects of haemolymph and cardioventilatory changes found for the test species demonstrate that unavoidable exposure to hypersaline conditions results in a lowered fitness and eventual death. Inevitably, this will impact negatively on commercial crustacean shellfisheries in and around the areas of brine discharge unless the discharge itself is managed and monitored appropriately.

Seagrass meadows are essential to coastal ecosystems and have experienced declines in abundance due to a series of environmental stressors including elevated salinity and incidence of disease caused by the pathogen Labyrinthula sp. This thesis evaluated the dynamics between T. testudinum and Labyrinthula concerning the impacts of short term elevated salinity stress on the early stages of infection in Thalassia testudinum (Chapter 2) as well as the presence of anti-labyrinthulid secondary metabolites produced by the tropical seagrass (Chapter 3). The results showed that short term exposure to hypersalinity alters some cellular processes but does not necessarily lead to an immediate increase in wasting disease susceptibility. Specifically, the occurrence of disease was significantly lower in the hypersalinity treatments possibly due to a direct osmotic shock to Labyrinthula or indirectly due to the increase in in vivo H2O2 concentrations that may have inhibited Labyrinthula growth. In addition, it was shown that 4 phenolic acids commonly found in turtlegrass leaf tissue were able to inhibit Labyrinthula growth in culture. Using a bioassay-guided fractionation technique, several purified fractions of T. testudinum leaf tissue showed anti-labyrinthulid activity, however the detailed characterization of the unknown compounds was inconclusive. The results presented in this thesis highlight the halotolerant characteristics of the seagrass T. testudinum as well as suggest that T. testudinum has the capability of defending itself against Labyrinthula infection using secondary metabolites.

The work undertaken for this thesis had the following two broad aims. The first was to determine the characteristics of the fish fauna of the Peel-Harvey Estuary in the mid 1990s, soon after the construction of a large artificial channel, the Dawesville Channel, into this estuary, and to compare these characteristics with those recorded in the early 1980s and thus prior to the construction of that channel. The second was to determine the characteristics of the ichthyofauna of the normally closed Wellstead Estuary, focusing in particular on elucidating the influence of both the extremely high salinities that are found in this system and the opening of the estuary mouth which occurs when freshwater discharge is sufficiently strong to breach the large sand bar at that mouth. The fish larvae on flood and ebb tides in the artificial Dawesville channel and the original Mandurah Channel of the Peel-Harvey Estuary were sampled at monthly intervals during 1997 using bongo nets. Postlarval, juvenile and adult fish in the Mandurah Channel and two regions in each of the large basins (Peel Inlet and Harvey Estuary) were sampled at regular intervals between the end of 1995 and end of 1997 using seine nets that were 5.5, 21.5 and 102.5 m in length. Nearshore, shallow and offshore, deeper waters of Wellstead Estuary were sampled at eight-weekly intervals between July 1996 and May 1998 using a 41.5 m seine net and composite gill nets, respectively. The number of fish species caught as larvae was far greater in the Dawesville Channel (49) than in the Mandurah Channel (34), a difference that was mainly due to a far greater number of marine stragglers, and often reef-associated species, in the former channel. The difference in number of species is presumably related to the presence of a better developed reef system just outside the Dawesville Channel and the fact that the velocity and volume of tidal water that is exchanged through this channel is much greater than through the Mandurah Channel. The number of fish larvae caught on flood tides was greater than on ebb tides in both channels, which suggests some individuals of marine species settle in the shallow and slower flowing regions in the channels or just inside the basins. Favonigobius lateralis and Atherinosoma elongata, which spawn in the estuary, tend to be transported out as preflexion larvae on ebb tides and inwards as postflexion larvae on flood tides. The species composition of the ichthyoplankton on both the flood and ebb tides in both channels underwent pronounced and consistent cyclical changes throughout the year, which was clearly related to differences in the spawning times of the various species within and outside the estuary. The catches of postlarval and early 0+ juvenile fish provide very strong evidence that the majority of marine species, that were caught as larvae on flood and ebb tides in the Mandurah and Dawesville channels, do not become established in the basins of the Peel-Harvey Estuary. However, the catch and length-frequency data for Hyperlophas vittatus indicated that large numbers of this clupeid enter this estuary as postlarvae, settle soon after they enter the estuary and then subsequently slowly penetrate into the basins. The use of Classification and Multidimensional scaling ordination demonstrated that the species composition of the fish fauna of nearshore, shallow waters in the large basins of the Peel-Harvey Estuary during the 1980s was influenced more by region within the estuary than by time of year, whereas the reverse pertained in the mid-1990s. The shift to a strong seasonal influence on species composition in the latter period is presumably related to the far greater tidal water movement that now occurs in the basin regions as a result of the constmction of the Dawesville Channel. This seasonality in the basins is attributable, in part, to differences in the patterns of immigration and emigration exhibited by the juveniles of marine species. The number of species and overall density of fish were positively correlated with salinity and inversely correlated with distance from estuary mouth. This trend was followed by all species except Leptatherina wallacei, which is known typically to occupy the upper reaches of estuaries where salinities are reduced. Since the construction of the Dawesville Channel, the density of fish in Peel Inlet has declined, presumably due to the reduction in the amount of macroalgae. Prior to the construction of the Dawesville Channel, when the basins, and in particular Peel Inlet, contained massive growths of macroalgae, the fauna of these regions was dominated by three weed-associated species, namely Relates sexlineatus, Apogon rueppellii and Genes sub fascial us. Although these species thus contributed nearly 60% to the total number of fish caught in the early 1980s, they contributed only about 8% in the mid 1990s after the construction of the Dawesville Channel, when, as a result of increased Hushing, there was a reduction in macroalgae. The construction of the Dawesville Channel has resulted in the Harvey Estuary becoming (1) directly connected with the ocean at its northern and seaward end, (2) better flushed and (3) far less susceptible to the development of blue-green algal blooms in the spring and early summer, which had previously been shown to have a deleterious effect on fish abundance. These changes account for the greater number of fish species and greater densities of fish that were recorded in the post- Dawesville period than pre- Dawesville period. Wellstead Estuary remained closed between October 1993 and September 1997 and then opened for just under a month, before once again becoming closed until the end of April 1998 when it opened and remained so until the end of the 24 month sampling period in May 1998. During the study period, mean monthly salinities underwent massive seasonal variations and sometimes varied markedly between regions. For example, mean monthly salinities in the lower estuary rose from 52.9%c in July 1996 to 111.7%c in the following March, before declining precipitously to 14.3%c in September 1997. In March 1997, they ranged greatly from 63.0%c in the upper estuary to 111.7%o in the lower estuary. A total of only 20 species were caught using seine and gill nets throughout this estuary. Not surprisingly, the fish fauna in nearshore, shallow waters was dominated by species which spawn in the estuary, with these species contributing over 98% of all fish caught. In contrast, marine species contributed approximately 58% of the fish caught in offshore, deeper waters. These species were larger teleosts which live for a number of years and moved in and out of the estuary when the bar at the estuary mouth was breached. The species composition in nearshore, shallow waters changed progressively and significantly between the lower, middle and upper estuary, reflecting in part the greater densities of Atherinosoma elongata and Aldrichetta forsteri towards the lower end of the estuary and of Acanthopagrus butcheri, Leptatherina presbyteroides. Pseudogobius olorum and Leptatherina wallacei towards the upper end. Since the fish typically found in nearshore, shallow waters represented species that complete their life cycles within estuaries, it is not surprising that the species composition did not change when the estuary mouth opened. In contrast, the species composition in offshore, deeper waters did not vary among regions but did change after the estuary mouth became open. This change in composition was due to the emigration of Mugil cephalus and Aldrichetta forsteri and the immigration of Arripis georgiana, Arripis truttaceus and Pomatomus saltatrix.

Mangrove stands are uncommon within semi-arid climates and rare within inland systems. It is uncertain whether the same environmental variables influence mangroves growing in a semi-arid climate as the trees growing in tropical and sub-tropical areas. Field studies conducted on the ecophysiological responses of the mangrove species Avicennia marina are few; however hydrological regimes are considered the key factor influencing mangrove stand zonation, structure and individual tree growth. The Gascoyne region of Western Australia provides a unique opportunity to investigate whether mangroves growing within an inland semi-arid environment display similar growth patterns and ecophysiological responses to their coastal counterparts. This study investigates the distribution, structure and condition of the mangrove A. marina growing at Lake MacLeod and coastal and riverine stands near Carnarvon, Western Australia. Hydrological categories based on freshwater inputs, tidal influences, distance from permanent water sources and sediment elevations were used to investigate the environmental conditions present within specific hydrological regimes. Mangrove tree responses to environmental conditions were evaluated by assessing above-ground biomass, shoot production, water-use efficiency, photosynthesis, specific leaf area, weight and total chloride content. The overarching objective was to determine the environmental factors influencing the presence, morphology and physiological state of A. marina growing at inland, coastal and riverine sites in a semi-arid climate. Soil moisture content, organic matter content, average and seasonal range in sediment EC, and distance from the permanent water sources were found to influence vegetation characteristics at Lake MacLeod. Soil moisture content was highest close to permanent ponds and at lower sediment elevations. Sediment salinity was highest close to pond edges, although the majority of the lake bed is hypersaline due to high evapoconcentration. The environmental gradients are complex at Lake MacLeod as a result of the unique hydrological regime. Seawater supply to permanent ponds is constant via an underground karst system which enters the lake through vents and seepages present along the western edge of the lake bed. It is evident that the constant supply of marine water is the key environmental factor supporting mangrove presence and structure. Average mangrove tree height, basal area, density and canopy cover are greatest near the permanent ponds. Mangrove density and height was also high, though patchy away from the ponds where saline seepages occurred. A high density of stunted mangroves was found on lake shorelines receiving periodic saline flooding via wind surges. Samphire cover was also greatest close to the permanent ponds, demonstrating that both mangrove and Samphire presence and importance is influenced by consistency of water availability. Sediment conditions were significantly different between inland and coastal sites, with sediment salinity and moisture content higher at Lake MacLeod. The ecophysiological responses displayed by A. marina in different categories of hydrological regimes revealed that consistency of water supply, irrespective of salinity, is an important driver of long and short-term productivity, water-use efficiency, leaf size and weight, and tree height. In general, short and long-term production was inversely proportional to distance from permanent water sources, although it was highly variable due to seepages away from the permanent ponds. Mangrove trees growing at the landward edge of coastal sites were the most water-use efficient (~ -28 δ¹³C), relative to the inland Lake MacLeod trees (~ - 26 δ¹³C), and was directly linked to water supply not quality. Photosystem health in trees growing at both the riverine stands (yield 0.66 ± 0.01) and inland stands found at greater distances from ponds (yield 0.065 ± 0.02), were significantly lower than all other trees in this study. Relative maximum electron transfer rate was also significantly lower at these sites, suggesting that the riverine trees were affected by other stresses such as herbicides. Mangrove trees near permanent water sources, or that received tidal flushing, displayed larger leaves and lower specific leaf weight, indicating that A. marina has the ability to not only tolerate hypersaline conditions but also acclimate to harsh and variable conditions via changes to ecophysiological responses and morphology. This research has developed a better understanding of how A. marina persists at Lake MacLeod and whether these trees are under greater stress as opposed to the mangroves growing at coastal stands. Sediment conditions between coastal and inland sites were significantly different, but it was distance from permanent water sources that influenced mangrove stand features. Therefore, the key environmental variable influencing distribution, structure and ecophysiological state of A. marina growing in a semi-arid climate is predominantly water availability.

The Pimpama estuarine plain in subtropical southeast Queensland is comprised of Quaternary sediments infilling older bedrock. These multilayered unconsolidated sediments have various depositional origins, and are highly heterogeneous. The plain is low-lying and the surface drainage is controlled by flood mitigation measures including tidal gates and channelised streams. The control of surface drainage potentially affects the shallow water table. This modification of hydrology has implications for future viability of agriculture and also the environmental health of waterways. Increased landscape modification and water management is likely in the coming years. The combination of sediment heterogeneity, low hydraulic gradients, and artificial drainage modification result in the plain being hydrogeologically complex. In order to understand hydrologic processes in this setting, a multi-disciplinary research programme was conducted which included a drilling program, overland electromagnetic induction and other geophysical surveys (downhole gamma log, electromagnetic induction and magnetic susceptibility) to initially establish the geologic framework. These surveys were followed by hydrogeochemical testing which includes for major and minor ions and also stable isotopes, and mineralogical analysis of drillhole material. Underlying basement rock occurs at up to 60 m depth. Unconsolidated gravel and sand deposits occur within incised paleo-valleys and are overlain by predominantly low-permeability fluvial sandy clays and estuarine and lagoonal muds. Fine-grained delta sands occur in the top 15 m of the sub-surface. Within the unconsolidated sediments, hydrodynamic trends clearly discriminated between upper unconfined and lower semi-confined aquifer systems. A comparison of surface water and shallow groundwater levels indicate limited interaction of groundwater and surface water. Hydrogeochemical analysis effectively distinguished between groundwater bodies, and also distinguished saline groundwater from seawater. Trends in major ion chemistry in the semi-confined system (particularly Na/Cl and Ca/Cl ratios) showed ion exchange accompanying saline intrusion. However, due to factors such as mineral dissolution, major ion chemistry does not clearly identify solute flux trends in the shallow aquifer system. Water stable isotope analysis (δ18O and δ2H) indicated the provenance of fresh and saline groundwater and also the relative importance of the principal hydrologic processes, i.e. evaporation and water uptake by plants. Groundwater exhibited a wide range in salinity, from very fresh to hypersaline. The formation of hypersaline groundwater was attributed largely to uptake of water by mangrove forests. Since mangrove forests were more extensive at the time of the Holocene maximum sea level (approximately 6,000 years ago) than at present, some of this groundwater may represent relict salinity from this earlier time. The relationship of relict salinity to low permeability sediments, particularly at intermediate depths, and their depositional history was examined. Vertical salinity gradients and hydrogeochemistry within these sediments varied according to position within the plain, suggesting deposition under various hydrological and sea level regimes. A preliminary investigation using analysis of stable sulfate isotopes (δ34S and δ18OSO4) was made. This study shows substantial potential for the application of this technique for quantification of solute flux and sulfur chemical transformations within settings such as this coastal plain. To establish shallow groundwater flow processes, a MODFLOW-based numerical model was used to inversely estimate aquifer parameters under various recharge scenarios. The model was designed to examine the relative importance of evapotranspiration and discharge to surface waters. However, largely due to the complexity of the drainage network and non-uniform surface water flows, the quantification of surface water- groundwater interaction by consideration of hydrodynamics is problematic. Therefore, the chemistry of groundwater and surface water was compared. While the estimated contribution of rainfall to groundwater level fluctuations was significant (46%), high evapotranspiration rates reduced net recharge and it was concluded that baseflow to drains and creeks during dry periods was insignificant, and groundwater velocities in the shallow aquifer are low. The study illustrates the value of both hydrodynamic and hydrogeochemical analyses in estuarine settings where relict salinity and groundwater-aquifer interactions impact significantly on water quality. Saline groundwater is chemically distinct from theoretical mixtures of seawater and freshwater. The study also demonstrates the value of particular chemical parameters, e.g. Na/Cl and SO4/Cl ratios and stable water isotopes, for identifying hydrologic processes in this setting.

The Pimpama estuarine plain in subtropical southeast Queensland is comprised of Quaternary sediments infilling older bedrock. These multilayered unconsolidated sediments have various depositional origins, and are highly heterogeneous. The plain is low-lying and the surface drainage is controlled by flood mitigation measures including tidal gates and channelised streams. The control of surface drainage potentially affects the shallow water table. This modification of hydrology has implications for future viability of agriculture and also the environmental health of waterways. Increased landscape modification and water management is likely in the coming years. The combination of sediment heterogeneity, low hydraulic gradients, and artificial drainage modification result in the plain being hydrogeologically complex. In order to understand hydrologic processes in this setting, a multi-disciplinary research programme was conducted which included a drilling program, overland electromagnetic induction and other geophysical surveys (downhole gamma log, electromagnetic induction and magnetic susceptibility) to initially establish the geologic framework. These surveys were followed by hydrogeochemical testing which includes for major and minor ions and also stable isotopes, and mineralogical analysis of drillhole material. Underlying basement rock occurs at up to 60 m depth. Unconsolidated gravel and sand deposits occur within incised paleo-valleys and are overlain by predominantly low-permeability fluvial sandy clays and estuarine and lagoonal muds. Fine-grained delta sands occur in the top 15 m of the sub-surface. Within the unconsolidated sediments, hydrodynamic trends clearly discriminated between upper unconfined and lower semi-confined aquifer systems. A comparison of surface water and shallow groundwater levels indicate limited interaction of groundwater and surface water. Hydrogeochemical analysis effectively distinguished between groundwater bodies, and also distinguished saline groundwater from seawater. Trends in major ion chemistry in the semi-confined system (particularly Na/Cl and Ca/Cl ratios) showed ion exchange accompanying saline intrusion. However, due to factors such as mineral dissolution, major ion chemistry does not clearly identify solute flux trends in the shallow aquifer system. Water stable isotope analysis (δ18O and δ2H) indicated the provenance of fresh and saline groundwater and also the relative importance of the principal hydrologic processes, i.e. evaporation and water uptake by plants. Groundwater exhibited a wide range in salinity, from very fresh to hypersaline. The formation of hypersaline groundwater was attributed largely to uptake of water by mangrove forests. Since mangrove forests were more extensive at the time of the Holocene maximum sea level (approximately 6,000 years ago) than at present, some of this groundwater may represent relict salinity from this earlier time. The relationship of relict salinity to low permeability sediments, particularly at intermediate depths, and their depositional history was examined. Vertical salinity gradients and hydrogeochemistry within these sediments varied according to position within the plain, suggesting deposition under various hydrological and sea level regimes. A preliminary investigation using analysis of stable sulfate isotopes (δ34S and δ18OSO4) was made. This study shows substantial potential for the application of this technique for quantification of solute flux and sulfur chemical transformations within settings such as this coastal plain. To establish shallow groundwater flow processes, a MODFLOW-based numerical model was used to inversely estimate aquifer parameters under various recharge scenarios. The model was designed to examine the relative importance of evapotranspiration and discharge to surface waters. However, largely due to the complexity of the drainage network and non-uniform surface water flows, the quantification of surface water- groundwater interaction by consideration of hydrodynamics is problematic. Therefore, the chemistry of groundwater and surface water was compared. While the estimated contribution of rainfall to groundwater level fluctuations was significant (46%), high evapotranspiration rates reduced net recharge and it was concluded that baseflow to drains and creeks during dry periods was insignificant, and groundwater velocities in the shallow aquifer are low. The study illustrates the value of both hydrodynamic and hydrogeochemical analyses in estuarine settings where relict salinity and groundwater-aquifer interactions impact significantly on water quality. Saline groundwater is chemically distinct from theoretical mixtures of seawater and freshwater. The study also demonstrates the value of particular chemical parameters, e.g. Na/Cl and SO4/Cl ratios and stable water isotopes, for identifying hydrologic processes in this setting.

碩士
國立中山大學
海洋生物研究所
94
This study has investigated the gene expression of ubiquitin、20S proteasome beta subunit type 1 (20sβ1)、ubiquitin-conjugating enzyme e2 (ucee2)、ATP-dependent caseinolytic protease regulatory subunit (clpC) in the marine macroalga Ulva fasciata Delile in relation to the hypersalinity-induced oxidative stress and protein oxidation. During the early stage (0-1 h), the water contents and TTC (2,3,5-tripheny tetrazolium chloride) reduction ability maintained unchanged but recovery ability and photosynthetic ability (PS II activity as indicated by Fv/Fm) were decreased along with accumulated H2O2, suggesting the occurrence of oxidative stress. Only ubiquitin expressed at this stage. During 1-3 h, water lost (approximately 33% of the control) with a further decrease in recovery ability, TTC reduction ability、PS II activity but more H2O2 accumulation and protein carbonyl compound. The transcripts of 20sβ1 and clpC and caseinolytic protease activity increased at this stage with the maximum of clpC at hour 3. In the 6-48 h, water lost seriously with high accumulated free amino acid at 6-12 h but low recovery ability. The transcript amounts of ubiquitin、20sβ1 and ucee2 increased marked during this stage, in which these might be related to programmed cell death caused by long-term exposure to hypersalinity. Reactive oxygen species (ROS) scavengers inhibited H2O2 accumulation, caseinolytic proteolytic activity increase, carbonyl compound formation and gene expression of ubiquitin、20sβ1、ucee2、clpC, indicating a role of ROS in the regulation of protease genes. A role of polyamines in the regulation of protease gene expression was tested. Spermidine and spermine inhibited the gene expression of ubiquitin、20sβ1 and ucee2, the oxidation of proteins (carbonyl groups) and the induction of caseinolytic protease activity in 90‰-treated thalli, whereas putrescine inhibited clpC expression, the oxidation of proteins and caseinolytic protease activity but enhanced the gene expression of ubiquitin、20sβ1 and ucee2. In conclusion, the results of the present investigation show that the degradation of oxidatively damaged proteins under hypersalinity conditions by increased caseinolytic protease activity is driven by the up-regulation of clpC gene expression via ROS and polyamines. It seems likely that the induction of ubiquitin、20sβ1 and ucee2 gene expression might be associated with the hypersalinity-mediated programmed cell death.

Over 18 billion barrels of waste fluids are generated annually from oil and gas production in the United States. As a large amount of water is used for oilfield operations, treating and reusing produced water can cut the consumption of fresh water in well sites. This research has helped to develop a membrane process train for a mobile produced water treatment unit for treating oilfield produced brine for reuse. To design the process train, over 30 sets of combination tests at pilot laboratory scale were performed using pretreatment, microfiltration and nanofiltration processes. Membrane performance was selected based on high flux separation efficiency, high tolerance for solids and fluid treatments. Over 95 % solids rejection and greater than 80 % oil removal efficiency were obtained in all these tests. Process train (pre-treatment and membrane) performance was monitored by chemical analysis of permeate and models fitting experimental data for the process. From the results, hydrocarbon rejection was analyzed; total organic carbon rejection was 47.9 %, total carbon content averaged 37.3 % rejection and total inorganic carbon rejection was at 3.66 %. BTEX removal efficiency ranged from 0.98 % to 52.7 % with the progressive pretreatment methods of using cartridge filters. The nanofiltration membrane showed significant reduction in total dissolved solids and in both anionic and cationic species. The process train is seen to follow a sequence of treatment from cartridge and oil removal filter treatment to microfiltration treatment to ultrafiltration, followed by nanofiltration for the purpose of this research. Further research still needs to be done on to determine the kind of analytical test which will give real time feedback on effectiveness of filters. In summary, the process train developed by TAMU-GPRI possesses distinct advantages in treating oilfield produced brine using membrane technology. These advantages include high quality of permeate, reduced sludge and the possibility of total recycle water systems. The small space requirement, moderate capital costs and ease of operation associated with the use of the mobile unit membrane technology also makes it a very competitive alternative to conventional technologies.

About 12,000 of the 67,000 described species of crustaceans occur in fresh water. Crustaceans have colonized almost every type of freshwater environment in most parts of all continents. A common theme in marine-to-freshwater transitions is not only acquisition of osmoregulatory capabilities to cope with hyposalinity, but also optimizing reproductive strategies to cope with ecological and environmental variability. A key reproductive adaptation for fresh water is direct rather than extended planktonic development. Some groups, such as peracarids, were preadapted, already having direct development, whereas others, such as decapods, had to acquire it. Other crustaceans, such as branchiopods, are adapted not only to hyposalinity (and hypersalinity) but also to surviving in transient waters. Crustaceans have been colonizing fresh waters since the Middle Cambrian to Early Ordovician and have independently adapted to life in inland waters many times throughout geological history. The pattern and timing of invasions has shaped present-day distributions. Contemporary distributions and diversity of crustaceans in surface waters are surveyed in the context of their paleohistory. Different groups of crustaceans have very different current distributions that reflect the differential influence of different patterns of colonization, geological history, ecology, and the constraints (or benefits) of their evolutionary heritage.

The aim of this project is to investigate engineering methods to reduce salinity in the cooling canals at the Florida Power & Light (FP&L) Turkey Point Power Plant. In order to stop discharging hot water from the plant into the adjacent Biscayne Bay, a cooling canal system was made operational in 1972 that occupies an area 3.2 km wide by 8.0 km long extending south of the plant. The 5,900 acre canal system has been measured at twice the salinity of the adjacent Biscayne Bay at as high as 68 ppt [Appendix i]. Florida Power & Light added a canal along the western perimeter of the cooling canal system to intercept seepage. The interceptor ditch enables FP&L to pump seepage back into the canal system during the dry season thus reducing the groundwater flow of hypersaline water to the west. The Florida Department of Environmental Protection (FDEP) and the South Florida Water Management District (SFWMD) are monitoring a saltwater plume migrating west of FP&L property (FDEP/SFWMD Miami-Dade Saltwater Intrusion Presentation pg 3). Tidal influences have a profound effect on saltwater intrusion, so it is difficult to quantify the influence of the canals on this plume. To ensure that FP&L has no culpability in the contamination of ground water, the cooling canals should either operate at a lower level of salinity or be isolated to restrict flow to underground sources of water. Isolation, however, is not an appealing option as the methods which have been conceptualized are highly invasive. Environmental concerns are abundant as the ecosystem within the cooling canals supports at least 17 protected species of birds and animals of South Florida. Over 25% of the world’s population of the American crocodile resides in the Turkey Point cooling canals. Very few organisms require a hypersaline condition to thrive; therefore, lowering the salt concentration of the canal system is not expected to have adverse effects upon the ecosystem. Careful attention must be paid to ensure wildlife survival during treatment and/or disposal system development and operation.