Brackish Water Environments Research Articles

Historical Review of Studies on Cyrtophorian Ciliates (Ciliophora, Cyrtophoria) from China.

The subclass Cyrtophoria are a group of morphologically specialized ciliates which mainly inhabit soil, freshwater, brackish water, and marine environments. In this study, we revise more than 50 publications on the taxonomy, phylogeny, and ecology of cyrtophorian ciliates in China since the first publication in 1925, most of which were carried out in coastal areas. The research history can be divided into three periods: the early stage, the Tibet stage, and the molecular stage. To date, 103 morpho-species (147 isolates) have been formally recorded in China, with ciliature patterns described for 82 of them. A species checklist and an illustrated identification key to the genera are provided. A total of 100 small subunit rDNA sequences have been obtained for 74 taxonomic hits (lowest taxonomic rank to species or genus). These sequences are used for the study of molecular phylogeny. Based on these morphological data and molecular phylogeny analyses, we synthesize the understanding of the phylogeny of cyrtophorian ciliates. We hypothesize that the key evolutionary event of cyrtophorian ciliates lies in the separation of the stomatogenesis zone (postoral kineties) from the left kineties, namely, the formation of an independent “sexual organelle”. We, furthermore, briefly summarize the ecological features of cyrtophorian ciliates and provide a comprehensive bibliography of related research from China. Finally, we give an outlook on the future research directions of these taxa.

Temporally stable small-scale genetic structure of Northern pike (Esox lucius) in the coastal Baltic Sea

The Northern pike (Esox lucius) is an important predator in freshwater and brackish water environments. In the Baltic Sea, Northern pike follows isolation by distance pattern across wide geographical scale. However, relatively little is known about the fine-scale population divergence and temporal genetic variation of Baltic pike, especially for populations inhabiting the eastern part of the Baltic Sea. Here, we characterize the population genetic structure of Northern pike and its temporal stability in six freshwater and one brackish water locations on the Island of Saaremaa (Estonia). To accomplish this, we collected 274 young-of-the-year (YOY) of two consecutive cohorts and 218 older specimens that were genotyped using ten microsatellite loci. Our results indicate a temporally stable population differentiation between geographically close locations and reduced diversity of the north-western Saaremaa populations. Furthermore, the correspondence analysis and a discriminant analysis of principal components showed a clear differentiation between north-western and the Gulf of Riga spawning grounds. Our findings support the idea that natal homing behavior, limited dispersal and facultative anadromy in Baltic pike likely promotes the existence of temporally stable genetic divergence among different populations at small geographical scale, representing an essential prerequisite for development of local adaptations. Thus, conservation, management and restoration efforts of coastal Baltic Sea pike should preserve the existing genetic differences between different populations and avoid actions, which potentially increase genetic homogenization.

Biodegradability Assessment of Bio-based Film Products (Lunch Sheets) in the Marine Environment

Plastic pollution is a current common problem and it causes a serious impact on the marine environment. Micro debris of plastics have accumulated in oceans and exhibit a natural tendency to interrelate with the ecosystem which can cause negative effects on both humans and animals. Polythene food wrappers are used worldwide as a packaging material. Considering the negative impact of polythene wrappers, biodegradable food wrappers have been produced in Sri Lanka following the Section 23 W of the National Environmental Act. The objective of the study was to determine the biodegradability of few bio-based film products (lunch sheets) available in the Sri Lankan market labeled as 100% biodegradable in the marine environment. The biodegradability of five different brands of biodegradable food wrappers were tested together with cellulose paper as the positive control and non-biodegradable food wrapper as the negative control in the marine environment. Laboratory models of three marine environments; inter tidal zone, pelagic zone and brackish water were selected and the biodegradability for a period of six months were tested using weight measurement and FT-IR analysis. Furthermore, several environmental parameters were tested for these three marine zones. Results indicated that the highest percentage weight loss was shown by brand 3 in all three marine environments. In the pelagic zone, percentage weight loss ranged from 8.60-48.92% while highest value of 48.92% was shown by brand 3. In the brackish water environment, brand 3 showed 73.51% of percentage weight loss and values ranged from 11.76-73.51%. The percentage weight loss, ranged from 68.29-89.99% in inter tidal zone and brand 3 showed the highest value as 89.99%. All the samples showed a considerable weight loss after six months duration in inter tidal zone compared to other zones and even the negative control has undergone physical disintegration. It is assumed that oxo-biodegradation leads to this disintegration in the food wrappers in this zone. The FT-IR results have shown that there is no significant degradation of the non-biodegradable food wrapper (negative control) while the cellulose paper (positive control) and the biodegradable food wrappers have undergone a considerable degradation. 
 Keywords: Biodegradability, Food wrappers, Marine environment

Sequence comparison of the mitochondrial genomes of five brackish water species of the family Neritidae: Phylogenetic implications and divergence time estimation.

Neritids are ancient gastropod species which can live in marine, brackish water, and freshwater environments. In this study, we sequenced and annotated the mitochondrial genomes of five brackish water neritids (i.e., Clithon corona, Clithon lentiginosum, Clithon squarrosum, Neritina iris, and Septaria lineata). The mitogenomes ranged from 15,618 to 15,975 bp, and all contain 13 protein‐coding genes (PCGs), 22 tRNA genes, and two rRNA genes, with a closed ring structure. We calculated the Ka/Ks values of all 13 PCGs of Neritidae species, all ratios are less than 1, under purification selection. Phylogenetic analysis of the 13 PCGs showed that Neritimorpha is a sister group with Vetigastropoda and Caenogastopoda, genus Clithon is a sister group with Neritina and Septaria. Estimation of divergence time for all species of Neritidae showed that the main differentiation of Neritidae occurred in Cenozoic period (65 Mya), C. corona and C. lentiginosum were differentiated in the Cenozoic Neogene, the other three species diverged in the Cenozoic Paleogene. These results will help to better understand the evolutionary position of Neritidae and provide reference for further phylogenetic research on Neritidae species.

Excellent source rocks found along the margin of a large lacustrine basin: Case study from the Ordos Basin, China

Whether the Chang 6 oil pools of the Triassic Yanchang Formation in the Ansai-Yanchang (AY) oil province on the Yishan slope of the Ordos Basin formed from near source rock or far source rock has long been debated. An understanding of the source rock's position will impact the formation mode and distribution of accumulations in this area. Based on the geochemical data of the Chang 7 source rock in six wells and 18 crude oil samples, the geochemical characteristics of Chang 7 source rock and its relationship with Chang 6 crude oil were studied. There are two types of source rocks, namely, black shales and dark mudstones, present in the AY area. The gross thickness of the Chang 7 black shale is 3.0–19.7 m, with a distribution area of 5500 km2. It has an average total organic carbon (TOC) content of 3.34%, with a chloroform bitumen “A" content of 0.512%, indicating good to excellent source rock potential. The kerogen assessment with core samples shows mixed type I-II1, and has reached peak oil generation, maximum pyrolysis temperatures (Tmax) ranging from 445 to 458 °C. In contrast, the average TOC content of the dark mudstone in Chang 7 is 0.91%, chloroform bitumen “A” is 0.079%, the main type of kerogen is type II2-II1, and Tmax varying from 446 to 461 °C, indicating only fair source rock potential overall. The Chang 7 source rocks in the AY area have a gammacerane index of 0.07–0.38, with an average value of 0.21, which reflects a low-salinity fresh to brackish water environment. The relative abundances of C27, C28, and C29 steranes are 29.7%, 23.1% and 47.2%, respectively, indicating that terrestrial higher plants and aquatic organisms provide similar contribution in the Chang 7 source rocks. Oils produced from the AY area of the Chang 6 member have similar geochemical signatures, but are significantly different from the Chang 6 crude oils in the Daozhen (DZ) area of Ganquan County and the Huaishuzhuang (HSZ) area of Fuxian County, which are located in the center of the lacustrine basin. They differ in terms of the maturity of the oil samples and the microscale composition of the parent material type. The closer the wells are to the center of the lacustrine basin, the higher the maturity of the source rock and the greater the contribution of aquatic organisms. The variation of carbon isotopic composition of Chang 6 crude oil in AY area is consistent with that of Chang 7 shale locally, but opposite to that of Chang 6 crude oil in DZ area. The ratios of nC21-/nC22+, tricyclic terpane/hopane and C29 sterane ββ/(ββ+αα) biomarker parameters of Chang 6 crude oils in AY area are similar to those of Chang 7 shale in local area, but deviate from those of DZ and HSZ area. These data results reveal that the Chang 6 crude oils in the AY oil province are dominated by the local Chang 7 excellent source rocks rather than by the long-distance migration of oils from the basin center.

Tolerance Level of Domesticated Asian Red-Tail Catfish Hemibagrus Nemurus to Salinity, Acidity, and Temperature Variability

The Asian redtail catfish Hemibagrus nemurus is Indonesian native fish proposed for catfish culture diversification project. Prior to be commercialized and widely distributed, it is imperative to evaluate environmental tolerances of the catfish for successful breeding programs and its aquaculture development program. This research was carried out to evaluate the optimum tolerance range and physiological responses of domesticated H. nemurus exposed to different salinity, acidity, and temperature. Fish used in this experiment were the second generation of H. nemurus produced at the Research Institute for Freshwater Aquaculture and Fisheries Extension (RIFAFE), Bogor, West Java, Indonesia. A total of 12 fish for each treatment were exposed to different salinity (0 ppt (control), 5 ppt, 10 ppt, 12.5 ppt, 15 ppt and 17.5 ppt), pH (4, 5, 7 (control), 9 and 10), and temperatures (15℃, 20℃, 25℃, 28.5℃ (control), 32.5℃, 35℃, and 40℃) for 12 days observation until fish reached their Loss of Equilibrium (LOE). Cortisol, hemoglobin, and glucose were investigated to study the stress response happened. This research reveals that the domesticated Asian redtail catfish are able to be acclimated to slightly brackish-water environment (≤10 ppt), have more resilience in acidic than alkaline water (pH 5.0 to 7.35), and can adjust in wide range of temperatures (25℃ to 32.5℃). In salinity exposure, significant physiological effects existed between controls and treatments (P<0.05) except glucose. For pH, cortisol was the best indicator to see the effect of exposure (P<0.05). The last for temperature exposure, the only cortisol was enabled to be used as the indicator of stress response. From the study, it found that cortisol level analysis was the best indicator to detect stress responses of the catfish that would be important to mitigate unpredictable environmental events and early warnings in the changes of environmental quality in culture system. We would recommend that the domesticated H. nemurus can be developed for the new catfish aquaculture candidate as it met a requirement to tolerance evaluation on different water quality levels which its responses was commonly similar compared to other existing aquaculture species.

Developmental responses and survival of Anopheles stephensi larval stages at different salinity levels.

Anopheles stephensi is a newly invaded vector in Sri Lanka. It has been identified in coastal areas in the northern and eastern parts of the country and evidences the ability to breed in brackish water environments. Laboratory investigations were conducted with batches of 100 first and third instar larvae exposed to a salinity gradient (0-40ppt). Survival rates at 1h, 24h and until pupation were recorded for first and third instar larvae at different salinity levels. The experiment was repeated four times for both instars. Data were analysed using the general linear model and probit analysis. Significant variations in adult emergence were observed from both larval stages at different salinity levels (p<0.05). The highest pupation rates were observed at 2.5ppt salinity. The survival rate of first instar larvae after 24h of salinity exposure was >80% up to 12.5ppt, while 100% mortality was observed for from the ≥25ppt level of salinity. More than 90% of the third instar larvae pupated from salinity levels <15ppt. The lowest survival rate was reported as 15.8±2.47% at 25ppt. This indicates a high potential of increasing density of A. stephensi in coastal ecosystems in lagoons and other saline water bodies. Hence it is high time to redesign vector control interventions for vector breeding in coastal ecosystems.

Phylogenetics of Archerfishes (Toxotidae) and Evolution of the Toxotid Shooting Apparatus.

SynopsisArcherfishes (Toxotidae) are variously found in the fresh- and brackish-water environments of Asia Pacific and are well known for their ability to shoot water at terrestrial prey. These shots of water are intended to strike their prey and cause it to fall into the water for capture and consumption. While this behavior is well known, there are competing hypotheses (blowpipe vs. pressure tank hypothesis) of how archerfishes shoot and which oral structures are involved. Current understanding of archerfish shooting structures is largely based on two species, Toxotes chatareus and T. jaculatrix. We do not know if all archerfishes possess the same oral structures to shoot water, if anatomical variation is present within these oral structures, or how these features have evolved. Additionally, there is little information on the evolution of the Toxotidae as a whole, with all previous systematic works focusing on the interrelationships of the family. We first investigate the limits of archerfish species using new and previously published genetic data. Our analyses highlight that the current taxonomy of archerfishes does not conform to the relationships we recover. Toxotes mekongensis and T. siamensis are placed in the synonymy of T. chatareus, Toxotes carpentariensis is recognized as a species and removed from the synonymy of T. chatareus, and the genus Protoxotes is recognized for T. lorentzi based on the results of our analyses. We then take an integrative approach, using a combined analysis of discrete hard- and soft-tissue morphological characters with genetic data, to construct a phylogeny of the Toxotidae. Using the resulting phylogenetic hypothesis, we then characterize the evolutionary history and anatomical variation within the archerfishes. We discuss variation in the oral structures and the evolution of the mechanism with respect to the interrelationships of archerfishes, and find that the oral structures of archerfishes support the blowpipe hypothesis but soft-tissue oral structures may also play a role in shooting. Finally, by comparing the morphology of archerfishes to their sister group, we find that the Leptobramidae has relevant shooting features in the oral cavity, suggesting that some components of the archerfish shooting mechanism are examples of co-opted or exapted traits. Sinopsis (Malay)Pelbagai jenis Ikan Sumpit (Toxotidae) dapat dijumpai di persekitaran air tawar dan payau di Asia Pasifik dan mereka terkenal dengan kebolehan mereka menembak air ke arah mangsa di darat. Tembakan air ini bertujuan untuk menyerang mangsa mereka dan menyebabkan mereka jatuh ke dalam air untuk ditangkap dan dimakan. Walaupun tingkah laku ini diketahui umum, terdapat hipotesis yang bersaing (hipotesis sumpitan vs. tangki tekanan) tentang cara ikan sumpit menembak dan struktur mulut yang terlibat. Pemahaman semasa tentang struktur menembak ikan sumpit adalah sebahagian besarnya berdasarkan dua spesies, Toxotes chatareus dan T. jaculatrix. Kami tidak pasti sama ada semua ikan sumpit mempunyai struktur mulut yang sama untuk menembak air, jika variasi anatomi terdapat dalam struktur mulut ini, atau bagaimana ciri-ciri ini telah berkembang. Tambahan pula, terdapat sedikit maklumat tentang evolusi Toxotidae secara keseluruhan, dengan semua penyelidikan sistematik sebelum ini memfokuskan pada hubungan saling keluarga. Kami pada mulanya mengkaji had spesies ikan sumpit ini menggunakan data genetik baharu dan yang diterbitkan sebelum ini. Analisis kami menunjukkan bahawa taksonomi semasa ikan sumpit tidak mematuhi hubungan yang kami perolehi. Toxotes mekongensis dan T. siamensis diletakkan bersama kesinoniman T. chatareus, Toxotes carpentariensis yang diiktiraf sebagai satu spesies dan dikeluarkan daripada kesinoniman T. chatareus, dan genus Protoxotes yang diiktiraf untuk T. lorentzi adalah berdasarkan hasil analisis kami. Kemudian kami mengambil pendekatan integratif, menggunakan analisis gabungan karakter morfologi tisu keras dan lembut diskret dengan data genetik, untuk membina filogeni Toxotidae. Menggunakan hipotesis filogenetik yang terhasil, kami kemudian mencirikan sejarah evolusi dan variasi anatomi dalam ikan sumpit. Kami membincangkan variasi dalam struktur mulut dan evolusi mekanisme berkenaan yang berkaitan dengan ikan sumpit, dan mendapati bahawa struktur mulut ikan sumpit menyokong hipotesis sumpitan tetapi struktur mulut tisu lembut juga mungkin memainkan peranan dalam cara menembak. Akhir sekali, dengan membandingkan morfologi ikan sumpit kepada kumpulan saudara mereka, kami mendapati bahawa Leptobramidae mempunyai ciri penangkapan yang relevan dalam rongga mulut mereka, menunjukkan bahawa beberapa komponen mekanisme penangkapan ikan sumpit merupakan contoh ciri-ciri yang diikut-sertakan atau diguna semula.

The distribution of intact polar lipid-derived branched tetraethers along a freshwater-seawater pH gradient in coastal East China Sea

In view of the application of microbial branched tetraether lipids (i.e., brGDGTs) in terrestrial pH reconstructions, their potential as seawater pH proxy is investigated from the Yangtze River Estuary (YRE) to the shelf region in the East China Sea (ECS). BrGDGTs occurring as ‘fossil’ core and in ‘living’ intact polar lipids (CL-brGDGTs and IPL-brGDGTs, respectively) in surface sediments are separately analyzed. The results show that riverine IPL-brGDGTs are rapidly lost at the transition from the YRE to the marine settings and sedimentary IPL-brGDGTs are predominantly produced in situ in brackish water environments. Among environmental parameters, surface water pH is a determinant factor controlling the cyclization of IPL-brGDGTs, with higher cyclization at higher pH. Hereby, two IPL-brGDGTs-based seawater pH calibrations are established in the brackish seawater environment in this study: surface pH = 7.28 + 1.08 × #Ringstetra (n = 18, r2 = 0.87, RMSE = 0.05, p < 0.01) and surface pH = 7.13 + 3.82 × f(Ic) + 4.29 × f(IIb') + 4.21 × f(IIIa) (n = 18, r2 = 0.90, RMSE = 0.04, p < 0.01), which are different from those established in terrestrial environments. This is the first work demonstrating that in situ produced microbial brGDGTs can trace seawater pH change in marine environment, which makes it promising to apply brGDGTs for seawater pH reconstructions in marine settings where the terrestrial inputs are negligible.

Studies on the artificial propagation of hybrid bream in brackish water

Hybrid bream (BBTB) is a high-quality bream derived from a hybrid lineage of blunt snout bream (Megalobrama amblycephala, 2n ​= ​48, BSB, ♀) ​× ​topmouth culter (Culter alburnus, 2n ​= ​48, TC, ♂). In this study, to explore the laws of artificial propagation of BBTB in a brackish water environment, 150 pairs of BBTB with an average weight of 1000 ​g were selected as brood fish, and a successful artificial propagation experiment was carried out at the Freshwater Fish Nansha (Nanfan) Breeding Center (2‰–5‰ brackish water). The fertilization and hatching rate was 86% and 78%, respectively, and a total of 1 ​800 ​000 larvae were obtained. After 26 days of cultivation, 400 ​000 larvae survived, showing a survival rate of 22%. This study is of great significance regarding the basic theories and applications of fish genetics.

Geochemical characteristics and depositional paleoenvironment of source rocks from the Lower Cretaceous Chijinbao Formation in Jiuxi Basin, China

The Lower Cretaceous Chijinbao Formation is one of the primary source rocks in the Jiuxi Basin in Northwest China. However, it is poorly studied due to the lack of a complete stratigraphic sequence exposed by drilling. In this research, an integrated analysis of palynofacies, organic geochemistry, and element geochemistry was systematically conducted on samples with longitudinal continuity collected from the Chijinbao Formation in the Hanxia Section of the Jiuxi Basin to determine the distribution of source rocks and the source and type of organic matter and to reconstruct the depositional paleoenvironment of the Chijinbao Formation. The lower part of the sequence, which is governed by poor source rocks with Type III organic matter, is characterized by palynofacies A (woody tissue–charcoal assemblage) grown in a proximal alluvial fan–shallow lacustrine environment. The excellent source rocks with mostly Type II 1 organic matter are considerable in the middle part of the sequence, which is marked by palynofacies B (amorphous organic matter assemblage), and occur in a distal semi-deep lacustrine–deep lacustrine environment. The upper part of the sequence is largely composed of poor and fair source rocks, represented by palynofacies C (amorphous organic matter–woody tissue assemblage), and a small amount of sporadically distributed good and excellent source rocks (approximately 1/3), which may be deposited in a proximal fan delta and a local semi-deep lacustrine–deep lacustrine environment. A semiarid–semi-humid climate and a freshwater–brackish water environment prevailed during the deposition of the Chijinbao Formation. The lower part of the sequence is characterized by the highest terrestrial detritus influx, strong weathering, humid paleoclimate, oxic water column conditions, and the lowest paleoproductivity. The middle part of the sequence has the lowest terrestrial detritus influx, relatively weak weathering, relatively arid paleoclimate, predominantly anoxic water environment, and the highest paleoproductivity. The climate became humid again during the deposition of the upper part, which is typified by an intermediate terrestrial detritus influx, strong weathering, fluctuations of oxic–anoxic bottom-water conditions, and moderate paleoproductivity. The correlation analysis of element proxies suggests that the increase in salinity during the deposition of the middle part is associated with an arid climate. Amorphous organic matter, which is derived mostly from aquatic organisms and degraded terrestrial higher plants, is the major hydrocarbon generation component in the source rocks of the Chijinbao Formation. It increases in abundance with an improvement in water reducibility and productivity, favoring the formation and preservation of excellent source rocks. • Excellent source rocks distribute in middle part of Chijinbao Formation. • AOM dominate organic components in excellent source rocks of Chijinbao Formation. • Excellent source rocks were deposited under anoxic and relative arid conditions. • High salinity correlates with arid climate during the deposition of middle part.

Microbial Community Composition in Thermal Waters from the Lindian Geothermal Field (Songliao Basin, North-Eastern China)

Geothermal systems represent discrete and relatively homogenous habitats for extremophiles; investigation into the microbial community is key to revealing the geochemical environment and the geochemical evolution of fluids in geothermal reservoirs. The reservoir of the Lindian geothermal field in Northeast China, is highly reducing and rich in methane, but the pathways of methane generation and the related microbial community structure are still unclear. In this research, five thermal water samples were collected and tested, and the microbial community structure and diversity were analyzed. The results show that in the sandstone reservoir belonging to the low-temperature (reservoir temperature &lt; 90°C) brackish water (total dissolved solids concentration between 1000 and 10,000 mg/L) environment, the richness of the microbial community is relatively high. The microbial community structure is different from other geothermal systems reported but similar to that of oilfields, which may be related to the highly reducing geochemical environment with abundant organic matter. According to the analysis of archaeal function, the biogas production in the Lindian geothermal field is dominated by hydrogen nutrition type methane production, while the H2 reducing methylamine type methane production is secondary, and results of Pearson correlation show that the archaeal communities are more strongly correlated to physicochemical factors than the bacterial communities.

Prospects of aquaculture of West Bengal, India under Changing climate

Climate variability refers to the variability observed in the climate record in periods when the state of the climate system is not showing changes. If the climate state changes, usually characterized by a shift in means, then the frequency of formerly rare events on the side to which the mean has shifted might occur more frequently with increasing climate variability. Natural variability is a characteristic of the global climate and occurs on both long and short-time scales. Aquaculture practices involve the breeding, rearing, and harvesting of aquatic organisms in freshwater, brackish water, or marine environments. Aquaculture is a rapidly growing sector of nutrition security in Gangetic West Bengal. A study was conducted on West Bengal in India, one of the eastern states of India. West Bengal state has different types of agroclimatic zones. Aquaculture in West Bengal has tremendous potential to grow as an industry. Residents of West Bengal must understand the value of local wetlands and the importance of the conservation of wet lands. Government institutes should collectively work with different educational hubs, scientists, and NGOs on beneficial issues of the state so that aquaculture conservation and development and appropriate adaptation strategies can be adopted.

Sedimentology and neoichnology of a muddy translating point bar in the fluvio-tidal transition, Serpentine River, BC, Canada

Point bars are common in the fluvio-tidal transition of rivers, yet detailed characterization of their sedimentology and neoichnology is rarely reported. Herein, we present sedimentological and ichnological descriptions for a seaward translating point bar located in the fluvio-tidal transition of the Serpentine River, BC, Canada. This bar accumulates in mainly polyhaline water, and channel flow is tide-dominated. The landward bar has steep channel banks and grain size fines from medium sand in the thalweg to mud in the upper intertidal zone. The seaward side of the bar forms a bench-like morphology that is steeply inclined in the intertidal zone, has a wide, gently dipping platform in the lower intertidal/uppermost subtidal zone, and a steep lower subtidal channel bank. Sediment sizes fine from coarse- to medium-grained sand in the thalweg, to mud in the lower intertidal zone. Medium-grained sand is deposited on the middle- and upper-intertidal zone of the seaward-side of the bar as a result of flow reversal and impingement of the flood tidal current against the seaward side of the translating point bar.The neoichnological assemblage of the intertidal part of the translating point bar is characteristic of brackish-water environments, and comprises low diversities of diminutive structures that occur locally in high densities (Bioturbation Indices 3–4). The neoichnological distribution correlates closely with the macrobenthos distribution, which in turn indicates marine-nutrient distribution. Marine nutrient supply is likely controlled by the bar's morphology. Biogenic structures attributable to Arenicolites, Skolithos, Polykladichnus and Siphonichnus mark the middle and upper intertidal zones, as well as the lower intertidal zone along the landward side of the bar. The trace makers that produce this trace assemblage are resilient to prolonged subaerial exposure and employ diverse feeding strategies. The lower intertidal zone along the seaward side of the bar is affected by decreasing current velocities across the wide bench-like morphology, which permits regular deposition of marine nutrients. Here, population counts are high and trace makers specialize in surface deposit- and filter-feeding. Traces include Gyrolithes-like structures and Siphonichnus. The Gyrolithes and Gyrolithes-like burrows that are produced by S. kowalevskii at the study site are hypothesized to potentially reflect the trace maker's anatomical predisposition, and not represent some spatial or anchoring advantage.This work represents the first published study on the neoichnology of a tide-dominated, translating point bar in the fluvio-tidal transition. The model we present is intended as an analog to show the variability in fluvio-tidal point bars and how they might be manifested in the sedimentary record.

Geochemistry of major and trace elements in sediments from the Lubei Plain, China: Constraints for paleoclimate, paleosalinity, and paleoredox environment

As has been greatly affected by sea-level fluctuations since the Holocene, the Lubei Plain is featured by typical marine and alluvial deposits that records abundant information on the environmental evolution. In this context, the Lubei Plain is a sensitive zone in response to global climate change. In this study, we comprehensively logged a section, here in the the CY section, which is 4.4 m long and corresponds to a time interval of 5250a according to the OSL dating. This section is divided into five sub-sections based on the features of the proxies for paleoclimate, paleosalinity, and paleoredox environment, which are labeled as stages V to I, respectively. The sediment of stage V (5250-3850a) is featured by low Rb/Sr and Mg/Ca ratios that show similar variation trends, which indicate a progressively arid climate with high precipitation. The deposition of stage IV (3850-3260a) is suggested to occur in a warm-wet, brackish-water environment, with sub-reduction to oxidation conditions. When it comes to stage III, its deposition (3260-2950a) is indicated to occur in a drier climate and less saline environment than stage IV, accompanied by sub-reduction conditions. As for stages II (2950-1580a) and I (1580a to present), their deposition occurs in a wet-to-dry transitional climate, which is concomitant with decreased water salinity, enhanced oxygen enrichment, gradual sea-level drop, and northward marine regression. Eventually, it is determined that various sedimentary facies alternatively take dominance since 5250a, including coastal-tidal flat facies, shallow marine facies, alluvial facies, tidal flat facies, and fluvial facies.

Contrasting nutrient availability between marine and brackish waters in the late Mesoproterozoic: Evidence from the Paranoá Group, Brazil.

Understanding the delayed rise of eukaryotic life on Earth is one of the most fundamental questions about biological evolution. Numerous studies have presented evidence for oxygen and nutrient limitations in seawater during the Mesoproterozoic era, indicating that open marine settings may not have been able to sustain a eukaryotic biosphere with complex, multicellular organisms. However, many of these data sets represent restricted marine basins, which may bias our view of habitability. Furthermore, it remains untested whether rivers could have supplied significant nutrient fluxes to coastal habitats. To better characterize the sources of the major nutrients nitrogen and phosphorus, we turned to the late Mesoproterozoic Paranoá Group in Brazil (~1.1Ga), which was deposited on a passive margin of the São Francisco craton. We present carbon, nitrogen and sulphur isotope data from an open shelf setting (Fazenda Funil) and from a brackish-water environment with significant riverine input (São Gabriel). Our results show that waters were well-oxygenated and nitrate was bioavailable in the open ocean setting at Fazenda Funil; the redoxcline appears to have been deeper and further offshore compared to restricted marine basins elsewhere in the Mesoproterozoic. In contrast, the brackish site at São Gabriel received only limited input of marine nitrate and sulphate. Nevertheless, previous reports of acritarchs reveal that this brackish-water setting was habitable to eukaryotic life. Paired with previously published cadmium isotope data, which can be used as a proxy for phosphorus cycling, our results suggest that complex organisms were perhaps not strictly dependent on marine nutrient supplies. Riverine influxes of P and possibly other nutrients likely rendered coastal waters perhaps equally habitable to the Mesoproterozoic open ocean. This conclusion supports the notion that eukaryotic organisms may have thrived in brackish or perhaps even freshwater environments.

Effects of dietary creatine on juvenile hybrid striped bass in low‐salinity and brackish waters

AbstractA 12‐week, two‐part feeding trial was conducted to evaluate the potential benefits of creatine supplementation in the diet of hybrid striped bass (HSB) under different water salinity and osmoregulatory conditions. A basal diet was formulated to contain 40% crude protein, contributed equally by menhaden fishmeal and soy protein concentrate, and 10% lipid. Three isonitrogenous experimental diets were prepared by supplementing 1, 2, and 4% creatine to the basal diet replacing cellulose and adjusting a 50/50 aspartate/glutamate premix. During the first 7 weeks, salinity of the recirculating system was maintained at 3 g/L (low salinity), then, for an additional 5 weeks, switched to 15 g/L (brackish water). No discernable differences in weight gain, feed efficiency, or survival of HSB were observed during the low‐salinity phase. However, significant improvements in weight gain were exhibited by fish fed diets supplemented with 2 and 4% creatine compared to those fed basal and 1% creatine diets during the brackish water phase. Muscle creatine levels significantly increased with dietary creatine supplementation during both culture phases. The positive effects of dietary creatine supplementation on HSB appeared to be due to increased energetic demands of the brackish water environment.

Hydrocarbon Generation Characteristics of Source Rocks from Different Saline Environments in the Dongpu Depression, Bohai Bay Basin, China

AbstractThe Dongpu Depression is a secondary salt‐bearing tectonic unit in the Bohai Bay Basin, eastern China. The depositional environment of this depression regarding its Paleogene strata is clearly different in plane, including the saltwater environment (SE) in the north, the freshwater environment (FE) in the south and the brackish water environment (BE) in the middle. The result of oil and gas exploration in the Dongpu Depression shows that more than 90% of the proven oil reserves are distributed in the northern saltwater environment. Previous studies indicate that the organic geochemistry characteristics and the hydrocarbon generation capacity of the source rocks are very clearly diverse under different environments, which results in the significant differences in the proved reserves between the north and the south. In order to further explore the differences in the hydrocarbon generation capacity of the source rocks under distinct depositional environments and the mechanism of their occurrence, three samples from different depositional environments (W18‐5 for SE, H7‐18 for BE, CH9 for FE) were used for confined gold tube pyrolysis experiments. The results show that the CH4 yields of W18‐5, H7‐18 and CH9 increase with increasing temperature, the maximum yields being 405.62 mg/g TOC, 388.56 mg/g TOC and 367.89 mg/g TOC, respectively. The liquid hydrocarbon yields of W18‐5, H7‐18 and CH9 firstly increase with increasing temperature and then decrease after the critical temperatures. The maximum yields of C6–14 are 149.54 mg/g TOC, 140.18 mg/g TOC and 116.94 mg/g TOC, the maximum yields of C14+ being 852.4 mg/g TOC, 652.6 mg/g TOC and 596.41mg/g TOC, respectively for W18‐5, H7‐18 and CH9. To summarize, the order of hydrocarbon potential from high to low is W18‐5, H7‐18 and CH9. On this basis, through analyzing the influencing factors of hydrocarbon differences, this paper reveals that the saltwater environment is characterized by 4 factors: higher salinity, halophilic algae, high paleo‐productivity and a strongly reducing environment, which are beneficial to the enrichment of organic matter and lead to the formation of high levels of sapropelite and exinite. According to the variation of oil and gas components in the pyrolysis experiments, the hydrocarbon generation process is divided into three stages: kerogen cracking, oil cracking and C2–5 cracking. Combined with hydrocarbon generation characteristics and stages, the evolutionary model of hydrocarbon generation for source rocks under different environments is established.

Environmental and Microbial Influences on Corrosion of Selected Types of Petroleum Industry Steel

This study explored the influence of brackish water sediment, mangrove swamp sediment, clayey/lateritic soil, and river water (freshwater) sediment on the corrosion rates of carbon, mild, and stainless steels and the species of sulphate reducing bacteria (SRB) and iron bacteria associated with the process. The material loss following burial of the steel samples for a 9-month period was assessed. Standard and specialised microbiological techniques were employed in the characterisation of the bacterial species. Qualitative assessment for corrosion was done via optical microscopy and macroscopy. Corrosion was highest on steel buried in brackish water sediment and lowest in that from river water sediment. Carbon steel was the most susceptible to corrosion while stainless steel was the most resistant. Sulphite, sulphide, nitrate and phosphate concentrations had a strong impact on corrosion rates. Thiobacillus, Leptothrix and Gallionella dominated amongst the iron bacteria while Desulfobacter and Desulfovibrio dominated amongst the SRB. There were significant differences in corrosion rates and bacterial abundance from one environment to the other. Iron bacteria showed greater abundance than SRB across the different environments and steel types. Iron bacteria counts, however, did not correlate positively with corrosion rates. The findings suggest that oil industry facilities in brackish water environments are more liable to corrosion than those located in fresh water ecosystems.

Growth performance of five different strains of Nile tilapia (Oreochromis niloticus) introduced to Tanzania reared in fresh and brackish waters

Five introduced strains of Nile tilapia (Oreochromis niloticus) were tested for growth performance both in fresh- and brackish-water (2 salinity units) environments for 56 days. The BIG NIN, GIFT, Chitralada, “Ruvu Farm” and Silver YY strains with initial mean average weight (± standard error) of 96.4 ± 6.90 g, 104.1 ± 7.19 g, 137.2 ± 7.21 g, 53.2 ± 6.98 g and 95.3 ± 7.11 g, respectively were used. Individuals were tagged and pooled in hapas (12 m × 8.5 m × 2 m each), aligned into different ponds (20 m × 20 m each). Stocking density of 5 fish/m2 and 350 g/kg crude protein diet were used. Overall, the average weight gain for GIFT strain was 7.5%, 32%, 45% and 86.5% higher than BIG NIN, Chitralada, “Ruvu Farm” and Silver YY strains, respectively, across both environments. All strains performed significantly better (p < 0.05) when reared in brackish-water than their respective counterparts in freshwater, except for the BIG NIN strain. The morphometric correlations for all strains in both environments ranged from moderate (0.50) to strong positive (0.92). The GIFT strain demonstrated superior growth and genotype by environment interaction was weak and not important to be prioritized in breeding programs.