Cold Water Bodies Research Articles

Investigating the differences in driving mechanisms for phytoplankton community composition under various human disturbances in cold regions

In river ecosystems, phytoplankton are essential components, and this study delves into their response to critical environmental indicators. We analyzed the spatiotemporal variations of phytoplankton diversity in cold regions, employing techniques such as Principal Component Analysis (PCA), Spearman correlation coefficient, and Generalized Additive Model (GAM) to unveil the critical environmental factors influencing phytoplankton diversity and habitat suitability under varying degrees of human interference. With 37 monitoring stations across two cold region rivers, phytoplankton and water bodies were monitored in spring, summer, and autumn, resulting in the collection and analysis of 111 phytoplankton samples and 13 environmental indicators at each station. By identifying critical water quality indicators and exploring nonlinear relationships, the study revealed intricate interactions between phytoplankton diversity and environmental factors. Our findings suggest that overall phytoplankton species diversity is lower in rivers with high human interference, with turbidity, NH4+-N, chlorophyll-a, and total phosphorus (TP) deemed critical factors. Conversely, chlorophyll-a, NH4+-N, and electrical conductivity (EC) were identified as important factors in rivers with lower human interference, indicating differences in phytoplankton driving mechanisms between the two rivers. These insights provide valuable references for the sustainable development and effective assessment of cold region river ecosystems in the Anthropocene.

Snow detection in alpine regions with Convolutional Neural Networks: discriminating snow from cold clouds and water body

ABSTRACT Accurately monitoring the variation of snow cover from remote sensing is vital since it assists in various fields including prediction of floods, control of runoff values, and the ice regime of rivers. Spectral indices methods are traditional ways to realize snow segmentation, including the most common one – the Normalized Difference Snow Index (NDSI), which utilizes the combination of green and short-wave infrared (SWIR) bands. In addition, spectral indices methods heavily depend on the optimal threshold to determine the accuracy, making it time-consuming to find optimal values for different places. Convolutional neural networks ensemble model with DeepLabV3+ was employed as sub-models for snow segmentation using (Sentinel-2), which aims to distinguish clouds and water body from snow. The imagery dataset generated in this article contains sites in global alpine regions such as Tibetan Plateau in China, the Alps in Switzerland, Alaska in the United States, Southern Patagonian Icefield in Chile, Tsylos Provincial Park, Tatsamenie Peak, and Dalton Peak in Canada. To overcome the limitation of DeepLabV3+, which only accepts three channels as input features, and the need to use six features: green, red, blue, near-infraRed, SWIR, and NDSI, 20 three-channel DeepLabV3+ sub-models, were constructed with different combinations of three features and then ensembled together. The proposed ensemble model showed superior performance than benchmark spectral indices method, with mIoU values ranging from 0.8075 to 0.9538 in different test sites. The results of this project contribute to the development of automated snow segmentation tools to assist earth observation applications.

Thyroid-Mediated Metabolic Differences Underlie Ecological Specialization of Extremophile Salmonids in the Arctic Lake El’gygytgyn

El’gygytgyn, the only “ancient lake” in the Arctic (3.6 MY), is a deep (176 m) and extremely cold (always ≤ 4°C) waterbody inhabited by unique salmonids, which colonized the ecosystem stepwise during the global fluctuations of the Quaternary climate. The descendant of the first-wave-invaders (long-finned charr) dwells in the deep waters and feeds on amphipods. The second-wave-invaders (smallmouth charr) consume copepods in the mid-waters. Recent third-wave-invaders (Boganida charr) are spread throughout the ecosystem and feed on insects when they are young shifting to piscivory at an older age. Here, we present the data on the charrs’ thyroid status and metabolic characteristics, confirming their ecological specialization. The long-finned charr exhibits an extremely low thyroid content, the substitution of carbohydrates for lipids in the cellular respiration, an increased hemoglobin level and a high antioxidant blood capacity. These traits are likely to be the legacy of anaerobic survival under perennial ice cover during several Quaternary glaciations. Moderate thyroid status and reduced metabolic rate of the smallmouth charr, along with an inactive lifestyle, could be regarded as a specialization to saving energy under the low food supply in the water column. The piscivorous Boganida charr could be sub-divided into shallow-water and deep-water groups. The former demonstrates a significantly elevated thyroid status and increased metabolism. The latter is characterized by a reduced thyroid level, metabolic rate, and lipid accumulation. Thus, the endemic El’gygytgyn charrs represent a wide spectrum of contrast physiological adaptation patterns essential to survive in sympatry under extremely cold conditions.

DNA barcoding of Schizothorax species from the Neelum and Jhelum Rivers of Azad Jammu and Kashmir

The mitochondrial Cytochrome Oxidase 1 gene is used as a standardized, authenticated, and reliable genetic marker for a global species-level bio-identification system. The present study was conducted to determine whether barcoding can help accurate species identification in fishes. The overall base composition of Schizothorax species was 29.6% of T, 25.5% of C, 26.5% of A, and 18.4% of G, A + T content 56.1% and G + C content 43.9%. The Ts/Tv bias (R) was 2.51. Complete COI gene was amplified using PCR and sequenced from 17 samples collected from river Neelum and Jhelum, and identification of species were done by following Mirza (1991), Jhingran (1991) classification and also through BOLD (99.3 to 99.9%) and NCBI (99.6 to 99.9%) reference sequences of those species. Multiple alignments of CO1 mtDNA gene resulted in a range of 1535–1551 base pairs. Out of 1535 consensus sites, 1490 were constant, 61 characters were variable, in which 54 were parsimony informative, and 7 variables were parsimony uninformative. This is the very first study reported from a reservoir of cold water bodies of Azad Kashmir which have a great potential for conservation of cold water fish species. We emphasized that, DNA barcoding is an accurate, reliable and has the great potential for identification of freshwater fish species.

The mitochondrial genome of Schizothorax esocinus (Cypriniformes: Cyprinidae) from Northern Pakistan

The mitochondrial DNA sequence represents a mainstay of phylogenetics. It allows biologists to elucidate the evolutionary relationships among species. It also permits an examination of the relatedness of populations, hence got importance in the field of biology. The current study was designed to know the mitochondrial sequence of Schizothorax esocinus, a delicious fish belonging to family Cyprinidae. In this study, the complete mitochondrial genome of S. esocinus from Northern Pakistan was determined. The mitogenome of S. esocinus was found to be 16 591 bp in length and consisted of 13 protein coding genes, 22 tRNA genes, two rRNA genes, and one control region. All genes were encoded on heavy strain except ND6 and few tRNA genes. The overall base composition was T 25.5%, C 27.0%, A 29.8% and G 17.7%, A + T content 55.3% and G + C content 47.7%. The length of control region (CR) was 938 bp and contained putative termination-associated sequence (TAS) and several conserved sequence blocks (CSB) and control region also contained a microsatellite region (TA). This is the very first study reported from a reservoir of large cold water bodies in Pakistan which have a great potential for conservation of cold water fish species. This mitogenome sequence would be useful to know the phylogenetic status of the fish.

Phytoplankton dynamics and water quality of Prashar Lake, Himachal Pradesh, India

Abstract Prashar Lake, an unexplored, high-altitude, shallow, and cold water body located in Himachal Pradesh (India) was studied through monthly surveys in two consecutive years (March 2008 to February 2010). The seasonal variations in chlorophyll a , abundance, and species composition of plankton in relation to hydrography were studied. A total of 67 species belonging to eight groups of phytoplankton were identified. Among 67 phytoplankton species, 19 species exhibited perennial habit. Both plankton and chlorophyll a showed bimodal pattern of fluctuation with peaks in May and September. Annual mean concentrations of chlorophyll a (mg L − 1 ) were recorded as 4.87 in 2008–09, and 4.03 in 2009–10. Palmer pollution index indicated absence of all the 20 pollution tolerant algal species. Pearson correlation revealed a significant relationship between physicochemical parameters and different algal groups. Important physicochemical parameters responsible for distribution of phytoplankton have been studied taking into account the portability of water for irrigation and drinking purposes as per permissible limits of WHO, ICMR, and ISI standards. The values of water quality index were 14.42 during 2008–09 and 16.51 during 2009–10. Based on water quality standards given by Central Pollution Control Board, the water quality at Prashar Lake was between “A and B”. Carlson’s trophic status classified Prashar Lake as oligotrophic with TSI values 17.085 (2008–09) and 14.57 (2009–10). The phytoplankton assemblage, as well as water quality data, suggest that water at Prashar Lake is unpolluted and could be used for various human purposes after disinfection.

Remote sensing observation and numerical modeling of an upwelling jet in Guangdong coastal water

An upwelling event that occurred in Guangdong coastal water on July 14–16, 2003 is observed by using satellite multisensor data including the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) and QuikSCAT ocean surface winds. Successive MODIS SST images reveal expansion process of a jet‐like upwelling cold water body in surface layer. The regional ocean model system (ROMS) is used to explore the upwelling dynamics. The modeling successfully reproduces the jet‐like shape of the surface upwelling water as well as the upwelling developing process. Analyses of modeling momentums reveal that the large offshore transport appeared on the west side of Honghai Bay as a result of high alongshore pressure gradient and nonlinear advections, and the enhanced horizontal advection also played an important role in developing the prominent upwelling in Honghai Bay. A numerical experiment is conducted to confirm that it was the wind driven upwelling rather than the wind‐induced vertical turbulent mixing that induced the surface cold water. Further numerical analyses suggest that strong internal tides occurred in Honghai Bay caused by the local bottom topography. The interaction between the upwelling and internal tides enhances the bottom water uplifting. The offshore expansion of the upwelling water is controlled by the cross‐shore topography slope: a gentle and offshore extended slope helps the bottom water climbing up to the surface in a wide range in cross‐shore direction, whereas a steep and narrow slope restricts the expansion of the upwelling water and confines the cold water in a narrow band along the shore.

Effect of Cold Energy Storage of Doublet-wells Aquifer Thermal Energy Storage in Sanhejian Coal Mine

Effective implementation of technology of aquifer thermal energy storage(ATES) must has sufficient stable cold water body as a basis. In this paper, taking Sanhejian Coal Mine as an example, we analyze the effect of cold energy storage in doublet-wells by analyzing the volume change of cold water body within different temperature ranges in different periods. Through the analysis of volume change of cold water body, it can prove as time goes, the proportion of 2-5°C cold water body is decreasing, the proportion of 5-10°C cold water body and 10-15°C cold water body are maintained at 14% and 28%. The 10-15°C cold water body predominants in cold energy storage aquifers, and the 5-10°C cold water body predominants in the 2-10°C cold water body. And from the 100th day to the 200th day of no pumping and no irrigation, the volumes of 2-5°C cold water body, 2-10°C cold water body and 2-15°C cold water body are decreasing. But with time, the volume of cold water body stabilizes. It proves that the effect of cold energy storage is good in aquifers.

Effect of Cold Energy Storage of Single-Well Aquifer Thermal Energy Storage in Sanhejian Coal Mine

Effective implementation of technology of aquifer thermal energy storage (ATES) must form a "ground cold water reservoir" or "ground warm reservoir". In this paper, taking Sanhejian Coal Mine as an example, we analyze the effect of cold energy storage in single-well by analyzing the volume change of cold water body within different temperature ranges. Through the analysis of volume change of cold water body, it can prove that with the same irrigation temperature, the increase of irrigation flow makes the volume and percentage of cold water body in aquifer within different temperature ranges. And the impact on the cold water of 2-5°C is more obvious. With the same irrigation flow, both the cold water body and its percentage of 2-10°C in the condition of 2°C irrigation temperature are more than those in the condition of 5°C. The increase of irrigation flow and the decrease of irrigation temperature are beneficial to cold energy storage, and the effect of cold energy storage of the condition 3 (100m3/h irrigation flow and 2°C irrigation temperature) is the best in these four conditions.

Effect of Cold Energy Storage of Multi-Wells Aquifer Thermal Energy Storage in Sanhejian Coal Mine

In practical work, implementation of the technology of aquifer thermal energy storage(ATES) is divided into energy storage phase and energy utilization phase. Sufficient cold/warm water is stored in energy storage phase, and the stored cold/warm water is consumed in energy utilization phase, so as to achieve the purpose of cooling or heating. In this paper, taking Sanhejian Coal Mine as an example, we analyze the effect of cold energy storage in multi-wells by analyzing the volume change of cold water body within different temperature ranges in different periods. Through the analysis of volume change of cold water body, it can prove in the cooling process, all of the 2-5°C cold water body is consumed, and then the 5-10°C cold water body is consumed. The volume of 10-15°C cold water body is stable, because with the consumption of colder water, part of low temperature water body changes into high temperature water body, adding the 10-15°C cold water body in aquifers. And in condition 1, there are almost the same volume of 2-5°C, 2-10°C and 2-15 °C cold water in the four cold energy storage wells.The running of 1-1’ wells, 2-2’ wells, 3-3’ wells and 4-4’ wells by sequence, all of the 2-5°C cold water body is consumed, and the 5-10°C cold water body is the mainly cold water body for cooling, and the consumption of 10-15°C cold water body is small. It proves that the cooling wells normally run, and the cold water body for cooling is sufficient, which can meet the need of cooling.

Long life cycles in insects

Long life cycles covering more than one year are known for all orders of insects. There are different mechanisms of prolongation of the life cycle: (1) slow larval development; (2) prolongation of the adult stage with several reproduction periods; (3) prolongation of diapause; (4) combination of these mechanisms in one life cycle. Lasting suboptimal conditions (such as low temperature, low quality of food or instability of food resources, natural enemies, etc.) tend to prolong life cycles of all individuals in a population. In this case, the larvae feed and develop for longer than a year, and the active periods are interrupted by dormancy periods. The nature of this dormancy is unknown: in some cases it appears to be simple quiescence, in others it has been experimentally shown to be a true diapause. Induction and termination of these repeated dormancy states are controlled by different environmental cues, the day-length being the principal one as in the case of the annual diapause. The long life cycles resulting from prolonged adult lifespan were experimentally studied mainly in beetles and true bugs. The possibility of repeated diapause and several periods of reproductive activity is related to the fact that the adults remain sensitive to day length, which is the main environmental cue controlling their alternative physiological states (reproduction vs. diapause). Habitats with unpredictable environmental changes stimulate some individuals in a population to extend their life cycles by prolonged diapause. The properties of this diapause are poorly understood, but results of studies of a few species suggest that this physiological state differs from the true annual diapause in deeper suppression of metabolism. Induction and intensity of prolonged diapause in some species appear to be genetically controlled, so that the duration of prolonged diapause varies among individuals in a group, even that of sibles reared under identical conditions. Thus, long life cycles are realized due to the ability of insects to interrupt activity repeatedly and enter dormancy. This provides high resistance to various environmental factors. Regardless of the nature of this dormancy (quiescence, annual or prolonged diapause, or other forms) and the life cycle duration, the adults always appear synchronously after dormancy in the nature. The only feasible explanation of this is the presence of a special synchronizing mechanism, most likely both exo- and endogenous, since the adults appear not only synchronously but also in the period best suited for reproduction. As a whole, the long life cycles resulting from various structural modifications of the annual life cycle, are typical of the species living under stable suboptimal conditions when the pressure of individual environmental factors is close to the tolerance limits of the species, even though it represents its norm of existence. Such life cycles are also typical of the insects living in unstable environments with unpredictable variability of conditions, those developing in cones and galls, feeding on flowers, seeds, or fruits with limited periods of availability, those associated with the plant species with irregular patterns of blossoming and fruiting, and those consuming low-quality food or depending on unpredictable food sources (e.g., predators or parasites). Long cycles are more common in: (1) insect species at high latitudes and mountain landscapes where the vegetation season is short and unstable; (2) species living in deserts or arid areas where precipitation is unstable and often insufficient for survival of food plants; (3) inhabitants of cold and temporary water bodies that are not filled with water every year. At the same time, long life cycles sometimes occur in insects from other climatic zones as well. It is also important to note that while there is a large body of literature dealing with the long life cycles in insects, it mostly focuses on external aspects of the phenomenon. Experimental studies are needed to understand this phenomenon, first of all the nature of dormancy and mechanisms of synchronization of adult emergence.

A decade of cloud‐to‐ground lightning in Canada: 1999–2008. Part 1: Flash density and occurrence

Flash density and occurrence features for more than 23.5 million cloud‐to‐ground (CG) lightning flashes detected by the Canadian Lightning Detection Network (CLDN) from 1999 to 2008 are analyzed on 20 × 20 km equal area squares over Canada. This study was done to update an analysis performed in 2002 with just three years of data. Flashes were detected throughout the year, and distinct geographic differences in flash density and lightning occurrence were observed. The shape and locations of large scale patterns of lightning occurrence remained almost the same, although some details were different. Flash density maxima occurred at the same locations as found previously: the Swan Hills and Foothills of Alberta, southeastern Saskatchewan, southwestern Manitoba and southwestern Ontario. A region of greater lightning occurrence but relatively low flash density south of Nova Scotia occurred at the same location as reported previously. New areas of higher flash density occurred along the US border with northwestern Ontario and southern Quebec. These appear to be northward extensions of higher flash density seen in the previous study. The greatest average CG flash density was 2.8 flash km−2 y−1 in southwestern Ontario, where the greatest single‐year flash density (10.3 flash km−2 y−1) also occurred. Prominent flash density minima occurred east of the Continental Divide in Alberta and over the Niagara Escarpment in southern Ontario. Lightning activity is seen to be highly influenced by the length of the season, proximity to cold water bodies and elevation. The diurnal heating and cooling cycle exerted the main control over lightning occurrence over most land areas; however, storm translation and transient dynamic features complicated the time pattern of lightning production. A large portion of the southern Prairie Provinces experienced more than 50% of flashes between 22:30 and 10:30 local solar time. The duration of lightning over a 20 × 20 km square at most locations in Canada is 5–10 h y−1, although the duration exceeded 15 h y−1 over extreme southwestern Ontario. Lightning occurred on 15–30 days each year, on average, over most of the interior of the country. The greatest number of days with lightning in a single year was 47 in the Alberta foothills and 50 in southwestern Ontario. Beginning and ending dates of the lightning season show that the season length decreases from north to south; however, there are considerable east‐west differences between regions. The season is nearly year‐round in the Pacific coastal region, southern Nova Scotia, southern Newfoundland and offshore.

Formation and evolution of the modern warm current system in the East China Sea and the Yellow Sea since the last deglaciation

To reconstruct the formation and evolution process of the warm current system within the East China Sea (ECS) and the Yellow Sea (YS) since the last deglaciation, the paleoceangraphic records in core DGKS9603, core CSH1 and core YSDP102, which were retrieved from the mainstream of the Kuroshio Current (KC), the edge of the modern Tsushima Warm Current (TWC) and muddy region under cold waters accreted with the Yellow Sea Warm Current (YSWC) respectively, were synthetically analyzed. The results indicate that the formation and evolution of the modern warm current system in the ECS and the YS has been accompanied by the development of the KC and impulse rising of the sea level since the last deglaciation. The influence of the KC on the Okinawa Trough had enhanced since 16 cal kyr BP, and synchronously the modern TWC began to develop with the rising of sea level and finally formed at about 8.5 cal kyr BP. The KC had experienced two weakening process during the Heinrich event 1 and the Younger Drays event from 16 to 8.5 cal kyr BP. The period of 7-6 cal kyr BP was the strongest stage of the KC and the TWC since the last deglaciation. The YSWC has appeared at about 6.4 cal kyr BP. Thus, the warm current system of the ECS and the YS has ultimately formed. The weakness of the KC, indicated by the occurrence of Pulleniatina minimum event (PME) during the period from 5.3 to 2.8 cal kyr BP, caused the main stream of the TWC to shift eastward to the Pacific Ocean around about 3 cal kyr BP. The process resulted in the intruding of continent shelf cold water mass with rich nutrients. Synchronously, the strength of the YSWC was relatively weak and the related cold water body was active at the early-mid stage of its appearance against the PME background, which resulted in the quick formation of muddy deposit system in the southeastern YS. The strength of the warm current system in the ECS and the YS has enhanced evidently, and approached to the modern condition gradually since 3 cal kyr BP.

The use of deep water cooling systems: Two Canadian examples

Deep water cooling involves using naturally cold water as a heat sink in a heat exchange system, eliminating the need for conventional air conditioning. The cold water is drawn from near the bottom or below the thermocline of a nearby water body. In this study Canadian deep water cooling systems in Halifax, Nova Scotia and Toronto, Ontario were documented. The expected economic and environmental benefits were realized, but barriers to large-scale adoption of the technology were apparent. This technology requires that a client with a large cooling need is near a deep, cold body of water, and payback times vary depending on the site. The public–private partnership approach proved to be beneficial in these two examples, and the Toronto approach in which many buildings are serviced at once by combining municipal pumping capacity can deliver cost savings on a shorter time span. Deep water cooling represents a successful example of a niche accumulation process and an example of electricity demand displacement. Many other locations in which heavy air conditioning users are located next to deep, cold water bodies could use this technology; several such sites exist in Canadian urban areas.

Hydrology and Diatom Phytoplankton of High Arctic Lakes and Ponds on Store Koldewey, Northeast Greenland

We document hydrological and phytoplankton characteristics of nine lakes and two ponds on Store Koldewey, a culturally undisturbed island off Northeast Greenland. The limnological survey included the recording of temperature, conductivity, oxygen concentration and saturation, pH, ionic composition, transparency, and the diatom phytoplankton community. In summer 2003, the lakes were cold, monomictic, thermally unstratified, alkaline and likely oligotrophic water bodies. Diatom phytoplankton was present in six lakes and consisted of four dominant species (Aulacoseira tethera, Cyclotella pseudostelligera, C rossii, and Fragilaria tenera). The concentration of planktonic diatoms varied distinctly between the lakes.

Hexachlorocyclohexanes in the North American atmosphere.

Annually integrated air concentrations of alpha- and gamma-hexachlorocyclohexane (HCH) were determined in 2000/2001 at 40 stations across North America using XAD-based passive air samplers to understand atmospheric distribution processes on a continental scale. Elevated levels of gamma-HCH in the atmosphere of the Canadian Prairies are consistent with the ongoing use of lindane as a seed treatment on canola and confirm the feasibility of detecting the agricultural use of a pesticide using long-term integrated passive air sampling. In contrast to gamma-HCH, the atmospheric concentrations of alpha-HCH show a rather uniform distribution across Canada and the United States, which is expected for a chemical with no current use on the continent. Higher levels in the atmosphere over Atlantic Canada can be explained by alpha-HCH evaporating from the waters of the Labrador Current, which is supported bythe chiral composition of alpha-HCH and the temperature dependence of its atmospheric concentrations along the east coast of Canada. Similarly, alpha-HCH is volatilizing from Lake Superior. Atmospheric HCH levels increase with elevation in the Canadian Rocky Mountains. The results suggest that evaporation, in particular from cold water bodies, is an important source of alpha-HCH to the North American atmosphere. Low levels of HCHs in Central America hint at efficient degradation under tropical conditions. Chiral analysis shows that (+)-alpha-HCH is often enriched in air over continental areas and at the Pacific Coast, which is opposite to the enantiomeric enrichment in the proximity to the Great Lakes and the Atlantic Ocean. Passive air sampling is a powerful tool to discern the large-scale variability of semivolatile and persistent organic chemicals in the atmosphere.

DNA signature of thermophilic bacteria from the aged accretion ice of Lake Vostok, Antarctica: implications for searching for life in extreme icy environments

We have used 16S ribosomal genes to estimate the bacterial contents of Lake Vostok accretion ice samples at 3551 m and 3607 m, both containing sediment inclusions and formed 20000–15000 yr ago. Decontamination proved to be a critical issue, and we used stringent ice chemistry-based procedures and comprehensive biological controls in order to restrain contamination. As a result, up to now we have only recognized one 16S rDNA bacterial phylotype with confident relevance to the lake environment. It was found in one sample at 3607 m depth and represents the extant thermophilic facultative chemolithoautotroph Hydrogenophilus thermoluteolus of beta-Proteobacteria, and until now had only been found in hot springs. No confident findings were detected in the sample at 3551 m, and all other phylotypes revealed (a total of 16 phylotypes, 336 clones including controls) are presumed to be contaminants. It seems that the Lake Vostok accretion ice is actually microbe-free, indicating that the water body should also be hosting a highly sparse life. The message of thermophilic bacteria suggests that a geothermal system exists beneath the cold water body of Lake Vostok, what is supported by the geological setting, the long-term seismotectonic evidence from 4He degassing and the ‘18O shift’ of the Vostok accretion ice. The seismotectonic activity that seems to operate in deep faults beneath the lake could sustain thermophilic chemolithoautotrophic microbial communities. Such a primary production scenario for Lake Vostok may have relevance for icy planets and the approaches used for estimating microbial contents in accretion ice are clearly relevant for searching for extraterrestrial life.

Retinal cytoarchitecture in Some Mountain-stream Teleosts of India

In this study, the cytoarchitecture of retina in 10 mountain-stream teleosts (seven cyprinid and three loach species) of India was examined by conventional light microscopy. The mountain-streams are shallow, cold water bodies having high turbidity in the Monsoon and clear water in the colder months. The incumbent fishes are, thus, periodically exposed to low and bright light of the streams, respectively. It was of particular interest to see whether their retina would reflect adaptations to the changing photic environments of the mountain streams. The retina of the cyprinids possess multiple cone types, a moderate cone density, high convergence ratios and prominent retinomotor responses. Triple cones occur only in the danio, Danio aequipinnatus; other cyprinids possess miniature, short and long single cones, and double or twin cones. In general, the cones are bulky in appearance. Cone droplets (ellipsosomes) are found in Garra lamta and G. gotyla gotyla. All cone types, including the miniature single cones, undergo elongation during dark adaptation. The common retinal features in the loaches are the bulky cones, ellipsosomes, low rod density and low convergence ratios. There is no area-like specialization of the retina in any of the species examined. No relationship is obvious between cone pattern and ambient light or food habit in any of those teleosts studied; row pattern is present throughout the retina of the surface-dwelling, total insectivores (cyprinids: Danio aequipinnatus and Barilius spp.), whereas square mosaic pattern is present in the bottom-dwelling total herbiovores (Garra spp.) as well as in the insectivores (loaches: Nemacheilus spp.). The retinal features have suggested that the cyprinids are well-adapted to both clear and turbid water (ellipsosomes, multiple cone types, bulky cones, high rod count and high convergence ratios); the loaches, on the other hand, are better adapted to clear water of the mountain streams.

Evaluation of aquatic toxicity and bioaccumulation of C8‐ and C9‐alkylphenol ethoxylates

AbstractThe extensive database of acute and chronic aquatic toxicity data for alkylphenol ethoxylates (APEs) and selected biodegradation intermediates was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish inhabiting cold and warm water bodies. Most acute toxicity studies that tested APE‐9 and APE‐10, the most common commercially relevant APEs, reported results that ranged from about 1,000 to 10,000 μg/L. Results from studies testing alkylphenols, intermediate by‐products of APE biodegradation, ranged from about 20 to 3,000 μg/L. Chronic values are a factor of about 2 to 10 lower. Although most studies used one of several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This toxicological database encompasses virtually all important types of aquatic habitats and classes of aquatic species. Bioaccumulation data from both laboratory and field studies indicate that alkylphenols have a low to moderate bioaccumulation potential. Fresh weight, nonlipid‐based bioconcentration factors (BCFs) measured in the laboratory ranged from < 1 to 1,250 for fish and 1 to 3,400 for invertebrates, whereas field bioaccumulation factors (BAFs) ranged from 6 to 487, with most values < 100. Overall, these data provide an extensive and useful database to support environmental risk assessment activities.

Numerical simulation of 2D buoyant jets in ice-covered and temperature-stratified water

A two-dimensional (2D) unsteady simulation model is applied to the problem of a submerged warm water discharge into a stratified lake or reservoir with an ice cover. Numerical simulations and analyses are conducted to gain insight into large-scale convective recirculation and flow processes in a cold waterbody induced by a buoyant jet. Jet behaviors under various discharge temperatures are captured by directly modeling flow and thermal fields. Flow structures and processes are described by the simulated spatial and temporal distributions of velocity and temperature in various regions: deflection, recirculation, attachment, and impingement. Some peculiar hydrothermal and dynamic features, e.g. reversal of buoyancy due to the dilution of a warm jet by entraining cold ambient water, are identified and examined. Simulation results show that buoyancy is the most important factor controlling jet behavior and mixing processes. The inflow boundary is treated as a liquid wall from which the jet is offset. Similarity and difference in effects of boundaries perpendicular and parallel to flow, and of buoyancy on jet attachment and impingement, are discussed. Symmetric flow configuration is used to de-emphasize the Coanda effect caused by offset.