Depth Of 7m Research Articles

Study of Unio shells in the Quaternary deposits, southern Iraq

Shells are useful in evolutionary biology and paleobiology. Freshwater shells compose the main types of mollusks, and can use as a key for ecological variations. Shell samples in the present study were collected on the highway of Nasyriah city-Samawa city, southern Iraq. The study area contains a large accumulation of shells at 6-7m depths, especially at 7m depth. The main types of these shells are Unio, Corbicula, and Melanoides tuberculata. Unio was the most species common in the study area. Unio species were used to detect the paleoenvironment in Quaternary deposits, in southern Iraq. Calcite and aragonite are the common minerals in the Unio shells. According to the distribution and percentage of calcite and aragonite in the Unio shells, it was found the calcite at 6m is more than 7m, whereas the aragonite at 7m is highest compared to 6m. Under X-Ray Fluorescence analyzers, found that calcium oxide, silica, magnesium oxide, and phosphor oxide are the major oxides in the Unio shells, while Zn, Sr, Pb, and Rb are the main trace elements. Strontium (Sr) has a high concentration in the Unio shells at 7m than 6m, while magnesium (Mg) is found in a high concentration at 6m than 7m. According to trace and some of the major elements concentrations, the paleotemperature, paleosalinity, and water contamination of rivers at 6m are more than 7m, and the river water at 7m depth was fresh water with a high abundance of nutrients and climate was suitable to growth mollusks shells like Unio shells.

Variations and Condition of Coral Lifeforms in the Coastal Area of Rendani Airport, Manokwari, Indonesia

Coral reefs are unique ecosystems and only occur in the tropics area. Diversity, distribution, and coral growth are influenced by environmental factors. Coral colonies morphologies or coral lifeform rates vary significantly between species and between environmental factors. This study aimed to determine the variations of hard coral based on their lifeform; and assess the condition of reefs by measuring the percent cover of live coral in the coastal area of Rendani Airport. Coral cover and coral damage data gathering used a survey approach with Point Intercept Transect (PIT) method. The results showed the variations of coral lifeform in the coastal area of Rendani was relatively low, as indicated by the absence of some coral lifeforms in the study site. The most variation lifeform was found at 7m depth with five lifeforms, while the lowest was found at 3m depth with three lifeforms. The live coral cover reached 77,66% at station 1 and 75,00% at station 2, and the lowest coverage was 11,33% at station 3. The highest average of rubble at station 1 at 4.33% and dead coral with algae was found to be highest at station 3 at 8.00%.

Assessment of the Leachate Contamination Level of Groundwater Resource at a Dumpsite, In Minna, North Central, Nigeria Using Resistivity Method

This research work focused on the use of direct current resistivity method to analyse data collected from refuse dumpsite at eastern bye pass Minna. The study area lies approximately on longitude 60 36’19.84”E to 6036’23.15”E and latitude 90 38’04.97”N to 9038’08.25”N, with a dimension of 100m x 100m within the basement complex of north central Nigeria. Vertical Electrical Sounding was carried out on the dumpsite with the aim of delineating the leachate contaminant plumes using resistivity method. Nine electrical resistivity profiles were measured on the site. Six transverse profiles were conducted on the dumpsite with thirty-six vertical electrical sounding (VES) point, three transverse profiles was also conducted on the control site which is 100 meters away from the dumpsite having nine vertical electrical sounding (VES) point and a dimension of 40m x 40m. The resistivity data obtained was analyzed using winresist software. The data obtained from the study area revealed three underlain layer they are the topsoil, fractured basement and fresh basement. The dumpsite was typified by A-types and H-types of curve and the control site was typified by H-type of curves. Iso–resistivity maps at various depths were observed, at the surface, 3m, 5m,7m, and 10m for the dumpsite and the control site. It can therefore be inferred from this study that the depth of contamination is 7 meter and aquifer found within this depth are most likely to be contaminated by leachate and water bearing formation beyond the depth of 7m is safe from contamination. The rate of contamination of the study area is approximately 1.0 meter per year.

Geotechnical Characteristics of Subsoil for Different Sectors of Islamabad

Geotechnical site investigations are essential in determining subsoil stratigraphy and soil strength and is considered mandatory for design of foundations. This study presents the generalized profiles for subsurface stratigraphy and insitu soil strength (average SPT N values) for different sectors of Islamabad on the basis of wide-ranging experimental work carried out by several agencies in fieldand laboratory testing carried out at the number of locations in the study area. Data from 208 geotechnical site investigations of Islamabad have been collected and subsurface profiling for those sectors is carried out that had more than four data points. The experimental data of the study area has shown potential for development of profile map for 11 different sectors of Islamabad using data of 144 geotechnical site investigations. Generalized soil profile and average SPT N values for each sector have been generated to a depth of 7m which is considered sufficient for lightly loaded structures with shallow foundations. Average SPT N value profile coupled with soil stratigraphy for each zone is established that can used to determine shear strength parameters and bearing capacity of soil using SPT based empirical correlations. The generalized soil profiles will be helpful during feasibility study and planning geotechnical site investigations for mega projects and can also be used to determine engineering properties of subsoil for small scale projects.

Succession in megafaunal assemblages of an artificial reef during a three-year monitoring in the Eastern Mediterranean basin

Succession in megafaunal assemblages of an artificial reef during a three-year monitoring in the Eastern Mediterranean basin

Environmental dissimilarity over time in a large subtropical shallow lake is differently represented by phytoplankton functional approaches

The aim of the present study was to understand how different phytoplankton functional approaches responded to environmental variability in a large shallow lake, namely Lake Mangueira, in southern Brazil. This coastal lake has a maximum depth of 7m and is ~90km long and ~3–10km wide. Physical and chemical variables, maximum linear dimension, life forms, functional and morphofunctional groups of phytoplankton were analysed. The results showed that the phytoplankton were primarily comprised Cyanobacteria (63.9%), followed by middle-sized algae (21–50μm; 46.7%) and colonial non-flagellated taxa (63%). The highest percentage of total biomass was accounted for by the functional group ‘K’ (as classified by Reynolds et al. 2002; 36.3%), large mucilaginous colonies (46.79%) according to morphologically based functional classification and other large colonies (mostly non-vacuolated; 36.7%) according to morphofunctional classification. Dissimilarity analysis indicated a significant correlation between abiotic data and functional approaches (P=0.001). The dissimilarity in the functional compositions of phytoplankton was related to nutrient and light conditions, especially to silicon content and water transparency, in all functional approaches. The highest correlation with abiotic variables was seen for morphologically based functional group community structure, although the functional group composition of phytoplankton sensu Reynolds et al. seemed to be the most effective system in describing environmental variability in Lake Mangueira over the long term.

Modeling the biogeochemical role of photosynthetic sulfur bacteria in phosphorus cycling in a managed eutrophic lake

Vertical distributions of total dissolved phosphorus (TDP), sulfide, chlorophyll, and primary production produced by photosynthetic sulfur bacteria (PSB) were studied in a small stratified, highly productive, and dimictic lake, Linsley Pond, CT, USA. The goal was to understand and model the role of PSB in a lake undergoing trophic transformation as a result of lake management involving reduced phosphorus loading. High levels of sulfide developed in the anoxic hypolimnion, though a decrease was observed compared to earlier years, possibly as a result of lake management under a Total Maximum Daily Load (TMDL) process. A deep chlorophyll maximum was observed, and absorption spectra confirmed that it was the result of photosynthetic sulfur bacteria. The summer chlorophyll maximum occurred at an interface marked by high amounts of sulfide and low, but adequate, levels of light. Primary production by PSB was found at a depth of 7m in July 2008, and thereafter extended slowly to 9m until late fall overturn. PSB only contributed a minor portion of total primary production in Linsley Pond that year, but a straightforward biogeochemical phosphorus model reveals that the existence of PSB serves as a significant biological barrier for phosphorus being transported back into the upper mixing zone. A large amount of TDP was trapped in the hypolimnion, and upward transport of TDP from the upper boundary of the hypolimnion to the mixing zone was about 30% of external phosphorus loading from the only tributary during the summer stratification period. By comparison, the amount of TDP assimilated by PSB and settling back to the hypolimnion was comparable to external phosphorus loading to the lake from its tributary. As lake management reduces external P loading and productivity, bottom sulfide is likely to decrease, suppressing PSB activity and having the undesired effect of allowing more TDP to be transported upward to the epilimnion as this biological barrier is suppressed.

Chlorination by-product concentration levels in seawater and fish of an industrialised bay (Gulf of Fos, France) exposed to multiple chlorinated effluents

Chlorination is one of the most widely used techniques for biofouling control in large industrial units, leading to the formation of halogenated chlorination by-products (CBPs). This study was carried out to evaluate the distribution and the dispersion of these compounds within an industrialised bay hosting multiple chlorination discharges issued from various industrial processes. The water column was sampled at the surface and at 7m depth (or bottom) in 24 stations for the analysis of CBPs, and muscle samples from 15 conger eel (Conger conger) were also investigated. Temperature and salinity profiles supported the identification of the chlorination releases, with potentially complex patterns. Chemical analyses showed that bromoform was the most abundant CBP, ranging from 0.5 to 2.2μgL−1 away from outlets (up to 10km distance), and up to 18.6μgL−1 in a liquefied natural gas (LNG) regasification plume. However, CBP distributions were not homogeneous, halophenols being prominent in a power station outlet and dibromoacetonitrile in more remote stations. A seasonal effect was identified as fewer stations revealed CBPs in summer, probably due to the air and water temperatures increases favouring volatilisation and reactivity. A simple risk assessment of the 11 identified CBPs showed that 7 compounds concentrations were above the potential risk levels to the local marine environment. Finally, conger eel muscles presented relatively high levels of 2,4,6-tribromophenol, traducing a generalised impregnation of the Gulf of Fos to CBPs and a global bioconcentration factor of 25 was determined for this compound.

Seasonal variability of emerging invertebrate assemblages in a sheltered soft-bottom sublittoral habitat

In the Humboldt Current upwelling ecosystem of northern Chile, seasonal variation in the assemblage structure of pelagic invertebrates is strongly coupled with seasonal oscillations in upwelling intensity, however, benthic assemblages apparently show no clear responses to seasonal changes in the environment. Herein, we assess seasonal variability in the structure of the emerging assemblage (i.e., invertebrates that migrate nocturnally from the seabed to the water column, returning to the seabed during the day). This assemblage uses both the pelagic and benthic habitats daily, and thus offers an interesting group to study in order to assess their response to seasonal variability. We carried out replicated sampling during the austral autumn, winter, and spring of 2012 and the summer of 2013 in the subtidal zone of Bolsico (northern of Chile), using traps specifically designed to capture emerging benthic invertebrates, at 7m depth in a sheltered soft-bottom habitat. We observed clear seasonal effects, with total abundance increasing during spring and a cyclical pattern in assemblage structure of the emerging benthos. Three main patterns characterized seasonal changes in species abundance; peaks of abundances during autumn (e.g. amphipods Eudevenopus gracilipes and Liljeborgia sp.), summer (e.g. amphipods Aora typica and Microphoxus sp.) and spring (e.g. copepods Tigriopus sp. and Corycaeus sp.). Strong seasonal patterns in emerging invertebrates closely resembled the pattern observed in the pelagic fauna.

Ecology and management of the invasive lionfish Pterois volitans/miles complex (Perciformes: Scorpaenidae) in Southern Costa Rica.

Invasive species alter ecosystem integrity and functioning and are considered one of the major threats to biodiversity on a global scale. The indopacific lionfish (Plerois volitans [Linnaeus, 1758] / miles [Bennet, 1882] complex) is the first non-native marine fish that has established itself in the Western Atlantic. It was first reported in Florida in the 1980s and then spread across the entire Caribbean in subsequent years. In Costa Rica, lionfish were first sighted by the end of 2008 and are now present in all South Caribbean reefs. Lionfish are a major problem for local fisherman by displacing native fish species. The aim of this study was to determine population density, size and diet of lionfish populations at four study sites along the Southern Caribbean coast of Costa Rica. Two of the sites were located inside the National Park Cahuita where regular lionfish removal occurs, whereas the other two study sides do not experiment this kind of management. Total length and wet weight of >450 lionfish individuals were determined between March and June 2011. Three relative metrics of prey quantity (percent number, percent frequency, and percent weight) were compared from approximately 300 lionfish caught with the polespear in shallow waters (<7 m depth). Population density was assessed weekly through visual transect surveys. Our results showed that lionfish preyed mostly upon teleosts and crustaceans. Teleosts dominated lionfish diet in percent frequency (71%) and percent weight (85%), whereas crustaceans had the highest percent number (58%). The top five teleost families of dietary importance were Pomacentridae, Acanthuridae, Blennidae, Labridae and Serranidae. The average total length (+/- SD) of lionfish was 18.7 (+/- 5.7)cm and varied significantly between sites (p<0.001). Mean density of lionfish was 92fish/ha with no significant differences between sites. Smallest fish and lowest densities were found at the two sites inside the National Park Cahuita. Despite management efforts on a regional scale, nationwide efforts are ineffective and lionfish control activities are poorly implemented. We conclude that there is an urgent need to develop an improved institutional framework for local lionfish control that promotes effective coordination among the relevant stakeholders in order to deal with invasive lionfish in Costa Rica.

Measurement error analysis of multibeam echosounder system mounted on the deep-sea autonomous underwater vehicle

The measurement error sources of the multibeam echosounder system (MBES) mounted on the deep-sea autonomous underwater vehicle (AUV) are analyzed according to the composition features of the system. By analyzing the AUV sailing poses, the installation deviation of the multibeam measuring probe and the navigation and positioning system, the depth error estimation model and the position error estimation model of MBES are established. Based on the models above, the simulation is carried out considering the installation error of MBES. The deep-sea AUV conducted a sea trial at a drilling well site in Bohai Sea with a fixed depth of 7m above the seafloor. The pose fluctuation of the AUV is derived. By comparing with topography in the area of the well site, the validity of the depth error estimation model and the position error estimation model are tested. The results provide design considerations of the integration installation of MBES to the AUV system. They are also important for the measurement data pose processing for MBES.

Historical evolution and Middle to Late Holocene environmental changes in Lake Shkodra (Albania): New evidences from micropaleontological analysis

The 7.5m long SK13 sediment core, drilled at Lake Shkodra (Albania) at a bottom depth of 7m in the central southern part of the lake, was selected for multidisciplinary analysis. The sediment core age spans from 4560calyrBP to present. The origin and the evolution of the lake are still debated and were never investigated in detail. In historical records, until the 15th century Lake Shkodra was never mentioned as such, but as a marshland or as a confluence between two rivers. Our research aims to reconstruct the past biodiversity and the Middle-Late Holocene palaeoenvironmental and palaeoclimatic changes using Ostracods, Characeae, and comparing the micropaleontological data with pollens and stable isotope curves. Thirteen ostracod and five charophyte species were identified. Amongst the ostracods Candona montenigrina and Limnocythere scutariense are endemic of the lake; Candona meridionalis, Paralimnocythere georgevitschi, Metacypris cordata, Candona ex gr. bimucronata, and Cyclocypris sp. have been collected for the first time in Lake Shkodra; the last three taxa occurred only in the lower portion of the sediment core. Amongst the charophytes, Lychnothamnus barbatus and Nitella hyalina are recorded for the first time in the lake and occurs with high frequency throughout the lower portion of the core. A drastic change occurs between 1274 and 1197calyrBP, when 8 ostracod species out of 13 and all charophytes disappear, and the frequency of the remaining 5 species dramatically increases. The micropaleontological data suggest a decrease of the lake biodiversity since around 1200calyrBP linked to the transition between an ancient marshland to a lacustrine environment. This drastic event seems to be independent from any global or local climate change but linked to the complex hydrographic setting of the lake and of its only outlet, the River Bojana, discharging in the Adriatic Sea.

Moon phase effects and timing of emerging macrobenthic assemblages in a sheltered soft-bottom sublittoral habitat

Several species of benthic macro and meio-invertebrates actively emerge from the seabed to the water column during the night. Such diel vertical migrations have important consequences for benthic–pelagic coupling, dispersal, connectivity and recovery after disturbance of benthic assemblages. However, this process has never been studied in the coast of the Humboldt Current ecosystem. Herein we examined the relationship between the emerging assemblage and moon phases (and co-variables) and the timing of emergence during the day/night cycle, in a sublittoral soft-bottom habitat. Sampling using emergence traps was conducted at 7m depth in the zone of Bolsico, a sheltered cove with low bottom hydrodynamics in northern Chile. Multivariable analysis showed that changes in the dissimilarity of the emerging assemblage were related to each moon phase. The percentage of moon illumination, bottom illumination and tide amplitude explained most of the variation of the emerging assemblage. Species showed differential responses to each moon phase; some were abundant at intermediate phases (e.g., harpacticoids), or peaked at full moon (e.g. ostracods) and others such as mysids emerged in equal abundances at all moon phases. The timing of assemblage emergence followed a consecutive sequence through the night/day period. Most of the studies dealing with the emergence processes have described species-specific responses. Our research shows that the examination at assemblage level may reveal new and distinct patterns of emergence in sublittoral soft-bottom habitats.

Assessing soil and groundwater contamination in a metropolitan redevelopment project

The purpose of this study was to assess contaminated soil and groundwater for the urban redevelopment of a rapid transit railway and a new mega-shopping area. Contaminated soil and groundwater may interfere with the progress of this project, and residents and shoppers may be exposed to human health risks. The study area has been remediated after application of first remediation technologies. Of the entire area, several sites were still contaminated by waste materials and petroleum. For zinc (Zn) contamination, high Zn concentrations were detected because waste materials were disposed in the entire area. For petroleum contamination, high total petroleum hydrocarbon (TPH) and hydrocarbon degrading microbe concentrations were observed at the depth of 7m because the underground petroleum storage tank had previously been located at this site. Correlation results suggest that TPH (soil) concentration is still related with TPH (groundwater) concentration. The relationship is taken into account in the Spearman coefficient (α).

Spatial and temporal variations in cadmium concentrations and burdens in the Pacific oyster (Crassostrea gigas) sampled from the Pacific north-west

Oysters from the north-west coast of Canada contain high levels of cadmium, a toxic metal, in amounts that exceed food safety guidelines for international markets. A first required step to determine the sources of cadmium is to identify possible spatial and temporal trends in the accumulation of cadmium by the oyster. To meet this objective, rather than sample wild and cultured oysters of unknown age and origin, an oyster “grow-out” experiment was initiated. Cultured oyster seed was suspended in the water column up to a depth of 7m and the oyster seed allowed to mature a period of 3years until market size. Oysters were sampled bimonthly and at time of sampling, temperature, chlorophyll-a, turbidity and salinity were measured. Oyster total shell length, dry tissue weights, cadmium concentrations (μgg−1) and burdens (μg of cadmium oyster−1) were determined. Oyster cadmium concentrations and burdens were then interpreted with respect to the spatial and temporal sampling design as well as to the measured physio-chemical and biotic variables. When expressed as a concentration, there was a marked seasonality with concentrations being greater in winter as compared in summer; however no spatial trend was evident. When expressed as a burden which corrects for differences in tissue mass, there was no seasonality, however cadmium oyster burdens increased from south to north. Comparison of cadmium accumulation rates oyster−1 among sites indicated three locations, Webster Island, on the west side of Vancouver Island, and two within Desolation Sound, Teakerne Arm and Redonda Bay, where point sources of cadmium which are not present at all other sampling locations may be contributing to overall oyster cadmium burdens. Of the four physio-chemical factors measured only temperature and turbidity weakly correlated with tissue cadmium concentrations (r2=−0.13; p<0.05). By expressing oyster cadmium both as concentration and burden, regional and temporal patterns were demonstrated, which may have been missed if just concentration was determined.

Organic compounds found in Dokai Bay, Japan.

Dokai Bay is a 13km-long narrow bay with average depth of 7m, which is located in north Kyushu in Japan. There had been ser ious environmental p o l l u t i o n caused by unt rea ted domestic and i ndus t r i a l wastewater in t h i s area. The po l lu t i on was acce le ra t ed by the c h a r a c t e r i s t i c s of t h i s enclosed shape with l i t t l e water exchange to open sea. Nowadays, the water q u a l i t y of t h i s bay has improved as a r e s u l t of the r egu la t ion of wastewater, the spreading of sewage t reatment system and the dredging of po l l u t ed sediment. But there are s t i l l many f a c t o r i e s producing chemicals, iron and s tee l around the bay. And large residence area s t r e t c h e s upstream. Therefore, many kinds of chemical substances may accumulate in t h i s area than in an open area.

Un exemple de sedimentation biodetritique holocene en climat tropical humide le “lac” Ahémé (Bénin, Afrique de l'Ouest)

The coastal atlantic margins of the Benin Republic presents an excellent example of a margino-littoral coastline with lagoons and vertically oriented river valleys. One of these is the river Couffo which runs out from the “lake” Aheme in the SW portion of the country. Hydrodynamic analysis shows that its alimentation principally downstream from sea waters and fresh waters originating from the Mono river. In this case, supplies or contributions are less important and the rate of feeling up is low. About one hundred superficial samples distributed across the entire bottom of the lake were colleced from depths that do not exceed 2,35m. Eight small bore-hole samples from 0,7 to 1,5m and two deep borehole samples from 7m depth are collected. Sedimentologic analysis (granulometry, exoscopy, heavy minerals, X-RAY diffractometry) suggest that the actual sedimentation conditions which are relatively calm, permitted the deposition of mud and sandy mud. This calm environment was followed up by a high energy environment which led to the deposition of coarse sands. The sands essentially originated from the neighbouring “Continental terminal” beds and were deposited before the nouakchottian transgression whose maximum was attained about 5700 years. The accumulation of vegetal materials in this mangrove surrounding at the edge of the lake within the margino-littoral environment was probably related to some exceptional events which disturbed the environmental conditions as well as the processes of sedimentation and hydrology. The emergence in anaerobic surrounding and neotectonic movements in relation with subsidence and epeirogenesis favour the evolution of vegetation and the formation of peat.