Semi-enclosed Environment Research Articles

Characteristics of the Temperature and Humidity Variations of Burial-Type Stone Relics and a Fitting Model

Burial stone relics remain in a humid, semi-enclosed environment for long periods, and temperature and humidity variations can cause deterioration acceleration. Yang Can’s tomb was selected as the research object, and field monitoring and simulations were performed to investigate the characteristics of temperature and humidity variations, after which the simulation results were evaluated. The monitoring results showed that solar radiation, rainfall, wind speed, and depth of entry are important factors affecting the variation in the temperature and humidity of burial stone relics. The temperature outside the chamber is greatly affected by seasonal variations, while the humidity inside the chamber is influenced by seasonal variations, so appropriate measures should be implemented inside and outside the chamber during different seasons to alleviate deterioration. On the basis of the above analysis, a temperature and humidity model for the interior chamber of burial stone relics was established in COMSOL software 5.6, combined with a porous medium heat transfer model and computational fluid dynamics (CFD) model. The temperature and humidity inside the chamber can be calculated by the temperature and humidity outside the chamber. This study provides data support for hydrothermal, condensation and other related studies of burial stone relics.

Holobiont dysbiosis or acclimatation? Shift in the microbial taxonomic diversity and functional composition of a cosmopolitan sponge subjected to chronic pollution in a Patagonian bay.

Dysbiosis and acclimatization are two starkly opposing outcomes of altered holobiont associations in response to environmental pollution. This study assesses whether shifts in microbial taxonomic composition and functional profiles of the cosmopolitan sponge Hymeniacidon perlevis indicate dysbiotic or acclimatized responses to water pollution. To do so, sponge and water samples were collected in a semi-enclosed environment (San Antonio Bay, Patagonia, Argentina) from variably polluted sites (i.e., eutrophication, heavy metal contamination). We found significant differences in the microbiome of H. perlevis with respect to the pollution history of the sites. Several indicators suggested that acclimatization, rather than dysbiosis, explained the microbiome response to higher pollution: 1) the distinction of the sponge microbiome from the water microbiome; 2) low similarity between the sponge and water microbiomes at the most polluted site; 3) the change in microbiome composition between sponges from the different sites; 4) a high similarity in the microbiome among sponge individuals within sites; 5) a similar ratio of common sponge microbes to opportunistic microbes between sponges at the most and least polluted sites; and 6) a distinctive functional profile of the sponge microbiome at the most polluted site. This profile indicated a more expansive metabolic repertoire, including the degradation of pollutants and the biosynthesis of secondary metabolites, suggesting a relevant role of these microbial communities in the adaptation of the holobiont to organic pollution. Our results shed light on the rearrangement of the H. perlevis microbiome that could allow it to successfully colonize sites with high anthropogenic impact while resisting dysbiosis.

Numerical evaluation of the use of vegetation as a shelterbelt for enhancing the wind and thermal comfort in peripheral and lateral-type skygardens in highrise buildings

Skygardens or skycourts are a unique architectural intervention in the built environment, enhancing the social, economic, and environmental values of the building. It allows occupants to connect and experience outdoor freshness within a semi-enclosed environment. However, skygardens located on a highrise building may generate intense wind gusts, endangering the safety of occupants. Using a validated computational fluid dynamics model, this study investigates the potential of various vegetative barriers or shelterbelts in attenuating the high wind speeds encountered in such spaces and the impact on wind and thermal comfort. Three skygarden configurations were investigated with and without vegetative barriers, simplified and modelled as porous zones, and their effect was studied on the velocity and temperature profile at the occupants’ level. The results indicate that while hedges and trees can offer resistance to airflow, trees provide higher temperature reduction. However, a combination of vegetative and geometrical barriers provides the most optimal condition in the skygarden. The study has identified the importance of assessing wind attenuation characteristics of tree plantations on highrise skygarden, and the results can be used in designing intervention strategies. Moreover, vegetation can attenuate pollutants and mitigate poor air quality by surface deposition, and future studies should investigate in that direction.

Strandings in St Vincent Gulf Bioregion, South Australia: 12-Year Study Monitors Biology and Pathology of Cetaceans

The semi-enclosed environment of the St Vincent Gulf Bioregion and its fauna are impacted by many human activities. Long-term monitoring of cetaceans is vital. Records of collected specimens (173) and those not examined by the South Australian Museum (98 non-specimens) from 2009–2020 were analyzed. Necropsies were carried out on most carcasses using gross, histopathological, and diagnostic assessment of pathogens, organs, and skin lesions. The relative age and circumstance of death were assigned. Baleen whales (five species) and odontocetes (eight species) were studied. Indo-Pacific bottlenose dolphins (Tursiops aduncus) and common dolphins (Delphinus delphis) were frequently recorded and analyzed in detail. Anthropogenic cases were prevalent (21%). Many dolphins (62%) were immature males. Disease (73%) was the most frequently recorded circumstance of death. The most common pathological change was inflammatory disease, including infectious pneumonia. In Indo-Pacific bottlenose dolphins, infectious disease was more prevalent in the greater St Vincent Gulf Bioregion than in the Adelaide Dolphin Sanctuary. Microbe testing confirmed 32 species of bacteria, 2 fungi, and 1 virus. Nematodes and trematodes were recorded throughout the study, sometimes in association with microbes. Toxoplasma gondii was observed in an Indo-Pacific bottlenose dolphin. Severe traumatic injury was recorded in many dolphins, including anthropogenic cases. A tumor (leiomyoma) was described from a single common dolphin. This study provides an important baseline for the future monitoring of emerging infectious and chronic diseases, and anthropogenic threats in the region.

Assessment of the physical impact of a short-term dredging operation on a semi-enclosed environment: South Euboean Gulf, Greece.

The potential influence of short-period (May-June 2012) dredging activities (for the installation of a submarine gas pipeline) on physical properties of the marine environment of two shallow-water sites in the Aliveri and Varnavas areas of South Euboean Gulf (Greece) has been evaluated. During the dredging operation in Varnavas, the induced dredge plume traveled up to ~ 750m from the shoreline, featured by light attenuation coefficient (cp) maxima of 4.01-4.61m-1 and suspended particulate matter (SPM) concentrations up to 6.01mgL-1. After dredging the previous parameters reduced to the ambient seawater condition, ~ 0.45m-1 and < 2.8mgL-1 on average, respectively. Likewise in Aliveri, the dredging-associated sediment plume drifted offshore up to ~ 400m from the shoreline, characterized by cp maxima of 2.11-4.86m-1 and SPM concentrations up to 13.07mgL-1. After the completion of the excavation and trenching activities, the cp and SPM values were restored to the pre-disturbance condition, ~ 0.6m-1 and < 2.2mgL-1 on average, respectively. The migration of the dredge plume in both dredging sites was accomplished through the formation of intermediate and benthic nepheloid layers, whose development and evolution were governed by seawater stratification and flow regime. The dredging-derived SPM levels appeared to increase within a distance of no more than 300m from the shoreline (near-field zone). Based on data from the literature, this SPM enhancement together with the deposition of a post-dredging residual mud veneer in the near-field zone could deteriorate local marine biota, but in a reversible way.

Quantitative evaluation of in-situ bioremediation of compound pollution of oil and heavy metal in sediments from the Bohai Sea, China

Owing to the semi-enclosed environment of the Bohai Sea, the ecological effects caused by an oil spill would be significant. A typical in- situ bioremediation engineering project for of oil-spilled marine sediments was performed in the Bohai Sea and a quantitative assessment of the ecological restoration was performed. The bioremediation efficiencies of n-alkane and PAHs in the sediment are 32.84 ± 21.66% and 50.42 ± 17.49% after 70 days of bioremediation, and 60.99 ± 10.14% and 68.01 ± 18.60% after 210 days, respectively. After 210 days of bioremediation, the degradation rates of two- to three ring PAHs and four-ring PAHs are 84.44 ± 23.03% and 26.62 ± 43.76%, respectively. In addition, the concentrations of the heavy metals first increased by 6.00% due to oil spill degradation and release, and then decreased by 72.60% with the degradation of oil caused by bioremediation or vertical migration. According to the continuous tracking monitoring, the composition of the microbial community in the restored area was similar to that in the control area and the clean area in Bohai Sea after 210 days of bioremediation. These results may provide some theoretical and scientific data to understand the degradation mechanism and assessing the ecological remediation efficiency for oil spills in open sea areas.

Vertical variation in Vibrio community composition in Sansha Yongle Blue Hole and its ability to degrade macromolecules

With the advantages of wide distribution, fast growth, and broad metabolic spectrum to organic carbon compounds, Vibrio may play an important role in organic carbon cycling. However, the ecological roles of Vibrio in many marine environments have not been explored. Here, the world’s deepest ‘blue hole’, the Sansha Yongle Blue Hole (SYBH) in the South China Sea, which is a geographically semi-enclosed environment featuring unique chemical characters, was investigated. The abundance, diversity and carbon source utilization capability of Vibrio were studied by quantification and high-throughput sequencing of Vibrio specific 16S rRNA genes and cultivation methods. The abundance of Vibrio in water column of the SYBH ranged from 3.78 × 104 to 7.35 × 106 16S rRNA gene copies L−1. Free-living Vibrio was more abundant than particle-associated Vibrio (~ 1.20 × 106 versus~ 2.68 × 105 gene copies L−1), indicating that Vibrio prefers a free-living life style. The Vibrio assemblages showed clear vertical stratification and could be divided into three groups: aerobic-transition, middle anaerobic and bottom anaerobic zones. Dissolved oxygen (DO), temperature, pH and salinity were the main environmental factors affecting the abundance and community composition. Cultivated Vibrio demonstrated a degrading capability to various macromolecular substrates, including starch, Tween 20/40/80, DNA, gelatin, alginate, casein, chitin, lecithin, κ-carrageenan, mannan, xylan and hyaluronic acid. This suggests that Vibrio could produce a variety of highly active extracellular enzymes. Our study provides new insights into the distribution pattern and possible role in carbon cycle of Vibrio in the unique environment of a ‘blue hole’.

Shallow sedimentation of Natal shelf and coastal erosion implications, NE Brazil

High-resolution seismic stratigraphic analysis to reconstruct the depositional history of the inner shelf Holocene successions was performed on the northeastern Brazilian, adjacent to Natal City. Boomer seismic data was collected between the coastline up to ~ 15-m water depth. Three seismic units and three seismic surfaces were observed with regional significance and low lateral variability. They represent the transgressive to highstand deposits lying on the Pleistocene/Holocene boundary surface S1—older, regional, and the irregular unconformity at ~ 35 m, forming a semi-enclosed environment near the coast. The basal unit (U1) is related to a moderate/high-energy environment and grade upward to units (U2 and U3) of lower energy conditions and thin thickness that decrease seaward with large through near coast on the west. Above this surface, chaotic and parallel internal configurations represent unit U1 that limited at the top by S2. The ravinement surface S2 at ~ 18 m reveals wave-tide influence in a very shallow inner shelf, which controlled the accommodation space and sediment transport. Unit U2 fills the scours with onlapping terminations over S2. The shallowest surface (S3) occurs at ~ 12 m below modern sea level probably associated with the maximum flooding surface underlying the U3 with dominant aggradation character in parallel/wavy configuration. U1 represents a shallow marine environment with a greater sediment supply controlled mainly by the water depth during the initial transgressive shelf inundation. The lower sediment accumulation of U2 and U3 indicates a decreasing of sediment supply, higher sediment transport or higher rates of erosion in shallow marine environments.

Depositional evolution of sediment drifts inside intra-slope basins on the lower southeastern slope of the Dongsha Islands (South China Sea) and their paleoceanographic implications

Confined drifts generally contain abundant paleoceanographic information. The lower southeastern slope of the Dongsha Islands, South China Sea, was partly disassembled into several intra-slope basins by igneous bodies formed during the post-spreading process. Based on a series of high-resolution, two-dimensional seismic profiles, this study presents seismic evidence of sediment drifts inside several intra-slope basins at present water depths between approximately 2100 and 2800 m. The main discontinuities in the study area since the middle Miocene were carefully correlated with nearby seismic lines reported by previous studies. Moreover, their accurate ages were determined according to the dating results of the China National Offshore Oil Corporation with microfossil combinations. From 15.97 to 7.16 Ma, sheeted drifts were formed near the obstacles, indicating fairly low-velocity bottom currents. Subsequently, low-relief mounded drifts and associated small-scale moats were formed along the obstacles (7.16–5.33 Ma), showing that bottom currents were relatively strong. From 5.33 Ma onwards, high-relief mounded drifts and associated large-scale moats prevailed, formed by intensified bottom currents. Additionally, high-relief mounded drifts associated with large-scale moats occurred near the northern obstacle, and low-relief mounded drifts and associated small-scale moats were only formed near the southern obstacle in the largest intra-slope basin. In contrast, in the narrowest intra-slope basin, high-relief mounded drifts were confined by large-scale moats at the foot of both obstacles. This stark difference is attributed to the lateral variation of bottom current intensities caused by the variable widths of the intra-slope basins, resulting in different confining effects on bottom currents. The changes recorded in the sediment drifts reveal that the sedimentary succession should be subdivided into three phases: the onset stage (15.97–7.16 Ma), the slow growth stage (7.16–5.33 Ma), and the rapid growth stage (since 5.33 Ma). The gradual intensification of bottom currents is closely related to the influx of the Northern Pacific Deep Water since ~ 7 Ma and the gradual formation of the semi-enclosed environment due to the eastward subduction of the South China Sea basin into the Philippine plate since the late Miocene.

Mineralogy and Geochemistry of Limonite as a Weathering Product of Ilvaite in the Yeshan Iron Deposit, Tongling, China

AbstractLimonite is mainly derived from weathering of Fe sulfide, iron-bearing carbonate, or silicate minerals. The weathering of Fe sulfide or carbonate minerals to yield limonite from the Tongling mineralization cluster has been studied extensively. Knowledge of the mineralogical and geochemical characteristics of the limonite from weathering of Fe-bearing silicate minerals is still incomplete, however. To address this, black limonite containing ilvaite (a silicate mineral) found in Yeshan iron deposit, Tongling, China, was studied using mineralogical and chemical analysis. The mineralogical characteristics indicated that Mn goethite was present as nano-granular (&lt;15 nm) or acicular (50–100 nm long, ~10 nm wide, i.e. high length/width ratio) crystals with low crystallinity. Groutite, ramsdellite, and pyrolusite were identified in the limonite as ~5 nm nanoparticles, and coated on the goethite surface. Amorphous Fe-Mn phases and silica were highly developed in the limonite studied. Ilvaite crystals showed idiomorphic granular morphology and were replaced by Fe-Mn oxides/hydroxides; pyrite was also present as inclusions within the ilvaite and the ilvaite structural formula calculated was Ca1.04(Fe1.57Mn0.31Mg0.04)(Fe1.09Al0.01)[Si1.95O]O(OH). According to the relatively high CuO and ZnO values and the low Al2O3 value in the black limonite, the negative correlations between (Fe2O3+MnO) and (CuO+ZnO+BaO), (Fe2O3+MnO) and Al2O3, high Mn and Si contents, and the characteristics of the textural relationships and compositions between the black limonite and ilvaite, a semi-enclosed environment with acidic to weakly alkaline conditions was deduced; ilvaite was found to be responsible for the formation and enrichment of limonite.

A GIS-based approach for detecting pollution sources and bioavailability of metals in coastal and marine sediments of Chabahar Bay, SE Iran

Chabahar Bay in SE of Iran is a shallow semi-enclosed environment affected by anthropogenic activities. In this paper, 19 sediment samples were collected and concentration of selected metals (Cu, Pb, Zn, Cd, Ni, Cr, Co, V and Fe) was determined using ICP-MS analytical method. Sediment samples from five stations were also selected for sequential extraction analysis and concentration of metals in each fraction was determined using ICP-OES. In order to investigate the environmental quality of Chabahar Bay, geographic information system (GIS) along with geochemical data, environmental indices and statistical analyses were used. Calculated contamination degree (Cd) revealed that most contaminated stations (Ch3, S1 and S3) are located SE of Chabahar Bay and contamination decreases in a NW direction. The S9 station, west of the bay, is also contaminated. High organic matter (OM) content in the sediments is most likely the result of fuel and sewage discharge from fishing vessels along with discharge of fishing leftovers. Significant correlation coefficient among OM, Fe, Cu, Pb, Zn and Cd seemingly reflects the importance of the role that OM and Fe oxy-hydroxides play in the metals mobility. The results of hierarchical cluster analysis (HCA), computed correlation coefficient and sequential extraction analysis suggest that Cu, Pb, Zn and Cd probably come from antifouling and sea vessel paints, while Ni, Cr, Co, V and Fe are most likely contributed by ophiolitic formations located north of the bay and/or deep sea sediments. Average individual contamination factors (ICFs) indicated that the highest health hazard from the bay is posed by Cu, Pb and Zn.

The main controlling factors and developmental models of Oligocene source rocks in the Qiongdongnan Basin, northern South China Sea

Coals developed in the Oligocene Yacheng and Lingshui formations in the Qiongdongnan Basin have high organic matter abundance, and the dark mudstones in the two formations have reached a good source rock standard but with strong heterogeneity. Through the analysis of trace elements, organic macerals and biomarkers, it is indicated that plankton has made little contribution to Oligocene source rocks compared with the terrestrial higher plants. The organic matter preservation depends on hydrodynamics and the redox environment, and the former is the major factor in the study area. During the sedimentary period of the Yacheng Formation, tidal fiats were developed in the central uplift zone, where the hydrodynamic conditions were weak and the input of terrestrial organic matter was abundant. So the Yacheng Salient of the central uplift zone is the most favorable area for the development of source rocks, followed by the central depression zone. During the sedimentary period of the Lingshui Formation, the organic matter input was sufficient in the central depression zone due to multiple sources of sediments. The semi-enclosed environment was favorable for organic matter accumulation, so high quality source rocks could be easily formed in this area, followed by the Yacheng salient of central uplift zone. Source rocks were less developed in the northern depression zone owing to poor preservation conditions.

Urban street canyons: Coupling dynamics, chemistry and within-canyon chemical processing of emissions

Street canyons, formed by rows of buildings in urban environments, are associated with high levels of atmospheric pollutants emitted primarily from vehicles, and substantial human exposure. The street canyon forms a semi-enclosed environment, within which emissions may be entrained in a re-circulatory system; chemical processing of emitted compounds alters the composition of the air vented to the overlying boundary layer, compared with the primary emissions. As the prevailing atmospheric chemistry is highly non-linear, and the canyon mixing and predominant chemical reaction timescales are comparable, the combined impacts of dynamics and chemistry must be considered to quantify these effects. Here we report a model study of the coupled impacts of dynamical and chemical processing upon the atmospheric composition in a street canyon environment, to assess the impacts upon air pollutant levels within the canyon, and to quantify the extent to which within-canyon chemical processing alters the composition of canyon outflow, in comparison to the primary emissions within the canyon. A new model for the simulation of street canyon atmospheric chemical processing has been developed, by integrating an existing Large-Eddy Simulation (LES) dynamical model of canyon atmospheric motion with a detailed chemical reaction mechanism, a Reduced Chemical Scheme (RCS) comprising 51 chemical species and 136 reactions, based upon a subset of the Master Chemical Mechanism (MCM). The combined LES–RCS model is used to investigate the combined effects of mixing and chemical processing upon air quality within an idealised street canyon. The effect of the combination of dynamical (segregation) and chemical effects is determined by comparing the outputs of the full LES–RCS canyon model with those obtained when representing the canyon as a zero-dimensional box model (i.e. assuming mixing is complete and instantaneous). The LES–RCS approach predicts lower (canyon-averaged) levels of NOx, OH and HO2, but higher levels of O3, compared with the box model run under identical chemical and emissions conditions. When considering the level of chemical detail implemented, segregation effects were found to reduce the error introduced by simplifying the reaction mechanism. Chemical processing of emissions within the canyon leads to a significant increase in the Ox flux from the canyon into the overlying boundary layer, relative to primary emissions, for the idealised case considered here. These results demonstrate that within-canyon atmospheric chemical processing can substantially alter the concentrations of pollutants injected into the urban canopy layer, compared with the raw emission rates within the street canyon. The extent to which these effects occur is likely to be dependent upon the nature of the domain (canyon aspect ratio), prevailing meteorology and emission/pollution scenario considered.

Ecosystem modeling: Towards the development of a management tool for a marine coastal system: Part I: General circulation, hydrological and dynamical structure

The semi-enclosed environment of Pagasitikos Gulf was the object of a holistic study during 1998–1999 following the appearance of mucilaginous events during summer. A major part of the INSEA project was the development and implementation of a coupled modeling system capable of reproducing all the major characteristics both in physical and biological environments. In the present work the hydrodynamic model based on the Princeton Ocean Model (POM) code is presented while the functioning of Pagasitikos Gulf is analyzed through the assessment of model results. Model results indicate intense seasonal variability with moderate flow patterns and substantial horizontal and vertical gradients. The main known climatological circulation features are found to be reproduced quite well by the model with a rich eddy field controlled by surface buoyancy and momentum fluxes. The ultimate goal is the development of a future operational forecasting system encompassing a detailed description of the ecosystem processes and advanced data assimilation techniques.

Elasmobranchs of the Persian (Arabian) Gulf: ecology, human aspects and research priorities for their improved management

Given widespread concern about the status of elasmobranch fishes globally, information on this group in the Persian (Arabian) Gulf is reviewed comprehensively for the first time. The Arabian region may be of overlooked significance to elasmobranch biogeography, and the environmentally unique Gulf has some highly distinctive elements of biodiversity: an endemic and critically endangered rajid skate, a rarely recorded carcharhinid shark, and preliminary molecular studies which indicate intriguing levels of distinctness from conspecifics elsewhere in the Indo-Pacific. Elasmobranchs also have a long history of association with, and exploitation by, humans around the Gulf. Despite this, Gulf elasmobranchs have been poorly researched, probably due to their low esteem as food. Information is scattered through a variety of literature, and only a handful of published works have been primarily concerned with aspects relevant to management. Key areas of concern include large reported landings by Iran; the export of fins to east Asian markets (particularly through the United Arab Emirates); potentially increasing demand for elasmobranchs for pharmaceutical products and human consumption; a reported change in elasmobranch community structure along the Iranian coast; and major degradation of the Gulf’s shallow, semi-enclosed environment. Priorities for research in the near future should include: resolution of taxonomic issues; species-level monitoring and reporting of fisheries landings by all Gulf states (including the species, pathways and fisheries involved in the fin trade locally); establishing the degree of connectivity of Gulf populations to those in adjacent waterbodies; and identification of key spatio-temporal sensitivities.

A synthesis of morphological evolutions and Holocene stratigraphy of a wave-dominated estuary: The Arcachon lagoon, SW France

This work presents the first synthesis of secular to millenary morphological evolutions and stratigraphy of a wave-dominated estuary, the Arcachon lagoon, from a combination of unpublished bathymetric maps (1865 and 2001), core results and high-resolution seismic profiles recorded for the first time in this lagoon. The Arcachon lagoon is located on the Atlantic coast of France, facing the wave-dominated shelf of the Bay of Biscay. It is a mesotidal semi-enclosed environment of about 160 km 2. The sediment budget of the Arcachon lagoon was computed by subtracting the 1865 bathymetric map from that of 2001. The computed volume difference is low (−9.9±35×10 6 m 3 in 136 yrs) and is the result of the balance between erosion and accretion that occurs within tidal channels and tidal flats, respectively. This morphological evolution pattern is explained by low sediment supply and also by the tidal distortion resulting from the morphology of the lagoon. Deep channels connected to the inlet are dominated by ebb currents inducing erosion. Tidal flats and transverse channels display weak or flood-dominated tidal currents leading to the deposition of silts. The areas of tidal flat siltation locally correlate with the presence of oyster farms, suggesting the influence of Man on the lagoon sediment-fill. Transverse channel-infill is related to weak tidal currents resulting from the hydraulically inefficient orientation of these channels which served as an ancient drainage network. Evidence for tidal channel-infill and channel abandonment are also provided by seismic profiling and cores. The upper stratigraphic succession of the lagoon (about 10 m thick) includes four main stratigraphic units dominated by channel-fills. The two lower units (around 7500–2800 yrs BP) display tabular-shape sandy channels interpreted to be records of the open estuarine phase of the Arcachon lagoon. The two upper units (around 2800 yrs BP to present-day) display U-shaped mixed sand-and-mud channel-fills interpreted to be records of the closure of the lagoon. Given that the basal estuarine units are transgressive and the upper lagoonal units are regressive, the main stratigraphic change at around 2800 yrs BP is interpreted as being the maximum flooding surface (MFS). This late MFS is explained by the low sediment supply. It is proposed that the transition from the estuarine to the lagoonal phase is related to the development of the Cap-Ferret spit in response to an increase in the ratio between wave power to tide power. This change in wave-to-tide ratio may be triggered by wave power increase following the Subboreal/Subatlantic climate instability or a decrease in tide power following a decrease in tidal prism related to the lagoon sediment-fill. Thus, the evolution of the Arcachon lagoon over the last millenaries was mainly controlled by its spit development, leading to a wave-dominated estuary in terms of its geomorphology. Once it was partially closed, extensive mud flats developed in the lagoon which became ebb-dominated.

Growth of Mediterranean reef of Cladocora caespitosa (L.) in the Late Quaternary and climate inferences

A sclerochronological analysis was performed on Cladocora caespitosa corals from Late Pleistocene terraces near Taranto (Apulia, Italy) to reconstruct the main palaeoenvironmental conditions at the time of their growth. The fossil corallites were sampled in the Santa Teresiola uplifted bank or ‘open frame reef’ attributed to the Last Interglacial Period. The typical, annual growth pattern of the temperate coral with two alternate high- and low-density bands allowed the reconstruction of two multidecadal growth curves of 61 and 95 years. Trend analysis showed oscillations in annual growth rates similar to those observed in recent, living colonies sampled along a north–south latitudinal transect around the Italian and Croatian coasts as far as Tunisia. The mean growth rate of the fossil reef (4.2 ± 2 mm year−1) is comparable to those measured on colonies living in the coldest part of the Mediterranean Sea. The comparison with data from living Croatian banks shows how fossil C. caespitosa lived in a semi-enclosed environment characterized by seasonal inputs of fresh, cold water. The greatest variations in decadal growth rates of the fossil colonies support the hypothesis of larger amplitude of the seasonal cycles in the past. The death of the fossil bank was probably due to a sudden alluvial input that suffocated the reef with a great amount of mud. Another possible cause of the death of the bank was a prolonged increase in summer temperatures that caused colony mortality and enhanced algal colonization.

Study of the Flow Structure of A Thermal Plume Evolving in an Unlimited and in A Semi-Enclosed Environment

The basic objective of this study was to better knowledge the fine flow structure of thermal plume created by a heated disk, evolving in an unlimited and in a semi-enclosed environment. The flow visualization and the study of the temperature fluctuations spectrum show clearly a considerable change of the turbulent structure of the internal flow in comparison with the free plume. This difference is especially caused by the thermosiphon effect. Indeed, this study shows that the thermosiphon affects the flow structure plume and causes the appearance of a supplementary zone, just at the system entrance, that is added to the two classic zones concerning the free plume, mentioned in the previous works. This zone is characterised by two symmetrical rotating rolls created in the vicinity to the hot source. The energy spectrum study permits to obtain certain spectral power laws, which characterize the energy transfer between the structures that are present in the flow. In fact, three qualitatively different regions were identified: first, a production region, secondly, a region with behavior as per n-3 associated with a buoyancy region and; finally, a dissipation region associated with an n-7 law. The n-1 Tchen low is observed for the free plume in the large frequency region. The existence of the n-1 region is related to an important turbulent production. These spectral regions characterize the energy transfers mechanisms among the length scales of flow investigated here.

Predator-prey relationships and trophic level reconstruction in a fossil fish community

All living species occupy an ecological niche, and are positioned within a trophic hierarchy. Extinct organisms presumably held similar behavioral and coevolutionary characteristics in the past, and were susceptible to the same kinds of natural ecological pressures operating today. Paleoecological investigations are limited by the incompleteness of the fossil record, and particularly by a lack of behavioral data that are so fundamental to ecological studies of living communities and habitats. Opportunities to examine the coevolutionary structure of ancient communities from empirical data are extremely rare. One such opportunity is provided by the Lower Cretaceous Santana Formation of north-eastern Brazil, a series of richly fossiliferous strata approximately 110 million years old. Many fossil fishes from the Santana Formation contain identifiable prey, including decapod crustaceans and fishes. A trophic hierarchy of these organisms is reconstructed here, and their ecological relationships are discussed. Comparison is made with a similar fish fauna from the Upper Jurassic Solnhofen Limestone of Germany. Low-level, intermediate and high-level predators are identified in each fauna. Predator-prey relationships in the Santana fauna are strongly hierarchical, and are more focussed at the intermediate predator level than in Solnhofen. Comparison with a model of predator-prey relationships between fishes and benthic fauna of the Baltic Sea (which like the Araripe Basin represents a semi-enclosed environment) suggests that heavy predation on teleosts such asRhacolepis, occupying an intermediate trophic level, may have permitted benthic decapods to proliferate and exclude other benthic organisms. Less intense predation on fishes at the intermediate trophic level would allow their numbers to increase, thereby increasing the intensity of predation on the benthos at the base of the trophic hierarchy.

Impinging cooling of a high temperature flat surface by multiple two-dimensional air jets.

Two-dimensional impinging jets in line have been used for many industrial applications for cooling and heating, but the effectiveness of the heat transfer augmentation has not been well established. The purpose of this study is to clarify the augmented heat transfer performance of impinging air jets in line by means of providing roughnesses on a heat transfer surface. The optimum position of the roughnesses are studied experimentally for the jet Reynolds number of 1×104 when the jet-to-plate spacing is equal to the jet slot width. It is clarified that, even though of no roughness the two jets increases the total heat transfer performance by about 1.4 times that of one jet without roughness regardless of the jet spacing, under the optimum condition the average surface heat transfer coefficient in a semi-enclosed environment increases by about 2.30 times that of one jet without roughness.