Water-filled Basin Research Articles

Participation of Local Communities in the Management of Post-Mine Areas in Cities

The management of post-mining reservoirs as part of urban blue infrastructure is linked to the implementation of pro-environmental policies at different levels (from local–municipal to European). Local communities, as beneficiaries of measures taken by city authorities, recognise the need for active participation in decision-making processes. They engage in making decisions on blue spaces in urban areas. These include public and natural watercourses and their surroundings, but also water-filled basins of various origins, including post-mining pits. This paper strives to answer how local communities are involved in activities for developing and managing post-mine areas filled with water within city limits. The methods used (including field observation, spatial analyses, and desk research) allowed us to classify post-mining pits according to their functions and the degree of social participation in their development process. The analysed post-mining pits were divided into three groups. The first group consisted of pit reservoirs transformed with the participation of local inhabitants into recreational grounds. The second comprised reservoirs transformed under local zoning plans (with residents consulted) expected to ultimately prop up the city’s green infrastructure. In turn, the third group consists of quasi-natural reservoirs deemed natural enclaves by city residents. The environmental analysis showed that pits were naturalised. One of them was subject to legal protection on account of biodiversity. Post-mine areas in Bydgoszcz play an important environmental role, and some are integral recreational sites, e.g., the Balaton reservoir. They materially affect the inhabitants’ daily contact with nature, which improves life quality.

P941Acute effects of electronic hookah smoking on endothelial function, inflammation and oxidative stress

Abstract Background Electronic nicotine delivery systems (ENDS) are a new rapidly growing global epidemic. More recently, electronic (e-) hookahs, have increased in popularity in the United States, with the greatest uptake by young female adults, who endorse marketing claims that these products are safer alternatives to traditional hookah tobacco smoking. Unlike other ENDS such as e-cigarettes, e-hookah bowls are used through traditional waterpipes, allowing the vapor–containing aerosolized nicotine, propylene glycol, glycerin, and flavorings–to pass through a water-filled basin, before it is inhaled through the user's mouth. Contributing to e-hookah bowls' popularity is the belief that e-hookah flavored smoke is detoxified as it passes through the water-filled basin, rendering e-hookah a safer tobacco alternative. However, an e-hookah bowl delivers flavored nicotine by creating a vapor of fine (<2.5 μm) and ultrafine particles (<0.1 μm) that could induce vascular toxicity. Purpose To test the acute effect of electronic hookah smoking on endothelial function, inflammation and oxidative stress. Methods In 17 healthy young adults who smoke hookah but not cigarettes (age 26±1 years, mean±SE; BMI 23.8±0.7 kg-m2), we measured brachial artery flow-mediated dilation (FMD) before and after a 30-minute e-hookah bowl smoking. To test for inflammatory mediation, pro-inflammatory cytokines hsCRP, TNF-α, and fibrinogen were collected before and after smoking. To test for oxidative stress mediation, on a separate day, the acute effect of e-hookah smoking on FMD was examined after intravenous infusion of Vitamin C, an effective antioxidant. Plasma nicotine levels were collected before and after the smoking session. The same measurements were performed before and after a subset of subjects (n=8) performed a sham-smoking control study. Results E-hookah smoking, which markedly increased plasma nicotine (Δ plasma nicotine: +6.07±1.87, p=0.018) and mean arterial pressure (Δ mean arterial pressure: +12±2 mm Hg, p<0.001), acutely decreased FMD from 8.04±0.68 to 6.14±0.52%Δ, p<0.001, indicating impaired endothelial function. While fibrinogen and TNF-α levels increased from 225.31±7.41 to 236.77±9.79, p=0.026 and from 0.80±0.04 to 0.87±0.05, p=0.036, respectively, hsCRP did not change (P=ns). Vitamin C administration prevented the acute FMD impairment by e-hookah smoking (P=ns). All parameters were unchanged during sham-control studies. Conclusions In contrast to the widespread popular belief that e-hookah is safe, the data herein show that each e-hookah session constitutes a potent vascular toxin acutely impairing endothelial function and inducing an inflammatory state. That the acute impairment in FMD with electronic hookah is restored with administration of the potent antioxidant Vitamin C suggest that elevated vascular oxidative stress as a key mechanism involved. These new data provide evidence to counter claims that e-hookah is a safer tobacco alternative. Acknowledgement/Funding This work was funded by the National Institutes of Health, National Heart, Lung, and Blood Institute 1R21HL145002-01 to MRH.

Hormotilopsis gelatinosa (Chlorophyceae, Chlorophyta), a Rare Species Newly Discovered in Bulgaria

Hormotilopsis gelatinosa (Chlorophyceae, Chlorophyta) is a very rare alga that has so far been found only in seven places around the world. Recently, it was discovered in two water-filled basins in Bulgaria. Based on observations made on the abundant material collected in situ, a detailed description of the species is presented.

Stratigraphy and mineralogy of Candor Mensa, West Candor Chasma, Mars: Insights into the geologic history of Valles Marineris

Candor Mensa, an interior layered deposit (ILD) in Valles Marineris, Mars, consists of two stratigraphically distinct units, the lower of which comprises the bulk of the mensa. This lower unit is approximately 5 km thick and composed of parallel layers, 4 to 14 m in thickness and associated with monohydrated sulfates. The lower unit is disconformably overlain by an upper unit composed of thinner (< 3 m) layers with diagnostic polyhydrated sulfate signatures. The original extent of proto-Candor Mensa and its lower unit included neighboring Baetis Mensa. We suggest that the source material for both units is airborne dust or ash but that the depositional environment for the units differs. First, the lower unit was deposited during the subsidence of an enclosed water-filled basin. This basin/lake could have been frozen periodically, with freeze-thaw episodes possibly linked to Martian obliquity cycles. Erosion, including the potential action of glaciers, was able to remove large volumes of material out of the basin during the tectonism that produced the current geometry of Valles Marineris. Deposition of the upper unit postdates this event and took place in the absence of standing water at high elevation. Groundwater or snowmelt may have provided the water required for sulfate formation and deposit induration. We conclude that the major break in sedimentation recorded by this ILD deposit coincides with linking of ancestral basins into the current geometry of Valles Marineris chasmata and that it was possible to form hydrated minerals after this event.

Development of a Gravid Trap for Collecting Live Malaria Vectors Anopheles gambiae s.l.

BackgroundEffective malaria vector control targeting indoor host-seeking mosquitoes has resulted in fewer vectors entering houses in many areas of sub-Saharan Africa, with the proportion of vectors outdoors becoming more important in the transmission of this disease. This study aimed to develop a gravid trap for the outdoor collection of the malaria vector Anopheles gambiae s.l. based on evaluation and modification of commercially available gravid traps.MethodsExperiments were implemented in an 80 m2 semi-field system where 200 gravid Anopheles gambiae s.s. were released nightly. The efficacy of the Box, CDC and Frommer updraft gravid traps was compared. The Box gravid trap was tested to determine if the presence of the trap over water and the trap’s sound affected catch size. Mosquitoes approaching the treatment were evaluated using electrocuting nets or detergents added to the water in the trap. Based on the results, a new gravid trap (OviART trap) that provided an open, unobstructed oviposition site was developed and evaluated.ResultsBox and CDC gravid traps collected similar numbers (relative rate (RR) 0.8, 95% confidence interval (CI) 0.6–1.2; p = 0.284), whereas the Frommer trap caught 70% fewer mosquitoes (RR 0.3, 95% CI 0.2–0.5; p < 0.001). The number of mosquitoes approaching the Box trap was significantly reduced when the trap was positioned over a water-filled basin compared to an open pond (RR 0.7 95% CI 0.6–0.7; p < 0.001). This effect was not due to the sound of the trap. Catch size increased by 60% (RR 1.6, 1.2–2.2; p = 0.001) with the new OviART trap.ConclusionGravid An. Gambiae s.s. females were visually deterred by the presence of the trapping device directly over the oviposition medium. Based on these investigations, an effective gravid trap was developed that provides open landing space for egg-laying Anopheles .

Transcatheter Valve Replacement: New concepts for Microsurgery inside the Heart

Transcatheter aortic valve implantation gained clinical relevance with an impressive and peerless power; however, the procedure induces unsolved complications such as paravalvular leakage, occlusion of coronary ostia, and vascular complications. The safe removal of bulky calcified valves will improve the outcome, well known through the open surgical procedure. In this article, a new stapler-based resection and implantation device as well as a new approach for valve isolation during normal heart cycle without extracorporeal circulation will be analyzed. First, a novel stapler-based instrument for transapical aortic valve replacement [removal and implantation; stapler-based aortic valve replacement (StapAVR)] was constructed and analyzed in an aortic debris model. Artificial aortic valves (N = 20), containing fluorescent granules to simulate the calcification, were placed into an aortic model in anatomical supine position (DP) and right-sided lateral position (RP). With the StapAVR, resection before implantation was performed in a water-filled basin. Black light was used for debris visualization. The procedures have been digitally recorded and analyzed due to procedural times, and the debris amount in thoracic side branches. Second, an enhanced prototype of the pulmonary valve isolation chamber (PVIC) was analyzed in porcine in vitro (n = 10) and in vivo models (n = 1). This PVIC contains a microaxial pump (Impella; Abiomed, Aachen, Germany) in the central bypass channel. It was deployed through the right ventricular wall. Once the PVIC was in place, the pump was started before isolating the valve. The complete hemodynamic monitoring was digitally recorded. The deployment of the StapAVR in the correct position and the valve resection time took a mean (SD) of 95.8 (19) seconds in DP and 90.1 (18) seconds in RP. Fluorescent debris was found: in the left coronary artery, 22% in DP and 7% in RP; in the ascending aorta, 0% in DP and 11% in RP; in the aortic bulbous, 5% in DP and 10% in RP; in the left ventricle, 8% in DP and 14% in RP; in the brachiocephalic trunk, 4% in DP and 9% in RP; and in the descending aorta, 46% in DP and 1% in RP. Consecutive valved stent implantation was performed without complications. The PVIC deployment time in vivo was 5 minutes, replacements included. The total valve isolation time was 21 minutes, with a mean (SD) bypass flow of 2.1 (0.4) L/min. The oxygen saturation showed a median of 91% (range, 83%-97%), and the median arterial blood pressure was 69 mm Hg (systolic; range, 47-120 mm Hg) and 40mm Hg (diastolic; range, 32-56 mm Hg) without the use of inotropes or vasopressors. Electrocardiogram confirmed sinus rhythm during isolation. The resection of the artificial valves followed by valved stent implantation was possible with the StapAVR. In vivo, the procedure will be carried out under rapid pacing and sudden vacuum; however, the results of this in vitro debris model underline the need for isolation or filter devices during transcatheter aortic valve implantation to avoid embolization. Secondly, the use of the pump-advanced PVIC showed stable heart function for 21 minutes under isolated pulmonary valve conditions. This time will be adequate to remove bulky calcifications and to implant a valved stent. Improvements of both prototypes are ongoing. Nevertheless, the presented concepts showed promising application possibilities in the future.

Reduced k-space acquisition to accelerate MR imaging of moving interventional instruments: a phantom study

The goal of this study was to investigate the impact of reduced k-space sampling rates on the visualization of a moving MR-compatible puncture needle and to demonstrate the feasibility of keyhole imaging in interventional magnetic resonance imaging (MRI). All experiments were performed in an open 1.0 Tesla MRI. MR images of a moving puncture needle were taken with different keyhole sampling rates from 15-100%, in 10% increments. The needle was submerged in a water-filled basin and was imaged in motion with a T1-weighted gradient-echo sequence with an initial acquisition rate of 1.4 s per image. An apparatus operated by a compressor unit enabled needle rotation and ensured reproducible needle movements. The median forward velocity of the needle tip was 2 cm/s. To evaluate the depiction of the needle, artifact diameter of the needle, contrast-to-noise ratio (CNR), and needle tip profiles (delineation) were measured. The needle position was determined with an longitudinal error of 3 mm and a transverse error of 0.8 mm with respect to the needle's orientation and the theoretically calculated trajectory. No significant correlation was found between the CNR and velocity. A reduction of k-space update rates caused neither a significant reduction of CNR nor a significant increase in artifact diameter or blurring of the needle profile. The application of keyhole imaging with update rates of greater than 15% is sufficient for the MR guidance of interventions with an signal-to-noise ratio >9 of the surrounding tissue and a target accuracy of >1 mm. Keyhole imaging can increase temporal resolution while ensuring unimpaired spatial resolution and image quality of the depicted instrument.

Task-Oriented Pain Management: A Patient's Perspective

"I'll tell your nurse." The wall speaker beeped off before I could respond to the person at the nurses' station. Frustrated, I yelled out my hospital room door, "You said that 20 minutes ago!" Having just had bilateral knee replacement surgery, my only access to the world beyond my hospital bed was the call button, but I expected this. During the preoperative patient education class that my family and I attended, we were told that the most important thing a postoperative patient could do would be to ask for help. Use a call button for even the slightest need, use ice packs as oft en as possible, and do not under any circumstances get up without help. Only a few days into rehabilitation I learned that if I needed something, it was going to take more than one push of the call button. Desperate for ice packs and a trip to the bathroom, I decided it was time to take matters into my own hands. There was a walker about three feet from my bed, just close enough for me to grab with the reaching stick provided by the occupational therapist. The question at this point wasn't whether or not I could make it to the bathroom. This wasn't the first time I had broken the rules and ventured past the confines of my bed alone, so I knew I could do it. The question was whether or not I'd make it to the bathroom in time. A nurse entered my room-the first response aft er four calls in 40 minutes- and helped me back into bed. "You know, you're not supposed to be walking around by yourself," the nurse advised as though I didn't know. On her way out, she asked if there was anything else I needed. Exhausted from a strenuous exodus to the restroom, I didn't remember until aft er she was gone: ice packs. My recent inpatient experience left me with a sense of inner conflict. As the daughter of a nurse, I had to try to reconcile what my mother taught me about nursing with what I experienced. "Nurses are a patient's number one advocate," Mom always said. "They are your eyes, ears, and voice when you are at your most vulnerable." The staff at the rehabilitation center ran a very tight ship. They had to; with few nurses on the unit and more than 30 patients screaming for pain medication, ice packs, and all the other needs, they were well trained to methodically provide care to the highest standards of a Magnet hospital. What I observed, however, is that when care is provided in the form of a regimented task list, stretching nurses far too thin, the patients suffer from the lack of compassion that comes from being treated like a checklist of responsibilities rather than a human being. Every day I awoke at five to the sound the curtain being drawn around my bed. A nurse had to take my vitals and draw my blood to check my Coumadin level. It was difficult to get back to sleep-the discomfort of two prosthetic joints made sleeping at all nearly impossible. The sound of clean towels and a water-filled basin dropping on my bed table roused me out of a lucid nap 2 hours later. To me, this was the first physical therapy session of the day. Getting myself up, bathing from a basin without spilling onto my sheets and reaching for my clothing was physically strenuous enough that by the time I was done, I needed a nap. My breakfast frequently got cold as it waited for me to finish my morning rituals. I wondered if my age had anything to do with the absence of assistance. I oft en heard the nursing staff comment on how unusually young 746B was, that 746B would probably recover faster than the other patients. They wondered what 746B did to need double knee replacement surgery before age 30. I wanted to scream, "746B has a name and needs help getting dressed!" Two different pain medications were administered every day: a controlledrelease drug given every 12 hours and a fast-acting narcotic given every 3 to 6 hours as needed. …

Preliminary biostratigraphy and 3D geometry of the Vouraikos Gilbert-type fan delta, Gulf of Corinth, Greece

Abstract Along the southern coast of the Gulf of Corinth, interactions between Pleistocene to Recent normal faults and a number of syn-rift Gilbert-type delta systems can be studied. These relationships are exemplified in the Vouraikos Gilbert delta, which has a complex internal sedimentary and structural geometry that was influenced by basin-forming and intra-deltaic planar and listric syn-sedimentary normal faults, as well as by later planar (second-order) extension faults. A thick alluvial succession, well exposed to the east of the Vouraikos delta, predates the delta system. Preliminary biostratigraphical (palynological) data indicate that the Vouraikos delta was deposited during the Early Pleistocene, and built out into a marine body of water, based on the presence of a newly observed shallow marine limestone, which is associated with distinctive coastal facies conglomerates and sandstones. Accommodation space for the >800 m thick Vouraikos delta was mainly created by up to 1000 m of vertical displacement on the north-dipping Pirgaki–Mamoussia Fault. The delta has a grossly concave-upward basal (diachronous) surface in transverse section, thought to be generated by the fixed location of the principal fluvial gravel input to the system. The largest foresets observed in the delta indicate building into a water-filled basin of 300–400 m depth, and a crudely radial form to the delta, shown by NW- and NE-inclined surfaces. The latest sediments of the delta are flat-lying topsets, which are overlain by thick, highly reddened soil sequences exposed in a number of plateaux. These predate the Late-Pleistocene marine terraces that incise the range front. To cite this article: F. Malartre et al., C. R. Geoscience 336 (2004).

Nonlinear capillary-gravity waves under an edge condition

The objective of this paper is to investigate the forced motion of nonlinear capillary-gravity waves in a waterfilled circular basin by a harmonic vibration applied to its side wall under Evans's or Hocking's edge condition at a contact line. The forcing frequency is near a resonance frequency under the classical edge condition of the basin. Two complex-amplitude equations for the excited eigenmode at the resonance frequency corresponding to these two edge conditions are derived. The solutions to these equations display quite different behavior and an edge condition indeed has a great influence on the excited surface waves.

The nutrient input by Harmattan dust to a forest ecosystem in Cote d'Ivoire, Africa.

During December and January, dry northeasterly surface winds (the Harmattan)distribute dust over West Africa. Rate of deposition and some chemical andphysical characteristics of Harmattan dust were measured in Tai NationalPark in the southwest corner of Cote d'Ivoire during the 1990–1991 dryseason. The dust deposition was estimated by the classical water-filled basinmethod and by using canopy drip to account for deposition on tree canopies.Contamination by local biotic debris in both, water-filled basin and canopydrip collectors, was corrected for by using Ti (which appears to be wholly ofatmospheric origin) as a reference element. Harmattan dust in Tai consistedmainly of kaolinitic silt finer than that collected in North Nigeria, closer tothe source area in the Chad basin. The estimates of seasonal deposition rateswere 33 to 47 kg ha-1 for the water-filled basin method andaround 80 kg ha-1 for the canopy drip method. The higher valuein canopy drip was in agreement with expected higher deposition of fine duston the canopies than on a water surface, and was therefore considered morereliable to estimate nutrient inputs by Harmattan dust deposition. The seasonalnutrient input by dust was thus estimated to be 0.11 kg ha-1for P, 2.5 kg ha-1 for K, 3.5 kg ha-1 for Caand 0.4 kg ha-1 for Mg.

Comment on “Mars as the parent body of the CI carbonaceous chondrites” by J.E. Brandenburg

Geological and chemical data refute a martian origin for the CI carbonaceous chondrites.I. IntroductionBrandenburg [1996] hypothesizes that the CI carbonaceouschondrites originated as water-deposited sediments on Mars,and seeks to show that CIs and recognized martian materials areso similar that a common origin is likely. However, that paperdoes not reconcile its hypothesis with available chemical andgeological data on the CIs, on Mars, and on martian materials.Most available data are inconsistent with a martian origin forthe CIs.In the scientific method, knowledge progresses by theproposal and testing of new hypotheses. A hypothesis must berejected if it and its predictions are inconsistent with theavailable data. Modified hypotheses can be proposed to explaininconsistent data, but such modifications can grow uponthemselves, yielding Gordian tangles of exceptions and specialcases. Occam's Razor cuts through such tangles - one shouldchoose the simplest hypothesis that fits the data. The simplesthypothesis consistent with all available data is that the CIcarbonaceous chondrites did not originate on Mars.Here, l will first consider Brandenburg's [1996] proposal thatthe Cls formed as water-deposited sediments on Mars, and thatthese sediments had limited chemical interactions with theirmartian environment. Finally, I will address oxygen isotoperatios, the strongest link between the CIs and the martianmeteorites.II. 'Martian Geology' of CIsBrandenburg [1996] proposes that the CI ehondrites formedas water-deposited sediments early in Mars' history, with thesediment derived from asteroidal material accreting onto Mars.This hypothesis is inconsistent with the petrography of the CIsthemselves, and inconsistent with the geology and geochemistryof early Mars.Above all, the CI meteorites are not sedimentary rocksdeposited from water. The Cls contain no petrographic featuresthat would be expected in a water.laid sediment, e.g., layeringin composition or grainsize, cross-bedding, or evidence of soft-sediment deformation [Dodd, 1981]. The Cls consist ofchemically distinct domains rich in clay and serpentine withsmall proportions of magnetite and anhydrous silicate mineralssuch as olivine and pyroxene [Dodd, 1981]. This structuresuggests that the Cls are breccias, and the ranges in O isotopiccompositions of their constituents [Rowe et al., 1994] suggestCopyright 1996 by the American Geophysical Union.Paper number 96GL03075.0094-8534/96/96GL-03075505.00that the Cls are polymict. In this light, it seems probable that theCIs are impact breccias of chondritic asteroidal materials,extensively altered in place.Further, it seems highly unlikely that a sediment formed ollMars during its early history could contain only extra-martianmaterial. The CI meteorites formed at ~ 4.5 Ga [MacDougall etaL, 1984; Endress et al., 1996], a time when Mars' surface wasbeing struck repeatedly by large meteorites and asteroids. Impactcrater scars from this time are abundant on the martian southernhighlands, and impacts would have distributed ejecta widelyacross Mars. It seems unlikely that a water-filled basin on Mars,putative site of CI sedimentation, could have avoided collectingsome of this impact ejecta. All known martian materials arederived from basaltic magmas, and the southern highlands crust(of which we have one meteoritic sample) also appears to bebasaltic [Singer and McSween, 1993; McSween, 1994; Treiman,1995]. These martian basaltic materials are quite distinct fromCls [Dreibus and Wiinke, 1985] and ought to be readilyrecognized within Cls. Yet Cls contain no known physical orchemical traces of this martian material (anhydrous silicates inCls are not martian, as their solar flare tracks suggest extendedinterplanetary exposure [Dodd, 1981 ]).III. Chemical ClosureBrandenburg [1996] hypothesizes further that some elementabundances and isotopic ratios in the 'CI sediments' are likethose of Mars, while others retain primordial compositions: CImaterial would be 'leftovers' of Mars accretion with solarcomposition and isotopics. It is not clear fromBrandenburg [1996] whether the C1 material had 'Martianisotopics' (presumably meaning of C, H, N, and O) after orbefore it landed on Mars, but neither option is reasonable.'Martian isotopics' after MarsIn the first option, with the CIs' Martian isotopics arisingthrough chemical interactions on Mars, the CIs must somehowbe prevented from exchanging elements other than C, H, O, andN with their martian environment. Alteration of hypothetical CIprecursors on Mars could have had little effect on mostelemental abundances - such 'isochemical' alteration is, in fact,the standard model for fbrmation of CIs [Dodd, 1981 ]. However,noble gases are readily exchanged during aqueous alteration[e.g., Drake et al., 1994], and one should expect that noble gasabundances and isotopic composition in 'martian Cls' wouldresemble those of Mars.In fact, the noble gases in CIs are quite distinct from those inany known martian source, and cannot have exchanged3275

Palynostratigraphy of the Lower Tertiary volcanics and marine clastic sediments in the southern part of the West Greenland Basin: implications for the timing and duration of the volcanism

Volcanic rocks, forming hyaloclastites and subaqueous lava flows, were deposited intercalated with clastic sediments in a water-filled basin in West Greenland in the Early Tertiary. Three main stages of basin infilling occurred in the Disko-Nuussuaq area. The distribution of dinoflagellate cysts in the sediments shows that the basin was marine in the first stage and non-marine in the second stage of infilling. In the third stage the basin was displaced towards the south and was marginally marine. The dinoflagellate cysts form a typical mid-Paleocene assemblage which may be correlated with the calcareous nannoplankton (NP) zonation. The stratigraphically lowest investigated localities are coeval with the uppermost part of nannoplankton zone NP4, whereas the overlying localities within the marine basin (first stage) may be correlated with NP5-6. The localities from the non-marine second stage cannot be correlated with the NP zonation because they do not contain dinoflagellate cysts. Localities from the third stage are coeval with NP7-8. Younger volcanics are subaerially deposited. The total known range of the volcanics now falls within the NP3 to NP8 interval, giving a minimum duration for the main plateau-building stage of the volcanism of 4–6 million years. The subaerial basalts have previously been found to be mainly reversely magnetised, with one normally magnetised sequence which can now be stratigraphically correlated with NP4, and thereby identified as anomaly 27. The basalts in East Greenland started erupting during the NP9 zone, so that the volcanic activity in East Greenland largely succeeded that in West Greenland. In relation to the postulated mantle plume in the North Atlantic this means that the volcanic activity started in the peripheral part of the plume and only later switched to the central part.

Little Salt Spring, Florida: A Unique Underwater Site

Little Salt Spring in southwest Florida, consisting of a shallow, water-filled basin above a deep, vertical underwater cavern, was a freshwater cenote in the peninsula's drier past. It collected and preserved perishable organic artifacts and other evidence of Paleo-Indian and Archaic Indian origin ranging in age from 12,000 to 9000 and from 6800 to 5200 years ago. An Archaic Period cemetery containing an estimated 1000 burials occupies an adjoining muck-filled slough and presently drowned portions of the basin of the spring. Artifacts and the nature of interment suggest a cultural link between the Archaic people and the much later Glades Tradition of southern Florida.

Tidal studies on Aldabra

The oceanic tide at Aldabra possesses a very large range for an atoll owing to the influence of the Mozambique Channel. The mean spring-tide range, expressed as 2 ( M 2 + S 2 ), is 2.74 m. This is much greater than the 0.5 m common to the majority of central Pacific atolls, and the 0.7 to 1.7 m for Indian Ocean atolls. Ten tide-recording stations were set up by members of the expedition. Foxboro—Yoxall tide-gauge records were obtained from most sites, though there are few accessible rock ledges near deep water suitable for the instrument, especially in the lagoon. Visual records were used extensively in a detailed study of the tidal system in Passe Houareau. Tidal predictions for Aldabra found in Admiralty Tide Tables possess marked lagoonal characteristics. They originate from ‘Grand Poste’, a site well within Grande Passe. It is recommended that records for Passe du Bois be taken as standard since they most closely represent the oceanic tide. Empirically derived tide-predicting graphs are presented for key stations around the atoll, using Kilindini as standard port. Reduction in tidal range is pronounced in the lagoon and is conspicuous even near the mouths of the major channels. Within Passe Houareau spring-tide amplitudes may be a mere 1.2 m only 500 m from the channel mouth where the oceanic range is 3.3 m. Time lag increases lagoonwards more rapidly at Passe Houareau than at either Passe du Bois or Grande Passe, and is greater at low water than at high because of the very shallow nature of the lagoon floor. The greatest recorded phase lag occurs at the head of Bras Cinq Cases, where high water is delayed by 4 1/4 h at major spring tides: at neaps the whole region is dry at high water. Harmonic analyses are presented for one oceanic and two lagoonal stations. Computer synthesis of neap tides in the lagoon demonstrates a monthly masking effect produced by prominent shallow water harmonics. This results in the lagoon being virtually tideless on the smallest neap tides. Strong higher harmonics are indicated by visual records for Ilot Marquoix at the eastern end of the lagoon. These are characterized by a plateau-like high water, where the level commonly remains stationary for over 3 h. Lagoon tide curves are markedly asymmetrical, and often show linear ebb profiles, indicating that the lagoon behaves as a simple water-filled basin in many areas. Drainage off lagoon platforms is slow, water level falling by only 3 to 5 cm h -1 . This results in the tide ebbing for to 10 h out of the 12 1/2 h cycle. Towards spring tides more water enters the lagoon through Passe Houareau than can drain away before the next tide. Water level gradually builds up until at major springs a foot of water covers the lagoon platform at low tide. Extreme low water coincides with neap tides. Because of this ponding effect significant differences in insolation are experienced by marine bottom communities. On oceanic platforms extreme low water coincides with spring tides and occurs at midday: in the lagoon, platforms are most exposed between 06h00 and 08h00 and are always covered at noon. The effects of solar insolation are therefore minimal throughout much of the Aldabra lagoon, but are at a maximum around the coast. Tidal currents were measured in each of the Passes. In the western channels maximum values of 1.5 m s -1 (3 knots) were recorded in Passe du Bois. In Passe Gionnet a peak ebb value of 3.7 m s -1 (7.2 knots) was attained at high springs, with 3 m s -1 (6 knots) sustained for over 2 h. Flow/ebb current reversals are rapid, and in Passe Gionnet accompanied by the development of standing waves. Many channels are floored with trains of reversing sand megaripples. Elsewhere scour is appreciable; a wire mesh shark cage on the floor of Passe du Bois being undercut by 25 cm in 2 weeks. Transitory megarippled sandbanks occur on the eastern flank of Passe Houareau, and bottom facies throughout the lagoon are sculptured by the strong tidal scour.

The Oriented Lakes of Arctic Alaska

Elongate thaw-lake basins forming in the frozen ground of the Alaskan Arctic Coastal Plain are aligned 10°-15° west of true north. Several previous workers have maintained that prevailing winds elongated these basins by generating currents or wave attack in the north and south ends. To test this hypothesis, detailed maps and velocity determinations of wind-controlled current systems were made with sodium fluorescein dye and aluminum floats. In addition, the effect of wave action was studied in basins of all sizes; morphology and sediment distribution were mapped in both drained and water-filled basins; and water temperatures were recorded with thermographs. Supporting investigations were made of moisture content and fluctuation of the active layer in the frozen ground. It was discovered that a combination of processes tends to produce a uniformly oriented basin morphology consisting of sublittoral shelves on the east and west sides of the lakes and a deeper central basin that extends to the north and sout...