Holocene changes in sea level: evidence in micronesia

Investigation of 33 islands, scattered widely across the Caroline and Marshall Island groups in the Central Pacific revealed no emerged reefs in which corals had unquestionably formed in situ, or other direct evidence of postglacial high stands of sea level. Low unconsolidated rock terraces and ridges of reefflat islands, mostly lying between tide levels, were composed of rubble conglomerates; carbon-14 dating of 11 samples from the conglomerates so far may suggest a former slightly higher sea level (nine samples range between 1890 and 3450 and one approaches 4500 years ago). However, recent hurricanes have produced ridges of comparable height and material, and in the same areas relics from World War II have been found cemented in place. Thus these datings do not in themselves necessarily indicate formerly higher sea levels. Rubble tracts are produced by storms under present conditions without any change in datum, and there seems to be no compelling evidence that they were not so developed during various periods in the past.     

Effects of hook and release on Atlantic salmon in the River Alta, northern Norway

The purpose of the study was to collect information on angling procedures and the effects of hook and release on Atlantic salmon in the River Alta, northern Norway, covering both grilse and multi-sea-winter salmon in a non-artificial setting with real anglers. Information on the angling procedure, handling of the fish and the condition of the fish at release was collected for individual salmon in catch logs (n=543, mean body length 82 cm), whereas physiological stress was studied in a sub-sample (n=15, mean body length 77 cm). To study post-release behaviour, survival and recapture rates, salmon were tagged with radio transmitters (n=30, mean body length 83 cm) and anchor T-tags (n=353, mean body length 79 cm). To evaluate the effects of the hook and release programme on the salmon population, number of spawning redds were recorded from a helicopter in 6 years during 1989–2000.

The results showed that at water temperatures 10.0–14.5 °C, a high proportion of the radio tagged salmon (97%) survived hook and release and stayed in known spawning areas during the spawning period. However, the behaviour after release seemed to be affected by hook and release. Only a small proportion (4%) of the anchor T-tagged salmon was caught more than once within the same season. Increased playing time, increased number of runs during the angling event, hooking in the throat, bleeding at the hook wound, increased handling time, air exposure and water temperature were factors that affected hooked and released Atlantic salmon negatively, either indicated by a poor condition at release, increased stress levels or unnatural behaviour after release. Number of spawning redds were more than doubled after the introduction of compulsory release of all angled salmon in Sautso (the upper 16% of the watershed inhabited by salmon) in 1998, which indicates that hook and release can be an effective management tool to enhance declining Atlantic salmon populations.     

Survey of tuberculin testing in Swedish zoos.

Tuberculin test results from 214 animals in three Swedish zoos, tested between the years 1993 and 2000, were compiled from a questionnaire sent out to zoo veterinarians. Comparative testing with bovine and avian tuberculin was used on various sites of injection. A total of five skin test reactors were found: three cotton-top tamarins (Saguinus oedipus) in one zoo and two tapirs (Tapirus terrestris) in another zoo. Postmortem culture from one of the tapirs revealed growth of Mycobacterium tuberculosis, and a stamping out policy was adopted in the herd. Tuberculosis in the primates was ruled out by further investigations. Zoo veterinarians should try to adopt a common scheme for the regular testing of zoo animals to improve the diagnostic ability and comparison of results between institutions.     

Alum Sludge Dewatering Using Moringa oleifera as a Conditioner

An active component of Moringa oleifera (MO) has been used in comparison with synthetic polymers and alum for the conditioning of chemical sludge from a drinking water treatment plant. The comparison was based on dewatering characteristics of the conditioned sludge determined by capillary suction time (CST), specific resistance to filtration (SRF), sand column drainage and shear strength tests. The results indicated that MO showed comparable conditioning effect as alum. Polyelectrolytes were more effective than MO and alum. Sludge conditioned with MO and alum, as in dual chemical conditioning, showed better results than MO alone. According to CST, SRF and sand drainage results, optimum doses for MO, alum and polyelectrolytes were 125, 63, and 1.8 kg/t, respectively. Comparison of the two polyelectrolytes showed that the cationic polyelectrolyte was more effective. For sand drainage tests both polyelectrolytes improved the drainage rate by 2 orders of magnitude. MO and alum improved the drainage rate by about 4.2 times. On the other hand, the improvements in cake solids concentration were similar for all the chemical conditioners. Flocs from MO and alum were relatively stronger compared to those of the polyelectrolytes. From the results of the study it could be concluded that MO alone or in combination could be effectively used and replace alum for dewatering of chemical sludge.     

An experimental study of two potential methylation agents of mercury in the atmosphere: CH3I and DMS

Experimental results from a study of the gas and aqueous phase reactions of elemental mercury (Hg⁰) with methyl iodide (CH₃I) and dimethyl sulfide (DMS) are presented. In aqueous phase experiments with CH₃I we found no observable increase in methyl mercury (MeHg). A small formation of MeHg, however, was observed in some (but not all) gas phase experiments in sunlight. A loss of Hg⁰ and a simultaneous formation of oxidized mercury (Hg(II)) was also observed in these experiments. No reaction, neither methylation or oxidation, was found between Hg⁰ and DMS under any conditions investigated. These experiments suggest that a simple homogeneous gas or aqueous phase methylation of Hg⁰ by DMS or CH₃I in the atmosphere cannot account for the significant levels of MeHg observed in precipitation.     

Mercury cycling in a northern wisconsin seepage lake: The role of particulate matter in vertical transport

During summer stratification, total mercury (Hg_τ) reached maximum concentrations in the O₂ :depleted, hypolimnion of Little Rock Lake, Wl. Initially, the hypolimnetic increase was attributed solely to redox-controlled release of Hg from bottom sediments. However, subsequent depth profiles of Hg indicated that hypolimnetic Hg enrichment could also result from the downward transport and recycling of particulate Hg prior to incorporation in the sediments. Contrasts between Fe and Hg cycles in this lake reinforce this notion. Increases in hypolimnetic Fe were observed during both summer and winter O₂ decreases. In contrast, hypolimnetic Hg concentrations declined during winter. In the ice-free season, the distribution of particulate mercury (Hg_p) correlated with the distribution of chlorophyllous particulates in this lake, re-emphasizing the importance of biotic processes in controlling Hg cycling in the hypolimnion.     

Seasonal variability in the Mercury speciation of Onondaga Lake (New York)

Dissolved and particulate Hg speciation was determined on four occasions in the Spring to Fall interval of 1989, at three depths of the water column of Onondaga Lake, New York; an urban system in which the sediments and fish flesh are contaminated with H_g. Species determined included total Hg (Hg_t), reactive (‘ionic’) Hg (Hg_i), monomethylmercury (CH₃HgX), elemental Hg (Hg°) and dimethylmercury (CH₃)₂Hg). Onondaga Lake was found to contain very high levels of Hg_t (2 to 25 ng L^?1 Hg), Hg_j (0.5 to 10 ng L^?1 Hg), and CH₃HgX (0.3 to 7 ng L^?1 Hg), which generally increased with depth in the lake. These concentrations represent a significant level of contamination, based upon comparisons with other polluted and pristine sites. Elemental Hg levels were typically about 0.05 ng L^?1 and (CH₃)₂Hg was near the limits of detection (?0.001 ng) L^?1 in most samples. The greatest CH₃HgX concentrations in the hypolimnion, as well as the largest gradients of both CH₃HgX and (Hg_t), were observed upon the first onset of stratification, in early summer. These concentrations did not become more pronounced, however, as stratification and H₂S levels in the hypolimnion increased throughout the summer. The very low concentrations of (CH₃)₂Hg in these MeHg and sulfide-rich waters calls into question the belief that CH₃HgX and H₂S will react to yield volatile dimethyl-mercury, which can then escape to the atmosphere by diffusion. Mercury speciation was highly dynamic, indicating active cycling within the lake, and an apparent sensitivity to changes in attendant Iimnological conditions that track the stratification cycle.     

Effect of pH on the bioaccumulation of low level,dissolved methylmercury by rainbow trout (Oncorhynchus mykiss)

An inverse relationship has been observed between pH and McHg concentration in freshwater fish. Many hypotheses exist regarding the mechanisms which lead to elevated levels of organic Hg in fish from low pH lakes. To determine if pH has a direct effect on the rate of McHg bioaccumulation in fish, rainbow trout fingerlings (Oncorhynchus mykiss) were exposed to a low concentration of aqueous methylmercuric chloride (1.38 ± 0.49 ng·L^?1) at four pH-levels (8.2, 7.0, 6.3, 5.8) for eight weeks. McHg and total Hg were specifically determined on whole fish homogenates and water samples. The pH was found to have a significant: inverse effect on the rate of McHg bioaccumulation in the fish only in the lowest exposure level. Fish held at pH 5.8 had an uptake rate of 1.11 ± 0.07 ng·g^?1·d^?1, while those at pH ≥ 6.3 had a MeHg tissue uptake rate of ≤ 0.64 ± 0.07 ng·g^?1·d^?1. Total body burden of MeHg in the fish held at pH 5.8 also showed an elevated level of MeHg when compared with fish held at higher pH-levels, but the difference was less dramatic. These results suggest that a portion of the Hg burden in fish from low pH systems may be due to the direct effects of low pH on bioaccumulation, but that a threshold may exist above which pH does not play a significant role.     

Benefits and costs of HIV testing.

The benefits and costs of human immunodeficiency virus (HIV) testing in employment settings are examined from two points of view: that of private employers whose profitability may be affected by their testing policies and that of public policy-makers who may affect social welfare through their design of regulations related to HIV testing. The results reveal that HIV testing is clearly not cost-beneficial for most firms, although the benefits of HIV testing may outweigh the costs for some large firms that offer generous fringe-benefit packages and that recruit workers from populations in which the prevalence of HIV infection is high. The analysis also indicates that the testing decisions of unregulated employers are not likely to yield socially optimal economic outcomes and that existing state and federal legislation related to HIV testing in employment settings has been motivated primarily by concerns over social equity.     

Hypergastrinaemia of sheep infected with Haemonchus contortus

Radioimmunoassay of plasma gastrin has shown that a hypergastrinaemia occurs in yearling sheep, after infection with 10(6) infective third stage larvae of Haemonchus contortus. Plasma gastrin concentrations began to rise two to four days after infection, that is, at about the same time as, or slightly before, the abomasal pH was observed to increase.