Effects of Selenium Supplementation on Arsenism: An Intervention Trial in Inner Mongolia

This paper reports the effects of a placebo-controlled Se-enriched yeast supplementation trial, conducted for 14 months, on arsenism in adult farmers living in a rural community in Inner Mongolia, China. The farmers had been naturally exposed to elevated concentrations of As in drinking water from tube-wells since 1983 but changed to arsenic-free drinking water when the trial began in June 1996. Blood and hair Se and As concentrations were analysed pre-intervention and at the end of the 3rd, 9th and 14th month, while skin lesions were assessed pre-intervention, as well as at the end of the 14th month, using the Arsenism Clinical Criteria established by the Ministry of Health, China. As the trial was a voluntary one, a number of farmers did not routinely have their blood and hair samples taken for analysis. Consequently, the data have been analysed in two categories. Fifty-four farmers from the Se-group and 29 from the placebo-group who were sampled on each occasion were considered as one group, which has been compared with the second group comprising up to a total of 100 farmers in the Se-group and 86 in the placebo-group. Results calculated for those farmers who were sampled on each occasion, showed that at the end of the trial, blood and hair Se concentrations of the Se-group increased from 0.130 to 0.186 µg ml^–1 and from 0.431 to 0.502 µg g^–1, respectively, while those of the placebo-groups remained constant. Blood and hair As concentrations of the Se-group decreased from 0.051 to 0.015 µg ml^–1 and from 2.57 to 0.680 µg g^–1, respectively, a greater reduction than those in the placebo-group that went from 0.064 to 0.024 µg ml^–1 and from 2.62 to 1.25 µg g^–1, respectively. When the data from all patients were examined, the analytical trends were similar. An evaluation of skin lesions in the category who were sampled for hair and blood on each occasion showed that 41.2% of hyperkeratosis, 50.0% of depigmentation and 44.7% of pigmentation in the Se-group improved one or more degrees, while those in the placebo-group improved by only 7.1, 12.0 and 6.7%, respectively. A total of 61.1% of the adults in Se-group improved in one or more type of skin lesion, but only 17.2% improved in the placebo-group. Comparable results were obtained when all the data from both categories of farmers were examined. Results from the trial showed that Se supplementation was more effective for the improvement of adults who were affected by double or triple skin lesions. In the placebo-group, most of the severely affected adults improved in only one kind of skin lesion, but in the Se-group, more adults improved in two or three kinds of skin lesions. Although the trial was limited by its relatively small size, the results have provided some evidence of the usefulness of Se supplementation for people affected by arsenism.     

Arsenism Clinical Stages and their Relation with Hair Arsenic Concentration of Residents of Bayinmaodao Rural District, Inner Mongolia, China

The clinical skin lesions of arsenism in men and women in Bayinmaodao rural district in Inner Mongolia, Peoples Republic of China, have been examined by doctors, and their hair and drinking water samples analysed for arsenic by hydride generation and ICP-AES. Altogether 311 arsenism patients with a 15.53% prevalence rate for the district were recorded. The disease prevalence rate was positively related to population, age, and their exposure to elevated arsenic concentrations in the drinking water from 1983 when new wells were dug and drinking of surface water was abandoned. Hyperkeratosis was the most serious skin lesion with the highest occurrence rate, then depigmentation and pigmentation in decreasing order. With increasing severity of the disease, ranging from skin lesion with single hyperkeratosis 1° to hyperkeratosis 3° with depigmentation 3° and pigmentation 3°, the results showed that arsenic concentrations in head hair had increased. Arsenic concentrations in hair were positively correlated with the arsenic concentrations in drinking water obtained from local wells.     

Uncertainty, learning, and the optimal management of wildlife

Wildlife management is limited by uncontrolled and often unrecognized environmental variation, by limited capabilities to observe and control animal populations, and by a lack of understanding about the biological processes driving population dynamics. In this paper I describe a comprehensive framework for management that includes multiple models and likelihood values to account for structural uncertainty, along with stochastic factors to account for environmental variation, random sampling, and partial controllability. Adaptive optimization is developed in terms of the optimal control of incompletely understood populations, with the expected value of perfect information measuring the potential for improving control through learning. The framework for optimal adaptive control is generalized by including partial observability and non-adaptive, sample-based updating of model likelihoods. Passive adaptive management is derived as a special case of constrained adaptive optimization, representing a potentially efficient suboptimal alternative that nonetheless accounts for structural uncertainty.     

Light availability and diurnal growth of a green macroalga (Caulerpa cupressoides) and a seagrass (Halophila decipiens)

The effects of daily light period on diurnal growth patterns of a green macroalga [Caulerpa cupressoides v.lycopodium f.elegans (J. Agardh) Weber-van Bosse] and a seagrass (Halophila decipiens Ostenfeld) were investigated in Salt River submarine canyon in the US Virgin Islands in summer 1984. The daily light period, in which quantum irradiance exceeded the light saturation point for photosynthesis of the macroalga and seagrass, was manipulated in situ using lamps and shades. Plant growth was measured every 6 h for 7 d under natural and experimental daily light periods.C. cupressoides grew at the same rate day and night.H. decipiens grew more during the day than at night, a pattern that persisted under continuous light and dark treatments, indicating endogenous control of diurnal growth. Growth vs daily light period curves indicate thatC. cupressoides grew faster thanH. decipiens in short daily light periods, consistent with the observation that the macroalga penetrates to deeper water than the seagrass in Salt River canyon. Overall growth (day + night) ofH. decipiens was unaffected in lengthened light periods and reduced in shortened light periods. Chlorophyll content ofC. cupressoides was not correlated with light availability, while that ofH. decipiens was positively correlated. The alga and seagrass had different diurnal growth patterns but similar overall growth responses to daily light periods. This study shows that diurnal growth patterns are probably under endogenous control, while overall growth is a response to in situ light conditions.Contribution^#193 from West Indies Laboratory and the National Undersea Research Program     

The density and size distribution of Diadema antillarum in Dominica (Lesser Antilles): 2001–2004

Diadema antillarum populations at many Caribbean locations have failed to recover from a wide-spread mortality event during the early 1980s. Quantitative assessments of Diadema in Dominica have only recently begun and can now be put into a regional context. Diadema and benthic algae were monitored in 4-month intervals at six 100 m² sites, spread over a distance of 38 km, along the west coast of Dominica. Diadema density surveys began in July 2001, while algal cover was monitored as of November 2001. Mean densities of individual sites ranged from 0.81 m⁻² (SD=1.02) to 2.98 m⁻² (SD=1.33), and overall means increased from 1.50 m⁻² (SD=0.12) in 2001, to 2.00 m⁻² (SD=0.05) in 2004. The weak negative relationship observed between the Diadema density and macroalgal cover (R ²=0.25, P=0.0030), indicates that Diadema play a limited role in controlling macroalgal species. In contrast, the abundance of turf algae was positively related to low Diadema densities, yet this relationship becomes negative beyond a critical point between 2.0 and 3.0 Diadema per m² (R ²=0.25, P=0.0075). As of November 2001 size measurements of 100 randomly sampled urchins at each site were included in the surveys, resulting in overall mean test size diameters ranging between 5.54 cm (SD=1.55) and 6.00 cm (SD=0.96). The mean test size diameter per site ranged from 4.54 cm (SD=1.91) at Tarou Point in November 2003 to 6.77 cm (SD=0.83) at Salisbury November 2001. Across all sites except Tarou Point, the most commonly occurring Diadema sizes throughout this study were within 1 cm, in the range between 4.5 and 7.5 cm. It is unclear how this Dominica scenario fits into the context of the pathogen-induced mass mortality events of the 1980s because neither qualitative nor quantitative records exist for that time in Dominica. The recent increase in Diadema density may be a symptom of recovery from Hurricane Lenny. Given the indiscriminant local pressure (affecting herbivorous fishes as well as fish predators of Diadema) Diadema’s role as grazer of algal turfs is highlighted. On a regional scale, its stable population of reproductive size classes may serve as source of larvae for nearby downstream islands.     

Distribution of algae on tropical rocky shores: spatial and temporal patterns of non-coralline encrusting algae in Hong Kong

Encrusting algae have been described as dominant space occupying species on rocky shores around the world. Despite their abundance, however, most studies classify species under generic names (e.g. Ralfsia sp.) or as a functional group (e.g. encrusting algae), thereby underestimating the number of species present and their ecological importance. Studies on six rocky shores of varying exposure, in Hong Kong, recorded eight common species of encrusting algae. The greatest abundance of encrusting algae was recorded on shores of intermediate exposure, where four distinct zonation bands could be identified; a cyanobacterial Kyrtuthrix-Zone in the upper midlittoral, a Bare-Zone below this, a Mixed-Zone in the lower midlittoral and a Coralline-Zone in the infralittoral fringe. Abundance declined on shores of greater and lower exposure to wave action, where bivalves and barnacles were competitively dominant. Certain species were found in greater abundance on exposed shores (e.g. Dermocarpa sp. and Hildenbrandia occidentalis), while others preferred more sheltered shores (e.g. Hildenbrandia prototypus and Kyrtuthrix maculans). With the exception of some cyanobacterial crusts, the abundance of encrusting algae was always greatest towards the low shore, an area of decreased physical stress and increased herbivore density. Zonation patterns showed seasonal variation associated with the monsoonal climate of Hong Kong. Most species increased in abundance during the cool season, while during the summer months the cover and vertical extent of encrusting algae decreased in relation to summer temperatures, although K. maculans increased in abundance during the summer. On Hong Kong shores, encrusting algae have a high species richness and exhibit within-functional group spatial and temporal variation which is mediated by herbivory and seasonal, physical stresses.     

Cross-shelf distribution of copepods and fish larvae across the central Great Barrier Reef

The distribution of total dry weight of zooplankton, copepod numbers and ichthyoplankton across the outer continental shelf in the central Great Barrier Reef was examined at bi-weekly intervals for three months over summer of 1983. Copepods were sampled (236 m net) within 10 m of the surface and within 10 m of the bottom. Mean densities in surface waters decreased markedly from the mid-shelf to outer shelf and the Coral Sea, but no cross-shelf gradient occurred in the bottom-water. Densities of copepods on the mid-shelf (surface and bottom waters) and in bottom-waters of the outer shelf were typically ca. 400 m^–3. Significantly lower densities (ca. 100 m^–3) occurred in surface waters of the outer shelf, except during outbursts of Acartia australis, when densities in these waters differed little from those elsewhere on the shelf. In oceanic waters, 10 km from the outer shelf station, copepod densities in surface waters were ca. 40 m^–3. Four of the five most abundant copepod taxa in surface waters, Paracalanus spp., Eucalanus crassus, Acrocalanus gracilis and Canthocalanus pauper, tended to be most abundant at the mid-shelf end of the transect. Acartia australis was sporadically very abundant in surface waters of the outer shelf, as was Paracalanus spp. in bottom-water of the outer shelf. An assemblage of Coral Sea species of copepod occurred in bottom-water of the outer shelf during two major intrusions, but not at other times. Densities of all common species varied considerably between cruises. Maximum densities of all common species except A. australis tended to be associated with diatom blooms linked to intrusions but a bloom did not necessarily mean all common species were abundant. Fish larvae included both reef and non-reef taxa, with reef taxa predominating on the outer shelf (approx 2:1 in density of individuals) and non-reef taxa dominating in nearshore samples (approx 2:1). Nine of the ten most abundant taxa analysed showed highly significant variation in numbers among stations and all but one of these also exhibited significant station x cruise interactions. Interactions generally reflected changes in the rank importance of adjacent stations from one cruise to the next or lack of any significant cross-shelf variation on some cruises where overall abundance of the taxa was low.     

Variation in Vitamin C content of sprat larvae (Sprattus sprattus) in the Irish Sea

Sprat (Sprattus sprattus) eggs and larvae were sampled from plankton and the Irish Sea in 1988 and 1989 and analysed forl-ascorbic acid (Vitamin C) content, which is considered an index of the nutritional well being and thus indicative of the status of the population in relation to environmental (physical and biological) structures. In one month, the Vitamin C content of larvae in different developmental stages decreased from 800 to 300µg g^–1 in the youngest larvae (4 to 14 mm) and to 250µg g^–1 in the oldest larvae (14 to 28 mm). No significant differences in the Vitamin C content per unit weight were found between larvae collected at four sites located in western stratified waters, central stratified, central mixed and eastern mixed waters. The mean Vitamin C content per larva, as well as mean length and wet weight of larvae were lowest in central mixed and eastern mixed waters in May–June. The estimated increases in Vitamin C, length and weight of individuals in the population of larvae varied significantly from April to June and between western stratified and eastern mixed areas. Highest rates coincided with stratified water conditions and with suitable quantity and quality of food, which seemed to constitute the most favourable environmental conditions for abundance and growth of sprat larvae.     

Plankton of the fladen ground during FLEX 76 II. Population dynamics and production of Thysanoessa inermis (Crustacea: Euphausiacea)

Samples taken in the northern North Sea with the Continuous Plankton Recorder (CPR), the Undulating Oceanographic Recorder (UOR) and the Longhurst-Hardy Plankton Recorder (LHPR) during the Fladen Ground Experiment in 1976 (FLEX 76) are used to describe the vertical distribution and population dynamics of Thysanoessa inermis (Krøyer) and to provide estimates of the production and carbon budget of the population from 19th March to 3 June 1976. Spawning occurred in late April and early May, in near synchronisation with the start of the spring bloom of phytoplankton. Eggs, nauplii and calyptopes reached maximum abundance in succession, and furciliae were numerous when sampling ceased in early June. Adults increased in length from a mean of 12.1 mm in mid-March to 17.5 mm in early June and the estimated production was 2.40 mg m^-3 over the 74 d period. Total carbon ingested by the population of T. inermis was estimated to be 10 mg C m^-2 d^-1 in the upper 100m which was only 1.5% of the daily primary production of 0.68 gC m^-2 measured over the FLEX period 26 March to 4 June 1976. The grazing by T. inermis on the phytoplankton population was assumed to have little effect on the control and depletion of the spring phytoplankton bloom during FLEX 77.JOSDAP Contribution No. 50     

Zooplankton of the Bristol Channel and Severn Estuary. The distribution of four copepods in relation to salinity

The seasonal variations in distribution and abundance of the common zooplankton species in the Bristol Channel and Severn Estuary were related to the salinity regimes observed over the period November 1973 to February 1975. The dominant constituents in all regions were the calanoid copepods, which reached maximum densities in July: approximately 100 times their winter levels. Four zooplankton assemblages were recognised using an objective classification program which computed similarity coefficients and used group-average sorting. The assemblages existed along the salinity gradient observed from the Severn Estuary to the Celtic Sea. The assemblages were classified as true estuarine, estuarine and marine, euryhaline marine and stenohaline marine and were characterized by the copepods Eurytemora affinis (Poppe) (<30S), Acartia bifilosa var. inermis (rose) (27 to 33.5S), Centropages hamatus (Lilljeborg) (31 to 35S) and Calanus helgolandicus (Claus) (>33S), respectively.