Concentrations of inorganic elements in bottled waters on the Swedish market

This study presents the concentrations of about 50 metals and ions in 33 different brands of bottled waters on the Swedish market. Ten of the brands showed calcium (Ca) concentrations ≤10 mg L⁻¹ and magnesium (Mg) levels <3 mg L⁻¹, implying very soft waters. Three of these waters had in addition low concentrations of sodium (Na; <7 mg L⁻¹), potassium (K; <3 mg L⁻¹) and bicarbonate (HCO₃ ≤31 mg L⁻¹). These brands were collected from barren districts. Nine of the brands were collected from limestone regions. They showed increased Ca-levels exceeding 50 mg L⁻¹ with a maximum of 289 mg L⁻¹. Corresponding Mg-levels were also raised in two brands exceeding 90 mg L⁻¹. Two soft and carbonated waters were supplemented with Na₂CO₃ and NaCl, resulting in high concentrations of Na (644 and 648 mg L⁻¹) and chloride (Cl; 204 and 219 mg L⁻¹). Such waters may make a substantial contribution to the daily intake of NaCl in high water consumers. The storage of carbonated drinking water in aluminum (Al) cans increased the Al-concentration to about 70 μg L⁻¹. Conclusion As there was a large variation in the material as regards concentrations of macro-elements such as Ca, Mg, Na, K and Cl. Supplementation with salts, e.g., Na₂CO₃, K₂ CO₃ and NaCl, can lead to increased concentrations of Na, K and Cl, as well as decreased ratios of Ca/Na and larger ratios of Na/K. Water with high concentrations of e.g., Ca and Mg, may make a substantial contribution to the daily intake of these elements in high water consumers. Al cans are less suited for storage of carbonated waters, as the lowered pH-values may dissolve Al. The levels of potentially toxic metals in the studied brands were generally low.     

Arsenic in groundwaters of the Lower Mekong

Increasing incidence and awareness of arsenic in many alluvial aquifers of South-east Asia has raised concern over possible arsenic in the Lower Mekong Basin. Here, we have undertaken new research and reviewed many previous small-scale studies to provide a comprehensive overview of the status of arsenic in aquifers of Cambodia and the Cuu Long Delta of Vietnam. In general natural arsenic originates from the Upper Mekong basin, rather than from the local geology, and is widespread in soils at typical concentrations of between 8 and 16 ppm; (dry weight). Industrial and agricultural arsenic is localised and relatively unimportant compared to the natural alluvial arsenic. Aquifers most typically contain groundwaters of no more than 10 μg L⁻¹, although scattered anomalous areas of 10 to 30 μg L⁻¹ are also quite common. The most serious, but possibly ephemeral arsenic anomalies, of up to 600 μg L⁻¹, are associated with iron and organic-rich flood-plain sediments subject to very large flood-related fluctuations in water level, resulting in transient arsenopyrite dissolution under oxidizing conditions. In general, however, high-arsenic groundwaters result from the competing interaction between sorption and dissolution processes, in which arsenic is only released under reducing and slightly alkaline conditions. High arsenic groundwaters are found both in shallow water-tables, and in deeper aquifers of between 100 and 120 m depth. There is no evidence of widespread arsenicosis, but there are serious localised health-hazards, and some risk of low-level arsenic ingestion through indirect pathways, such as through contaminated rice and aquaculture. An almost ubiquitous presence of arsenic in soils, together with the likelihood of greatly increased groundwater extraction in the future, will require continuing caution in water resources development throughout the region.     

Polygyny and male parental care in Savannah sparrows: effects on female fitness

Summary To determine the effects of male mating status on female fitness, we compared the reproductive success, survival, and future fecundity of female Savannah sparrows (Passerculus sandwichensis) mated to monogamous vs. polygynous males in a 5-year study on Kent Island, New Brunswick, Canada. The proportion of males with more than one mate varied from 15 to 43% between years and sites. Polygynous and monogamous males fledged young of equal size in every year of the study. Females who shared paternal care with other females laid as many eggs per clutch and clutches per season as monogamously mated females. In most years polygynously mated females showed no delay in laying a second clutch, and they suffered no reduction in fecundity the following year. Recruitment of a female's offspring into the breeding population was generally independent of her mating status. Fitness costs of being mated to a polygynous male were only apparent in one year of the study, during which females mated to polygynous males had higher over-winter mortality than those mated to monogamous males. That same year, young raised by polygynous males were only one-third as likely to survive to reproductive maturity (as inferred by returns) as those raised by monogamous males. A male's mating status had no effect on his own survivorship. A male's mating status did not necessarily reflect his contributions to raising nestlings, which may partially explain why monogamously and polygynously mated females had equal fitness. At 35 nests the proportion of food deliveries brought by individual males varied from 0 to 75%; on average, males brought fewer than 30% of all food deliveries. Yet parental care by polygynous males was no less than that of monogamous males, at least at the nests of their primary females. Secondary females tended to receive less male assistance during the nestling stage, but their reproductive success was indistinguishable from that of primary females. Females feeding young without male assistance made as many food deliveries/h as did pairs in which males brought at least 30% of all food deliveries. Unassisted females did not suffer diminished fledging success or produce smaller fledglings. The benefits of polygyny for male Savannah sparrows are clear: polygynous males recruit more surviving offspring into the breeding population than monogamous males. The fitness of females, on the other hand, appears to be unaffected by whether their mate was monogamous or polygynous except in occasional years. Polygyny may be maintained in this population by the constraints of a female-biased sex ratio, the inability of females to predict a male's paternal care based on his morphology or behavior, the poor correlation between a male's mating status and his assistance at the nest, and inconsistent natural selection against mating with a polygynous male. Correspondence to: N.T. Wheelwright     

Tolerance of marine calanoid resting eggs: Effects of freezing,desiccation and Rotenone exposure - a field and laboratory study

Tolerance of calanoid resting eggs from bottom sediment in a manipulated marine enclosure (Svartatjønn, western Norway) to freezing, desiccation and exposure to the insecticide Rotenone was examined in 1989 and 1990, both in situ and in the laboratory. Egg abundances in the sediment were compared before and after draining followed by Rotenone treatment. The drained parts of the basin were exposed to both drying and freezing. A significant decrease in hatching success was found in the drained parts during the study (p<0.05,t-test) and in the deepest parts, which were exposed to Rotenone. No significant difference was found in an intermediate zone around the new water level established by the draining. Both drying (at 20°C) and freezing (at –15°C) caused total mortality of the eggs in laboratory experiments. Laboratory experiments also showed that Rotenone concentrations higher than 0.5 ppm resulted in significantly reduced hatching rates, indicating that resting eggs of calanoids tolerate 20 to 100 times higher Rotenone concentrations than do later ontogenetic stages. The operational procedure (i.e. draining and Rotenone treatment) employed in enclosed ponds used for marine fish fry production will, within a 1-yr cycle, reduce the abundance of resting eggs and therefore the potential for self-recruitment of the zooplankton stocks.     

Benthic energy dynamics in a southern Baltic ecosystem

Benthic components and metabolic activity at two stations in the Darss-Zingst estuary (eastern German Baltic coast) were investigated over a seasonal cycle from April 1985 to August 1986. As has been established for temperate and boreal ecosystems, peaks in the biomass of benthic microphytes occurred in the spring and late autumn to winter, presumably caused by settling phytoplankton blooms. Metabolic activity of the benthos did not increase with rising ambient temperatures. Rather, the highest values of oxygen consumption were recorded during the cooler months (spring and winter), when increased numbers of organisms were also observed. This may be a response to a greater food supply to the sediment in the form of settling phytoplankton during these times of year.     

Impact of predation-disturbance by large epifauna on sediment-dwelling harpacticoid copepods: Field experiments in a subtidal seagrass bed

The hypothesis was tested that predation-disturbance by epibenthic macrofauna affects the abundance of sediment-dwelling harpacticoid copepods. The copepods inhabited a subtidal seagrass (Zostera marina L.) bed in British Columbia, Canada. The response of the harpacticoid community was observed in controlled field experiments in which epibenthic predators-disturbers were excluded from portions of the seagrass bed. Controlled, exclusion-cage (0.8 m² area, 7-mm mesh) experiments were conducted within the seagrass bed from late March/early April to mid-June in both 1986 and 1987. Sampling was conducted biweekly. Exclusion of large epibenthic predators-disturbers had little effect on sediment-dwelling harpacticoid copepod density. Total harpacticoid numbers and abundances of dominant species generally did not increase in the exclusion treatment relative to the control. Shifts in species composition of the harpacticoid community did not occur. The treatment control was adequate in simulating the exclusion cage structure. It appears that large epibenthic predators-disturbers have little impact on the abundance of harpacticoid copepod populations at this study site.     

Proximate composition of Antarctic mesopelagic fishes

Eleven mesopelagic fish species from the Weddell/Scotia Sea region of the Antarctic captured during the austral spring 1983, austral fall 1986, and austral winter 1988, were analyzed for proximate composition. Water, ash level, protein, lipid and carbohydrate were examined in relation to depth of occurrence and season. No depth-related trends were evident, primarily due to a low species diversity and minimal differences in those species' vertical distributions. The Antarctic speciesElectrona antarctica showed a significant increase in lipid level (% wet wt and % ash-free dry wt) between spring, fall and winter. The increase may signify an accumulation over the productive season, possibly as a reserve for the winter months. Lipid levels (% wet wt and % ash-free dry wt) were significantly lower in the Weddell Sea specimens examined in this study than in previously examined identical and congeneric species taken during the same season from a more productive near-shore Antarctic region. Comparisons with congeners and confamilials from tropical-subtropical and temperate systems revealed variable trends. The Antarctic speciesE. antarctica andCyclothone microdon had lower water and protein (% wet wt) levels than similar species from tropical-subtropical or temperate regions. Lipid levels of the two species are similar to temperate individuals, while energy levels are slightly higher. In contrast, species of the genusBathylagus show no trends in composition as a function of latitude. Differences in productivity, water-column temperature-structure, and seasonality are important considerations when examining trends among mesopelagic species.     

Diets of piscivorous fishes in a tropical Australian estuary,with special reference to predation on penaeid prawns

The diets of fish from the tropical Embley Estuary in the eastern Gulf of Carpentaria, Australia, were analysed with particular reference to piscivory and predation on juveniles of commercially important penaeid prawns from October 1986 until July 1988. Of the 77 species caught, 52 were piscivorous, and of these 37 ate penaeid prawns. The most numerous piscivores wereScomberoides commersonianus, Arius proximus, Lates calcarifer, Polydactylus sheridani andRhizoprionodon acutus, the first four of which accounted for over 90% of all prawns eaten. Twenty species are commercially important species of prawns. The proportions of penaeids in the diets varied seasonally, according to the density of penaeids in the estuary. The proportion was highest during the pre-wet period (November) and lowest during the dry period (July–August). Predation on prawns was highest in the lower and middle reaches of the river. Estimates of the rates of predation on the two most common juvenile commercial prawns,Penaeus merguiensis andP. semisulcatus, are presented and discussed.     

Biomasses,catch rates and abundances of demersal fishes,particularly predators of prawns,in a tropical bay in the Gulf of Carpentaria,Australia

The demersal fish fauna of Albatross Bay, in the eastern Gulf of Carpentaria, northern Australia, was sampled on seven cruises from August 1986 to November 1988, using a random stratified trawl survey. Four depth zones between 7 and 45 m were sampled during both day and night. The mean biomass of fish from all seven cruises was 297 kg ha^–1 for days trawls and 128 kg ha^–1 for night trawls. The overall mean catch rates were 922 kg h^–1 for day trawls and 412 kg h^–1 for night trawls. There were marked differences between cruises in both the biomass and catch rate. Approx 890 000 fish of 237 species were collected. Of these, 25 species comprised 82% of the total biomass and 74% of the overall catch rate. The dominant families were Leiognathidae, Haemulidae and Clupeidae, with Sciaenidae and Dasyatidae important at night.Leiognathus bindus was the most abundant species. Twenty-five species occurred in more than 50% of trawls, withCaranx bucculentus the most frequently caught (96% of all trawls). Thirty four species were predators on prawns; their absolute mean biomass was 50 kg ha^–1 during the day and 39 kg ha^–1 at night. The corresponding catch rates were 171 and 125 kg h^–1. Multiple-regression analyses were used to discriminate the effects of diel, seasonal, depth and cruise patterns. Of the 31 most abundant species, 15 showed diel patterns of abundance; 11 species showed seasonal patterns of abundance; 23 species had differential depth distribution; and 13 species showed significant cruise-to-cruise variation in abundance. Cruise variations in abundance were tested against salinity, temperature, tidal exchange, plankton biomass and prawn abundances as well as periods (and lags) of total rainfall prior to sampling. Only total rainfall showed any significant correlation. Total rainfall over a period of 6 wk immediately prior to sampling showed significant positive correlations with the abundances of five species, with overall daytime catch rates, and with the suite of 34 prawn predators. Rainfall and river runoff into Albatross Bay were significantly correlated. In Albatross Bay, the complex of factors affecting fish abundances and the magnitude of between-cruise differences indicate that such tropical communities may be unpredictable and are not seasonally constant. The high catch rates in Albatross Bay relative to similar tropical areas elsewhere are discussed and attributed to the light exploitation of the Albatross Bay stocks. Other than a prawn fishery, there is no commercial trawling in Albatross Bay. Hence, the only fishing mortality is a result of by-catch from prawn trawling. The annual total of such fish by-catch is probably less than 10% of the estimated standing stock of 93 000 tonnes.