Uptake of arsenate, trimethylarsine oxide, and arsenobetaine by the shrimp Crangon crangon

Common shrimp, Crangon crangon (L.), were exposed to inorganic arsenic (arsenate), trimethylarsine oxide, or arsenobetaine in sea water (100 μg As l⁻¹) or in food (1 mg As g⁻¹ wet wt) for up to 24 d, followed by 16 d depuration in clean sea water with undosed food, in order to determine the efficiency of uptake and retention of the compounds. Accumulation of arsenic in the tail muscle, gills, midgut gland, exoskeleton, and remaining tissues was found to depend on the chemical form of the arsenic and the route of exposure. No arsenic was accumulated by C. crangon exposed to arsenate or trimethylarsine oxide in sea water. Shrimps exposed to waterborne arsenobetaine initially accumulated a small amount of arsenic in their tail muscle and gills. After 16 d, C. crangon fed arsenate, trimethylarsine oxide, or arsenobetaine had accumulated arsenic in their tail muscle to levels ∼2-, 2-, or 40-times, respectively, that of the control group. A roughly linear rate of accumulation was shown by shrimps fed trimethylarsine oxide or arsenobetaine, but C. crangon fed arsenate accumulated arsenic for 16 d, then lost arsenic such that their concentration on Day 24 was not significantly different from that of the control group. Patterns of arsenic accumulation in the gills of shrimps fed the compounds were similar to those seen in the tail muscle. On a whole animal basis, C. crangon retained ∼1.2% of the arsenate, 1.6% of the trimethylarsine oxide, and 42% of the arsenobetaine consumed over the first 16 d of exposure, with roughly half present in the tail muscle in each case. Data obtained support the view that the direct uptake of arsenobetaine from sea water does not make a significant contribution to the relatively high concentrations of this compound in marine crustaceans, and that food is the primary source. Naturally occurring arsenic compounds in C. crangon and possible transformations of the administered arsenic compounds were examined by high performance liquid chromatography using an inductively coupled plasma mass spectrometer as the arsenic-specific detector. Control C. crangon contained arsenobetaine as the major arsenic compound (>95% of total arsenic); tetramethylarsonium ion (0.7%) and an unknown arsenic compound (1.7%) were also present as minor constituents. Shrimp ingesting arsenobetaine accumulated it unchanged. Shrimp ingesting arsenate did not form methylated arsenic compounds; they appeared to contain their accumulated arsenic as unchanged arsenate only, although the possibility that some of the arsenic was reduced to arsenite could not be excluded. C. crangon ingesting trimethylarsine oxide biotransformed the compound predominantly to dimethylarsinate. Received: 9 October 1997 / Accepted: 11 February 1998     

Vulnerability of the copepod Acartia tonsa to predation by the scyphomedusa Chrysaora quinquecirrha : effect of prey size and behavior

Although scyphomedusae have received increased attention in recent years as important predators in coastal and estuarine environments, the factors affecting zooplankton prey vulnerability to these jellyfish remain poorly understood. Current models predicting feeding patterns of cruising entangling predators, such as Chrysaora quinquecirrha (Desor, 1948), fail to account for the selection of fast-escaping prey such as copepods. Nevertheless, our analysis of gastric contents of field-collected medusae showed that this scyphomedusa fed selectively on the calanoid copepod Acartia tonsa (Dana, 1846) and preferentially ingested adult over copepodite stages. We measured feeding rates in a planktonkreisel while simultaneously videotaping predator–prey interactions. C. quinquecirrha consumed adult A. tonsa ten times faster than copepodites. Differences in prey behavior, in the form of predator–prey encounter rates or post-encounter escape responses, could not account for the elevated feeding rates on adults. Prey size, however, had a dramatic impact on the vulnerability of copepods. In experiments using heat-killed prey, feeding rates on adults (1.5 times longer than copepodites) were 11 times higher than on copepodites. In comparison, medusae ingested heat-killed prey at only two to three times the rate of live prey. These results suggest that during scyphomedusan–copepod interactions, prey escape ability is important, but ultimately small size is a more effective refuge from predation. Received: 26 September 1997 / Accepted: 20 May 1998     

Seasonality of polypide recycling and sexual reproduction in some erect Antarctic bryozoans

The seasonality of polypide cycling has been investigated for three species of erect bryozoans from Antarctica: Isoseculiflustra rubefacta (Kluge, 1914), Nematoflustra flagellata (Waters, 1904) and Himantozoum antarcticum (Calvet, 1905). Approximately ten colonies of each species were collected monthly by SCUBA divers over a 14 mo period during 1992/1993, and the status of each individual zooid was classified as differentiating/regenerating, active (feeding autozooids), degenerate (brown body) or sexually reproductive (ovicells present, or zooid containing a larva). Polypide cycling in all three species was distinctly seasonal. New zooids formed at the growth margin and typically contained actively feeding polypides for ≃9 mo before these polypides degenerated into brown bodies in the austral winter (June). Very few polypides were active in the period from June to August, when water-column food levels were at their lowest; after this period new polypides differentiated. Individual zooids typically underwent a total of five (I. rubefacta and N. flagellata), or at least four (H. antarcticum) complete polypide cycles before becoming senescent. Polypide lifetimes generally became shorter as the age of the zooid increased. Sexual reproduction was also distinctly seasonal in these species, with bands of ovicells or sexually reproductive zooids being formed each year in late summer once a given colony had grown to a threshold size (or age). Larvae were then brooded for ≃10 mo before being released in January/February (N. flagellata) or February/March (H. antarcticum). The seasonal patterns of polypide cycling are related clearly to the variations in food availability, and these species appear to have the longest zooid lifetime (≃5 yr) and the slowest polypide cycling (once per year with polypide lifetimes up to 10 mo) reported for any bryozoan so far. Received: 7 May 1995 / Accepted: 19 November 1997     

Potential fluorosis problems around Chandidongri, Madhya Pradesh, India

The area around Chandidongri (latitude 21 deg 02 prime N and longitude 80 deg 37 prime E) is covered by granitic gneisses and amphibolites of the Amgaon Group and granites and rhyolites of the Dongargarh super group. The granites which cover the major portion of the area have been intruded into by a number of dolerite and epidiorite dykes and traversed by a few N–S trending shear zones. A well-known fluorite deposit is located along the Lamtidongri–Kotnapani shear zone. Besides this deposit, the authors have located a few occurrences of fluorite along other shear zones where epidiorite dykes are in association with granites. A number of cases of fluorosis have been reported from those parts of Rajasthan and Andhra Pradesh which are covered by granitic rocks and also from the eastern parts of Bhandara district which are adjacent to the area described here. The Chandidongri area is mainly covered by granitic rocks, which at places show the presence of fluorite mineralisation. Taking into consideration these facts, the authors have investigated the area to study the cases of fluorosis if any, and the impact of geology and fluorite mining on the water quality in this region. During the survey, we have not come across any cases of fluorosis in this region. The pH is more than 7 and the fluoride concentration is within the permissible limit.     

Bioaccumulation of heavy metals in fish tissues of a freshwater lake of Bhopal

Contamination of heavy metals, namely, lead, cadmium, zinc, nickel, copper, chromium and mercury was evaluated in the samples of water and tissues of Labeo rohita and Ctenopharyngodon idella of Upper Lake of Bhopal collected during summer, rainy and winter seasons of 2005–2006. Different organs of the fishes accumulated varying quantities of different heavy metals. In L. rohita, accumulation of heavy metals was in the sequence liver > kidney > gills > muscles, and in C. idella, it was gills > liver > kidney > muscles. Zn was the highest accumulating metal in fish, whilst Hg was the lowest and was well corroborated with those of water. The values of heavy metals were so far well within the maximum permissible standard value of heavy metals for drinking water and for fish culture as prescribed by various national and international agencies.     

Hydrogeochemical data as a tool for exploration and mapping: a case study from part of Afikpo Basin southeastern Nigeria

Fourteen (14) characters from six (6) water samples collected from springs, ponds, and streams located in Lower Cretaceous sedimentary area of Afikpo Basin have been analyzed. These include pH, turbidity, conductivity, total dissolved solid, hardness, Fe²⁺, Ca²⁺, Mg²⁺, K⁺, NO₃ ^?, Cl^?, SO₄ ^2?, and Na⁺. These sediments, which are Turonian and Coniacian in age, are subdivided into two by a basic rock dyke. Results of the analyses show clearly that the Turonian sediments, intruded by dolerite, have net Fe²⁺, HCO₃ ^?, Ca²⁺, Mg²⁺, Mn²⁺, Cl^?, and SO₄ ^2? concentration while those from the younger Coniacian sediment have net higher amounts of K⁺, Na⁺, and Mn²⁺. The overriding mafic minerals in the basic intrusive rock possibly led to higher leaching into ground water system near it. On the other hand, the presence of feldsparthic to kaolinitic sands of the younger Coniacian units led to higher K⁺ and Na⁺ matter in the water from these zones. The formations dip away from the older sediments. Concentrations of these characters are within acceptable drinking water standards by World Health Organization but noticeable anomalous zones for Fe²⁺, Mg²⁺, and Ca²⁺ are zones of basic rock suites. Areas with greater Na⁺ and K⁺ are traceable to sandy units. It is thus concluded that more analysis of surface, subsurface, and pond water samples can be utilized for minerals search and geological mapping. At this stage, it forms a veritable reconnaissance tool.     

Arsenic in shallow aquifer in the eastern region of Bangladesh: insights from principal component analysis of groundwater compositions

Probable sources and mechanisms of arsenic (As) release in shallow aquifer in eastern Bangladesh are evaluated using statistical analysis of groundwater compositions. Dissolved As in 39 samples ranged from 8.05 to 341.5 μg/L with an average of 95.14 μg/L. Ninety seven percent of wells exceed the WHO limit (10 μg/L) for safe drinking water. Principal component analysis is applied to reduce 16 measured compositional variables to five significant components (principal components—PCs) that explain 86.63% of the geochemical variance. Two component loadings, namely PC 1 and PC 2 (45.31% and 23.05%) indicate the natural processes within the aquifers in which organic matter is a key reactant in the weathering reactions. Four groups of wells are defined by the PCA and each group of wells represents distinct physicochemical characteristics. Among them, group III groundwater shows higher As concentration together with high concentrations of Fe, Mn, dissolved organic carbon, $\text{PO}_{4}^{3-}$ and $\text{HCO}_{3}^{-}$ than groups I and II. Speciation calculations suggest that only wells of group III are saturated with respect to siderite, and all groups of samples are supersaturated with respect of rhodochrosite. The relationship of As with these parameters in the different groups of wells of the study area suggests that reductive dissolution of Fe–Mn oxyhydroxides with microbially mediated degradation of organic matter is considered to be the dominant processes to release As in groundwater.     

The hydrochemistry of groundwater in the Densu River Basin, Ghana

Hydrochemical analyses of groundwater samples were used to establish the hydrochemistry of groundwater in the Densu River Basin. The groundwater was weakly acidic, moderately mineralized, fresh to brackish with conductivity ranging from of 96.6 μS cm^???1 in the North to 10,070 μS cm^???1 in the South. Densu River basin have special economic significance, representing the countries greatest hydrostructure with freshwater. Chemical constituents are generally low in the North and high in the South. The order of relative abundance of major cations in the groundwater is Na^?+??> Ca^2?+??> Mg^2?+??> K^?+? while that of anions is Cl^????> HCO $_{3}^{-} >$ SO $_{4}^{2-} >$ NO $_{3}^{-}$ . Four main chemical water types were delineated in the Basin. These include Ca–Mg–HCO₃, Mg–Ca–Cl, Na–Cl, and mixed waters in which neither a particular cation nor anion dominates. Silicate weathering and ion exchange are probably the main processes through which major ions enter the groundwater system. Anthropogenic activities were found to have greatly impacted negatively on the quality of the groundwater.     

Impact of overland traffic on heavy metal levels in highway dust and soils of Istanbul, Turkey

The purpose of this study was to investigate the impact of overland traffic on the spatial distribution of heavy metals in urban soils (Istanbul, Turkey). Road dust, surface, and subsurface soil samples were collected from a total of 41 locations along highways with dense traffic and secondary roads with lower traffic and analyzed for lead (Pb), zinc (Zn), and copper (Cu) concentrations. Statistical evaluation of the heavy metal concentrations observed along highways and along the secondary roads showed that the data were bimodally distributed. The maximum observed Pb, Zn, and Cu concentrations were 1,573, 522 and 136 mg/kg, respectively, in surface soils along highways and 99.3, 156, and 38.1 mg/kg along secondary roads. Correlation analysis of the metal concentrations in road dust, surface and 20-cm depth soils suggests the presence of a common pollution source. However, metal concentrations in the deeper soils were substantially lower than those observed at the surface, indicating low mobility of heavy metals, especially for Pb and Zn. A modified kriging approach that honors the bimodality of the data was used to estimate the spatial distribution of the surface concentrations of metals, and to identify hotspots. Results indicate that despite the presence of some industrial zones within the study area, traffic is the main heavy metal pollution source.     

Metal fractionation study on bed sediments of Hussainsagar Lake, Hyderabad, India

Hussainsagar Lake in the heart of Hyderabad City (India) receives toxic substances through five streams draining from a catchment area of 245 km². Of particular interest are heavy metals received from urban runoff as well as municipal sewage and industrial effluents. Heavy metals entering the lake get adsorbed onto the suspended sediments, which eventually settle down in the bottom of the lake. In this study, fractionation of metal ions has been studied on the bed sediments of Hussainsagar Lake in order to determine the ecotoxic potential of metal ions. Comparison of sediments with average shale values indicated anthropogenic enrichment with copper, nickel, lead, cadmium, and zinc. The risk assessment code as applied to the present study reveals that 10–17% of manganese, 10–18% of nickel, 14–24% of chromium, 10–19% of lead, 21–30% of cadmium, and 18–28% of zinc exist in exchangeable fraction and, therefore, comes under medium risk category and may enter into food chain. The association of these metals with the exchangeable fraction may cause deleterious effects to aquatic life. The present database will help in formulating guidelines for carrying out dredging operations under restoration programs in the Hussainsagar Lake.