The Chemical Speciation of Fe(III) in Freshwaters

Dialysis and chemical speciation modelling have been used to calculate activities of Fe³⁺ for a range of UK surface waters of varying chemistry (pH 4.3–8.0; dissolved organic carbon 1.7–40.3 mg l⁻¹) at 283 K. The resulting activities were regressed against pH to give the empirical model: . Predicted Fe³⁺ activities are consistent with a solid–solution equilibrium with hydrous ferric oxide, consistent with some previous studies on Fe(III) solubility in the laboratory. However, as has also sometimes been observed in the laboratory, the slope of the solubility equation is lower than the theoretical value of 3. The empirical model was used to predict concentrations of Fe in dialysates and ultrafiltrates of globally distributed surface and soil/groundwaters. The predictions were improved greatly by the incorporation of a temperature correction for , consistent with the temperature dependence of previously reported hydrous ferric oxide solubility. The empirical model, incorporating temperature effects, may be used to make generic predictions of the ratio of free and complexed Fe(III) to dissolved organic matter in freshwaters. Comparison of such ratios with observed Fe:dissolved organic matter ratios allows an assessment to be made of the amounts of Fe present as Fe(II) or colloidal Fe(III), where no separate measurements have been made. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Stable isotopes and heavy metal distribution in Dreissena polymorpha (Zebra Mussels) from western basin of Lake Erie, Canada

 Dreissena polymorpha is an exotic freshwater bivalve species which was introduced into the Great Lakes system in the fall of 1985 through the release of ballast water from European freighters. Utilizing individual growth rings of the shells, the stable isotope distribution (δ¹⁸O and δ¹³C) was determined for the life history of selected samples which were collected from the western basin of Lake Erie. These bivalves deposit their shell in near equilibrium with the ambient water and thus reflect any annual variation of the system in the isotopic records held within their shells. Observed values for δ¹⁸O range from -6.64 to –9.46‰ with an average value of –7.69‰ PDB, while carbon values ranged from –0.80 to –4.67‰ with an average value of –1.76‰ PDB. Dreissena polymorpha shells incorporate metals into their shells during growth. Individual shell growth increments were analyzed for Pb, Fe, Mg, Mn, Cd, Cu, and V concentrations. The shells show increased uptake of certain metals during periods of isotopic enrichment which correspond with warmer water temperatures. Since metals are incorporated into the shells, the organism may be useful as a biomonitor of metal pollution within aquatic environments. Received: 31 October 1996 · Accepted: 21 May 1997     

Growth,abundance, morphometric and metabolic parameters of three populations of Diplodon chilensis subject to different levels of natural and anthropogenic organic matter input in a glaciar lake of North Patagonia

Three populations of Diplodon chilensis (Hiridae, Bivalvia) from North Patagonia (Lacar lake, Argentina) have been studied to determine how organic matter (OM) influence their growth, density, morphometric and metabolic parameters in two pristine sites (Yuco and Nonthué) and in a growing touristic locality (San Martín de los Andes Bay, site SMA) affected by urban discharges. In Nonthué (chemical and biological oxygen demand ratio COD/BOD ratio of 4.7), a dense neighboring forest provides higher quantities of vegetal detritus compared to Yuco, while in SMA the OM input increase is related to anthropogenic impact, mainly sewage discharges, which is more biodegradable (COD/BOD ratio of 1.7). Our results show that population's size distribution and growth rates are affected positively by increased OM, independently of its natural or anthropogenic origin. The modal shell length interval for SMA and Nonthué is two-fold higher (70 mm), in agreement to the growth rate increase (k = 0.079), compared to Yuco (35 mm, k = 0.045). The morphometric relationships between size–size and size–mass show a higher slope for SMA and Nonthué, which underline allometric differences between these two populations and the Yuco's one. The lower population densities in both sites (SMA 33 ind./m² and Nonthué 76 ind./m²) compare to Yuco (176 ind./m²) and the absence of individuals younger than 7 and 5 years old, respectively, in SMA and Nonthué could be related to the higher allochthonous OM content in the sediments and total suspended solids in water. Increased OM due to urban pollution in SMA bivalves leads to higher oxidative damage to lipids, which is not counterbalanced by the higher detoxification enzyme glutathione-S-transferase activity. Hence, we can conclude that pollution would explain the drastic reduction in population density, probably related to a high impair in the juvenile's survival/recruitment, the higher observed mortality and the lower population longevity. When increased OM is supply by the forest, like in Nonthué, this has less negative effect on population density and no effect on longevity at all. However, a negative effect of oxygen depletion due to increased OM (either anthropogenic or natural) on juvenile survival cannot be discarded, but further studies should be carried out to support this idea.     

Small is profitable: No support for the optimal foraging theory in sea stars Asterias rubens foraging on the blue edible mussel Mytilus edulis

Doubt has been shed recently on the most popular optimal foraging theory stating that predators should maximize prey profitability, i.e., select that prey item that contains the highest energy content per handling time. We hypothesized that sea stars do not forage on blue mussels according to the classical optimal foraging theory but are actively avoiding damage that may be caused by e.g. capture of foraging on too-strong mussel shells, hence the sea stars will have a stronger preference for mussels that are smaller than the most profitable ones. Here we present experimental evidence of the sea star Asterias rubens as a predator that indeed chooses much smaller blue mussels Mytilus edulis to forage on than the most profitable ones. Hence this study does not support the optimal foraging theory. There may be other constraints involved in foraging than just optimizing energy intake, for example predators may also be concerned with preventing potential loss or damage of their foraging instruments.     

Freshwater mollusc biodiversity and conservation in two stressed Mediterranean basins

This paper reviews the environmental factors that influence biodiversity of freshwater mollusc communities and conservation status of watercourses in two Mediterranean acid mine drainage-impacted basins of the southern Iberian Peninsula. We found 17 mollusc species: 14 gastropods (10 native and 4 introduced) and 3 bivalves. We found five distribution patterns: native headwater (Arganiella wolfi, Stagnicola palustris, Unio delphinus, Pisidium casertanum and Pisidium personatum) and mouth (Hydrobia acuta, Peringia ulvae and Myosotella myosotis) sensitive-stenochoric species, intermediate sensitive-widely distributed species (Planorbarius metidjensis and Radix balthica), insensitive-eurychoric species (Ancylus fluviatilis), and erratic-distribution pattern species (Galba truncatula and Planorbis carinatus). The highest biodiversity indices have been found in non-impacted headwaters and, to a lesser extent, in tidal streams. The biodiversity of the middle reaches, with varying degrees of impact by acid mine drainage and high water deficit, was scarce and dominated by introduced species. Over 30% of the variation in native and introduced species richness is explained by environmental gradients related to heterogeneity (instream macrophytes cover and Fhi and Qbr indices) and acid runoffs (pH, conductivity, turbidity and concentration of sulphides). Severely impacted sites have no mollusc species. The conservation status of watercourses is also very remarkably influenced by the heterogeneity and contamination of the environment. Conservation values are higher in water bodies located in protected northern and southern sites in both basins.     

Glacial Lake Vitim, a 3000-km outburst flood from Siberia to the Arctic Ocean

A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500 km² and held a volume of ~ 3000 km³. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~ 13 cal ka BP inferred from Arctic Ocean sediments.     

河蚌养殖对水域环境的影响及养殖模式的优化

综述了河蚌养殖育珠对水域水质影响以及养殖模式优化,指出采用适当的养殖模式养殖育珠,可修复水域环境与改善水质状况.     

Comparison of the effects of pollution on the marine bivalve Donax trunculus in the vicinity of polluted sites with specimens from a clean reference site (Mediterranean Sea)

The physiological and biochemical characteristics of tissue samples of the marine mussel, Donax trunculus, from an oil-polluted site (Qiryat Yam) and from a site adjacent to an industrial factory (Frutarom) producing polyvinyl chloride (PVC) were compared with samples from a clean reference site (Akko). All sites were located along the sandy shores of the Israeli Mediterranean Sea. The mussels from the oil-polluted site showed increased activity of the system of active transport of organic anions (SATOA) in the gills and the renocardial organ and also of the multixenobiotic resistance transporter (MXR) in the gills. In contrast, samples collected near the PVC factory showed a decrease in SATOA activity and no increase in the activity of MXR in the gills. Specimens from the reference site demonstrated a redox state of equilibrium between energy production and utilization, while in Donax from both the oil polluted and the PVC-polluted sites, the mitochondrial redox state reflected intensive consumption of energy. No significant changes were found in the activity of reduced glutathione s-transferase (GST) in the cytosolic fraction of the digestive gland of Donax collected from any of the three sites. The data demonstrate a differential increase in the anti-chemical defense systems and an intensification of energy metabolism in the mussels exposed to pollution.     

Multimetric Macroinvertebrate Index Flanders (MMIF) for biological assessment of rivers and lakes in Flanders (Belgium)

The European Water Framework Directive requires that member states assess all their surface waters based on a number of biological elements, including macroinvertebrates. Since 1989, the Flemish Environment Agency has been using the Belgian Biotic Index for assessing river water quality based on macroinvertebrates. Throughout the years, the Belgian Biotic Index has proven to be a reliable and robust method providing a good indication of general degradation of river water and habitat quality. Since the Belgian Biotic Index does not meet all the requirements of the Water Framework Directive, a new index, the Multimetric Macroinvertebrate Index Flanders (MMIF) for evaluating rivers and lakes was developed and tested. This index was developed in order to provide a general assessment of ecological deterioration caused by any kind of stressor, such as water pollution and habitat quality degradation. The MMIF is based on macroinvertebrate samples that are taken using the same sampling and identification procedure as the Belgian Biotic Index. The index calculation is a type-specific multimetric system based on five equally weighted metrics, which are taxa richness, number of Ephemeroptera, Plecoptera and Trichoptera taxa, number of other sensitive taxa, the Shannon-Wiener diversity index and the mean tolerance score. The final index value is expressed as an Ecological Quality Ratio ranging from zero for very bad ecological quality to one for very good ecological quality. The MMIF correlates positively with dissolved oxygen and negatively with Kjeldahl nitrogen, total nitrogen, ammonium, nitrite, total phosphorous, orthophosphate and biochemical and chemical oxygen demand. This new index is now being used by the Flemish Environment Agency as a standard method to report about the status of macroinvertebrates in rivers and lakes in Flanders within the context of the European Water Framework Directive.     

Estimating Net Primary Productivity and Nutrient Stock in Plant in Freshwater Marsh,Northeastern China

We have investigated the contributions of three dominant macrophyte species, Deyeuxia angustifolia, Carex lasiocarpa, and Carex pseudocuraica (covering about 10 304 km²), to carbon (C), nitrogen (N), and phosphorus (P) stocks in the largest freshwater marsh (17 300 km²) in China for a 3‐year period (from 2002 to 2004). The monthly biomass, seasonal, and annual net primary productivity (NPP), and nutrient concentrations of three species were measured. All three plant species showed rapid growth in the rainy season. The maximum and minimum production rates in the freshwater marsh were ～36.19 and ～9.92 g m^?2 day^?1, respectively. The total NPP accounts 1900–2700 g m^?2 year^?1 in the studied area. Total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) concentrations in roots were higher than those in stem and leaf tissues. The vast beds of the three studied species comprise 80% of the grass covered marsh of Sanjiang plain, contributing annual nutrient stocks of ～10.99 × 10⁶, ～788.36 × 10³, and ～18.10 × 10³ t (tonnes) for TOC, TN, and TP, respectively. Our results suggest that the nutrient bioaccumulation capacity in freshwater marshes depend mainly on plant species, which are decided by hydrological conditions. The nutrient stocks in the Sanjiang plain marsh have been greatly reduced because some of the area occupied by C. lasiocarpa was replaced by D. angustifolia as a result of succession caused by the changes of water table.