Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River

Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside.     

Incorporation of 35SO 4 2− into sediments of three New York lakes

Intact sediment cores were obtained from three New York lakes in May, July, and October 1981. Radioactive S (as ³⁵SO ₄ ²⁻ ) was added to the overlying water and cores were incubated without atmospheric exchange for one week near lake bottom temperatures. Headspace flux of 0₂ as an index of sediment respiration rates varied among lakes and seasonally within lakes. Acidic South Lake had the lowest respiration rate at all seasons and also the smallest net incorporation of the ³⁵SO ₄ ²⁻ . Summer net isotope transformation into ester sulfate and non-HI reducible S (pyrite and C-bonded S) constituents was 88.6%, 89.4%, and 59.7% of total sediment isotope for Oneida, Deer, and South, respectively. Seasonal variation of net isotope incorporation was observed in each lake as were differences in ³⁵SO ₄ ²⁻ partitioning into major S pools. Of the S constituents analyzed, HCl digestible S (volatile sulfides) was the smallest pool, while ester sulfate and non-HI reducible S together accounted for greater than 50% of S isotope transformation in all lakes. In addition, ester sulfate is the major product of dissolved SO ₄ ²⁻ transformation and its formation results in less alkalinity generation than the formation of non-HI reducible S constituents. Thus ester sulfate transformation processes must be considered in calculating alkalinity generation by lake sediments. Financial support provided by Office of Water Research Technology (Project No. 13-096-NY). Financial support provided by Office of Water Research Technology (Project No. 13-096-NY).     

Nitrate depletion in the riparian zone of a small woodland stream

Field enrichments with nitrate in two spring-fed drainage lines within the riparian zone of a small woodland stream near Toronto, Ontario showed an absence of nitrate depletion. Laboratory experiments with riparian substrates overlain with nitrate enriched solutions revealed a loss of only 5–8% of the nitrate during 48 h incubation at 12°C. However, 22–24% of the initial nitrate was depleted between 24 and 48 h when a second set of substrate cores was incubated at 20°C. Short-term (3 h) incubations of fresh substrates amended with acetylene were used to estimate in situ denitrification potentials which varied from 0.05–3.19 g N g^–1 d^–1 for organic and sandy sediments. Denitrification potentials were highly correlated with initial nitrate content of substrate samples implying that low nitrate levels in ground water and riparian substrates may be an important factor in controlling denitrification rates. The efficiency of nitrate removal in spring-fed drainage lines is also limited by short water residence times of < 1 h within the riparian zone. These data suggest that routes of ground water movement and substrate characteristics are important in determining nitrate depletion within stream riparian areas.     

Pigment and lipid compositions of algal and bacterial communities in Ace Lake,Vestfold Hills,Antarctica

The compositions of carotenoids, chlorophylls and lipids at four depths in Ace Lake have been determined as a means of studying the vertical zonation of species in the lake and for comparison with the lipids found in the bottom sediments. The four major species of phytoplankton found in the lake were identified by electron microscopy. The most abundant phytoplankter was Pyramimonas gelidicola McFadden (Chlorophyta, Prasinophyceae) which occurred in greatest numbers at 10 m, the base of the oxylimnion. The pigments and lipids at this depth were mainly derived from this alga. At 11 m (the top of the anoxylimnion) only traces of lipids and pigments attributable to P. gelidicola were found, indicating only limited settling of algal cells through to the anoxylimnion, at least in summer. The pigments at 11 m were dominated by bacteriochlorophylls c derived from green photosynthetic bacteria Chlorobium spp. These pigments were also abundant at 23 m suggesting the presence of intact bacterial cells which had settled out from higher in the water column. Major non-polar lipid classes in the sediments included sterols, alcohols, hydrocarbons and an unusual suite of very long-chain unsaturated ketones and esters which have not previously been reported from antarctic environments. Several novel compounds, not found previously in either sediments or organisms, are reported. These include tri- and tetra-unsaturated straight-chain C₃₉ methyl ketones and C₄₀ ethyl ketones and the methyl ester of a tetra-unsaturated straight-chain C₃₆ fatty acid. The distributions of lipids in the sediment were markedly different from those in the water column indicating extensive bacterial degradation and recycling of labile lipids.     

Quantity and quality of seston in an impounded and a free-flowing river in Virginia,U.S.A.

Seston in the impounded North Anna River (NAR) was analyzed and compared to that in the free-flowing South Anna River (SAR) in Virginia, U.S.A. A wet filtration technique was used to separate seston into five size classes. The overall quantity of organic seston was much lower in the NAR than in the SAR. The seston in the NAR was composed of more living organisms, in particular zooplankters in the medium large (234–864 µm) and small (105–234 µm) size classes and diatoms and other algae in the fine (43–105 µm) and very fine (25–43 µm) size classes. The percentage of zooplankton declined sharply before reaching the downstream study site (32 km). The seston in the NAR tended to consist of slightly larger particles, but 80–85% of the seston in both rivers was in the ultrafine (0.45–25 µm) size class, which was almost entirely composed of detritus. One indication of seston food quality, the organic/inorganic ratio, was considerably higher for the medium large and small size classes in the NAR immediately below the dam and for the fine and very fine size classes farther downstream. Another indication of food quality, the usable caloric content, showed that the seston in the NAR contained considerably less total assimilable energy as far as 32 km downstream from the dam, but that the medium large and small size classes were rich in assimilable energy immediately below the dam because of zooplankton released from the reservoir. Thus, the overall quantity and quality of seston was lower in the NAR, but the quality of the seston, for at least a short distance below the dam, was higher in a well-defined size range that can be effectively utilized by certain filter feeders.     

Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO²⁻₄/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO²⁻₄/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 10²–10³ acetate, lactate and propionate oxidising SRB/ml. No low- M _r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment.     

The formation and biotransformation of cysteine conjugates of halogenated ethylenes by rabbit renal tubules

The nephrotoxicity of chlorotrifluoroethylene (CTFE) was examined using isolated rabbit renal tubules suspensions. Exposure of the tubules to CTFE resulted in consumption of CTFE, formation of a glutathione conjugate and inhibition of active organic acid transport. Synthetic cysteine, N-acetylcysteine or glutathione conjugates of CTFE inhibited transport indicating S-conjugation as a possible toxic pathway. 1,2-dichlorovinyl glutathione (DCVG), a model synthetic glutathione conjugate, was used to examine the degradation and toxicity of these conjugates. DCVG inhibited rabbit renal tubule transport in vivo and in vitro. The DCVG was found to be degraded with the evolution of glutamine and glycine to produce the ultimate nephrotoxicant, dichlorovinyl cysteine. Dichlorovinyl cysteine is then bioactivated with the release of ammonia. This sequential degradation explains the latency of DCVG-induced renal transport inhibition relative to dichlorovinyl cysteine. It is now evident that certain halogenated ethylenes are capable of being biotransformed to glutathione conjugates in the kidney with their subsequent hydrolysis to nephrotoxic cysteine conjugates.     

The effects of low concentrations of particulates from paper mill effluent on the macroinvertebrate community of a fast-flowing stream

The effects of a paper mill effluent on the macroinvertebrate community were assessed for the riffle areas of a large fast-flowing stream, the lower reaches of the Saranac River of northern New York State, U.S.A. The effluent caused few changes in dissolved oxygen concentration, pH, biochemical oxygen demand, temperature or nutrient content; however, significant differences in transmitted light, concentrations of particulates and accumulated debris on the substrate were observed. A moderate decrease in invertebrate diversity correlated with increased levels of particulates and substrate debris. An analysis of the response of invertebrate functional groups revealed the effluent had little effect on the density of gathering collector organisms. The functional groups most severely reduced in density were the filtering collectors and scrapers. Predators showed a moderate reduction in density in response to the effluent. The alterations in invertebrate densities were attributed largely to the alterations in seston and substrate caused by the introduction of particulates composed mainly of paper fiber and inert dye.     

Influence of ammonium and extracellular pH on the amino and organic acid contents of suspension culture cells of Acer pseudoplatanus

The effects of supplied ammonium and nitrate on the amino and organic acid contents and enzyme activities of cell suspension cultures of Acer pseudoplatanus L. were examined. Regardless of nitrogen source the pH of the culture medium strongly affected the malate and citrate contents of the cells; these organic acid pools declined at pH 5, but increased at pH 7 and 8. Over a period of two days, ammonium had little effect on the responses of the organic acid pool sizes to the pH of the medium. In contrast, ammonium had a strong influence on amino acid pool sizes, and this effect was dependent on the pH of the medium. At pH 5 there was no increase in cell ammonium or amino acid contents, but at higher pH values cellular ammonium content rose, accompanied by accumulation of glutamine, glutamate and asparagine. Over several days, supplied ammonium led to an increase in activity of glutamate dehydrogenase irrespective of any changes in internal ammonium and amino acid contents. If the pH of the medium was allowed to fall below pH 4 in the presence of ammonium, phosphoenolpyruvate (PEP) carboxylase activity declined to a very low value over several days; at higher pH, the activity of this enzyme, and that of NAD malic enzyme and NAD malate dehydrogenase, remained substantial irrespective of whether the nitrogen source was NH⁺₄ or NO-₃.