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Notes: Abstract Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO2 fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO2 fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO2 fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO2 incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO2 incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found.

Notes: : A variety of management options are used to minimize losses of nitrogen (N), phosphorus (P), and other potential pollutants from agricultural source areas. There is little information available, however, to indicate the effectiveness of these options (sometimes referred to as Best Management Practices, or BMPs) on basin scales. The objective of this study was to assess the water quality effectiveness of BMPs implemented in the 3240 ha Lincoln Lake basin in Northwest Arkansas. Land use in the basin was primarily forest (34 percent) and pasture (56 percent), with much of the pasture being regularly treated with animal manures. The BMPs were oriented toward minimizing the impact of confined animal operations in the basin and included nutrient management, dead bird composter construction, and other practices. Stream flow samples (representing primarily base flow conditions) were collected bi-weekly from five sites within the basin from September 1991 through April 1994 and analyzed for nitrate N (NO3-N), ammonia N (NH3-N), total Kjeldahl N (TKN), ortho-P (PO4-P), total P (TP), chemical oxygen demand (COD), and total suspended solids (TSS). Mean concentrations of PO4-P, TP, and TSS were highest for subbasins with the highest proportions of pasture land use. Concentrations of NH3-N, TKN, and COD decreased significantly with time (35–75 percent/year) for all sub-basins, while concentrations of other parameters were generally stable. The declines in analysis parameter concentrations are attributed to the implementation of BMPs in the basin since (a) the results are consistent with what would be expected for the particular BMPs implemented and (b) no other known activities in the basin would have caused the declines in analysis parameter concentrations.

Notes: : Agricultural practices such as cattle grazing and animal manure application can contribute to relatively high runoff concentrations of fecal coliform (FC) and fecal streptococcus (FS). Available information, however, is inconsistent with respect to the effects of such practices as well as to measures that can discriminate among candidate sources of FC and FS. The objective of this study was to assess the effects of grazing, time of year, and runoff amounts on FC and FS concentrations and to evaluate whether FCIFS concentration ratios are consistent with earlier values reported as characteristic of animal sources. Runoff from four Northwest Arkansas fields was sampled and analyzed for fecal coliform (FC) and fecal streptococcus (FS) for nearly three years (1991–1994). Each field was grazed and fertilized, with two fields receiving inorganic fertilizer and two receiving animal manure. Runoff amount had no effect on runoff concentrations of FC or FS. There were no consistent relationships between the presence of cattle and FC and FS runoff concentrations. Both FC and FS concentrations were affected by the season during which the runoff occurred. Higher concentrations were observed during warmer months. Runoff FC concentrations exceeded the primary contact standard of 200 cfu/100 mL during at least 89 percent of all runoff events and the secondary contact standard of 1000 cfu/100 mL during at least 70 percent of the events. Ratios of FC to FS concentrations varied widely (from near zero to more than 100), confirming earlier findings that FC/FS ratios are not a reliable indicator of the source of FC and FS.

Notes: Mechanical harvesting of intertidal bivalve molluscs inevitably leads to the physical disturbance of the substratum and its associated fauna. Hence, it is necessary to consider the consequences of such activities for the requirements of other species (e.g. fish and birds) which utilize these areas. The present study reports a long-term experiment that studied the effects of Manila clam, Tapes philippinarum Adams & Reeve, cultivation on an estuarine benthic habitat and its fauna. The study began with the initial seeding of the clams, and continued through ongrowing, and finally, harvesting 30 months later. Earlier observations revealed that plots covered with netting elevated sedimentation rate, and hence, encouraged the proliferation of certain deposit-feeding worm species which persisted throughout the cultivation cycle until harvesting took place. The immediate effects of harvesting by suction dredging caused a reduction of infaunal species and their abundance by ∼80%. Recovery of the sediment structure and the invertebrate infaunal communities, judged by similarity to the control plots on both the harvested and unharvested but originally netted plots, had occurred 12 months after harvesting. Comparisons with other similar studies demonstrate that, in general, suction harvesting causes large short-term changes to the intertidal habitat. The rate at which recolonization occurs and sediment structure is restored varies according to local hydrography, exposure to natural physical disturbance and sediment stability. The management of clam farming procedures and other forms of mechanical harvesting should incorporate a consideration of site selection, rotational seeding, cultivation and harvesting to create fallow areas, and seasonal harvesting to ameliorate the recovery of sites.

Notes: A new transparent conducting oxide (TCO), which can be expressed as Ga3−xIn5+xSn2O16; 0.2≤x≤1.6, has been identified. The equilibrium phase relationships of this new material with respect to three other TCOs in Ga2O3–In2O3–SnO2 are reported. The optical properties of this phase are slightly superior to Sn-doped indium oxide (ITO) and depend on composition. A room-temperature conductivity of 375 Ω cm−1 was obtained for H2-reduced Ga2.4In5.6Sn2O16. This value is an order of magnitude lower than commercial ITO films, but comparable to values reported for bulk, polycrystalline Sn-doped In2O3. © 1997 American Institute of Physics.

Notes: With increasing awareness of the use of the coastal zone, it is necessary to understand the potential environmental effects of aquaculture practices. This is especially important when non-native species, which may be competitively superior to native species, are cultivated. A 5-year experiment was established to study the environmental effects of the various stages of Manila clam. Tapes philippinarum Adams & Reeve, cultivation, from seeding, through on-growing, harvesting and post-harvesting. The aim was to monitor changes in biological and physical variables in the sediment which may be useful in formulating an environmental management strategy for the cultivation of this species. This paper describes the biological and physical changes that occur in the sediment during the early phase of clam cultivation. We compared the changes in netted plots (with and without clams) and unnetted control areas, 6 months before and after laying the clams. The clams were planted in April 1992 under netting at a density of 500 m-2 (0.16 kg m-2), and in 6 months, had increased their weight to 3.2 kg m-2 but decreased their number to 410 m-2. A significant, but small increase in organic content (net only plots, 3.37%; control plots 2.42%) and in phaeopigment (netted plots, 8.6 mg m-2; control, 5.6 mg m-2) of the sediment in the netted plots relative to the control areas were seen. Short-term sedimentation rates on the netted plots were up to four times higher than in the control areas. The netting also encouraged the settlement of Enteromorpha sp. which, in turn, attracted Littorina littorea to feed on these plots. The infaunal community in the control areas was similar to that in samples 12 months earlier and continued to be dominated by the predatory polychaete Nephtys hombergii. Netted plots (with and without clams) had a greater abundance of deposit feeding polychaetes. particularly Ampharete acutifrons and Pygospio elegans, which were the dominant fauna in these plots. Within the clam treatments, the density of clams had a negative effect on the abundance of cirratulids, although mean abundance was generally greater than in the control areas. There were few physical changes to the experimental area after 6 months. The most important effect appears to be the increased sedimentation rate over plots with netting, which has led to an increase in productivity of those areas.

Notes: A study of the environmental effects associated with the trestle cultivation of Pacific oysters, Crassostrea gigas Thunberg, was conducted at a commercial cultivation site in the River Exe estuary, Devon, England. Small, but significant, changes were detected in the macrofaunal community sampled beneath oyster trestles compared with that found in adjacent uncultivated areas. These changes were associated with an increase in organic and silt composition and a reduction in the depth of the oxygenated layer of the sediment beneath the trestles. Water velocity was decreased by the presence of the trestles which probably led to the increase in sedimentation rate observed beneath them. Although biological and physical changes were observed, they were relatively minor compared with the extreme environmental changes associated with the suspended culture techniques used for other bivalve species and fishes. However, other studies suggest that the environmental effects associated with oyster cultivation become more severe in areas of large-scale (hectares) cultivation.

Notes: Simulated depuration trials with Manila clams. Tapes philippinarum Adams and Reeve, were undertaken to test the effect of stocking density, seasonal temperature, water flow rate, salinity and the addition of cultured algae on oxygen levels and some other variables of water quality. Equations produced by multilinear regression analysis provided useful systems-management information for predicting the conditions required to maintain oxygen levels within known limits for satisfactory depuration of other commercial species of bivalve molluscs in temperate climates.

Notes: Concentrations of soluble aluminum (Al) and manganese (Mn) frequently reach phytotoxic levels in acid soils. While dose response relationships for these metals are well documented, the effects of combined exposure have received less attention. We have examined the effect of combinations of Al and Mn on growth and metal accumulation in Vigna unguiculata (L.) Walp. grown in solution culture under conditions of low ionic strength (conductivities typically 〈 100 µS cm−1). The nature of interaction between these metals varied with the specific physiological response, the part of the plant investigated, and the relative amount of stress imposed. Analysis of growth data provided evidence for amelioration of metal toxicity (antagonistic effects), although this effect was dose dependent. Analysis of metal content data provided evidence for antagonistic and synergistic (exacerbation of toxicity) effects, again depending on dose. Analysis of foliar symptoms also provided evidence for antagonisms and synergisms, with the nature of the response dependent on the specific physiological response and specific plant part investigated. In contrast with previous reports, evidence for antagonistic, synergistic, and multiplicative effects on growth, metal uptake, and expression of foliar symptoms have been obtained under physiologically and environmentally relevant conditions. These results suggest a more detailed analysis of the potential for interactions between metals in the environment is required.