HARVESTING AS A CONTROL FOR AQUATIC PLANTS1

Studies of the effects of harvesting on hydrophytes in Lake Mendota, Wisconsin indicate that one harvest reduced growth by at least 50%, two harvests reduced it by 75% and three harvests virtually eliminated plant material for the year. The studies also indicated that harvesting one year reduced the biomass the following year, especially in deep water. Three harvests during the previous year were most effective in controlling biomass the second year.     

Dueling Land Ethics: Uncovering Agricultural Stakeholder Mental Models to Better Understand Recent Land Use Conversion

The aim of this paper is to investigate how alternative land ethics of agricultural stakeholders may help explain recent land use changes. The paper first explores the historical development of the land ethic concept in the United States and how those ethics have impacted land use policy and use of private lands. Secondly, primary data gathered from semi-structured interviews of farmers, ranchers, and influential stakeholders are then analyzed using stakeholder analysis methods to identify major factors considered in land use decisions, priorities of factors of each group, and to define relevant mental models describing each group’s view of the land ethic concept. Results show that these stakeholder groups prioritize land use factors qualitatively differently and possess strikingly different land ethics. It is concluded that shifts in stakeholder land ethics have contributed to recent land use changes. Lastly, we discuss how current agricultural policy sends mixed signals about preferred land use and the potential ramifications based on the different land ethics we’ve described.     

Benthic polychaete assemblages and their relationship to the sediment in Port Madison,Washington

Two indices of community association and a 3 dimensional ordination of stations were used to elucidate the relationship between small-scale changes in species, composition of polychaete assemblages and changes in the physical character of the sediment, at 9 stations along a 1.5 km subtidal transect. There were no faunal or physical discontinuities that might have been used to delineate boundaries of polychaete communities, except at a very shallow station where the effects of extreme fluctuations of temperature and salinity were evident. The degree of similarity between assemblages was related to the similarity of the sediments at the different stations. In particular, the changes in species composition appeared to correspond most clearly to differences in the clay content of the sediment.     

THE USE OF OVERWINTER DRAW DOWN FOR AQUATIC VEGETATION MANAGEMENT1

ABSTRACT: Overwinter draw down can be a useful technique for aquatic plant management. Its effectiveness depends largely on the susceptibility of nuisance species to draw down. A single overwinter draw down provided good control of aquatic plants in a flowage dominated by Potamogeton robbinsii Little additional control was gained by a second draw down the following winter. Rapid reinvasion of plants after draw down ceased dictates continued management. To avoid fish kills caused by low dissolved oxygen levels caution is advised when using overwinter draw down. The growth of Zizania aquatica was not negatively influenced by draw down. The influence on water quality of nutrient release from decaying vegetation and exposed bottom sediments was uncertain.     

Use of Stable Nitrogen Isotopes and Permeable Membrane Devices to Study what Factors Influence Freshwater Mollusk Survival in the Conasauaga River

Recent biological inventory data shows severe declines in freshwater mussel abundance and biodiversity in the Conasauga River Basin in Northwest Georgia, USA. Based on assessments of habitat conditions, mussel populations should be sustainable. We conducted a study of sediment and water quality to evaluate the impact of anthropogenic contamination on mussel populations. Permeable membrane devices (PMD), polar organic chemical integrative samplers (POCIS™), conventional water and sediment quality analyses, and stable nitrogen isotope ratio analyses (δ¹⁵N) of snails and sediments were used to assess sediment and water quality at target sites throughout the basin. Ambient concentrations of organic contaminants in water were well below any aquatic life criteria; concentrations of some nutrients were detected above aquatic life criteria levels. Most mussel species in the river are endangered or threatened; therefore, snails were collected for δ¹⁵N analyses. Mean δ¹⁵N values for snails collected at forested upper watershed sites (national forest areas) were significantly lower than δ¹⁵N values from snails in agricultural areas. δ¹⁵N values for raw cow manure and manure-treated soil were similar to δ¹⁵N values for snails collected in agricultural areas. Dissolved nitrate from water samples had elevated δ¹⁵N values similar to the upper range of δ¹⁵N values for snails in agricultural areas. Data, particularly stable nitrogen isotope data, indicates that a land use change from national forest land to agriculture alters nitrogen sources to the basin and snails. Implications of nutrient release on freshwater molluscan reproduction, growth, and survival are discussed.     

Lionfish alter benthic invertebrate assemblages in patch habitats of a subtropical estuary

Invasive lionfish (primarily Pterois volitans) have spread throughout the Caribbean region, Gulf of Mexico, and the Southeast US coast, and resulting impacts on reef fish populations have been well documented. We examined whether lionfish can likewise affect benthic invertebrate communities, using an in situ caging experiment, in the Loxahatchee Estuary, Florida, USA. We found that lionfish caused significant declines in the three most abundant benthic invertebrate species, driving an overall shift in assemblage composition. For example, grass shrimp (Palaemonidae) abundance was reduced by nearly 90 % in the presence of lionfish. Species richness of benthic organisms was significantly higher when lionfish were present, suggesting potentially complex emergent effects of lionfish predation on benthic assemblages. Despite the fact that this experiment was conducted in just a single location using relatively small experimental units, we show altered benthic invertebrate communities could well be an additional outcome of the lionfish invasion.     

Lipid composition and partitioning of deepwater chondrichthyans: inferences of feeding ecology and distribution

The composition of lipids and fatty acids was determined for the livers, muscle, pancreas, kidney and stomach fluids of deepwater chondrichthyan species (including 11 squaliformes, 3 chimaeriformes, 1 hexanchiforme and 3 carcharhiniformes) caught as bycatch from continental waters off south-eastern Australia. The lipid class, fatty acid and fatty alcohol composition differed markedly in each tissue and in each species. The lipid and fatty acid composition of large, lipid-rich (38–70% wet weight, ww) livers demonstrated the multifunctional role of this organ in: lipid distribution, storage and biosynthesis, and buoyancy regulation. In the liver, the importance of certain lipids (including squalene, diacylglyceryl ethers, triacylglycerols and to a lesser extent wax esters) as mediators of buoyancy varied according to lifestyle and habitat. Less variability was observed in the muscle profiles, characterized by low lipid content (<1.0% ww) and high relative levels of polar lipids (>70%). The lipid and fatty acid profiles of the kidney and pancreas showed the highest intraspecific variability, suggesting these organs also have complex roles in lipid storage and metabolism. Overall intra- and interspecific differences in the tissue fatty acid profiles could be related to differences in a number of factors including phylogeny, habitat (depth), buoyancy regulation and diet and presumably also reflect different ecological roles. The lipid and fatty acid profiles are the first published for Rhinochimaera pacifica, Chimaera lignaria and Figaro boardmani and the first to demonstrate interspecific variation in lipid profiles of various tissues of deepwater chondrichthyans. The application of multivariate analysis to lipid class and fatty acid tissue profiles in chondrichthyans inferred dietary differences and metabolic preferences between species and habitats. These results have important implications for the future use of fatty acids as dietary tracers in chondrichthyan research.     

Denitrification with carbon addition--kinetic considerations

The Blue Plains Advanced Wastewater Treatment Plant (Washington, D.C.) uses methanol as an external carbon source in a postdenitrification process, to achieve low effluent total nitrogen concentrations. This becomes more difficult in winter, at lower mixed liquor temperatures and higher flows, as a consequence of the kinetic behavior of the methanol-utilizing heterotrophs. The paper reports on an experimental batch test study conducted on Blue Plains postdenitrification sludge to investigate (1) the maximum specific growth rate of methanol-utilizing heterotrophs (Mu(METH)); (2) the temperature dependency of the growth rate; and (3) the efficacy of alternate substrates (ethanol, acetate, and sugar). A limited number of tests were conducted on sludge from two other treatment plants with methanol addition.     

The impact of vegetation on sedimentary organic matter composition and PAH desorption

Relationships between sedimentary organic matter (SOM) composition and PAH desorption behavior were determined for vegetated and non-vegetated refinery distillate waste sediments. Sediments were fractionated into size, density, and humin fractions and analyzed for their organic matter content. Bulk sediment and humin fractions differed more in organic matter composition than size/density fractions. Vegetated humin and bulk sediments contained more polar organic carbon, black carbon, and modern (plant) carbon than non-vegetated sediment fractions. Desorption kinetics of phenanthrene, pyrene, chrysene, and C₃-phenanthrene/anthracenes from humin and bulk sediments were investigated using Tenax^® beads and a two-compartment, first-order kinetic model. PAH desorption from distillate waste sediments appeared to be controlled by the slow desorbing fractions of sediment; rate constants were similar to literature values for k_slow and k_{very slow}. After several decades of plant colonization and growth (Phragmites australis), vegetated sediment fractions more extensively desorbed PAHs and had faster desorption kinetics than non-vegetated sediment fractions.     

离体模型预测鱼体肝脏清除速率：鲑鱼肝细胞和肝脏S9组分的比较

将离体肝细胞和肝脏S9组分用于获取鱼类的体外生物转化数据可以优化模拟评估对化学物质的生物富集作用。然而涉及2种方式之间的直接对比的研究却几乎没有。本研究采用冷藏保存的鲑鱼肝细胞来测定对于6种多环芳烃(PAHs)的体外本征清除速率。我们运用测定结果推测体内本征清除速率,并将其作为输入值输入一种充分搅匀的肝脏模型中来预测肝清除速率。将事先由体外灌流肝脏测定的速率作为参考来评价预测结果。在2种竞争结合的假说前提下,由鲑鱼肝细胞测出的肝清除速率与实现的测定结果基本一致(6种多环芳烃中的5种都保持在2.1倍差异以下)。尽管多环芳烃的高代谢率是可能的原因之一,这些发现与之前由肝脏S9组分得出的结果相似。对苯并芘这一种化合物而言,由S9数据得出的体内本征清除速率是由肝细胞得出结果的10倍左右,这一结果可能是由细胞吸收速率造成的传播限制引起的。尽管苯并芘的结果差异较大,由任何一种体外测试方法得出的体内本征清除速率结果通常是一致的。这些结果显示离体肝细胞和肝脏S9组分2种系统均可用于优化鱼类的生物富集评估,尤其对于体外反应速率较高的情况。不同系统在化工领域的应用性是否相同则需要进一步的研究工作。
精选自Kellie A. Fay, Patrick N. Fitzsimmons, Alex D. Hoffman, John W. Nichols. Comparison of trout hepatocytes and liver S9 fractions as in vitro models for predicting hepatic clearance in fish. Environmental Toxicology and Chemistry: Volume 36, Issue 2, pages 463–471, July 2017. DOI: 10.1002/etc.3572
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3572/full