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The fate of chromium (Cr) – a redox sensitive metal – in surface sediments is closely linked to early diagenetic processes. This review summarizes the main redox pathways that have been clearly identified over recent decades concerning the behavior of Cr(III,VI) in aquatic environments, and applies them to surface sediments where data for redox speciation remain limited. Overall, abiotic redox reactions that govern the speciation of Cr involve manganese (Mn) (III,IV) (hydr)-oxydes for Cr(III) oxidation, Cr(VI)-reducing species (dissolved iron (Fe) (II) and hydrosulfide (HS)−), and Cr(VI)-reducing phases (ferrous and sulfide minerals, as well as Fe(II)-bearing minerals). Bacterial activity is also responsible for the redox interconversion between Cr(III) and Cr(VI): biotic reduction of Cr(VI) to Cr(III) is observed through either detoxification or dissimilatory reduction. Whereas Mn(II)-oxidizing bacteria are known to promote indirect oxidation of Cr(III) to Cr(VI), the reaction mechanisms are unresolved. Conversely, oxygen (O2), nitrate (NO3 −), and nitrite (NO2 −) do not appear to play any role in Cr(III) oxidation. Additionally, Mn(II) and ammonium (NH4 +) are not known to promote Cr(VI) reduction. Once reduced, the mobility of Cr(III) in sediments is significantly restricted and regulated by precipitation and sorption processes. Finally, even if the role of natural organic matter in sediment has been determined, further research is required to identify the complexation mechanisms.

The goal of the study was to identify the beetle fauna of a small lowland river valley against its spatial arrangement and the directions of beetle migrations between habitats, as well as to determine which environmental factors affect the characteristics of water beetle populations in a river valley's lentic water bodies. The field studies were carried out in various types of water bodies. 112 species of beetles with various ecological characteristics were identified. It was demonstrated that the diversity of water bodies in the valley is conducive to high local species richness. At the same time, the observed high degree of faunistic individualism may be regarded as a sign of poor symmetry in the directions of fauna propagation, particularly that of stagnobionts. The authors argue that high individualism is the consequence of poor hydrological contact between the water bodies due to topography and rare instances of high tide in the river, which, in turn, is the reason for active overflights remaining the main mean of migration between those water bodies. The factors restricting migration of fauna between the water bodies include certain landscape characteristics of the catchment which form topographical obstacles, mainly numerous and dense forest areas. The character of fauna in the respective types of water bodies is affected also by internal environmental factors, particularly the degree to which they are overgrown with macrophytes, type of bottom, type of mineral and organic matter as well as physical parameters of water, such as saturation, pH, temperature and biological oxygen demand. Le but de l'étude était d'identifier la faune de coléoptères d'une petite vallée d'une rivière de plaine en fonction de son paysage et des directions des migrations des coléoptères entre les habitats, ainsi que pour déterminer quels facteurs environnementaux influent sur les caractéristiques des populations de coléoptères aquatiques dans les plans d'eau d'une vallée. Les études sur le terrain ont été effectuées dans divers types de masses d'eau. 112 espèces de coléoptères avec diverses caractéristiques écologiques ont été identifiées. Il a été démontré que la diversité des masses d'eau dans la vallée est propice à la haute richesse des espèces locales. Dans le même temps, le degré élevé observé de l'hétérogénéité faunistique peut être considéré comme un signe de mauvaise symétrie dans les directions de propagation de la faune, en particulier celle des stagnobiontes. Les auteurs soutiennent que la forte hétérogénéité est la conséquence d'un mauvais contact hydrologique entre les masses d'eau en raison de la topographie et de rares inondations de la rivière, ce qui, à son tour, est la raison pour laquelle les survols actifs restent le principal moyen de migration entre ces masses d'eau. Les facteurs limitant la migration de la faune entre les masses d'eau comprennent certaines caractéristiques du paysage du bassin versant qui forment de nombreux obstacles topographiques et les zones forestières denses. Le caractère de la faune dans les différentes masses d'eau est affecté aussi par des facteurs environnementaux internes, en particulier le degré auquel elles sont envahies par les macrophytes, le type de fond, le type de matières minérales et organiques ainsi que des paramètres physiques de l'eau, tels que l'oxygénation, le pH, la température et la DBO5.

The influence of day/night conditions on individual animal/plant species has been widely studied, but diel cycle studies of the entire stream macroinvertebrate community are extremely rare. This study explored potential dissimilarities between daytime and nighttime macroinvertebrate assemblages by extensive fieldwork conducted in the Lemme stream, a natural water course of NW Italy. Here numerous structural and functional metrics (richness, abundance, biomass, indicator taxa, composition, biomonitoring values and feeding groups) were evaluated at the family level. Small-scale environmental variables were investigated to understand possible differences between macroinvertebrate assemblages in the daytime/nighttime. After collecting and identifying 21 459 organisms of 50 taxa, Chironomidae (Diptera) was the most abundant under both day and night conditions. Our findings stressed that similar results and biological information on daytime/nighttime data were obtained. No marked differences could be related to various factors: heterotrophic condition of small-order streams, presence of aquatic predators under night and day conditions, absence of taxa with a specific phototaxis. Of all the environmental variables, velocity was always the most important in both situations, with some differences detected in the importance of the second variable (riverbed substrate diameter). This research, and future studies on different conditions and geographic areas, will contribute knowledge on stream macroinvertebrate diel activity, and provide useful information about efficient sampling strategies. L’influence des conditions jour/nuit sur les espèces animales et végétales a été largement étudiée, tandis que les études à propos du cycle diurne de l’entier de la communauté des macro-invertébrées fluviales sont extrêmement rares. Dans le cadre de cette étude, les différences potentielles entre les assemblages de macro-invertébrés lors du jour et de la nuit ont été explorées grâce à un travail de terrain très appuyé. L’expérience a été conduite près du Lemme, un cours d’eau naturel situé dans le nord-ouest de l’Italie où des nombreux indicateurs structurels et fonctionnels (richesse, abondance, biomasse, taxons indicateurs, composition, valeurs de biosurveillance et groupes d’alimentation) ont été évalués au niveau Famille. Les variables environnementales à petite échelle ont été évaluées aussi dans le but de comprendre les différences possibles entre les assemblages de macro-invertébrés durant le jour et la nuit. Un total de 21 459 organismes appartenant à 50 taxons ont été collectés et identifiés, montrant que le Chironomidae (Diptera) est le plus présent le jour comme la nuit. Nos trouvailles nous ont montré que des résultats similaires ont été obtenus dans des conditions diurnes comme nocturnes. L’absence de différences marquées peut être due à plusieurs facteurs, parmi lesquels les conditions hétérotrophes des cours d’eau de petite portée, la présence de prédateurs aquatique le jour comme la nuit et l’absence de taux avec phototaxie spécifique. En ce qui concerne les variables environnementales, la vitesse a été la plus importante dans le deux situations, alors que des différences ont été détectées avec le diamètre du substrat du lit du fleuve. Cette recherche, comme d’éventuels futures études portant sur différentes conditions et les zones géographiques, contribue à la connaissance de l’activité diurne de macro-invertébrés et peuvent fournir des informations utiles sur l’efficacité des stratégies d’échantillonnage.

More than 200 specimens of Limnobiophyllum scutatum (Dawson) Krassilov have been recovered from lacustrine claystones in the Paleocene Paskapoo Formation near Red Deer, Alberta. The plant was a floating, aquatic angiosperm with helically arranged, ovate leaves attached in small rosettes. Rosettes are interconnected by stolons and bear simple adventitious roots as well as larger branching roots that appear to have vascular tissue. Leaves are pubescent, aerenchymatous, with 12-14 campylodromous primary veins that curve toward the apex, joining a fimbrial vein, often an apical notch. Staminate flowers with two, four-loculate stamens, are borne in the axils of second leaves. Anthers contain monoporate, globose, echinate pollen, 20-25 micrometer in diameter. The pollen wall is 0.8 micrometer thick, with a homogeneous foot layer, granular to slightly columellate infratectal layer and an echinate tectum. Pollen most closely resembles the sporae dispersae genus Pandaniidites Elsik. The completeness of L. scutatum has allowed for its inclusion in a numerical cladistic analysis to resolve relationships among taxa of the Lemnaceae, Pistia, and selected genera of Araceae. Results of the analysis indicate that the Lemnaceae plus Pistia form a monophyletic group within the Araceae

Reactive oxygen species (ROS) are increasingly appreciated as down-stream effectors of cellular damage and dysfunction under natural and anthropogenic stress scenarios in aquatic systems. This comprehensive volume describes oxidative stress phenomena in different climatic zones and groups of organisms, taking into account specific habitat conditions and how they affect susceptibility to ROS damage. A comprehensive and detailed methods section is included which supplies complete protocols for analyzing ROS production, oxidative damage, and antioxidant systems. Methods are also evaluated with respect to applicability and constraints for different types of research. The authors are all internationally recognized experts in particular fields of oxidative stress research. This comprehensive reference volume is essential for students, researchers, and technicians in the field of ROS research, and also contains information useful for veterinarians, environmental health professionals, and decision makers.

We report, in 15 Ecuadorian mountainous lakes, dissolved concentrations of CO2, CH4, and N2O and a suite of ancillary biogeochemical variables (dissolved inorganic nutrients, oxygen, major cations, dissolved and particulate organic carbon, and the stable isotope composition of dissolved inorganic carbon and water). The sampled lakes were located in the páramos of Salve Facha and Antisana y Mojanda (northern region of Ecuadorian Andes), along an elevational gradient from 2213 to 4361 m above sea level, as well as a gradient of lake surface area (0.003–6.1 km2) and depth (1–74 m). Most lakes were characterized by lower values of the partial pressure of CO2 (pCO2) (644–2152 ppm) than usually attributed to tropical lakes (~ 1900 ppm). Three lakes influenced by volcanic inputs were characterized by the highest pCO2 values (3269–10,069 ppm), while two lakes bordered by large cities were characterized by the lowest pCO2 values (208–254 ppm). Dissolved CH4 concentrations ranged between 170 and 24,908 nmol/L and were negatively correlated to lake area and depth. N2O saturation levels ranged between 64% and 101%. The surface waters were undersaturated in N2O with respect to atmospheric equilibrium, probably due to inputs of soil–water with low N2O levels owing to denitrification in soils. The data obtained in the sampled highland lakes was combined with published data from lowland lakes (elevation < 500 m, n = 17 for CO2 and n = 16 for CH4) to derive relations between CO2 and CH4 and lake surface area, allowing to compute CO2 and CH4 lacustrine emissions at the scale of the Amazon basin using the HydroLAKES spatial data set. The CO2 and CH4 emissions from highland lakes (elevation > 500 m) only represented 0.4% and 2% of the total lacustrine emissions at the scale of the Amazon basin, respectively. Total CO2 and CH4 emissions from lakes represented a small fraction (8.6%) of total lentic and lotic CO2 and CH4 emissions at the scale of the Amazon basin. The lake and river emissions of CH4 represented ~ 3% of total CH4 emissions from all compartments of the Amazon basin, mainly attributable to wetlands.

The aquatic weevil genus Neohydronomus Hustache has three species in the Neotropical Region from south central Mexico south to Argentina and from Cuba. All are associated with water lettuce, Pistia stratiotes Linnaeus. The genus and two species are redescribed, and one new species, N. elegans, is described. A generic diagnosis and a key to the species are included. For each species there are habitus photographs, geographical distribution, discussion of variation, comparative notes, and illustrations of the phallus and the spermatheca. For the type species, N. pulchellus Hustache, illustrations of the eighth sternite and of the entire sclerotized portion of the female reproductive system are included, as well as illustrations of the male tegmen and spiculum gastrale of N. affinis Hustache. Neohydronomus affinis (under the name N. pulchellus) has been introduced as a potential biological control agent of water lettuce in Australia, Papua New Guinea, South Africa, and southeastern United States (south central Florida).

Salt marshes as an ecological part of coastal farming in the northeastern part of the North American continent are studied. Salt marshes can be used to provide dating accuracy for tectonic land changes, to understand air pollution over time and to determine the extent of cultivation in near-by areas.

Sialis bilobata is described as a new species of the alderfly family Sialidae from Los Angeles County, California. A brief description of the species, illustrations, and diagnosis that compares it with Sialis arvalis Ross are provided.