Variability in the performance of juvenile Chinook salmon is explained primarily by when and where they resided in estuarine habitats

Estuarine habitats provide rearing opportunities for the juvenile life stage of anadromous fishes. Because survival is positively correlated with juvenile performance, these estuarine habitats play an important role in population abundance and productivity. To provide information for the recovery of several depressed stocks of Chinook salmon in the Columbia River Basin, we sought to identify the factors that explain variability in performance. Using otolith‐derived estimates of juvenile somatic growth rate as an index of recent performance, we observed a negative nonlinear relationship between growth rate and day of year, and a decreasing and increasing trend of growth rate over the 8 years of this study and distance from the river mouth respectively. Using a generalised linear modelling approach, we found that variability in juvenile somatic growth rate was best explained by where and when individuals were collected, their body size, contaminant loads, stock of origin, and whether a fish was hatchery produced or unmarked. Lastly, we argue that a considerable improvement to the growth rate of juveniles in estuarine habitats is physiologically possible. The results of this 8‐year study provide a baseline of the performance of juvenile Chinook salmon to evaluate habitat restoration programs and to compare against future anthropogenic conditions.     

Ecological impacts of small hydropower plants on headwater stream fish: from individual to community effects

Hydroelectricity is increasingly used worldwide as a source of renewable energy, and many mountain ranges have dozens or hundreds of hydropower plants, with many more being under construction or planned. Although the ecological impacts of large dams are relatively well known, the effects of small hydropower plants and their weirs have been much less investigated. We studied the effects of water diversion of small hydropower plants on fish assemblages in the upper Ter river basin (Catalonia, NE Spain), which has headwater reaches with good water quality and no large dams but many of such plants. We studied fish populations and habitat features on control and impacted reaches for water diversion of 16 hydropower plants. In the impacted reaches, there was a significantly lower presence of refuges for fish, poorer habitat quality, more pools and less riffles and macrophytes, and shallower water levels. We also observed higher fish abundance, larger mean fish size and better fish condition in the control than in impacted reaches, although the results were species‐specific. Accordingly, species composition was also affected, with lower relative abundance of brown trout (Salmo trutta) and Pyrenean minnow (Phoxinus bigerri) in the impacted reaches and higher presence of stone loach (Barbatula quignardi) and Mediterranean barbel (Barbus meridionalis). Our study highlights the effects of water diversion of small hydropower plants from the individual to the population and community levels but probably underestimates them, urging for further assessment and mitigation of these ecological impacts.     

Über die Empfindlichkeit von Syrphidenlarven gegen Pflanzenschutzmittel

Zusammenfassung In einigen nach verschiedenen Methoden durchgeführten Testversuchen wird festgestellt, daß Syrphidenlarven durch eine Reihe von aphidiziden Pflanzenschußmitteln völlig oder zum Teil ausgeschaltet werden; dies gilt insbesondere für direkten Kontakt mit diesen Mitteln. Junglarven sind giftempfindlicher als Altlarven. Durch Applikation systemisch wirkender Mittel an syrphidenfreie Teile der Pflanzen kann die Mortalität dieser Blattlausfeinde beträchtlich gesenkt werden.     

Population genetics of traditional landraces of <Emphasis Type="Italic">Cucurbita pepo</Emphasis> L., 1753 in the cloud forest in Baja Verapaz,Guatemala

Little is known regarding the effect of fragmentation and human agricultural management on the genetic variation and gene flow of Cucurbita pepo L., 1753 in moderate fragmented areas in central Guatemala. We hypothesize that the genetic variation of C. pepo is affected by forest fragmentation and by traditional agricultural management. Therefore, we aim to determine: (1) the genetic diversity and genetic structure of C. pepo in the Cloud Forest Corridor (CFC) (2) the extent of genetic admixture between commercial variety (CV) and traditional landraces (TL) of C. pepo, (3) the effect of habitat fragmentation in the population genetics of C. pepo with a landscape approach, and (4) the potential relationship between traditional management practices and genetic diversity of C. pepo in the CFC. We detected the existence of high level of genetic diversity (AR = 3.43; He = 0.50), inbreeding (Fis = 0.25) and moderate population structure of C. pepo in the CFC (Fst = 0.16). No correlation between landscape and genetics was found. Also, we found high genetic admixture between CV and TL. It seems that human practices, mainly related with seed exchange patterns, could affect genetic diversity of C. pepo in the CFC. C. pepo populations in the CFC are structured, with inbreeding, and show admixture with the CV, an aspect that could affect its genetic diversity. The agricultural management influenced the population genetics of C. pepo in the CFC, but the landscape did not. We suggest that special efforts should be made to preserve the diversity of this important indigenous food source for Guatemalan people as well as their management practices.     

Metam Sodium (MS) in Water and Cane Juice at Different Processing Conditions According to the Industrial Case. Part 1. Effects of Matrix,pH, Temperature,Processing Time,and Photolysis

The process for extracting sugarcane juice (Saccharum officinarum) represents the point of greatest contamination in sugarcane mills. Sodium dithiocarbamate also known as metam-sodium or MS is added to inhibit the growth of microorganisms especially Leuconostoc mesenteroides which is responsible for forming polysaccharides. Metam-sodium, upon decomposition, produces highly toxic byproducts. According to literature, under acidic conditions, MS is hydrolyzed resulting in methylamine (MA), CH₃NH₂, and carbon disulfide (CS₂), and in dilute alkaline solutions, MS produces an oxidation reaction characterized by the formation of elemental sulfur (S) and methyl isothiocyanate (MITC). In this paper, it was studied how MS decomposes to MITC and/or MA considering the effects of the matrix (methanol and water); of temperature (4 and 25 °C); of processing time (0, 1, 2, 3, 4 days); and of pH (4.0, 4.5, 7.0). A second experimental design considering the effects of the matrix (water and sugarcane juice); of temperature (4, 25, 35, 45 °C); of processing time (30, 300 min); and of pH (4.0, 4.5, 7.0) was derived from the results obtained considering MITC and/or MA formation. According to the statistical analysis of these results (p < 0.05), the order of the influential factors was as follows: time > matrix > pH > temperature. Results also indicated that the water matrix at pH = 4.5 and 45 °C had the lowest degradation rate (k), with a value of 8.82 day^?1, while for the sugarcane juice matrix at the same pH and temperature conditions was larger, with a k value of 30.07 day^?1. These results show that the matrix is also important for the degradation of dithiocarbamate to MITC and to MA.     

Distribution of Metal Extractable Fractions during Anaerobic Sludge Treatment in Southern Spain WWTPs

A new European Union legislation on sludge treatment isbeing introduced that will replace the one currently in force.The control of heavy metals is an important aspect of this newlegislation. The most common methodology to examine the metalcontent of sludges is determination of total metal contentafter total or pseudo total digestion of the sludge samples.Nevertheless, this kind of analysis is not informative on theavailability or mobility of the metals; a metal speciationanalysis is therefore required. In this study, sludge samplesfrom conventional activated sludge wastewater treatment plants(WWTP) were collected at different stages of an anaerobicsludge treatment process. In these samples, the total metalcontent and the distribution of metal species were determined(Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Ti, Zn) followinga protocol of sequential extraction. Only 14% of the metalwas present in readily available forms in the treated sludges.In composted sludges, this value dropped to 6%.