Search results for "Lean"
showing 10 items of 3611 documents
Decomposition of nest material in tree holes and nest-boxes occupied by European Starlings Sturnus vulgaris: an experimental study
2017
Numerous bird species depend on the availability of tree cavities, and most non-excavators fill their cavities with considerable amounts of nest material. If not removed, this material can accumulate and render cavities unusable, as recorded in some nest-box studies. Data from earlier studies of tree cavities, however, showed that nest material can decrease mostly due to in situ decomposition, but the relative difference between nest decomposition in tree holes and nest-boxes is still unknown. We undertook parallel studies of decay in tree holes and nest-boxes used by European Starlings Sturnus vulgaris in oak-hornbeam stands (SW Poland). We inserted into its tree holes and nest-boxes litte…
Echo-sounding can discriminate between fish and macroinvertebrates in fresh water
2008
SUMMARY 1. Acoustic scattering from fish and macroinvertebrates was studied in a boreal Finnish lake at three echosounder frequencies (38, 120 and 200 kHz). Split-beam transducers with partly overlapping 7� beams were employed. Acoustic, fish and invertebrate sampling were undertaken simultaneously. Vertical gradients of temperature and oxygen concentration were measured during the exercise. 2. At all frequencies, a narrow scattering layer coincided with the thermocline. At 38 kHz, fish were detected well with practically no reverberation from invertebrates while 200 kHz detected both fish and invertebrates. 3. Minor differences in the magnitude of acoustic scattering from fish were found b…
The development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish in the salmon aquaculture industry
2017
Norway leads the world aquaculture production of Atlantic salmon Salmo salar and farmed Norwegian Atlantic salmon is currently consumed around the globe. However, sea lice infestation is a major problem faced by the salmon aquaculture industry in Norway and elsewhere. The use of wild-caught cleaner fish, mainly wrasses, has been recommended over the other available methods as the most economical and environmentally friendly option to control sea lice infestation in salmon farming. Here, we review the development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish. In this document, we address the sea lice problem and introduce the main wrasse species employed as cleaner f…
Spatial variability of stable carbon and nitrogen isotope ratios in a Mediterranean coastal lagoon
2005
Exploring the trophic pathway of organic matter within the Mauguio lagoon (southern France, western Mediterranean), we found spatial differences in the isotopic composition (both δ13C and δ15N values) of organic matter sources (primary producers, particulate and sedimentary organic matter), which were mirrored in the upper trophic levels (invertebrates and fish). On average, δ13C was heavier by about 1.5–2‰ in the location under marine influence than in the sites influenced by freshwater discharge. The opposite trend was found for δ15N, which attained maximum values in the north-central zone influenced by freshwater delivery. For both C and N stable isotope ratios, the highest spatial varia…
Triterpene saponins of the root bark of Olax obtusifolia De Wild
2018
Abstract Four undescribed triterpenoid saponins together with five known and oleanolic acid were isolated from root bark of Olax obtusifolia De Wild. Their structures were elucidated by spectroscopic methods including 1D and 2D NMR experiments, in combination with mass spectrometry as 3-O-α- l -rhamnopyranosyl-(1→4)-α- l -rhamnopyranosyl-(1→3)-β- d -glucuronopyranosyloleanolic acid, 3-O-α- l -rhamnopyranosyl-(1→4)-α- l -rhamnopyranosyl-(1→3)-β- d -glucuronopyranosyloleanolic acid 28-O-β- d -glucopyranosyl ester, 3-O-α- l -rhamnopyranosyl-(1→3)-β- d -glucopyranosyl-(1→2)-[β- d -glucopyranosyl-(1→3)]-β- d -glucuronopyranosyloleanolic acid and 3-O-α- l -rhamnopyranosyl-(1→3)-β- d -glucopyranos…
Taxonomic identity and phytoplankton diet affect fatty acid composition of zooplankton in large lakes with differing dissolved organic carbon concent…
2015
An increase in loading of dissolved organic carbon (DOC) from terrestrial to freshwater ecosystems has recently been documented in several boreal regions. We studied how transfer of important biomolecules, fatty acids, may be connected to DOC in pelagic food webs of large boreal lakes. We collected nine zooplankton taxa during three seasons from six lakes along a gradient of DOC (5–10 mg C L−1). Taxonomic identity explained 62% of the variation in zooplankton fatty acids, while the effects of DOC and season were less pronounced. This suggests that the community composition of zooplankton is important in determining the quality of food available for higher trophic level consumers. Seasonal d…
Antimicrobial secondary metabolites from the medicinal plant Crinum glaucum A. Chev. (Amaryllidaceae)
2020
Abstract Medicinal plants are known as sources of potential antibacterial compounds including alkaloids. The aim of the present study was to evaluate the antibacterial activities of the extract, fractions, and some secondary metabolites isolated from the leaves of Crinum glaucum A. Chev. (Amaryllidaceae). The antibacterial activities were performed with the ethanol (EtOH) extract, as well as with ethyl acetate (EtOAc) and n-butanol (n-BuOH) fractions. Repeated column chromatography of the fractions led to the isolation of several compounds and their structures were elucidated mainly by means of extensive spectroscopic analysis [(one-dimensional (1D) and two-dimensional (2D) nuclear magnetic…
The killer shrimp, Dikerogammarus villosus, invading European Alpine lakes: a single main source but independent founder events with an overall loss …
2017
16 pages; International audience; 1. The effects of biological invasions are generally more detrimental in isolated ecosystems than in the interconnected ones and freshwater lakes appear to be particularly fragile. The Ponto-Caspian freshwater amphipod Dikerogammarus villosus (Pontogammaridae), also known as the killer shrimp, is a highly invasive species that can have significant ecological impacts on receiving ecosystems. It has colonised most of the European main inland waterbodies, including at least 12 lakes in the Alps – an area of high conservational priority and, at the same time, heavily affected by anthropogenic changes. Particularly, overland translocations of boats among tourist…
Partitioning net carbon dioxide fluxes into photosynthesis and respiration using neural networks
2020
Abstract The eddy covariance (EC) technique is used to measure the net ecosystem exchange (NEE) of CO2 between ecosystems and the atmosphere, offering a unique opportunity to study ecosystem responses to climate change. NEE is the difference between the total CO2 release due to all respiration processes (RECO), and the gross carbon uptake by photosynthesis (GPP). These two gross CO2 fluxes are derived from EC measurements by applying partitioning methods that rely on physiologically based functional relationships with a limited number of environmental drivers. However, the partitioning methods applied in the global FLUXNET network of EC observations do not account for the multiple co‐acting…
The Impact of Climate Change on Lakes in Northern Europe
2009
In Northern Europe, most lakes are characterized by extended periods of winter ice cover, high spring inflow from snow melt and brown water produced by the transport of dissolved organic carbon (DOC) from the surrounding catchments. In this chapter, the potential impact of climate change on the dynamics of these lakes is addressed by: (i) Describing the historical responses of the lakes to changes in the weather. (ii) Summarizing the results of modelling studies that quantify the impact of future changes in the climate on the lakes and the surrounding catchments. Many existing water quality problems could well be exacerbated by the effects of climatic change. It is therefore important to as…