54 research outputs found
Discovering hidden biodiversity: the use of complementary monitoring of fish diet based on DNA barcoding in freshwater ecosystems
Ecological monitoring contributes to the understanding of complex ecosystem functions. The diets of fish reflect the surrounding environment and habitats and may, therefore, act as useful integrating indicators of environmental status. It is, however, often difficult to visually identify items in gut contents to species level due to digestion of soft-bodied prey beyond visual recognition, but new tools rendering this possible are now becoming available. We used a molecular approach to determine the species identities of consumed diet items of an introduced generalist feeder, brown trout (Salmo trutta), in 10 Tasmanian lakes and compared the results with those obtained from visual quantification of stomach contents. We obtained 44 unique taxa (OTUs) belonging to five phyla, including seven classes, using the barcode of life approach from cytochrome oxidase I (COI). Compared with visual quantification, DNA analysis showed greater accuracy, yielding a 1.4-fold higher number of OTUs. Rarefaction curve analysis showed saturation of visually inspected taxa, while the curves from the DNA barcode did not saturate. The OTUs with the highest proportions of haplotypes were the families of terrestrial insects Formicidae, Chrysomelidae, and Torbidae and the freshwater Chironomidae. Haplotype occurrence per lake was negatively correlated with lake depth and transparency. Nearly all haplotypes were only found in one fish gut from a single lake. Our results indicate that DNA barcoding of fish diets is a useful and complementary method for discovering hidden biodiversity. In this paper sequence-based DNA barcoding was applied to determine the diet of a generalist predator (brown trout, Salmo trutta) based on gut analyses. Subsequently, the results were compared with data derived from visual inspection. Based on our results, we discuss the potential of using prey organisms in fish gut contents as a supplementary monitoring tool to reveal hidden biodiversity
Atom lasers: production, properties and prospects for precision inertial measurement
We review experimental progress on atom lasers out-coupled from Bose-Einstein
condensates, and consider the properties of such beams in the context of
precision inertial sensing. The atom laser is the matter-wave analog of the
optical laser. Both devices rely on Bose-enhanced scattering to produce a
macroscopically populated trapped mode that is output-coupled to produce an
intense beam. In both cases, the beams often display highly desirable
properties such as low divergence, high spectral flux and a simple spatial mode
that make them useful in practical applications, as well as the potential to
perform measurements at or below the quantum projection noise limit. Both
devices display similar second-order correlations that differ from thermal
sources. Because of these properties, atom lasers are a promising source for
application to precision inertial measurements.Comment: This is a review paper. It contains 40 pages, including references
and figure
Robust optima and tolerance ranges of biological indicators: a new method to identify sentinels of global warming
Discovering hidden biodiversity: the use of complementary monitoring of fish diet based on DNA barcoding in freshwater ecosystems
14 páginas, 4 figuras, 5 tablasEcological monitoring contributes to the understanding of complex ecosystem
functions. The diets of fish reflect the surrounding environment and habitats
and may, therefore, act as useful integrating indicators of environmental status.
It is, however, often difficult to visually identify items in gut contents to species
level due to digestion of soft-bodied prey beyond visual recognition, but new
tools rendering this possible are now becoming available. We used a molecular
approach to determine the species identities of consumed diet items of an
introduced generalist feeder, brown trout (Salmo trutta), in 10 Tasmanian lakes
and compared the results with those obtained from visual quantification of
stomach contents. We obtained 44 unique taxa (OTUs) belonging to five phyla,
including seven classes, using the barcode of life approach from cytochrome
oxidase I (COI). Compared with visual quantification, DNA analysis showed
greater accuracy, yielding a 1.4-fold higher number of OTUs. Rarefaction curve
analysis showed saturation of visually inspected taxa, while the curves from the
DNA barcode did not saturate. The OTUs with the highest proportions of haplotypes
were the families of terrestrial insects Formicidae, Chrysomelidae, and
Torbidae and the freshwater Chironomidae. Haplotype occurrence per lake was
negatively correlated with lake depth and transparency. Nearly all haplotypes
were only found in one fish gut from a single lake. Our results indicate that
DNA barcoding of fish diets is a useful and complementary method for discovering
hidden biodiversity.The project was funded by The Korea
National Long-Term Ecological Research
Project (2013), Galathea 3, Sino-Danish
Centre for Education and Research (SDC) and
Aarhus University (AU).Peer reviewe
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Warming Effects on Periphyton Community and Abundance in Different Seasons Are Influenced by Nutrient State and Plant Type: A Shallow Lake Mesocosm Study
Periphyton plays an important role in lake ecosystems processes, especially at low and intermediate nutrient levels where periphyton contribution to primary production can be similar to or exceed that of phytoplankton. Knowledge of how periphyton responds to key drivers such as climate change and nutrient enrichment is, therefore, crucial. We conducted a series of mesocosm experiments over four seasons to elucidate the responses of periphyton communities to nutrient (low and high, TN-0.33 mg L-1 TP-7.1 mu g L-1 and TN-2.40 mg L-1 TP-165 mu g L-1, respectively), temperature (ambient, IPCC A2 scenario and A2 + 50%) and plant type (two submerged macrophytes with different morphological structural complexity: Potamogeton crispus and Elodea canadensis, and their corresponding plastic imitations with similar size and structure). We found a noticeable seasonality in the abundance and composition of periphyton. In spring and summer, periphyton abundances were significantly higher in the turbid-high-nutrient state than in the clear-low-nutrient state, and in summer they were notably higher at ambient temperature than in climate scenario A2 and A2 + 50%. In contrast, periphyton abundances in autumn and winter were not influenced by nutrient and temperature, but they were notably higher on plants with a more complex morphological structure than simple ones. The genus composition of periphyton was significantly affected by nutrient-temperature interactions in all seasons and by plant type in winter. Moreover, periphyton functional composition exhibited noticeable seasonal change and responded strongly to nutrient enrichment and temperature rise in spring, summer, and autumn. Our results suggest that the effect of warming on periphyton abundance and composition in the different seasons varied with nutrient state and host plant type in these mesocosms, and similar results may likely be found under field conditions
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