scholarly journals Biotic and abiotic factors investigated in two Drosophila species – evidence of both negative and positive effects of interactions on performance

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Michael Ørsted ◽  
Mads Fristrup Schou ◽  
Torsten Nygaard Kristensen
Keyword(s):  
Abiotic Factors ◽  
Drosophila Species ◽  
Biotic And Abiotic Factors ◽  
Positive Effects

scholarly journals Effects of Microbial Activity and Environmental Parameters on the Degradation of Extracellular Environmental DNA from a Eutrophic Lake

2019 ◽  
Vol 16 (18) ◽  
pp. 3339 ◽  
Author(s):  
Nur Syahidah Zulkefli ◽  
Keon-Hee Kim ◽  
Soon-Jin Hwang
Keyword(s):  
Microbial Activity ◽  
Degradation Rate ◽  
Abiotic Factors ◽  
Environmental Parameters ◽  
Environmental Dna ◽  
Eutrophic Lake ◽  
Freshwater Ecosystems ◽  
Extracellular Dna ◽  
Biotic And Abiotic Factors ◽  
Positive Effects

Extracellular DNA (exDNA) pool in aquatic environments is a valuable source for biomonitoring and bioassessment. However, degradation under particular environmental conditions can hamper exDNA detectability over time. In this study, we analyzed how different biotic and abiotic factors affect the degradation rate of extracellular environmental DNA using 16S rDNA sequences extracted from the sediment of a eutrophic lake and Anabaena variabilis cultured in the laboratory. We exposed the extracted exDNA to different levels of temperature, light, pH, and bacterial activity, and quantitatively analyzed the concentration of exDNA during 4 days. The solution containing bacteria for microbial activity treatment was obtained from the lake sediment using four consecutive steps of filtration; two mesh filters (100 μm and 60 μm mesh) and two glass fiber filters (2.7 μm and 1.2 μm pore-sized). We found that temperature individually and in combination with bacterial abundance had significant positive effects on the degradation of exDNA. The highest degradation rate was observed in samples exposed to high microbial activity, where exDNA was completely degraded within 1 day at a rate of 3.27 day−1. Light intensity and pH had no significant effects on degradation rate of exDNA. Our results indicate that degradation of exDNA in freshwater ecosystems is driven by the combination of both biotic and abiotic factors and it may occur very fast under particular conditions.

scholarly journals The impact of invertebrate pests on pasture persistence and their interrelationship with biotic and abiotic factors

2011 ◽  
Vol 15 ◽  
pp. 109-117
Author(s):  
S.M. Zydenbos ◽  
B.I.P. Barratt ◽  
N.L. Bell ◽  
C.M. Ferguson ◽  
P.J. Gerard ◽  
...  
Keyword(s):  
Soil Fertility ◽  
Plant Pathogens ◽  
Management Practices ◽  
Abiotic Factors ◽  
Insect Damage ◽  
Long Term Effects ◽  
Pasture Management ◽  
Biotic And Abiotic Factors ◽  
Positive Effects ◽  
The Impact

New Zealand pastures are host to a range of native and exotic invertebrates. Many of these are pests that feed on the sown plant species, often causing plant death and deterioration in the productivity and persistence of the sward. While most research has focused on pest biology and control, studies of plant productivity show dramatic acute (short-medium term) and chronic (longterm) effects. For example, grass grub has been reported to cause 50% losses to ryegrass swards and Argentine stem weevil can cause a 20% loss of productivity, but the long term effects through loss of the sown species and changes in composition can be even more severe. Insect damage can be exacerbated by other biotic (e.g. weed invasion, grazing animals, plant pathogens) or abiotic factors (e.g. climate, soil fertility) to further reduce plant persistence. Some biotic and abiotic factors may interact with insect pests to have positive effects on pasture persistence, e.g. biocontrol agents that reduce pest density or addition of fertiliser to enable plants to recover from insect damage. For many pasture pests, knowledge of their ecology is based on research from over 20 years ago that, while still valid, needs to be updated to account for modern intensive pasture management practices, such as intensive grazing with a lack of reseeding, and new cultivars. To improve pasture persistence, integrated research programmes are needed that examine the relative importance of all factors contributing to plant survival and develop strategies to mitigate their effects. Keywords: Argentine stem weevil, black beetle, clover root weevil, drought, grass grub, grazing pressure, manuka beetle, nematodes, pasture persistence, pasture quality, pasture yield, porina, soil fertility, striped chafer.

scholarly journals Flow cytometric measurements as a proxy for sporulation intensity in the cultured macroalga Ulva (Chlorophyta)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Omri Nahor ◽  
Cristina F. Morales-Reyes ◽  
Gianmaria Califano ◽  
Thomas Wichard ◽  
Alexander Golberg ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Life Cycle ◽  
Abiotic Factors ◽  
Physiological Status ◽  
Seaweed Cultivation ◽  
Reproductive Growth ◽  
Biotic And Abiotic Factors ◽  
Flow Cytometric ◽  
Abiotic Stimuli ◽  
Fundamental Shift

Abstract Controlling the life cycle of the green macroalga Ulva (Chlorophyta) is essential to maintain its efficient aquaculture. A fundamental shift in cultivation occurs by transforming the thallus cells into gametangia and sporangia (sporulation), with the subsequent release of gametes and zoids. Sporulation occurrence depends on algal age and abiotic stimuli and is controlled by sporulation inhibitors. Thus, quantification of sporulation intensity is critical for identifying the biotic and abiotic factors that influence the transition to reproductive growth. Here, we propose to determine the sporulation index by measuring the number of released gametes using flow cytometry, in proportion to the total number of thallus cells present before the occurrence of the sporulation event. The flow cytometric measurements were validated by manually counting the number of released gametes. We observed a variation in the autofluorescence levels of the gametes which were released from the gametangia. High autofluorescence level correlated to phototactically active behaviour of the gametes. As autofluorescence levels varied between different groups of gametes related to their mobility, flow cytometry can also determine the physiological status of the gametes used as feedstock in seaweed cultivation.

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