Influence of salmon carcasses on stream productivity: response of biofilm and benthic macroinvertebrates in southeastern Alaska, U.S.A.

1998 ◽  
Vol 55 (6) ◽  
pp. 1503-1511 ◽  
Author(s):  
Mark S Wipfli ◽  
John Hudson ◽  
John Caouette
Keyword(s):  
Block Design ◽  
Dry Mass ◽  
Feedback Mechanism ◽  
Artificial Streams ◽  
Natural Stream ◽  
Incomplete Block Design ◽  
Natural Streams ◽  
Positive Feedback Mechanism ◽  
Salmon Carcass ◽  
Salmon Carcasses

This study was conducted to determine if salmon carcasses (from spawning adults) increased stream biofilm ash-free dry mass (AFDM) and benthic macroinvertebrate abundance in southeastern Alaska, U.S.A. Thirty-six once-through artificial streams were situated along, and received water and drifting invertebrates from, a natural stream. Two treatments (salmon carcass, control) were sampled six times during a 3-month period in a randomized incomplete block design with a 2 x 6 factorial treatment structure. Additionally, two natural stream sites were sampled once for biofilm and macroinvertebrates, one site receiving 75 000 adult salmon migrants during 1996 and the other upstream of spawning salmon. While biofilm AFDM was 15 times higher in carcass-enriched reaches of Margaret Creek, there were no detectable treatment differences in the artificial streams. Total macroinvertebrate densities were up to eight and 25 times higher in carcass-enriched areas of artificial and natural streams, respectively; Chironomidae midges, Baetis and Cinygmula mayflies, and Zapada stoneflies were the most abundant taxa. The increased biofilm in Margaret Creek and macroinvertebrate abundance in both systems suggest that salmon carcasses elevated freshwater productivity. This marine-based positive feedback mechanism may be crucial for sustaining aquatic-riparian ecosystem productivity and long-term salmonid population levels.

Influence of salmon spawner densities on stream productivity in Southeast Alaska

1999 ◽  
Vol 56 (9) ◽  
pp. 1600-1611 ◽  
Author(s):  
Mark S Wipfli ◽  
John P Hudson ◽  
Dominic T Chaloner ◽  
John P Caouette
Keyword(s):  
Chlorophyll A ◽  
Pink Salmon ◽  
Dry Mass ◽  
Trophic Levels ◽  
Oncorhynchus Gorbuscha ◽  
Southeast Alaska ◽  
Natural Stream ◽  
Forest Stream ◽  
Natural Streams ◽  
Freshwater Salmon

We conducted this study to determine the relationship between salmon spawner abundance and stream biofilm and benthic macroinvertebrate abundance in Southeast Alaska. Experiments took place in outdoor artificial and natural streams. Six pink salmon (Oncorhynchus gorbuscha) carcass treatments (0.00, 1.45, 2.90, 4.35, 5.80, and 7.25 kg wet mass) placed in artificial channels were subsampled repeatedly for biofilm ash-free dry mass (AFDM), chlorophyll a, and macroinvertebrates. In a small (nonanadromous) forest stream, we sampled benthos throughout a 66-m reach 17 days after distributing 60 carcasses along the lower half of that reach. All response variables significantly increased in response to carcass additions in both artificial and natural streams. Chlorophyll a continued to increase across all loading rates, while AFDM and total macroinvertebrate densities showed no further response to loading beyond the first treatment (1.45 kg) in artificial streams. In the natural stream, AFDM and chironomid densities continued increasing across loading levels. These results indicated that increased spawner densities increased lower trophic level abundance until a trophic capacity was reached. Salmon escapement goals should consider food web effects, especially on trophic levels that support juvenile salmonids, that ultimately affect freshwater salmon production.

Effects of salmon carcass decomposition on biofilm growth and wood decomposition

1999 ◽  
Vol 56 (5) ◽  
pp. 767-773 ◽  
Author(s):  
Amy K. Fisher Wold ◽  
Anne E Hershey
Keyword(s):  
Mass Loss ◽  
Woody Debris ◽  
Dry Mass ◽  
Wood Decomposition ◽  
Biofilm Growth ◽  
Salmon Carcass ◽  
Stream Biota ◽  
Significant Mass Loss ◽  
Salmon Carcasses ◽  
Significant Mass

Salmon carcasses from spawning migrations can be retained in stream ecosystems behind woody debris, boulders, and other substrata where they contribute nutrients and organic matter to the stream biota. We hypothesized that carcasses would enhance algal and microbial growth and wood decomposition. To test this, we placed wood and clay pot substrata directly downstream of decomposing salmon in the Little Knife River, Minn., U.S.A., and compared total biofilm biomass on substrata in the vicinity of decomposing salmon and upstream of salmon carcasses. After 335 days in the stream, there was a significant mass loss of wood but no apparent effect of carcass decomposition on wood mass loss. Significantly, more chlorophyll a was found on both wood and pots when carcasses were present (p < 0.05) compared with controls. Stable isotope analyses suggest that the fish-derived nitrogen was taken up by the periphyton and total biofilm. Biofilm on the pots and wood near fish showed a significant increase in ash-free dry mass (p < 0.05). We conclude that fish-derived nutrients enhanced algal and total biofilm growth but did not significantly influence wood decomposition.

scholarly journals HOPF BIFURCATION FROM NEW-KEYNESIAN TAYLOR RULE TO RAMSEY OPTIMAL POLICY

2020 ◽  
pp. 1-33
Author(s):  
Jean-Bernard Chatelain ◽  
Kirsten Ralf
Keyword(s):  
Hopf Bifurcation ◽  
Optimal Policy ◽  
Ad Hoc ◽  
Taylor Rule ◽  
Dynamic Properties ◽  
Feedback Mechanism ◽  
New Keynesian ◽  
Negative Feedback Mechanism ◽  
Positive Feedback Mechanism ◽  
Forward Looking

This paper compares different implementations of monetary policy in a new-Keynesian setting. We can show that a shift from Ramsey optimal policy under short-term commitment (based on a negative feedback mechanism) to a Taylor rule (based on a positive feedback mechanism) corresponds to a Hopf bifurcation with opposite policy advice and a change of the dynamic properties. This bifurcation occurs because of the ad hoc assumption that interest rate is a forward-looking variable when policy targets (inflation and output gap) are forward-looking variables in the new-Keynesian theory.

scholarly journals Nitrogen and potassium supply and the morphogenic and productive characteristics of marandu palisadegrass

2010 ◽  
Vol 39 (8) ◽  
pp. 1666-1675 ◽  
Author(s):  
Marcio Mahmoud Megda ◽  
Francisco Antonio Monteiro
Keyword(s):  
Leaf Area ◽  
Dry Matter ◽  
System Development ◽  
Block Design ◽  
Dry Mass ◽  
Dry Matter Production ◽  
Root System Development ◽  
Randomized Block Design ◽  
Matter Production ◽  
Specific Length

The objective of this work was to study morphogenic characteristics, and dry matter production of roots and shoots of marandu palisadegrass (Brachiaria brizantha cv. Marandu) submitted to combinations of nitrogen and potassium, in a nutritive solution, employing silica as substrate. The experiment was carried out in a greenhouse during the summer. It was used a 5² fractionated factorial scheme with 13 combinations of nitrogen and potassium, which were distributed in a randomized block design, with four replications. The nitrogen × potassium interaction was significant for the number of tillers and leaves, for leaf area, for shoots and root section dry mass, for total length and surface and specific length and surface in the roots. Production of aerial part dry mass positively correlated with the number of tillers and leaves and grass leaf area. Nitrogen rates modulated the root system development, and the root specific length and surface decreased when high rates of nitrogen and potassium were supllied. Nitrogen and potassium influence Marandu palisadegrass morphogenic characteristics, which are determinant for grass dry matter production.

scholarly journals A positive feedback mechanism ensures proper assembly of the functional inner centromere during mitosis in human cells

2018 ◽  
Vol 294 (5) ◽  
pp. 1437-1450 ◽  
Author(s):  
Cai Liang ◽  
Zhenlei Zhang ◽  
Qinfu Chen ◽  
Haiyan Yan ◽  
Miao Zhang ◽  
...  
Keyword(s):  
Positive Feedback ◽  
Histone H3 ◽  
Causal Link ◽  
Feedback Mechanism ◽  
Histone H2a ◽  
Defective Mutant ◽  
Chromosomal Passenger ◽  
Phosphatase 2A ◽  
Elevated Rate ◽  
Positive Feedback Mechanism

The inner centromere region of a mitotic chromosome critically regulates sister chromatid cohesion and kinetochore–microtubule attachments. However, the molecular mechanism underlying inner centromere assembly remains elusive. Here, using CRISPR/Cas9-based gene editing in HeLa cells, we disrupted the interaction of Shugoshin 1 (Sgo1) with histone H2A phosphorylated on Thr-120 (H2ApT120) to selectively release Sgo1 from mitotic centromeres. Interestingly, cells expressing the H2ApT120-binding defective mutant of Sgo1 have an elevated rate of chromosome missegregation accompanied by weakened centromeric cohesion and decreased centromere accumulation of the chromosomal passenger complex (CPC), an integral part of the inner centromere and a key player in the correction of erroneous kinetochore–microtubule attachments. When artificially tethered to centromeres, a Sgo1 mutant defective in binding protein phosphatase 2A (PP2A) is not able to support proper centromeric cohesion and CPC accumulation, indicating that the Sgo1–PP2A interaction is essential for the integrity of mitotic centromeres. We further provide evidence indicating that Sgo1 protects centromeric cohesin to create a binding site for the histone H3–associated protein kinase Haspin, which not only inhibits the cohesin release factor Wapl and thereby strengthens centromeric cohesion but also phosphorylates histone H3 at Thr-3 to position CPC at inner centromeres. Taken together, our findings reveal a positive feedback–based mechanism that ensures proper assembly of the functional inner centromere during mitosis. They further suggest a causal link between centromeric cohesion defects and chromosomal instability in cancer cells.

scholarly journals MORPHOLOGICAL AND PRODUCTIVE CHARACTERIZATION OF FORAGE CACTUS VARIETIES

2015 ◽  
Vol 28 (3) ◽  
pp. 230-238 ◽  
Author(s):  
PHILIPE LIMA DE AMORIM ◽  
JANAINA AZEVEDO MARTUSCELLO ◽  
JOSÉ TEODORICO DE ARAÚJO FILHO ◽  
DANIEL DE NORONHA FIGUEIREDO VIEIRA DA CUNHA ◽  
LIANA JANK
Keyword(s):  
Block Design ◽  
Morphological Characteristics ◽  
Correlation Coefficients ◽  
Dry Mass ◽  
Negative Effects ◽  
Breeding Programs ◽  
Area Index ◽  
Promising Alternative ◽  
Randomized Block Design ◽  
Use Efficiency

ABSTRACT: Cultivars of the genus Nopalea are known in Brazil for being tolerant to cochineal carmine attacks, thus making the cultivation of this genus a promising alternative for mitigating the negative effects of this insect on the production of biomass. With the objectives of characterizing morphologically spineless forage cactus varieties and identify morphological characteristics that may be the focus in spineless forage cactus breeding programs, an experiment was conducted in a completely randomized block design with 11 treatments and four replications. The variety Alagoas showed the highest values of weight, area and volume of cladodes. The varieties Negro Michoacan F7 and V7, Tamazunchale V12 showed the highest values of the cladode area index, the total volume of cladodes and total fresh mass production. The varieties Negro Michoacan V7 and F7 presented the highest water use efficiency and dry mass yield. Cladode volume showed the highest correlation coefficients with the fresh weight of cladodes. Aiming the release of varieties for biomass production, varieties Negro Michoacan F7, V7 and Tamazunchale V12 may substitute the Miúda variety. The number and cladode area index may be used as criteria for selection of superior varieties in breeding programs.

scholarly journals Hedgehog signaling activates a positive feedback mechanism involving insulin-like growth factors to induce osteoblast differentiation

2015 ◽  
Vol 112 (15) ◽  
pp. 4678-4683 ◽  
Author(s):  
Yu Shi ◽  
Jianquan Chen ◽  
Courtney M. Karner ◽  
Fanxin Long
Keyword(s):  
Transcriptional Activation ◽  
Positive Feedback ◽  
Hedgehog Signaling ◽  
Osteoblast Differentiation ◽  
Akt Signaling ◽  
Feedback Mechanism ◽  
Genetic Deletion ◽  
Positive Feedback Mechanism ◽  
Igf Signaling

Hedgehog (Hh) signaling is essential for osteoblast differentiation in the endochondral skeleton during embryogenesis. However, the molecular mechanism underlying the osteoblastogenic role of Hh is not completely understood. Here, we report that Hh markedly induces the expression of insulin-like growth factor 2 (Igf2) that activates the mTORC2-Akt signaling cascade during osteoblast differentiation. Igf2-Akt signaling, in turn, stabilizes full-length Gli2 through Serine 230, thus enhancing the output of transcriptional activation by Hh. Importantly, genetic deletion of the Igf signaling receptor Igf1r specifically in Hh-responding cells diminishes bone formation in the mouse embryo. Thus, Hh engages Igf signaling in a positive feedback mechanism to activate the osteogenic program.

scholarly journals Effect of plant regulators on growth and flowering of 'Meyer' zoysiagrass

2013 ◽  
Vol 31 (3) ◽  
pp. 695-703 ◽  
Author(s):  
S.R. Marchi ◽  
D. Martins ◽  
N.V. Costa ◽  
J.R.V. Silva
Keyword(s):  
Plant Height ◽  
Mass Production ◽  
Untreated Control ◽  
Block Design ◽  
Dry Mass ◽  
Zoysia Japonica ◽  
Visual Effects ◽  
Visual Symptoms ◽  
Randomized Complete Block Design ◽  
Prohexadione Calcium

This trial aimed to evaluate the effect of sequential applications of different plant regulators over growth and flower rachis emission of 'Meyer' zoysiagrass (Zoysia japonica). The study was conducted on 15-month old green turfgrass under a randomized complete block design with four replications. The following plant regulator and doses were tested: trinexapac-ethyl (113+113, 226+113, 226+226, 452+113, 452+226, 452+452, 678+339 e 904+452 g a.i./ha-1), prohexadione-calcium (100+100 e 200+200 g a.i. ha-1) and bispyribac-sodium (40+40 e 60+60 g a.i. ha-1), as well as an untreated control. The turfgrass was mowed again at 3.0 cm aboveground and the second plant regulator was applied when 'Meyer' zoysiagrass was between 5.0 and 6.0 cm high. The effect of the treatments was visually rated for visual injury, plant height, height and number of flower rachis, and total dry mass production of clippings. Only bispyribac-sodium had visual symptoms of injury on 'Meyer' zoysiagrass, and no intoxication was observed at 28 days after the second application (DAAB). The sequential applications of trinexapac-ethyl, prohexadione-calcium and bispyribac-sodium reduced by more than 80% the total clipping dry mass produced by 'Meyer' zoysiagrass. All the plant regulators tested also showed promising results in reducing the height and emission of rachis, especially when trinexapac-ethyl was applied at the doses 452+452, 678+339 and 904+452 g a.i. ha-1. 'Meyer' zoysiagrass turfgrass can be handled with the sequential application of a plant regulator, which reduces the need for mowing over a period up to 110 days after the application of the second plant regulator, and it also avoids deleterious visual effects over turfgrass.

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