scholarly journals Experimental evidence for enhanced top-down control of freshwater macrophytes with nutrient enrichment

Oecologia ◽  
2014 ◽  
Vol 176 (3) ◽  
pp. 825-836 ◽  
Author(s):  
Elisabeth S. Bakker ◽  
Bart A. Nolet
2019 ◽  
Author(s):  
Chris Robert Harrison Brown

Attention has long been characterised within prominent models as reflecting a competition between goal-driven and stimulus-driven processes. It remains unclear, however, how involuntary attentional capture by affective stimuli, such as threat-laden content, fits into such models. While such effects were traditionally held to reflect stimulus-driven processes, recent research has increasingly implicated a critical role of goal-driven processes. Here we test an alternative goal-driven account of involuntary attentional capture by threat, using an experimental manipulation of goal-driven attention. To this end we combined the classic ‘contingent capture’ and ‘emotion-induced blink’ (EIB) paradigms in an RSVP task with both positive or threatening target search goals. Across six experiments, positive and threat distractors were presented in peripheral, parafoveal, and central locations. Across all distractor locations, we found that involuntary attentional capture by irrelevant threatening distractors could be induced via the adoption of a search goal for a threatening category; adopting a goal for a positive category conversely led to capture only by positive stimuli. Our findings provide direct experimental evidence for a causal role of voluntary goals in involuntary capture by irrelevant threat stimuli, and hence demonstrate the plausibility of a top-down account of this phenomenon. We discuss the implications of these findings in relation to current cognitive models of attention and clinical disorders.


2016 ◽  
Vol 476 ◽  
pp. 31-40 ◽  
Author(s):  
Karine Gagnon ◽  
Joakim Sjöroos ◽  
Juho Yli-Rosti ◽  
Marjo Stark ◽  
Eva Rothäusler ◽  
...  

2012 ◽  
Vol 367 (1605) ◽  
pp. 2962-2970 ◽  
Author(s):  
Malte Jochum ◽  
Florian D. Schneider ◽  
Tasman P. Crowe ◽  
Ulrich Brose ◽  
Eoin J. O'Gorman

Climate change has complex structural impacts on coastal ecosystems. Global warming is linked to a widespread decline in body size, whereas increased flood frequency can amplify nutrient enrichment through enhanced run-off. Altered population body-size structure represents a disruption in top-down control, whereas eutrophication embodies a change in bottom-up forcing. These processes are typically studied in isolation and little is known about their potential interactive effects. Here, we present the results of an in situ experiment examining the combined effects of top-down and bottom-up forces on the structure of a coastal marine community. Reduced average body mass of the top predator (the shore crab, Carcinus maenas ) and nutrient enrichment combined additively to alter mean community body mass. Nutrient enrichment increased species richness and overall density of organisms. Reduced top-predator body mass increased community biomass. Additionally, we found evidence for an allometrically induced trophic cascade. Here, the reduction in top-predator body mass enabled greater biomass of intermediate fish predators within the mesocosms. This, in turn, suppressed key micrograzers, which led to an overall increase in microalgal biomass. This response highlights the possibility for climate-induced trophic cascades, driven by altered size structure of populations, rather than species extinction.


Author(s):  
Zhiwei Shi ◽  
Hong Hu ◽  
Zhongzhi Shi

Recent fruitful progresses on brain science have largely broadened our understanding of the cerebrum. These great works led us to propose a computational cognitive model based on a graphical model that we carried out before. The model possesses many attractive properties, including distinctive knowledge representation, the capability of knowledge accumulation, active (top-down) attention, subjective similarity measurement, and attention-guided disambiguation. It also has “consciousness” and can even “think” and “make inference.” To some extent, it works just like the human brain does. The experimental evidence demonstrates that it can give reasonable computational explanation on the human phenomenon of forgetting. Although there are still some undetermined details and neurobiological mechanisms deserving consideration, our work presents a meaningful attempt to give further insights into the brain’s functions.


2002 ◽  
Vol 62 (4b) ◽  
pp. 835-846 ◽  
Author(s):  
B. KOZLOWSKY-SUZUKI ◽  
R. L. BOZELLI

Non-treated sewage disposal is one of the main impacts to which Imboassica Lagoon has been subjected. The aim of this study was to evaluate the effect of a potential increase in the artificial enrichment on the environmental conditions and zooplankton of this system. To this end, an experimental study was conducted in mesocosms where nutrients were added daily. Bacterial numbers, chlorophyll-a, and picoplanktonic cyanobacteria densities showed an increase with the availability of nutrients. Bacterio- and phytoplankton seemed to be regulated by the rotifers Brachionus rotundiformis and Hexarthra brandorffi.


2016 ◽  
Vol 53 (4) ◽  
pp. 1138-1147 ◽  
Author(s):  
Örjan Östman ◽  
Johan Eklöf ◽  
Britas Klemens Eriksson ◽  
Jens Olsson ◽  
Per‐Olav Moksnes ◽  
...  

2004 ◽  
Vol 65 (3) ◽  
pp. 285-298 ◽  
Author(s):  
Nicolas Loeuille ◽  
Michel Loreau

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