Assessing the relevance of top-down and bottom-up effects as phytoplankton structure drivers in a subtropical hypereutrophic shallow lake

2019 ◽  
Vol 53 (2) ◽  
pp. 265-280 ◽  
Author(s):  
Diego Frau ◽  
Yamila Battauz ◽  
Patricio Francisco Alvarenga ◽  
Pablo Augusto Scarabotti ◽  
Gisela Mayora ◽  
...  
2015 ◽  
Vol 66 (12) ◽  
pp. 1106 ◽  
Author(s):  
Diego Frau ◽  
Melina Devercelli ◽  
Susana José de Paggi ◽  
Pablo Scarabotti ◽  
Gisela Mayora ◽  
...  

Bottom-up and top-down control of phytoplankton is one of the most important hypothesis that explains and predicts the structure of aquatic community. Our aim was to elucidate whether predation and resource limitation can control phytoplankton composition and abundance in a subtropical shallow lake with groundwater connection to the river system. During 12 months, the lake was sampled at three points. Physico-chemical parameters, phytoplankton and zooplankton were sampled fortnightly, whereas fish were sampled every 3 months. The results showed that Euglenophyta dominated the total biovolume, followed by Dinophyta and Cryptophyta. As for the species composition, Chlorophyta was the dominant group (80 species recorded), followed by phylum Cyanobacteria (26 species recorded). Redundancy analysis (RDA) indicated that temperature and nitrate + nitrite concentration mainly explained biovolume changes, with zooplankton predation not having any measurable effect on phytoplankton during the high-water (HW) period. During low-water (LW) period top-down by fish was more important. At higher taxonomic resolution (species biovolume), phosphorus was another controlling factor. We concluded that phytoplankton in this lake is mainly regulated by hydrological changes as a macrofactor that affects nutrient availability and other environmental conditions. Even though bottom-up top-down forces do not have a central effect, we found evidence of positive nutrient influences at the HW period and fish effect at the LW period.


2018 ◽  
Vol 25 (2) ◽  
pp. 504-521 ◽  
Author(s):  
Francisco Rivera Vasconcelos ◽  
Sebastian Diehl ◽  
Patricia Rodríguez ◽  
Per Hedström ◽  
Jan Karlsson ◽  
...  
Keyword(s):  
Top Down ◽  

PsycCRITIQUES ◽  
2005 ◽  
Vol 50 (19) ◽  
Author(s):  
Michael Cole
Keyword(s):  
Top Down ◽  

Author(s):  
Sadari Sadari ◽  
Nurhidayat Nurhidayat ◽  
Rafiqah Rafiqah
Keyword(s):  
Top Down ◽  

Humanisme religius telah mengantarkan pada era kesadaran bahwa peradaban manusia harus memiliki dua arus yang saling menunjang. Selama ini arus balik dalam bidang ekonomi hanya menonjolkan arus balik vertikal atas kebawah (model top down) yang didominasi oleh sistem ekonomi kapitalis dan sosialis, sedangkan di sisi lain mengesampingkan arus balik vertikal dari bawah ke atas (model bottom up) yang didominasi oleh sistem ekonomi syariah, sehingga dampaknya adalah adanya kesenjangan ekonomi yang sangat tajam. Paper ini mewujudkan peran penting, yakni menghubungkan dua arus tersebut secara timbal-balik, yakni mempertemukan arus pertama dengan arus balik kedua, sehingga akan menghasilkan dampak yang positif, progresif, kreatif dan produktif, kemudian pada akhirnya akan dapat meng-optomal-kan ekonomi syariah untuk menciptakan goodgovernance, post goodgovernance secara berkelanjutan, tentunya dengan bantuan peran media kontemporer yang kian update. Ekonomi syariah juga merupakan pilar dan nilai dasar, dari sikap keyakinan dan sikap rasionalitas untuk sanggup menciptakan terwujudnya pemberdayaan dan kesejahteraan sekaligus pengentasan kemiskinan dalam masyarakat di Indonesia.


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