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

Autor: Diego Frau, Gisela Mayora, Patricio Francisco Alvarenga, Pablo Augusto Scarabotti, Rodrigo Sinistro, Yamila Battauz
Rok vydání: 2019
Předmět:
Zdroj: Aquatic Ecology. 53:265-280
ISSN: 1573-5125
1386-2588
DOI: 10.1007/s10452-019-09687-3
Popis: Although several studies explain the trophic cascade in water systems, we lack knowledge about top-down–bottom-up effects on phytoplankton from eutrophic lakes. In this study, we tested the importance of trophic cascades on phytoplankton structure, predicting that environmental variations are the main drivers. We performed a monthly sampling during a year to measure environmental variables, phytoplankton and zooplankton, plus two samplings (winter and summer) to assess fish structure. Furthermore, we analyzed zooplanktivorous fish stomach-gut contents and completed a hatching zooplankton resting egg experiment to assess the effect of fish on dormant populations. We ran a partial redundancy analysis (pRDA) for phytoplankton using zooplankton, nutrient availability and environmental variables as predictor variables. We finally calculated several ratios of the zooplankton:phytoplankton biovolume to assess potential predation effects. Phytoplankton was correlated with variations in temperature and conductivity plus nutrients (pRDA: 63.4%, F = 4.6, P = 0.001) and was dominated alternatively by diatoms and cyanobacteria. Zooplankton was dominated by microphagous rotifers (> 45% of the total biovolume), and only the ratio of microphagous rotifer:small chlorophytes was significant during summer and autumn (F = 10.6, P = 0.005). The fish community was dominated by insectivorous-planktivorous fish (> 65% of total density), yet a negative selection of zooplankton items (Ivlev’s index
Databáze: OpenAIRE
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