Study about Top-Down and Bottom-Up Controls in Regulating the Phytoplankton Biomass in a Eutrophic Reservoir in Northeastern Brazil

Abstract

This study aims to analyze the effects of nutrients and predation by zooplankton on phytoplankton biomass (chlorophyll <i>a</i>) in a eutrophic reservoir in Brazil (Apipucos Reservoir, State of Pernambuco), through experiments in microcosms. For this, samples of water were placed in 1 L Erlenmeyer flasks and kept for seven days. Treatments included the addition of nutrients (nitrogen combined with phosphorus and isolated additions of nitrogen and phosphorus), with presence and absence of zooplankton and a control which contained the reservoir water without any manipulation. The addition of nutrients did not stimulate phytoplankton growth. However, zooplankton significantly decreased phytoplankton biomass in the treatments it was added to (p < 0.05). The results of this study showed that for the reservoir studied, predation by zooplankton is the most significant factor in the regulation of phytoplankton, contradicting several studies which show that phytoplankton biomass is more strongly controlled by nutrients (bottom-up control) than by predation (top-down control)

Bottom-up and top-down effects on phytoplankton communities in two freshwater lakes

“…However, the reduced zooplankton density in our study did not show measurable top-down effects of zooplankton on phytoplankton. Although some studies have shown that phytoplankton were under the top-down regulation of zooplankton, these studies were normally conducted in eutrophic ecosystems, such as eutrophic reservoirs, lakes, and bays [19,39]. Under field studies on bottom-up and top-down effects, the environmental complexity obscured the effects between phytoplankton and zooplankton with the participation of higher-level predators.…”

“…Some studies have indicated that nutrients influence the density and species composition of phytoplankton through bottom-up effects while predation by zooplankton (top-down effects) controlled the size, distribution, and abundance of phytoplankton [14][15][16]. Zhang et al [17] and Song et al [18] found that phytoplankton was more influenced by the bottomup effects of environmental factors, while Severiano et al [19] indicated that the top-down effects of zooplankton had a more significant influence on phytoplankton. Experimental studies have suggested that phytoplankton is controlled more by the bottom-up effects of nutrients than the top-down effects of zooplankton when zooplankton are under strong predation pressure from fish [20,21].…”

Abundance and Biomass Estimates of Commercial Fish Species Using Hydro-Acoustic Method in Jakarta Bay, Indonesia

“…Hartati et al (2014) found that the salinity level in the eastern and central part of bay was relative similar about 31.5 ‰ and the dissolved oxygen (DO) level was high throughout the bay. These circumstances are associated with rich density of phytoplankton and zooplankton on those areas characterized by bottom up control interaction (Severiano et al, 2012;Hartati et al, 2014). Estuarine plankton has main effects on fish communities assemblages, while others indirect factors were river flow and temperature.…”