Abstract
The aim of this study was to investigate whether the bacterioplankton activity in the meso-eutrophic Conceição Lagoon would increase significantly under allochthonous inputs of inorganic nutrients and organic carbon. Abundance and biomass of bacterioplankton were evaluated under three treatments: light (14 h light/10 h dark), complete darkness (dark-control), and nutrient (C + N + P—dark, 100 : 10 : 1) enrichments during 72 h. Nutrient enrichments promoted a significant increase in abundance (maximum of 19.0 ×109 cells·L−1 in the first 32 hours) and biomass of the heterotrophic bacterioplankton, which induced the formation of large clusters. Bacterial biomass remained constant in the non-enriched incubations (dark-control and light). Bacterial growth rates were significantly higher after nutrient additions (1.35 d−1), followed by control (0.79 d−1), and light (0.63 d−1) treatments, which were statistically equal (p > 0.05). Bacterial production rates were also significantly higher under nutrient additions (1.28 d−1), compared to the control and light (0.50 d−1 and 0.44 d−1, respectively), demonstrating that bacterial growth and production in this meso-eutrophic lagoon are under an immediate “bottom-up” regulation, followed by a potential top-down effect. These facts reinforce the urgency on improving the local wastewater management plan in order to prevent further expansion of anoxic waters.
Highlights
Bacterial growth rates were significantly higher after nutrient additions (1.35 d−1), followed by control (0.79 d−1), and light (0.63 d−1) treatments, which were statistically equal (p > 0.05)
Bacterial production rates were significantly higher under nutrient additions (1.28 d−1), compared to the control and light (0.50 d−1 and 0.44 d−1, respectively), demonstrating that bacterial growth and production in this meso-eutrophic lagoon are under an immediate “bottom-up” regulation, followed by a potential top-down effect. ese facts reinforce the urgency on improving the local wastewater management plan in order to prevent further expansion of anoxic waters
Bacterioplankton activity in this meso-eutrophic lagoon was significantly stimulated after the addition of dissolved organic carbon and inorganic nutrients, demonstrating the
Summary
Academic Editor: Hidetoshi Urakawa e aim of this study was to investigate whether the bacterioplankton activity in the meso-eutrophic Conceição Lagoon would increase significantly under allochthonous inputs of inorganic nutrients and organic carbon. Bacterial growth rates were significantly higher after nutrient additions (1.35 d−1), followed by control (0.79 d−1), and light (0.63 d−1) treatments, which were statistically equal (p > 0.05). Bacterial production rates were significantly higher under nutrient additions (1.28 d−1), compared to the control and light (0.50 d−1 and 0.44 d−1, respectively), demonstrating that bacterial growth and production in this meso-eutrophic lagoon are under an immediate “bottom-up” regulation, followed by a potential top-down effect. 1. Introduction e comprehension of the pelagic bacterioplankton abundance and activity in coastal aquatic environments is of major importance in order to predict shifts in the microbial communities in response to frequent changes in such systems [1]. With the simultaneous addition of inorganic nutrients and glucose, several studies have shown a significant response in bacterial abundance and production [14,15,16,17]. e heterogeneity observed in the results has been related to the different trophic states of each environment [9]
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