Abstract
AIM: Estimating bacterioplankton density and biomass and their regulating factors is important in order to evaluate aquatic systems' carrying capacity, regarding bacterial growth and the stock of matter in the bacterial community, which can be consumed by higher trophic levels. We aim to evaluate the limnological factors which regulate - in space and time - the bacterioplankton dynamics (abundance and biomass) in five tropical coastal lagoons in the state of Rio de Janeiro, Brazil. METHOD: The current study was carried out at the following lagoons: Imboassica, Cabiúnas, Comprida, Carapebus and Garças. They differ in morphology and in their main limnological factors. The limnological variables as well as bacterioplankton abundance and biomass were monthly sampled for 14 months. Model selection analyses were performed in order to evaluate the main variables regulating the bacterioplankton's dynamics in these lagoons. RESULT: The salt concentration and the "space" factor (i.e. different lagoons) explained great part of the bacterial density and biomass variance in the studied tropical coastal lagoons. When the lagoons were analyzed separately, salinity still explained great part of the variation of bacterial density and biomass in the Imboassica and Garças lagoons. On the other hand, phosphorus concentration was the main factor explaining the variance of bacterial density and biomass in the distrophic Cabiúnas, Comprida and Carapebus lagoons. There was a strong correlation between bacterial density and biomass (r² = 0.70, p < 0.05), indicating that bacterial biomass variations are highly dependent on bacterial density variations. CONCLUSION: (i) Different limnological variables regulate the bacterial density and biomass in the studied coastal lagoons, (ii) salt and phosphorus concentrations greatly explained the variation of bacterial density and biomass in the saline and distrophic lagoons, respectively, and (iii) N-nitrate and chlorophyll-a concentrations, water color and mean depth are important factors to explain bacterial density and biomass variance in some specific lagoons.
Highlights
Bacterioplankton are historically related to dead organic matter decomposition and to inorganic nutrients release in the environment
Amado et al (2013) observed that bacterioplankton respiration is higher in tropical inland ecosystems than it is in temperate ones, suggesting that there are differences of bacterial dynamics between tropical and temperate aquatic ecosystems
Amado et al (2013) highlighted the need for more studies focusing on bacterioplankton dynamics in tropical ecosystems in order to better understand the role played by such community in the aquatic ecosystems
Summary
Bacterioplankton are historically related to dead organic matter decomposition and to inorganic nutrients release in the environment. Bacterioplankton were incorporated to planktonic food webs, through the microbial loop concept (Pomeroy, 1974; Azam et al 1983). According to such concept, planktonic bacteria incorporate dissolved organic matter into bacterial biomass, which is consumed by higher trophic level organisms, such as protozoa, rotifers and cladocerans. Amado et al (2013) highlighted the need for more studies focusing on bacterioplankton dynamics in tropical ecosystems in order to better understand the role played by such community in the aquatic ecosystems In a recent review, Amado et al (2013) observed that bacterioplankton respiration is higher in tropical inland ecosystems than it is in temperate ones, suggesting that there are differences of bacterial dynamics between tropical and temperate aquatic ecosystems. Amado et al (2013) highlighted the need for more studies focusing on bacterioplankton dynamics in tropical ecosystems in order to better understand the role played by such community in the aquatic ecosystems
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