title: Fluctuations of the population of Daphnia laevis Birge 1878: a six-year study in a tropical lake.
abstract: The fluctuation of the population of Daphnia laevis in Lake Jacaré (Middle River Doce, Minas Gerais) was monitored monthly (at one point in the limnetic region) for six years (2002-2007) as part of the Program of Long-Term Ecological Research (LTER/UFMG). The following parameters were also monitored: water temperature, pH, electrical conductivity, dissolved oxygen, chlorophyll a, total phosphorus, phosphate, total nitrogen, nitrate, nitrite, ammonia, and densities of Chaoborus and ephippia of Daphnia laevis in the sediment. A seasonal pattern was observed in the fluctuation of D. laevis, with higher densities recorded during periods of circulation (May-August). A significant correlation was found between the density of D. laevis and temperature (r = -0.47, p = 0.0001), chlorophyll-a (r = -0.32, p = 0.016) and indicators of the lake's trophic status (total phosphorus, r = 0.32, p = 0.007 and trophic state, r = 0.36, p = 0.003), as well as Chaoborus density (r = 0.43 and p = 0.002). These results indicate that changes in the physical and chemical characteristics of the water related with stratification and circulation of the lake may have a direct (temperature, total phosphorous) or an indirect (food availability, presence of predators, ephippia eclosion) influence on the fluctuation of the D. laevis population.
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. lucianapmb@hotmail.com
authors.forename: L P M
authors.initials: LP
authors.lastname: Brandão
authors.forename: T
authors.initials: T
authors.lastname: Fajardo
authors.forename: E
authors.initials: E
authors.lastname: Eskinazi-Sant'anna
authors.forename: S
authors.initials: S
authors.lastname: Brito
authors.forename: P
authors.initials: P
authors.lastname: Maia-Barbosa
mesh_terms: D000818:Animals; D001938:Brazil; D003621:Daphnia / Q000502:physiology*; D004784:Environmental Monitoring / Q000379:methods*; D060106:Lakes / Q000032:analysis*; D011156:Population Density; D011157:Population Dynamics; D012621:Seasons; D014329:Tropical Climate