Diel patterns of temperature, conductivity and dissolved oxygen in an Amazon floodplain lake: description of a friagem phenomenon

Abstract

AIM: The aim of this work was to study the diel stratification parameters temperature, dissolved oxygen and conductivity, providing a more detailed description of a friagem event. METHODS: the mixing behavior of the limnetic water column in Lago Catalão, an Amazon floodplain lake flooded by two of the world’s largest rivers (Solimões and Negro), was studied through diel profiling of temperature, conductivity and dissolved oxygen, between 2006 and 2007. Measurements were made every four hours at 1m depth intervals to the lake bottom. RESULTS: The water column remained stratified during most of the year with the exception of one month with low water level, when nocturnal mixing occurred and one friagem event during high water (May 2007) when an isothermal temperature profile and an atypical orthograde oxygen profile were observed. CONCLUSIONS: The friagem event, a large drop in air temperatures due to the intrusion of a polar air mass in the Amazon, constitutes an important force in the dynamics of the water column, which produces a profound redistribution of dissolved gases and solutes in the system. This is the first time that the effects of the friagem on the mixing patterns in a lowland Amazon lake have been documented in detail. The decline in air temperature, observed during the friagem event destabilized the normally stratified water column, which can be associated with an environmental disturb.

Seasonal dynamics of the fish assemblage in a floodplain lake at the confluence of the Negro and Amazon Rivers

“…Lago Catalão is completely connected with both rivers during the flood season and may be totally isolated during the dry season (Brito et al ., ). Limnological studies in this region show that lake water characteristics are mainly controlled by the flood pulse regime of the two rivers (Almeida & Melo, ; Brito et al ., ; Caraballo et al ., ). Although the lake receives a large input of water from both rivers, the Negro appears to have greatest influence on water quality during the early rising‐water period, resulting in lower values of conductivity and pH, and the Amazon has dominant influence during most other periods (Brito et al ., ; Caraballo et al ., ).…”

“…The largest lake in this floodplain is Lago Catalão. Limnological studies have revealed that each river influences the lake's water quality during particular phases of the annual flood pulse (Brito et al ., ; Caraballo et al ., ), which changes the water level c . 10 m on average (Bittencourt & Amadio, ).…”

Effect of depth on food‐web interactions in a thermally stratified floodplain lake following inundation

“…As stratified lakes are characterized by steep gradients, vertical heterogeneity over a small depth interval is evident. Even in shallow waters, minor differences in temperature between surface‐ and bottom‐water layers result in stably stratified water columns (Petrucio, Barbosa, & Furtado, ), as was found in floodplain lakes (Caraballo, Rider Forsberg, Ferreira de Almeida, & Galdino Leite, ; Marshall, ; Townsend, ) and river sections as well (Engel & Fischer, ). If the stratification of floodplain lakes persists during inundation, it might increase habitat heterogeneity and, consequently, enhance floodplain biodiversity (Ward, Tockner, & Schiemer, ).…”

“…Habitat heterogeneity also preserves the biogeochemical functioning of aquatic ecosystems (Foulquier, Dehedin, Piscart, Montuelle, & Marmonier, ). Therefore, thermal stratification is an important process that could significantly explain floodplain functioning but has not been frequently investigated yet (Caraballo et al, ; Marshall, ; Townsend, ).…”

In vitro effects of increased temperature and decreased pH on blood oxygen affinity of 10 fish species of the Amazon

“…Owing to climate change, mean freshwater temperatures, including the water of the Amazon, are predicted to rise by up to 4° C (IPCC, ). In many Amazonian habitats, such as the shoreline of floodplain areas, the water temperature changes may be even higher as a consequence of other regional events (Sioli, ; Caraballo et al ., ). These situations, i.e .…”