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Flood Pulse (flood + pulse)
Selected AbstractsComplementary pathways of dissolved organic carbon removal pathways in clear-water Amazonian ecosystems: photochemical degradation and bacterial uptakeFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006André M. Amado Abstract Dissolved organic carbon (DOC) photochemical reactions establish important links between DOC and planktonic bacteria. We hypothesize that seasonal changes in DOC quality, related to the flood pulse, drive the effects of light,DOC interactions on uptake by planktonic bacteria uptake in clear-water Amazonian ecosystems. Water samples from two ecosystems (one lake and one stream) were incubated in sunlight during different hydrological periods and were then exposed to bacterial degradation. Photochemical and bacterial degradation were driven by seasonal DOC inputs. Bacterial mineralization was the main degradation pathway of autochthonous DOC in the lake, while allochthonous DOC was more available for photochemical oxidation. We suggest that sunlight enhances the bacterial uptake of refractory DOC but does not alter uptake of labile forms. We also observed a positive relationship between sunlight and bacterial degradation of DOC, instead of competition. We conclude that photochemical reactions and bacteria complementarily degrade the different sources of DOC during the flood pulse in Amazonian clear-water aquatic ecosystems. [source] Priming the productivity pump: flood pulse driven trends in suspended algal biomass distribution across a restored floodplainFRESHWATER BIOLOGY, Issue 8 2006DYLAN S. AHEARN Summary 1. Chlorophyll a (Chl a) distribution across a 0.36 km2 restored floodplain (Cosumnes River, California) was analysed throughout the winter and spring flood season from January to June 2005. In addition, high temporal-resolution Chl a measurements were made in situ with field fluorometers in the floodplain and adjacent channel. 2. The primary objectives were to characterise suspended algal biomass distribution across the floodplain at various degrees of connection with the channel and to correlate Chl a concentration and distribution with physical and chemical gradients across the floodplain. 3. Our analysis indicates that periodic connection and disconnection of the floodplain with the channel is vital to the functioning of the floodplain as a source of concentrated suspended algal biomass for downstream aquatic ecosystems. 4. Peak Chl a levels on the floodplain occurred during disconnection, reaching levels as high as 25 ,g L,1. Chl a distribution across the floodplain was controlled by residence time and local physical/biological conditions, the latter of which were primarily a function of water depth. 5. During connection, the primary pond on the floodplain exhibited low Chl a (mean = 3.4 ,g L,1) and the shallow littoral zones had elevated concentrations (mean = 4.6 ,g L,1); during disconnection, shallow zone Chl a increased (mean = 12.4 ,g L,1), but the pond experienced the greatest algal growth (mean = 14.7 ,g L,1). 6. Storm-induced floodwaters entering the floodplain not only displaced antecedent floodplain waters, but also redistributed floodplain resources, creating complex mixing dynamics between parcels of water with distinct chemistries. Incomplete replacement of antecedent floodplain waters led to localised hypoxia in non-flushed areas. 7. The degree of complexity revealed in this analysis makes clear the need for high-resolution spatial and temporal studies such as this to begin to understand the functioning of dynamic and heterogeneous floodplain ecosystems. [source] Terrestrial invertebrates inhabiting lowland river floodplains of Central Amazonia and Central Europe: a reviewFRESHWATER BIOLOGY, Issue 4 2002JOACHIM ADIS 1.,Amazonian terrestrial invertebrates produce high population densities during favourable periods and may suffer a drastic decrease during occasional floods and droughts. However, the monomodal, predictable flood pulse of the larger Amazonian rivers favours the development of morphological (respiratory organs, wing-dimorphism), phenological (synchronization of life cycles, univoltine mode of life), physiological (flooding ability, gonad dormancy, alternating number of developmental stages), and behavioural adaptations (migration, temporal diving) with numerous interactions. 2.,In lowlands of Central Europe, the flood pulse of large rivers is less predictable than in Central Amazonia and is superimposed by the seasonal light/temperature pulse (summer/winter regime). Some terrestrial invertebrates show physiological resistance against inundation or drought, phenologies fitting the normal annual rhythm of water level fluctuation (quiescence or diapause of eggs or adult invertebrates), high dispersal ability and migration. However, most species survive simply using a `risk strategy', combining high reproduction rates, dispersal and reimmigration following catastrophic events. 3.,The diversity of species in terrestrial invertebrates is lower in lowland riverine ecosystems of Central Amazonia and Central Europe compared with the respective uplands because of flood stress in these systems. However, floodplains in Central Amazonia possess a greater number of endemic species in comparison with Central European floodplains because of long periods of fairly stable climatic conditions in comparison with large palaeoclimatic changes in Central Europe. [source] Nitrogen fixation and denitrification in a floodplain forest near Manaus, BrazilHYDROLOGICAL PROCESSES, Issue 7 2003Heidi Kreibich Abstract The Amazon floodplain (várzea) is seasonally affected by water level fluctuations of the Solimőes/Amazon River. The drastic environmental changes that occur also include microbiological processes, such as nitrogen (N2) fixation and denitrification. Both processes were measured in the soil by the acetylene reduction assay and the acetylene block method in a várzea forest on Ilha de Marchantaria, Central Amazonia, Brazil. In the surface soil horizon (0,5 cm), N2 fixation was highest during the exposed period (0·04,0·26 nmolN h,1 g,1 dry weight (dw)). In contrast, denitrification varied from 0 to 1·40 nmolN h,1 g,1 dw, with high rates during the submerged and the transition periods. No significant difference between locations with legume trees, with non-legume trees and without trees could be observed. N2 fixation rates of incubations (litter down to 450 cm depth) for samples collected during the exposed period ranged from 0 to 0·11 nmolN h,1 g,1 dw, with highest rates in the surface soil horizon (0,5 cm). Denitrification ranged from 0 to 0·05 nmolN h,1 g,1 dw, with the highest rate at 250,300 cm depth, which was just below the water table. The maximum N2 fixation rate (0·89 nmolN h,1 g,1dw) and denitrification rate (0·09 nmolN h,1 g,1 dw) occurred in the litter layer. On average, at least three times as much N is lost from the surface soil horizon via denitrification than is gained by N2 fixation annually, but the rates are strongly influenced by the flood pulse. Copyright © 2003 John Wiley & Sons, Ltd. [source] Hydrological connectivity in coastal inland systems: lessons from a Neotropical fish metacommunityECOLOGY OF FRESHWATER FISH, Issue 1 2010P. H. M. De Macedo-Soares de Macedo-Soares PHM, Petry AC, Farjalla VF, Caramaschi EP. Hydrological connectivity in coastal inland systems: lessons from a Neotropical fish metacommunity. Ecology of Freshwater Fish 2010: 19: 7,18. © 2009 John Wiley & Sons A/S Abstract,,, We assessed the influence of hydrological connectivity in structuring fish communities through seasonal samplings of environmental variables and fishes in a coastal lagoon and associated pools in the Restinga de Jurubatiba National Park, Brazil. Community structure attributes such as species richness, numerical density and biomass, Shannon,Wiener diversity index and evenness were compared between periods of the lowest and highest hydrological connectivity, while the environmental gradient and fish zonation were explored through ordination techniques. The greater hydrological connectivity established in the rainy season promoted the homogenisation of most environmental variables and fish species, which differed markedly from the arrangement observed in the dry season. Despite variation in fish species composition, community attributes showed non-significant differences between the dry and rainy seasons. The patterns of composition and numerical density in pools were strongly influenced by local factors, especially salinity, dissolved oxygen, total phosphorous concentration and water colour in the dry season, in addition to total nitrogen concentration and depth in the rainy season. Comparable to the role played by flood pulses in river-floodplain systems, the hydrological connectivity in these tropical coastal waterbodies seems to strongly influence fish community structure, and, therefore to determine regional biodiversity. [source] | ||||||||||