Amazon Floodplain Lake Research Articles

Limitation of bacterial growth by inorganic nutrients in an Amazonian floodplain lake

Limitation of bacterial growth by inorganic nutrients in an Amazonian floodplain lake

Nutrient limitation of bacteria and sources of nutrients supporting nutrient-limited bacterial growth in an Amazonian floodplain lake

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 39:57-67 (2005) - doi:10.3354/ame039057 Nutrient limitation of bacteria and sources of nutrients supporting nutrient-limited bacterial growth in an Amazonian floodplain lake Danny Rejas1,2,*, Koenraad Muylaert3, Luc De Meester1 1Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, Debériotstraat 32, 3000 Leuven, Belgium2Unidad de Limnología y Recursos Acuáticos, Universidad Mayor de San Simón, casilla 471, Cochabamba, Bolivia3Section Protistology & Aquatic Ecology, Department of Biology, University Gent, Krijgslaan 281 – S8, 9000 Gent, Belgium *Email: drejas@supernet.com.bo ABSTRACT: Laguna Bufeos is a white-water floodplain lake located in the upper Amazon basin (Ichilo River, Bolivia). To study nutrient limitation of bacteria and to determine the sources supporting nutrient-limited bacterial growth, 5 nutrient deletion/dilution experiments were carried out in Laguna Bufeos. We carried out 3 experiments during 3 consecutive low-water seasons and 2 experiments during 1 high-water season. No evidence of N or P limitation was observed during the 2 experiments in the high-water season. Conversely, bacteria were limited by P in the 3 experiments in the low-water season. Limitation by N occurred only in one of the low-water experiments. Nutrient-limited bacterial growth rates equaled 37 to 86% of nutrient-saturated growth rates. Nutrients recycled by microzooplankton, mainly heterotrophic nanoflagellates and oligotrich ciliates, were the major nutrient source supporting P- or N-limited growth. Our results suggest a strong control of bacterial growth rates by P in Amazonian white-water lakes during the low-water season, while this limitation is alleviated during the high-water season, probably through supply of new nutrients from the river. The strong nutrient limitation of bacteria and the dependence of bacteria on nutrients supplied by their predators can be expected to slow down the decomposition of organic matter in Amazonian floodplain lakes. This may partly explain why these ecosystems are often rich in organic matter. KEY WORDS: White water · Amazon · Floodplain lake · Bacteria · Nutrient limitation · Phosphorus · Nutrient deletion/dilution experiments Full article in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 39, No. 1. Online publication date: April 28, 2005 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2005 Inter-Research.

Carbon sedimentation at Lago Grande de Curuai, a floodplain lake in the low Amazon region: insights into sedimentation rates

We studied recent organic carbon sedimentation in an Amazonian floodplain using sediment trap samples and one core. Sediment traps were placed in several lakes of the “Lago Grande de Curuai” floodplain during different water-level phases: the end of the period of water-level reduction (‘falling water’) and the start of the period of water-level increase (‘rising water’). Vertical seasonal fluxes of settling particles (SP) are very difficult to estimate and interpret, especially during ‘falling water’ periods, when the concentration of suspended matter in the water column is greater than during ‘rising water’ periods, probably due to resuspension processes. Vertical fluxes of settling particles (SP) varied between ca. 4 and 2000 g m−2 day−1. Fluxes of organic carbon ranged between (5–50 g C m−2 day−1) during the ‘falling water’ and between (0.041–4 g C m−2 day−1) during the ‘rising water’. The core is characterised by two laminated, sedimentological units. Sediments in the upper unit, which generally coarsens upwards, are interpreted as a progradation sequence of the sand and silt flat at the entrance of an inflow channel where the core was collected. This unit is composed of three sub-units: a superficial layer reworked by bioturbation, a lower sub-unit characterised by horizontal and sub-horizontal laminations of fine sands and silts, and a basal sub-unit composed of horizontal laminations of fine silts and clays. The lower unit is characterised by horizontal and sub-horizontal laminations of fine sands and silts and corresponds to the top of an older accumulating sequence. These changes show that the sedimentary environment is very dynamic at the centennial scale. Sedimentation rates generally ranged between 0.42 and 1.34 cm year−1, and were estimated to range from 0.56 to 1.35 cm year−1 after normalisation for clay-sized particles (<4 μm). Floodplain sediment accumulation generally varies between 0.42, 1.16, and 1.10 g m−2 year−1, within the first, second and third sub-units, respectively. In the second unit the non-supported 210Pb date is close to the detection limit. Carbon content is relatively low, around 1% sediment weight through the core, although mean carbon accumulation rates are very high, generally 100 g m−2 year−1 and peaking at 250 g m−2 year−1. These results suggest that Amazon floodplain lakes may constitute an important sink for organic carbon.

Carbon sedimentation at Lago Grande de Curuai, a floodplain lake in the low Amazon region: insights into sedimentation rates

We studied recent organic carbon sedimentation in an Amazonian floodplain using sediment trap samples and one core. Sediment traps were placed in several lakes of the “Lago Grande de Curuai” floodplain during different water-level phases: the end of the period of water-level reduction (‘falling water’) and the start of the period of water-level increase (‘rising water’). Vertical seasonal fluxes of settling particles (SP) are very difficult to estimate and interpret, especially during ‘falling water’ periods, when the concentration of suspended matter in the water column is greater than during ‘rising water’ periods, probably due to resuspension processes. Vertical fluxes of settling particles (SP) varied between ca. 4 and 2000 g m −2 day −1. Fluxes of organic carbon ranged between (5–50 g C m −2 day −1) during the ‘falling water’ and between (0.041–4 g C m −2 day −1) during the ‘rising water’. The core is characterised by two laminated, sedimentological units. Sediments in the upper unit, which generally coarsens upwards, are interpreted as a progradation sequence of the sand and silt flat at the entrance of an inflow channel where the core was collected. This unit is composed of three sub-units: a superficial layer reworked by bioturbation, a lower sub-unit characterised by horizontal and sub-horizontal laminations of fine sands and silts, and a basal sub-unit composed of horizontal laminations of fine silts and clays. The lower unit is characterised by horizontal and sub-horizontal laminations of fine sands and silts and corresponds to the top of an older accumulating sequence. These changes show that the sedimentary environment is very dynamic at the centennial scale. Sedimentation rates generally ranged between 0.42 and 1.34 cm year −1, and were estimated to range from 0.56 to 1.35 cm year −1 after normalisation for clay-sized particles (<4 μm). Floodplain sediment accumulation generally varies between 0.42, 1.16, and 1.10 g m −2 year −1, within the first, second and third sub-units, respectively. In the second unit the non-supported 210Pb date is close to the detection limit. Carbon content is relatively low, around 1% sediment weight through the core, although mean carbon accumulation rates are very high, generally 100 g m −2 year −1 and peaking at 250 g m −2 year −1. These results suggest that Amazon floodplain lakes may constitute an important sink for organic carbon.

Number, seasonal movements, and residency characteristics of river dolphins in an Amazonian floodplain lake system

The size and structure of a community of Amazon river dolphins or botos, Inia geoffrensis (de Blainville, 1817), was investigated using boat surveys and long-term observations of recognisable animals. Year-round, some 260 botos occurred in or near the 225-km2 Mamirauá várzea floodplain lake system, of which half were permanent residents by our definition. Seasonal variation in water levels influenced distribution between habitats but not the overall number of botos. Ninety percent of marked botos encountered within the lake system were permanent residents. There appeared to be a cline in site fidelity between those that always live in or near the system and those that visit at intervals of years. We estimated that 270 botos were "significant users" of the lake system (i.e., occurred within it for sufficient periods in a year to be observed at least once) and that many others visited for short periods. Individuals moved many tens to hundreds of kilometres along the rivers, but there was no broad-scale seasonal migration. The boto population of the central Amazon, at least, may be structured on the basis of floodplain lake systems, with extensive animal movement between systems. We estimate that 13 000 botos occur in the 11 240 km2 Mamirauá Sustainable Development Reserve, which covers an estimated 11%–18% of várzea habitat in Brazil.

Effect of Campsurus notatus on NH+4, DOC Fluxes, O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment‐Water Interface of an Amazonian Lake Impacted by Bauxite Tailings

AbstractThe aim of this study was to evaluate the influence of Campusurus notatus Eaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH4+) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment‐water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment‐water interface. The cores were incubated with 0 to 2,388 ind m–2 of Campsurus notatus nymphs, and the changes in NH4+, DOC, O2 concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p &lt; 0.05, multiple regression) and oxygen uptake (F = 11.8, p &lt; 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two‐way ANOVA, p &lt; 0.05) in bacterial production (0.44 μg C l–1 h–1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH4+) at the sediment‐water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production.

Decomposition of Echinochloa polystachya and its contribution to nutrient cycling in a Central Amazonian floodplain lake

Decomposition of <i>Echinochloa polystachya</i> and its contribution to nutrient cycling in a Central Amazonian floodplain lake

Fish catches among riverside communities around Lago Grande de Monte Alegre, Lower Amazon, Brazil

Forty‐six families living around the Amazon floodplain lake of Lago Grande de Monte Alegre, Brazil, were monitored between April 1993 and March 1995 with respect to their fish catches. The average catch per fisherman was 22 kg day‐1. There were significant differences between subsistence and commercial fishing, and also across different seasons of the year. Catch was higher in the dry season and in the lake environment, followed by the river environment. The flooded forest was exploited in the rainy season. Out of a total of more than 70 fish species, 10 taxa comprised 75% of the catch. The catch in the Monte Alegre region concentrated on smaller species for local consumption. Prochilodus nigricans (Spix &amp; Agassiz) was the most important species, followed by Liposarcus pardalis (Castelnau) and Plagioscion spp. Comparisons between quantities of fish consumed and fish marketed indicated that the fishery has a much more important role in the region than previously thought.

Evaluation of groundwater input as major source of solutes in an Amazon floodplain lake during the low water period

Evaluation of groundwater input as major source of solutes in an Amazon floodplain lake during the low water period

Methane emissions from an Amazon floodplain lake: Enhanced release during episodic mixing and during falling water

Methane fluxes to the troposphere were measured inLake Calado, a dendritic floodplain lake located inthe central Amazon Basin. Methane concentrations inthe surface water of the lake were less than 0.5 µM during a period of high and rising water inApril and May, except when episodic, deep mixingoccurred and surficial concentrations reached as highas 4.8 µM. Diffusive fluxes ranged from ca.2–20 mg CH4 m−2d−1 (mean: 6.6 mg CH4 m−2d−1) normally, but increased up to 220 mg CH4 m−2d−1 during the passageof a rare cold front. During six weeks of risingwater, the volume-weighted methane content of the lakeincreased during periods of stable thermalstratification (accumulation rates ranging from16–1411 mg CH4 m−2d−1) and decreasedduring episodes of partial mixing (rates of decreaseranging from 63–1792 mg CH4 m−2d−1). Surface water methane concentrations during low andfalling water in September varied by more than anorder of magnitude (range, 0.3–9 µM), anddiffusive fluxes ranged from 3–158 mg CH4m−2d−1 (mean, 54 mg CH4 m−2d−1). During falling water in September, total methane flux from the lake to the troposphere measured with a floating chamber rangedfrom 53–328 mg CH4 m−2d−1 (mean, 163 mgCH4 m−2d−1). Ebullitive flux averaged 69% of total flux. Total methane flux was highest when thermal stratification was lost due to decreasing lake depth.

Phytoplankton in an Amazonian flood-plain lake (Lago Batata, Brasil): diel variation and species strategies

Phytoplankton diel variations in an Amazonian flood-plain lake (Lago Batata) were studied quarterly for 1 year, according to the hydrometric level fluctuation of the Trombetas river (39.7-47.0 m over sea level), to which the lake is permanently connected. Hydrological and hydro- graphic conditions determined mixing patterns of the water column and phytoplankton distribution. When the lake is deep (>4.0 m), sparse phytoplankton communities are found at the bottom, by thermal discontinuities, and may remain so for a short duration (days). When the lake is shallow (<4.0 m), mixing of the waters ensures a nearly even distribution of organisms throughout the water column. The weak stability of stratification is a major influence on the distribution of phytoplankton popu- lation densities in this shallow flushed lake. The highest phytoplankton densities during the second part of the day, mentioned in the literature, are observed only during decreasing water level. During the other phases of the hydrological cycle (increasing, high and low water levels), no differences in phytoplankton population density were observed throughout the diel cycle. Assemblages, or groups of descriptor species of systems having similar features, have recently been proposed. Assemblages of flushing-tolerant nano-algae (X1) and of mixing-dependent species (T, S) have shown that the physical properties of the environment were often the strongest determinants of the phytoplankton strategies.

Methane turnover in exposed sediments of an Amazon floodplain lake.

In the Amazon floodplain large areas of unvegetatedlake sediments are exposed to air during low water. Imeasured methane fluxes from exposed sediments of anAmazonian floodplain lake and assessed the regulatingfactors. Methane emission decreased from values between 10 and 40 μmol CH4 mminus 2 hminus 1to zero when the sediments were exposed to air. Meanfluxes were about 3.7 μmol CH4mminus 2 hminus 1. Fluxes were low compared tomeasurements taken from flooded habitats makingexposed lake sediments a negligible source ofatmospheric CH4. This was mainly due to the lackof ebullition which governs methane flux in theflooded phase. Methane oxidation at the sedimentsurface consumed up to 75% of the methane enteringthe oxidised zone. Compared with CO2 emissionmethane turnover was of minor importance for thecarbon budget of the sediments.

Silica-scaled Chrysophytes from an Amazonian flood-plain lake, Mussurá Lake, northern Brazil

Silica-scaled Chrysophytes from an Amazonian flood-plain lake, Mussurá Lake, northern Brazil

The influence of bauxite tailings on the light regime and its consequence on phytoplankton primary production in an Amazonian floodplain lake

The influence of bauxite tailings on the light regime and its consequence on phytoplankton primary production in an Amazonian floodplain lake

Causes of hydrochemical seasonality of major cations in Lake Camaleão, a Central Amazonian floodplain lake

Causes of hydrochemical seasonality of major cations in Lake Camaleão, a Central Amazonian floodplain lake

Phytoplankton biomass of a central Amazonian floodplain lake

Phytoplankton biomass of a central Amazonian floodplain lake

Phytoplankton periodicity and sequences of dominance in an Amazonian flood-plain lake (Lago Batata, Pará, Brasil): responses to gradual environmental change

The composition of the phytoplankton of Lago Batata,a flood-plain lake connected to Rio Trombetas,undergoes a conspicuous annual cycle which is relatedto the hydrology (depth of water, rate of fluvialflushing) and the hydrography (stability, frequency ofmixing of the water) of the lake. From a sparsenanoplankton at high-water and high flushing, the lakepasses to desmid-diatom dominance and finally tofilamentous cyanobacteria when the lake is barely 2 mdeep. As it refills, the lake again becomes desmid-dominated; then, when the turbidity is least and thestratification most stable, Botryococcus becomesa major component. Eventually flushing becomes toorapid for any but the relatively fastest-growingspecies. These changes are gradual and, at the scaleof algal generation times, cannot be explained assharp or sudden disturbances. Neither do they have theproperties of ecological successions but ratherrepresent compositional responses to a progressiveenvironmental modification analogous to the floristicphenomenon of gradual climate change.

Phytoplankton composition and abundance of a central Amazonian floodplain lake

The phytoplankton community of Lake Camaleao, a smallfloodplainlake influenced by a large whitewater river, the Solimoes, was monthlyinvestigated for the composition and abundance of itsphytoplankton. The seasonal influence of the floodregime on biomass, species richness and diversity, andits relation with physical and chemical factors(temperature, pH, dissolved oxygen, electricalconductivity, total seston and inorganic nutrients)was analyzed and subjected to principal componentanalysis. Diversity was variable along the seasonalcycle: relatively high values were observed at the endof the dry season supported by high nutrientconcentrations. The phytoplankton was comprised of 262 taxa,with strong dominanceof euglenoids (81%). The three sample stations did not differamong each other, except in the dry season, due todata cluster in relation to theprincipal axis (1 and 2), explaining 63% of thevariation. Biomass accumulation as a function of lakearea reduction contributed to theseresults, indicating that the phytoplankton dynamicswere hydrology-driven.

A simple modelling approach towards hydrochemical seasonality of major cations in a Central Amazonian floodplain lake

To identify causes of hydrochemical seasonality, dynamic mass balance models are developed. They describe a hypothetical floodplain lake designed according to literature data supplemented by unpublished data on Lago Camaleão, an island channel lake in the lower Solimões River. The conservative model accounts for advective and atmospheric cation fluxes, the non-conservative model additionally for biogenic cation fluxes due to growth and decomposition of the macrophyte vegetation. During much of the hydroperiod, seasonal evolutions observed for Na, Ca, and Mg, were in accordance with conservative expectation. Increasing concentrations during falling water were not explained by the conservative model. Differences between predictions of the conservative, and the non-conservative model were negligible. Thus, for the evolution of Na, Ca, and Mg, biogenic fluxes are insignificant. We suggest that cation loading during falling water is caused by an abiotic process. Evolution of K was non-conservative during much of the hydroperiod. Deviations from conservative expectation due to K loading during rising, as well as during falling water, were in accordance with predictions of the non-conservative model. Hence, during rising water, macrophyte-derived influxes of K are the key factor for deviations from conservative expectation. During falling water, however, macrophyte decomposition is still poorly understood, and unknown processes causing Na, Ca, and Mg loadings might also procure additional K loading, and thus biogenic K fluxes might not be the sole cause for increasing concentrations.

Spatial and seasonal variation of methane emission from an Amazon floodplain lake

Methane (CH4) emission from a floodplain lake in central Amazonia was measured during a complete annual cycle using a static chamber method. The results show significant differences in the CH4 flux rates from different habitats in the lake: open water, floating vegetation (mainly the aquatic grass Paspalum repens) and floodplain forest. The highest CH4 emission rates (10–198 mg CH4 m−2 d−1) were recorded during inundation in the seasonally flooded forest. Lower emission rates occurred in the floating vegetation (3–79 mg CH4 m−2 d−1), which is found in areas with a short subaerial phase and in the permanently aquatic part of the lake (4–65 mg CH4 m−2 d−1) free of macrophytes and with the lowest productivity. Seasonal fluctuations in water level resulted in distinct seasonal patterns in CH4 release at different sites in the lake. The permanently aquatic part of the lake had lowest emission rates during periods of water inflow and subsurface oxygen replenishment into the lake. At the periodic aquatic...