Temporary fat storage, an adaptation of some fish species to the waterlevel fluctuations and related environmental changes of the Amazon river

Analysis of Amazonian freshwater fish exhibited great differences in water- and fat content. Migratory species which deposit huge amounts of eggs in a single spawning act accumulate at high water-level great amounts of fat in various parts of the body. Nonmigratory species which spawn small quantities of eggs several times per year show little or no seasonality in fat storage. Fat storage is related to the energy requirements of the species and is considered a very successful strategy by which many Amazonian fish species survive drastic environmental and related food supply changes, which are a result of the great monomodal waterlevel fluctuations of the Amazon and its big tributaries

Investigations on the ecology and production-biology of the "floating meadows" (Paspalo-Echinochloetum) on the Middle Amazon. Part 1: The floating vegetation and its ecology

Investigations on the "floating meadows" (Paspalo-Echinochloetum) of the vârzea- region of central Amazonia in the surroundings of Manaus were made from May 1967 until October 1968. The ecology of the dominating species Pasþalum reþens BERG, Pasþalum fasciculatum WILLD., Echinocltloa þoþstaclqta (H. B. K.) HITCCHKOCK, Leersia ltexandra Swart (Fam. Gramineae) and diverse subsidiary species (Oryza þerennis Moench, Hymeachne amþlexicaalis (Rudge) Nens, Panicum chloroticum Nens (.Fam. Gramineae), Scirþus cubensis Poepp Kunth. (Fam. Cyperaceae) etc., was studied in details. Regarding Pasþalum reþens Berg, various floating and one terrestrial forms of growth were observed. Further, quantitative investigations on primary production and the development of populations of this species were made. As shown by 4 Pasþalum reþens- populations which were growing under different environmental conditions, conclusions on age and rapidity of growth of the population could be drawn from the relation between quantity of stems and number of shoots. The preliminary conditions for a "secondary colonization" of floating populations by non-floating plants and the repercussions of such sort of colonization on the primary populations are discussed. The vârzea-waters are subdivided into 3 biotopes with regard to the floating vegetation, and the factors responsible for them are discussed: l) Bank- and sedimentation-zones in the Solimões-Amazon. Dominating species: Pasþalumfasciculatum, Pasþalum reþens, Echinocltloa poþstaclgta, 2) Vârzea lakes with high fluctuations of water level. Dominating species: Pasþalum fasciculatum, Pasþalum. reþens, Echinocltloa þoþstachya. Sometimes, however, as well all other mentioned species occur in masses. Biotope richest in species. 3) Várzea lakes with relatively little fluçtuations of water level. Dominating species: Leersia hexandra, Scirþus cubensis, Pasþalum reþens. Both the current-region of the Solimões-Amazon as a biotope of its own and the influence of black-water on the vegetation are discussed

Investigations on the ecology and production-biology of the "floating meadows" (Paspalo-Echinochloetum) on the Middle Amazon. Part II. The aquatic fauna in the root zone of floating vegetation

Besides their importance for primary production, (JUNK 1970) the floating vegetation in the varzea region of the Amazon must be taken into consideration as a very important factor for the secondary production in the waters of this region as well. The floating stands represent a biotope which, with few exceptions, offers very good living conditions for aquatic animals. Accordingly they are populated with a large number of individuals and species. The maximum values found using a net of mesh size 223 microns were 780 000 individuals per m² which is equal to 11.6 g dry weight /m² (62 g fresh weight). The plants are used by the animals as a substratum and partly for nutrition. Experiments with excelsior as a substratum have shown that phytoplankton and detritus, trapped in the roots, are very important for nutrition for the population. High quantities of inorganic suspended material in combination with current (flowing white water) strongly reduce the number of individuals especially the filtering forms. Under such conditions, Cyclestheria hislopi BAIRD (Fam. Conchostraca) was not found. In dense floating islands, which are several years old, the oxygen content can be the limiting factor for the population of aquatic animals. In general we can say that the development of the aquatic fauna is influenced more by local than regional factors. Because of the complex composition of the fauna it can be shown that the short term variations of the ecological factors are shown better by the number of individuals than by the biomass. Animals with a fast succession of generations react to changes in the ecological conditions, and have a greater influence on the number rather than the biomass of individuals, due to their small size. From the point of view of the colonization by aquatic invertebrate fauna the floating vegetation could be divided into three different types, which are briefly characterized in Table 12. The factor which lead to this division and their effects on the animals have been investigated and discussed extensively. For further clarification of the relationship between fauna and substratum, experiments have been conducted with an artificial substratum, excelsior

Sedimentological studies of the "Ilha de Marchantaria" in the Solimões/Amazon River near Manaus

Sedimentological studies on the Ilha de Marchantaria an island in the Amazon river near Manaus reveal the existence of four different structural main units. A: Sandy channel bars consisting of giant ripples constitute deposits for the formation of islands or newly formed areas of the Varzea. B: Gradual accumulation on the channel bars leads to the formation of point bar ridges which consist chiefly of small-scale ripples. C: Between point bar ridges of different ages there exist swales. During rising water level the river water flows from the downward side into the swales where finegrained sediments are deposited. D: Permanent lakes are formed mainly in the centre of the islands. During low water periods the lakes may be cut of from the river. During high water periods when the whole island is flooded by the river, additional sedimentation takes place especially in the upstream area of the island. There is however, extensive erosion of the banks on the upstream side of the island. By erosion of the upstream end and sedimentation processes on the downstream end the island moves slowly downstream

Herbaceous plants of the Amazon floodplain near Manaus: Species diversity and adaptations to the flood pulse

In the floodplain of the Amazon river near Manaus, 388 herbaceous plant species, excepting epiphytes, were collected belonging to 64 families and 182 genera. 330 species are considered terrestrial, 34 aquatic, the others have an intermediate status. Most of the species occur in relatively small numbers. Only 17 species formed large monospecific stands. The largest number of species (273) was found during the dry phase in disturbed areas on the levees, as for instance in abandoned fields, because of a reduced impact of the flood and high light intensity. Low numbers were recorded during low water period from the floor of floodplain forest (25) because of insufficient light conditions and from low lying lake beds (26), which were dominated by a few highly adapted species. The following attributes were found to favour the occurrence of herbaceous plants in the Amazon floodplain: resistance of seeds and spores to flooding and dessication; short reproductive cycles; high reproduction rates; high primary production; tolerance of adult plants to flooding and drought; adaptations to waterlevel fluctuations (for example a floating way of life). Short life cycles and high reproduction rates allow the quick colonization of disturbed habitats and the substitution of population losses (r-strategy). This strategy is supported by the elevated nutrient status of the Amazon river floodplain in comparison with the floodplain of the Negro River, where herbaceous plants are scarce. The number of ruderal species and weeds including a rising number of neophytes is large. The great species diversity is related to great habitat diversity, fertility of sediments and water, predictability of the floodpulse and the reduction of interspecifìc competition due to the annual set back of the populations by the flooding and drought. The observations are in concordance with the predictions of the floodpulse concept

The effect of flooding on the exchange of the volatile C₂-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere

Nutrient dynamics of decomposing leaves from Amazonian floodplain forest species in water

Decomposition experiments were performed in freshwater tanks using fresh leaves of four Amazonian tree species from blackwater and whitewater floodplain forests. Weight loss, loss of the major elements, Na, K, Mg, Ca, N and P from the leaves, and release of these elements into the water were studied during a four month period. Based on the nutrient contents of fresh multispecies leaf litter and data on the shedding of this litter, nutrient inputs from leaves into bodies of blackwater and whitewater in the forests during flood period were calculated. The input of dissolved inorganic N, P and K may be as great or even greater than input from river water, indicating the importance of the floodplain forest as nutrient pump from sediments into the water

The trophic status of the fish fauna in Lago Camaleão, a macrophyte dominated floodplain lake in the middle Amazon

Food offer and consumption by the fish fauna were studied at medium and high waterlevels in a macrophyte dominated and strongly hypoxic floodplain lake of the middle Amazon. Detritus was shown to be the main food item, followed by terrestrial invertebrates and periphyton. Low aquatic macrophyte consumption is related to its low nutrient value in comparison with other abundant foods and its seasonal availability