Runa realism: Upper Amazonian attitudes to nature knowing

Stories about the forest recounted in a Quichua-speaking Runa village in Ecuador's Upper Amazon point to an element of ecological understandings that is rarely studied; these are primarily about capturing and sharing the experience of the process of knowing rather than trafficking in stabilized tokens of ecological knowledge. Runa understanding of nature is achieved through a poetic language rich in what philosopher Charles S. Peirce terms iconic and indexical signs. This way of talking about forest experience is advantageous because these forms of representation can capture qualities and events in the world in ways that what Peirce terms symbols cannot. Iconic and indexical signs mediate the world in distinctive ways. Accordingly, this article suggests some implications that iconically and indexically rich modes of communicating experience have for engaging with the nonhuman realm, acquiring knowledge of the world, and establishing a certain kind of interpersonal social intimacy.     

Pressurized gas transport in Amazonian floodplain trees

Trees of Central Amazonian whitewater floodplain forests are subjected to extended flood periods lasting several months. They must therefore be highly adapted to long-term flooding and to oxygen shortage in the soil and roots which is expected to be the main stress factor in this environment. The improvement of oxygen transport to the roots by pressurized gas transport, known for some tree species of the temperate zone, is one specific adaptation to flooding. To evaluate its significance, gas transport measurements were carried out under experimental conditions with saplings of five Amazonian tree species. Internal aeration of the roots was improved under conditions of pressurized gas transport as shown by polarographical measurements of oxygen exchange between root and rhizosphere. Tracer gas measurements using sulphur hexafluoride (SF₆) showed gas permeability of transport pathways between stem base and roots. Based on the data, we suppose that pressurized gas transport significantly contributes to internal aeration of roots in Amazonian floodplain saplings growing on the higher levels in the flooding gradient, with low water columns, and is an important adaptation for establishment in these temporarily inundated habitats also in the weeks of rising and lowering water levels.     

Phytoplankton composition and abundance of a central Amazonian floodplain lake

The phytoplankton community of Lake Camaleão, a smallfloodplainlake influenced by a large whitewater river, the Solimões, 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.     

The interplay of top-down planning and adaptive self-organization in an African floodplain

Natural floodplains are complex social-ecological systems in which human livelihoods are tightly coupled with flooding dynamics. In this paper, we argue that hydraulic planning in such systems, including to mitigate extreme floods, must consider three key features of adaptive self-organizing systems in floodplains - connectivity, learning feedbacks, and rhythms - to support the resilience of floodplain communities to extreme floods. We illustrate this argument with a case study of the Logone Floodplain, Cameroon. Based on hydrological data, ethnographic research and a series of focus group interviews with floodplain villagers, we analyze the interplay of top-down planning and adaptive self-organization in response to two extreme floods in 2012 and 2015. We show that recent top-down strategies of hydraulic control in the floodplain have led to more hydraulic uncertainty for local populations, and curtailed the conditions for sustainable self-organization in the floodplain.     

保护区的湖泊在萎缩

<正>花湖的湖岸已经退却了50多米,水面下降了近1米。1976年,年轻的扎科作为青年突击队长,带领乡里几百个青壮劳力在若尔盖的沼泽地里开沟修挖排水渠。沼泽里的水很深,藏语称"根没",意为无底的。据扎科回忆,当时沼泽的水深到用12米的绳子吊一个秤砣     

Regulation and stability in fish assemblages of neotropical floodplain lakes

Neotropical floodplain lakes provide an excellent opportunity to examine the regulation and stability of fish assemblages. At low water, when lakes are separated, fish are concentrated in the lakes and are presumably subject to strong interspecific interactions that can shape assemblage structure. At high water, when the lakes and river channels become broadly interconnected, ample potential exists for alteration of assemblage structure because eggs, larvae, and older fish may undergo spatial reshuffling among waterbodies. Twenty lakes of the Orinoco River floodplain in Venezuela were surveyed in the early and late dry seasons of two consecutive years. Marked differences in assemblage structure among lakes were established in the early dry season. Changes in assemblage structure during the dry season were large and detectable even at the ordinal level; they reflected a strong reduction of visually oriented fish relative to fish with adaptations to low light. Changes were similar in the two years and were apparently due to species-specific differences in mortality, which was high over the dry season. The annual flood is a strong natural fluctuation that greatly modifies assemblage properties during the wet season. Nevertheless, the potential for alteration of assemblage structure by reshuffling was not realized: assemblage properties early and late in the dry season were similar in the two years, indicating a regular and predictable annual cycle of change in assemblage structure. This regularity can be explained by mechanisms of regulation which appear to be linked to piscivory and the optical environment. In contrast with the prevailing views on neotropical fish assemblages, there seems to be a strong deterministic component to assemblage structure and dynamics in Orinoco floodplain lakes.     

High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats

Seed dispersal is a critical stage in the life history of plants. It determines the initial pattern of juvenile distribution, and can influence community dynamics and the evolutionary trajectories of individual species. Vertebrate frugivores are the primary vector of seed dispersal in tropical forests; however, most studies of seed dispersal focus on birds, bats and monkeys. Nevertheless, South America harbors at least 200 species of frugivorous fishes, which move into temporarily flooded habitats during lengthy flood seasons and consume fruits that fall into the water; and yet, we know remarkably little about the quality of seed dispersal they effect. We investigated the seed dispersal activities of two species of large-bodied, commercially important fishes (Colossoma macropomum and Piaractus brachypomus, Characidae) over 3 years in Pacaya-Samiria National Reserve (Peru). We assessed the diet of these fishes during the flood season, conducted germination trials with seeds collected from digestive tracts, and quantified fruit availability. In the laboratory, we fed fruits to captive Colossoma, quantified the proportion of seeds defecated by adult and juvenile fish, and used these seeds in additional germination experiments. Our results indicate that Colossoma and Piaractus disperse large quantities of seeds from up to 35% of the trees and lianas that fruit during the flood season. Additionally, these seeds can germinate after floodwaters recede. Overexploitation has reduced the abundance of our focal fish species, as well as changed the age structure of populations. Moreover, older fish are more effective seed dispersers than smaller, juvenile fish. Overfishing, therefore, likely selects for the poorest seed dispersers, thus disrupting an ancient interaction between seeds and their dispersal agents. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dietary–morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain

Morphological correlates of diet were examined in 48 species of freshwater fishes from floodplain lakes in the central part of the Mamoré River (Bolivian Amazon). The species were classified, according to the percentage occurrence of seven food items, into eight broad trophic categories: mud feeders, algivores, herbivores, terrestrial invertivores and omnivores, carnivores, zooplanktivores, aquatic invertivores and piscivores. There were significant relationships between the diet and morphology of the fishes even when the effect of taxonomical relatedness between species was eliminated. Relative gut length was the main morphological variable used to order species on a carnivore to mud feeder gradient. Standard length and head and mouth size were the morphological variables most closely associated with prey size. Mud feeder, algivore and piscivore species appeared as the most dietary and morphologically specialized. These results support both the hypotheses that species morphology influences the diet and that morphological similarity is conserved even in comparison with taxonomically unrelated species.     

Invasion of exotic piscivores causes losses of functional diversity and functionally unique species in Japanese lakes

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Central Amazonian floodplain forests: Tree adaptations in a pulsing system

Amazonian floodplain forests are characterized by an annual flood pulse with changes of the water table that exceed 10 meters. Seedlings and adult trees are waterlogged or submerged for continuous periods lasting up to seven months per year. The monomodal flood pulse of the rivers causes drastic changes in the bioavailability of nutrients, oxygen levels, and concentrations of phytotoxins. The aquatic phase occurs during a period in which temperature and light conditions are optimal for plant growth and development, implying the need for adaptations. Not only do trees persist in a dormant state, they grow vigorously during most of the year, including the aquatic period. The regularity of flooding may have enhanced the evolution of specific traits, which partially are well known from floodplain trees in other tropical and in temperate regions. Different kinds of adaptations are found at the level of structural, physiological, and phenological traits. Combinations of adaptations regarding seed germination, seedling development, and traits of roots, shoots, and leaves result in a variety of growth strategies among trees. These lead to specific species distributions and zonations along the flooding gradient and within Amazonian floodplain systems (nutrient-rich white-water várzea and nutrient-poor black-water igapó).     

Patterns in the top-down versus bottom-up regulation of heterotrophic nanoflagellates in temperate lakes

The importance of resources versus that of predators in determiningthe abundance of organisms is modulated by several factors whichvary over time and space. Here, we evaluate the abundance ofheterotrophic nanoflagellates (HNF), the main predators of planktonicbacteria, in the plankton of 16 Quebec lakes as a function ofthe abundance of resources and zooplankton (predators). We analyzethe data at two different scales: among lakes varying in resourcesupply and within lakes. Resource factors (total phosphorus,chlorophyll, bacterial concentration) best explained the abundancesof HNF among lakes differing in resource availability. Whenthe effect of resource availability was removed, the biomassof cladocerans became an important determinant of HNF abundance,with abundance declining and the ratio of bacteria per flagellateincreasing, as the cladocerans increased. Within lakes, HNFabundance was not a direct function of resource concentration.Multiple regression models based on data for many lakes showedthat both bottom-up (food) and top-down (predation) variablespredicted HNF abundance quite well. An examination of the seasonalpattern among individual lakes showed each group of variablesdiffering in importance: bottom-up variables were more importantin spring and top-down variables in midsummer. An examinationof the effects of different assemblages of zooplankton on HNFshowed cladocerans to exert the highest negative impact on HNFand to be responsible for keeping low HNF numbers during mostof the summer with that probably affecting the pathways of energyflux in those lakes dominated by cladocerans versus those dominatedby other zooplankton. The absolute, as well as the relative,importance of the different biotic and abiotic factors examinedin predicting the abundance of HNF is a function of the scaleof the investigation. Among lakes varying greatly in resourcesupply, resources are found to better correlate with HNF abundance.When the analysis is performed at another scale, within lakes,the relative importance of resources and predation in determiningHNF abundances changes depending on the variability superimposedby other factors (seasonality and lake food web structure).     

Establishing the pattern of heterotrophic bacterial activity in three Central Amazonian lakes

Three lakes of the Central Amazon were studied in depth for a year. Patterns of heterotrophic activity were seen to develop as the result of a variety of factors in the three lakes. Primary mechanisms that appear to control the heterotrophic activity were the water levels, the nutrient concentrations, including labile carbon, and the chlorophyll-a levels. Heterotrophic activity (V_max) in the three lakes varied from values comparable to extreme oligotrophic to eutrophic in each of the lakes studies. The large range (0.045–9.644 µg 1^–1 h^–1) of V_max is viewed as a part of the cycle of growth and renewal which is characteristic of the Central Amazonian Ria and Varzea lakes.     

Flood pulse regulation of bacterioplankton community composition in an Amazonian floodplain lake

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The composition and importance of the phytoneuston in two floodplain lakes in south-eastern Australia

Normans Lagoon and 3-Gum pond are small floodplain water bodies adjacent to the Murray River, south-eastern Australia, and often have a visible film/sheen across their surface. Since few studies have provided quantitative comparisons of the surface and subsurface layer communities of shallow freshwater lakes, we determined the contributions of the surface and subsurface populations to overall algal biomass when a surface film was visible, and when it was not visible. We examined the algae and cyanobacteria present at the air–water interface of each water body, and compared the findings with those for the water immediately below the surface, and for the overall water column. The algal groupings Trachelomonas spp., other Euglenophyceae (principally Euglena spp.), Chlorophyceae and Cyanobacteria usually comprised >95% of the measured biovolume within all samples. Samples from the air–water interface were considerably enriched (up to 200-fold) with respect to algal biovolume, whether or not a visible surface film was present, and elevated cell counts were observed within the air–water interface for motile organisms such as Trachelomonas spp. and green unicellular flagellates. The reverse was true for the cyanobacterium Planktolyngbya however, with greater concentrations occurring at depth. In terms of its contribution to the overall algal/cyanobacterial populations within each water body, the surface layer was found to be responsible for <1–20% of the biovolume over the entire water column. Multivariate statistical analysis confirmed there were significant differences between the communities of the air–water interface and those of the water below, and that these differences occurred both in the presence and absence of a visible surface film/sheen. Handling editor: D. Ryder     

On the different nature of top-down and bottom-up effects in pelagic food webs

SUMMARY 1. Each individual planktonic plant or animal is exposed to the hazards of starvation and risk of predation, and each planktonic population is under the control of resource limitation from the bottom up (growth and reproduction) and by predation from the top down (mortality). While the bottom-up and top-down impacts are traditionally conceived as compatible with each other, field population-density data on two coexisting Daphnia species suggest that the nature of the two impacts is different. Rates of change, such as the rate of individual body growth, rate of reproduction, and each species' population growth rate, are controlled from the bottom up. State variables, such as biomass, individual body size and population density, are controlled from the top down and are fixed at a specific level regardless of the rate at which they are produced.
2. According to the theory of functional responses, carnivorous and herbivorous predators react to prey density rather than to the rate at which prey are produced or reproduced. The predator's feeding rate (and thus the magnitude of its effect on prey density) should hence be regarded as a functional response to increasing resource concentration.
3. The disparity between the bottom-up and top-down effects is also apparent in individual decision making, where a choice must be made between accepting the hazards of hunger and the risks of predation (lost calories versus loss of life).
4. As long as top-down forces are effective, the disparity with bottom-up effects seems evident. In the absence of predation, however, all efforts of an individual become subordinate to the competition for resources. Biomass becomes limited from the bottom up as soon as the density of a superior competitor has increased to the carrying capacity of a given habitat. Such a shift in the importance of bottom-up control can be seen in zooplankton in habitats from which fish have been excluded.     

Bacterioplankton and bacteriobenthos of some floodplain lakes in the course of the lower Amur river

The main structural and functional characteristics of bacterioplankton and bacteriobenthos of three lakes in the lower course of the Amur River are presented: the total number of bacteria (TNB), biomass, the numbers of bacteria of certain aerobic and anaerobic groups; the intensities of methanogenesis (MG), methane oxidation (MO), assimilation of 14C-compounds, sulfate reduction (SR); and gross estimate of organic matter decomposition (D). Depending on the reservoir type and the anthropogenic load, TNB constituted (2.27 to 16.1) x 10(6) cells/ml in water and (1.06 to 10.35) x 10(9) cells/ml in sediments; MO was 0 to 0.28 ml CH4/(1 day) in water and 0 to 8.4 ml CH4/(dm3 day) in sediments; MG in sediments was 0.001 to 40 ml CH4/(dm3 day); SR varied from 0.001 to 24.8 mg S/(dm3 day); D was 0.3 to 25 g C/(m2 day) in water and 0.2 to 4.9 g C/(m2 day) in sediments. The role of anaerobic microbial processes of organic matter decomposition was shown to increase with an increase in the anthropogenic load, attaining 95% of the total D in the ecosystem of an accumulating pond.