High Water Season Research Articles

Pitfall Traps and Mini-Winkler Extractor as Complementary Methods to Sample Soil Coleoptera.

We compared abundance, species richness, and capture efficiency with pitfall traps and mini-Winkler extractors to examine their use as complementary methods for sampling soil Coleoptera during dry (2010) and high water seasons (2011) in three areas, including inundated and non-inundated regions, in the Pantanal of Poconé, Mato Grosso, Brazil. We paired treatments with two 10 × 10 m plots in inundated and non-inundated locations that were repeated three times in each location for a total of 18 plots. In each plot, we used nine pitfall traps and collected 2 m(2) of leaf litter and surface soil samples with mini-Winkler extractors. We collected a total of 4260 adult beetles comprising 36 families, 113 genera, and 505 species. Most were caught in pitfalls (69%) and the remainder in the mini-Winkler extractors (31%). Each method provided distinct information about the beetle community: 252 species were captured only in pitfall traps, 147 using only the mini-Winkler extractors, and these methods shared another 106 species. Pitfall and mini-Winkler contribute in different ways for the sampling of the soil beetle community, and so they should be considered complementary for a more thorough assessment of community diversity.

Remote sensing of Andean mountain snow cover to forecast water discharge of Cuyo rivers

In the Argentinian Dry Andes, although the melting of glaciers is seen as a threat for the long-term water availability needed by the piedmont crops, the annual snowmelt is the main source of superficial water and aquifer recharge. In this study, we analyse the link between the seasonal and interannual variations in the discharge measured upstream of the first dams on four rivers (Mendoza, Tunuyan, Diamante, Atuel) of the Argentinian Cuyo region (in the Federal Province of Mendoza) and those of the snow bed extent as mapped by optical remote sensing (MODIS MOD10A2 product) on a weekly basis in the 2001-2014 period, at the scale of each watershed.For the four snow-glacier regime rivers, seasonal variations in the discharge appear directly related to those of the snow bed surface area in each watershed, as shown previously (Masiokas et al., 2006). We observed that the high-water period (September-April) discharge is directly related to the snow extent at the beginning of the snowmelt period, i.e. in September and October, as revealed by a correlation of about 0.8. Moreover, the decreasing trend in the winter snow bed extent from 2001 to 2014 clearly explains the observed decreasing trend in the annual water discharge.Agriculture and human activities in these oases mostly depend on river discharge, which from our results clearly depends on the snow extent. Our research indicates that it is possible to use remote sensing to forecast the average discharge in the September-April period (high-water season) from MOD10A2 images with an average uncertainty of 15%. As MOD10A2 data are freely available ten days after acquisition, it is possible to anticipate in early October the risk of water shortages in the coming summer.

Distribution and origin of glossic horizons in soils of the western Great Lakes Region, USA

The glossic horizon results from degradation of an argillic or other clay-rich diagnostic horizon whereby clay and free iron oxides are redistributed, creating E/B and/or B/E genetic horizons. An examination of the US Department of Agriculture Natural Resources Conservation Service database revealed that 17% of the soil series in the western Great Lakes region contain a glossic horizon. These soil series account for 63% of those in the USA containing a glossic horizon. Seventy-three percent of the soils with a glossic horizon in the Great Lakes region of Minnesota, Wisconsin, and Michigan are classified into five subgroups: Haplic, Aquic, and Oxyaquic Glossudalfs and Alfic and Alfic Oxyaquic Haplorthods. The glossic horizon in 284 soil series averages 31±24cm in thickness and occurs (i) between an ochric or albic horizon and an argillic horizon, (ii) between a spodic horizon and an argillic horizon, or (iii) entirely within the argillic horizon. Glossic soils occupy a belt to the north of the tension zone across the three states, which corresponds approximately with the boundary between the mesic (≥8°C) and frigid (<8°C) soil-temperature regimes, the location of major late Wisconsinan end moraines containing primarily loamy till, and the boundary between non-forest and forest cover. Glossic horizons likely originate from a seasonal high water table accompanied by redox conditions, whereby Fe and clay are removed from the upper argillic horizon.

Seasonal fluctuation of riverine navigation and accessibility in Western Amazonia: An analysis combining a cost-efficient GPS-based observation system and interviews

Accessibility and transportation possibilities are key factors influencing societal conditions and land use patterns in rural areas. Thus, information on the spatial patterns of accessibility and transportation can be of paramount importance in understanding regional differences in development, human livelihood and land use patterns. Analysing spatio-temporal transportation patterns is particularly challenging in areas where everyday transportation is based on unscheduled public transportation and a naturally controlled seasonal transportation network, such as rivers. Here, our aim is to provide information on the seasonal dynamics of riverine transportation and its effects on accessibility patterns in Peruvian Amazonia. We analysed riverine transportation speeds using a low-cost GPS-based riverboat observation system. Spatio-temporal accessibility patterns were generalised from the GPS-observations that were classified according to seasons into the high water season, intermediate season and low water season. We show that navigation along the rivers has a clear seasonal and directional (upstream/downstream) variation, which varies with different types of rivers based on channel morphology. In addition, we conducted interviews with local people to study their perceptions of the seasonal changes in navigation and the accuracy of transportation schedules. As the travel distances in Peruvian Amazonia are generally long, seasonal and directional differences have clear impacts on the overall accessibility patterns in the area and on the livelihoods of riverine inhabitants. Furthermore, the lack of clearly scheduled transportation causes considerable uncertainty about transportation options for local communities. The baseline information of the seasonal and directional variation of riverine transportation and travel speeds provided by our work is usable in further accessibility and livelihood analyses for Peruvian Amazonia, but it may also be useful in other areas relying on riverine transportation.

Effects of water level fluctuations on phytoplankton in a Changjiang River floodplain lake (Poyang Lake): Implications for dam operations

Abstract As one of the few remaining lakes that is freely connected with the Changjiang (Yangtze) River, Poyang Lake exhibits highly variable water level fluctuations. In this study, we examined the phytoplankton biomass and community including two hydrological and climatic variables (high water flow velocity, low water temperature in low water season and low water flow velocity, high water temperature in high water season). Diatoms dominated (40–87% of total) the community in periods of low water levels. In periods of high water levels, the community was dominated by cyanobacteria (45–93% of total). Various functional groups were also analyzed to assess the effects of hydrological conditions on phytoplankton community structure. The well-developed populations during the low water periods were representatives of functional groups P ( Aulacoseira granulata , 28.7% of total) and Y ( Cryptomonas spp., 12.4% of total). In the high water periods, A. granulata and Microcystis spp. (M and L M ) increased to 39.8% and 12.7% of the total phytoplankton biomass, respectively. We then used parabolic curves to identify the optimal lake water levels for each phytoplankton group. The total phytoplankton, diatom, cyanobacteria, and green algae responded positively to low water level and negatively to high water level. The water level of 14–15 m is crucial for phytoplankton biomass patterns and succession through the alternations of washing-out and dilution effects and biological competition. These results support the hypothesis that water level control projects (e.g., dams) may affect phytoplankton biomass and assemblage structure patterns in Poyang Lake by altering its seasonal hydrology.

FEEDING ECOLOGY OF &lt;i&gt;Cichlasoma amazonarum &lt;/i&gt; (Teleostei, Cichlidae) IN THE CENTRAL AMAZON LAKES, BRAZIL.

The diet of the cichlid Cichlasoma amazonarum was investigated through an analysis of 270 gastric contents obtained from monthly samples collected from five lakes located in the Central Brazilian Amazon, throughout the year of 2012. The composition of the diet was assessed using the methods of frequency of occurrence and relative dominance (frequency of biomass), which were combined in the Alimentary Importance Index (AIi) in accordance with the hydrological cycle’s extreme periods of drought and high waters. The intestinal coefficient was investigated to demonstrate the feeding tendencies of the species. The breadth and diversity of the trophic niche were also compared for these periods. The intestinal coefficient for the species (0.95), combined with the results of the analysis of food content, showed a species that demonstrates carnivorous/insectivorous habits. During the high water season, the diet is composed of unidentified animal matter, unidentified larvae and insects; and in the drought season, plant matter, unidentified animal matter and insects. Although there was no significant difference in dietary diversity between seasonal extremes, the analysis of the breadth of the trophic niche characterises the species as feeding specialists.

Wetlands of the Lowland Amazon Basin: Extent, Vegetative Cover, and Dual-season Inundated Area as Mapped with JERS-1 Synthetic Aperture Radar

Wetland extent, vegetation cover, and inundation state were mapped for the first time at moderately high (100 m) resolution for the entire lowland Amazon basin, using mosaics of Japanese Earth Resources Satellite (JERS-1) imagery acquired during low- and high-water seasons in 1995–1996. A wetlands mask was created by segmentation of the mosaics and clustering of the resulting polygons; a rules set was then applied to classify wetland areas into five land cover classes and two flooding classes using dual-season backscattering values. The mapped wetland area of 8.4 × 105 km2 is equivalent to 14 % of the total basin area (5.83 × 106 km2) and 17 % of the lowland basin (5.06 × 106 km2). During high-water season, open water surfaces accounted for 9 % of the wetland area, woody vegetation 77 %, and aquatic macrophytes 14 %. Producer’s accuracy as assessed using high-resolution digital videography was better than 85 % for wetland extent. The mapped flooding extent is representative of average high- and low-flood conditions for latitudes north of 6° S; flooding conditions were less well captured for the southern part of the basin. Global data sets derived from lower-resolution optical sensors capture less than 25 % of the wetland area mapped here.

Participatory Monitoring and Management of Subsistence Hunting in the Piagaçu-Purus Reserve, Brazil

The Sustainable Development Reserve (RDS) model in Brazil provides legal context for monitoring wildlife with the involvement of local populations in gathering data and developing strategies for sustainable use. We present results of one year of self monitoring by hunters in five communities within the RDS-PP, discuss how the observed patterns reflect local hunting regulations, and suggest how this information could be incorporated into a formal management system. In addition to the offtake data, we interviewed hunters, inquiring about informal community hunting norms and agreements, and analysed the content of 19 rules in the reserve's management plan. 509 hunting events were recorded by 37 of the 104 families present (35%). Self monitoring permitted the evaluation of temporal and spatial fluctuations of hunting activities, notably regarding ease of canoe transport during the high-water season. Though communities have been apprehensive about developing regulations for subsistence hunting, one of the communities had developed a set of formal rules. Hunting for commercial sale to outsiders and restrictions on external hunters are concerns shared by the local population and the reserve management agencies. Such data and understanding are crucial to the management of protected areas in the Brazilian Amazon, where governance is often limited.

The importance of forest cover for fish richness and abundance on the Amazon floodplain

Flooded forest is one of the most important fish habitats in Neotropical rivers, and one that is increasingly subjected to negative impacts from logging, agriculture, and other human activities. The purpose of our study was to test quantitatively whether fish richness and abundance in Amazonian floodplain lakes are associated with the area of flooded forest. We sampled fish and several other variables in 35 Amazonian floodplain lakes during the high-water season. Our results highlighted that fish richness and abundance were directly related to flooded forest, inversely related to distance from the river, and influenced by dissolved oxygen concentration <1 mg l−1. The same result applied to fish richness and abundance landed by fisheries. Other variables such as depth and area of open water habitat were also related but the results were less consistent and apparently reliant on sampling methodology. Our results suggest that conservation of the flooded forest is critical for the maintenance of fish assemblages in the Amazon, and that removal of flooded forest will reduce fish richness, fish abundance, and fisheries yield.

Riding the Elephant

Riding the Elephant Barbara Kingsolver (bio) A note from the author: This is an extract from a journal I kept while I traveled through South Asia some years ago on a writing assignment. I always keep journals when I travel, because some of the information might be useful later if it’s a research trip for a novel, or if I’m on assignment as a journalist. But I also do it because putting words to paper has always been my way of [End Page 32] processing experience. I had no plans for this entry, I just jotted it down at the end of the day. Apart from one grammatical realignment and a tiny bit of context I’ve tucked into it, I surrender it here, unretouched. If it contains any revelations about craft, they might be about writerly habits, and going to the source. I had no audience in mind—it’s a journal entry. But I’m surprised to see the level of detail, enough information to make the experience accessible to someone who wasn’t there. That’s habit, to pay attention to everything: sights, smells, sounds, physical sensations, the lay of the land. How can I say this? Writing involves no magic, only work. Attend, and translate everything into language as you go along. It becomes second nature. It becomes voice. It involves putting aside the self, and taking up everything else. Another thing that surprised me here was the incipient presence of narrative. It’s just a fragment, no real plot, but it does have a beginning and end. That, too, is a writer’s habit. The difference between fiction and real life is meaning. The story has to tell me something, or it wasn’t a story. Whenever some funny or appalling thing happens in my life, invariably someone says, “Oh, you’ll use that in a story.” And I think, no, I won’t. Not unless, or until, I can figure out what it means. It takes certain writerly muscles to extract insight from incident, but those muscles get stronger with practice. After these many years I tend to see little narratives everywhere I look. —BK After ten hours in a bus on the road from Kathmandu, I watched the steep, terraced mountainsides relax into the broad, flat plain that the Nepalese call the terai. The road followed alongside the river and bore the weary scars of heavy annual flooding, evidence of past springtime snowmelts from [End Page 33] the Himalayas that swell this river to a hundred times its present, lazy size. Our bus bounced along the silty floodplain furred with maize and buckwheat, and intermittently passed through little plots of saal forest whose jungly wildness spoke of a Nepal I’d not yet seen. Mountains comfort me, and so do forests, but these were such a far cry from home. From the high plains we’d descended into the sub-tropics, home of elephants, rhinos and tigers. We were headed for the Chitwan reserve, an uncharted forest straddling the Indian border, one of the largest pieces of habitat the world has left for these and other Asian jungle creatures. We entered from the northeast, leaving our bus at the park’s edge because such traffic is not allowed. We hoisted our luggage and then ourselves into the back of a big, rugged truck that bumped over the rocky span of floodplain and then peeled right through the river’s clear water. During the high water season, our driver explained, elephants carry visitors across. I couldn’t imagine it. We checked into the lodge, a collection of thatch-roofed huts scattered through the jungle. Inside we found narrow cots, cold water and no electricity, camping accommodations, which seemed perfect in this location. I am a rural person; I felt at home. These few days in the Chitwan forest were planned as a respite after several weeks of hard work. My assignment, interviewing lowest-caste, so-called Untouchable women, had taken me into some of the poorest neighborhoods and villages outside of Delhi and Kathmandu. Which is to say, some of the most challenging places that any human on this planet calls home...

Alimentación de Podocnemis Sextuberculata (Testudines: Podocnemididae) en la Reserva Mamirauá, Amazonas, Brasil

La alimentación es uno de los aspectos más importantes en la vida de los organismos. En el grupo de los quelonios acuáticos amazónicos del género Podocnemis este aspecto es descuidado para P. sextuberculata. En este trabajo se presentan los resultados de una investigación sobre la alimentación de esta especie en la Reserva de Desarrollo Sustentable Mamirauá-RDSM. Se analizaron 235 muestras de contenidos estomacales, 117 machos y 118 hembras. Para obtener muestras de contenido estomacal, se utilizó el método de lavado con agua. Los contenidos estomacales también fueron colectados por disecación de tracto digestivo. Materia vegetal fue el ítem predominante en la alimentación de P. sextuberculata. No hubo diferencia en la frecuencia de semillas en las temporadas de aguas bajas y altas de los ríos. En todos los hábitat el volumen total de las semillas fue muy alto. La especie está adaptada a los cambios de estación, siendo las áreas inundables el hábitat más apropiado, en relación a la abundancia de las especies de la familia Poaceae. La información obtenida destaca la importancia de proteger las especies vegetales y los hábitat usados por P. sextuberculata en la RDSM.

Distribution of groundwater nitrate contamination in GIS environment: A case study, Sonqor plain

Background: Nitrate is a pollutant of groundwater resources which can results health risks such as methemoglobinemia and formation of nitrosamine compounds in higher concentration limits. The present study was aimed to determine the nitrite level, causes of pollution and zonation of nitrite concentration in drinking water resources in the villages of Sonqor. Methods: In this descriptive-analytrical study, 73 samples of all groundwater resources of Sonqor plain were taken in ,high water (March 2010) and low water (September 2011) periods. Water nitrate levels were then determined by spectrophotometry. Results were compared by national standards and analyzed by SPSS and Arcview GIS 9.3 software. Finally, the concentration distribution mapping was carried out in GIS environment and the factors affecting nitrite changes were analyzed. Results: nitrate concentration of water resources of Sonqor plain was fluctuating at 3.09-88.5 mg per liter.In one station, nitrite concentrations in the high (88.5 mg/liter) and low (71.4 mg/liter) water seasons were higher than the maximum limit. Based on the maps, a relatively high concentration of nitrite was observed in the Eastern and Southeastern regions. Conclusion: The findings indicated a reverse correlation between nitrite concentration changes and changes of static surface depth. Low thickness of alluvium, location of wells in the downstream farmlands, farming condition of the region, nitrate leaching from agricultural soils and wide application of nitrogen fertilizers in agriculture were considered as the causes of the pollution in one station.

Methane emissions from Amazonian Rivers and their contribution to the global methane budget.

Methane (CH4 ) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio-temporal studies, are important to refine extrapolations. Here we assess the spatio-temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimões, Madeira, Tapajós, Xingu, and Pará Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58TgCH4 yr(-1) . Thus, our estimates of CH4 flux from all tropical rivers and rivers globally were, respectively, 19-51% to 31-84% higher than previous estimates, with large rivers of the Amazon accounting for 22-28% of global river CH4 emissions.

Assessment of chemical quality of drinking water in rural areas of Qorveh city, Kurdistan province, Iran

Abstract Abstract Abstract Groundwater aquifers as one of the main sources of water supplies are faced with different risks such as level dropping due to lack of precipitation, and natural and non-natural pollutants. Thus, it is extremely necessary to monitor ground water quality. In the present study, the concentration of cations, anions, and some toxic metals was evaluated in 21 rural water supplies in Qorveh plain in two stages. Data were analyzed with Rockwork and Arc GIS software. Results from Hydro chemical analysis showed that all the studied parameters had lower concentrations than the permitted limits, except for arsenic (As) and selenium (Se) in some of water resources. As concentration in 20% of studied resources were higher than recommended standards. There was a significant difference between nitrate (NO 3 −) concentrations in the two low- and high-water seasons (P < 0.01). Bicarbonate (HCO 3 − ) and calcium (Ca 2+ ) were the prevalent anion and cation, respectively, meaning that samples type was calcium-bicarbonate. Wilcox diagram classified the samples in C2-S1 and C3-S1 classes. Correlation coefficient between chemical parameters showed that HCO 3 − and Ca 2+ had the highest correlation. Finally, it can be said that except for As and Se, other water characteristics have a good quality for drinking water application. However, current and uncontrolled application of the studied water supplies, especially in agricultural activities, can change and decrease their quality. Therefore, it is important to prevent the health threats of such process.

The Use of Multiple Tracers to Evaluate the Impact of Sewered and Non‐Sewered Development on Coastal Water Quality in a Rural Area of Florida

When onsite wastewater treatment and disposal systems (OSTDS) are not sited appropriately or installed properly, wastewater constituents can be a source of adverse environmental impacts to soil and groundwater, which can lead to potential public health risks. A paired monitoring design developed to compare water quality in sewered and non-sewered areas is presented here. It is suggested as a possible monitoring scheme for assessing the impact of sewer installation projects. As such, two sets of single-family, rural residential Florida neighborhoods were evaluated over a two-year period to gain insight into the effects of small-community use of OSTDS on coastal water quality. One set of two neighborhoods were connected to the sanitary sewer network and the other set of two were served exclusively by OSTDS. Water quality sampling was conducted at the paired sites during seasonal high water table (SHWT) and seasonal low water table (SLWT) events. Measured surface water quality during the SHWT showed indications of environmental impacts from OSTDS in terms of nutrients, microbial pathogen indicators, and other water quality measures, such as turbidity and conductivity. However, during the SLWT events, no obvious impacts attributable to OSTDS were detected. The water quality results indicate that OSTDS impacts may be measureable in rural areas. Other factors, such as microbial indicator survival and regrowth potential, may confound the understanding of water quality impacts of sewer projects. For example, the microbial indicators Escherichia coli and enterococci were found to persist over time and therefore did not always represent true comparisons of OSTDS and sewered areas between seasons. The timeframe for evaluating the effects of sewer projects may be longer than anticipated because of this survival and regrowth phenomenon.

Profiles in History

1990 When it comes to loving soils, few individuals have the kind of enthusiasm that Frank Watts of Hilliard, FL has exhibited for many years. Watts, who served for 35 years as a soil scientist with USDA-SCS/NRCS, led efforts in the late 1980s to establish Myakka fine sand as Florida's official state soil. Above, Watts poses with a Myakka monolith in 1990. Frank Watts with Florida's state soil monolith. Watts, a Kentucky native, received his B.S. and M.S. degrees in soil science from Murray State University, Murray, KY. He began his career in Kentucky with USDA-SCS in 1968 by contributing to two published soil surveys. In 1970, Watts transferred to Florida, where he contributed to 16 published soil surveys throughout the state and served as soil survey project leader in six counties before retiring in 2003. He was instrumental in developing methodology to interpret soil morphological features for determining depth to seasonal high water tables and in developing hydric soil indicators. Frank Watts was the senior author of “History of Establishing a State Soil: Florida's Myakka Fine Sand,” and “Determining Depths to the Seasonal High Water Table and Hydric Soils in Florida,” which were publish in Soil Survey Horizons in the early 1990s. Watts is the senior author of Soils of Florida, a book published by the Soil Science Society of America in 2008, which shows the beauty of soils with its 168 color photos of Florida soil profiles. 1969 Kan Kim Chang, best known as Kim Chang, is shown describing a Milham soil while working on the Soil Survey of Kern County, California, Northwestern Part. Upon graduating from California Polytechnic State University in San Luis Obispo in 1959, Chang was hired as a fulltime soil scientist by USDA-SCS. After being drafted in 1961, Chang served for two years in the U.S. Army Corps of Engineers, testing soils, asphalt, and concrete. Upon returning to USDA-SCS in 1963, Chang worked on the Soil Survey of Eastern Fresno Area, California, prior to his project leader work on the Soil Survey of Kern County, Northwestern Part, which he authored in 1988. Kim Chang describes soil in California's San Joaquin Valley. Chang completed the second half of his illustrious 43-year career as the Area Soil Scientist for the USDA-NRCS in Fresno, CA. He was known as an excellent field soil scientist and trainer of soil scientists. In his job as Area Soil Scientist he was responsible for field reviews of soil surveys being conducted by three U.S. government agencies. As an Area Soil Scientist, Chang worked as a soil liaison with many USDA-NRCS field offices throughout California. He is also known for the valuable assistance he has provided to FFA land judging competitions in the San Joaquin Valley for more than 50 years. Information courtesy of Kerry Arroues, NRCS, Soil Scientist (retired), Hanford, CA. 1939 An accelerated program of soil survey and classification was initiated within the Tennessee Valley in 1935, shortly after the inception of the TVA. It developed as a cooperative project within the overall objectives described in the Memorandum of Understanding signed on November 20, 1934, by TVA, USDA, and the agricultural colleges of the seven valley states, specifying for a coordinated program of agricultural research, extension, and land-use planning. The need for an up-to-date inventory of available soil resources was recognized as a necessity for making adjustments in land use and development of agriculture in the Tennessee Valley region. Flooding, soil erosion, and abuse of farmland were very serious problems throughout the Tennessee Valley at this time. At initiation of the project, only 38 of the Tennessee River watershed counties had soil surveys, and most of these were inadequate, even by 1935 standards, and needed updating. Soil surveyors in the Tennessee Valley. The photograph above was taken in May of 1939 during a field inspection trip in Scott County, VA. Soil surveyors are (left to right): H.H. Perry, H.C. Porter, D.D. Mason, J.W. Moon (Regional Inspector, Soil Survey, USDA), Dr. S.S. Obenshain (Virginia Polytechnic Institute Soil Classification Project Leader), R.C. Jurney, C.S. Coleman, E.F. Henry, and A.C. Orvedal. Information courtesy of Dr. John M. Soileau, Research Soil Scientist (retired), Tennessee Valley Authority, Florence, AL.

Food webs of the Paraná River floodplain: Assessing basal sources using stable carbon and nitrogen isotopes

Food webs in floodplain ecosystems may be based on a variety of aquatic, terrestrial or amphibious food resources. Here, we determined which of the basal resources mostly contribute to the food webs in a floodplain lake of the Middle Paraná River using isotopic composition of C and N ( δ 13 C and δ 15 N) of potential food sources in the Paraná floodplain (Argentina). We analyzed if organic matter sources isotope of C and N differ between flooding and low water seasons, and analyzed the isotopic niche representations of consumers in order to characterize niches width and intraguilds overlapping. To estimate the contribution of different sources of carbon to primary consumers, we measured the stable isotopic compositions of bottom sediment organic matter, coarse particulate organic matter, biofilm, suspended particulate organic matter, epiphyton, phytoplankton, C3 and C4 macrophytes and riparian tree leaves, benthic macroinvertebrates, aquatic orthopterans and fishes in dry and flooding seasons. The packages Stable Isotope Analysis and the Stable Isotope Bayesian Ellipses algorithm in R were calculated to compare the C and N isotopic variability between the primary consumers and their sources. The energy sources available for benthic organisms mainly originated from autochthonous sources based on the C3 photosynthesis pathway. The isotopic signatures of sources and primary consumers did not differ significantly between low and high water seasons. Our results demonstrated a higher contribution to primary consumers of C3 macrophytes and low contributions of C4 for herbivores; biofilm and benthic organic matter for gatherer collectors (Oligochaeta and Chironominae); epiphyton for ephemeropterans, amphipods and fishes, whereas biofilm was the most important source for mussels.

Length-weight relationships of 38 fish species of the Magdalena River floodplain lakes

Summary This study reports length–weight relationships for 38 fish species belonging to 18 families inhabiting the Magdalena River floodplain lakes of Colombia. Samples were taken during the high water season of 2008, 2010 and 2011. Two species are presented for the first time. Maximum total length records for 24 species exceed those in FishBase.

Co-management and Spatial Features Contribute to Secure Fish Abundance and Fishing Yields in Tropical Floodplain Lakes

Empirical data are needed to show the efficacy of co-management, which is regarded as a promising approach to achieve conservation goals. In this study, we addressed the potential influence of fisheries co-management to increase fish abundance and fishing yields in the lower Tocantins River Basin (Brazilian Amazon), downstream from a large dam. We analyzed 590 fish landings (6.7 t of fish) from five fishing villages and 48 fish samples obtained using gillnets (10,378 fish from 101 species) in 12 floodplain lakes in four regions: two with incipient co-management and two unmanaged. The fish species richness did not differ among the regions, but the lakes in the regions that were co-managed had higher fish abundance (biomass and number of individuals) and a higher mean proportion of fish reproducing during the high water season. Fishers had higher catches per unit of effort in the co-managed regions than fishers in the non-managed regions. These results were also influenced by geographic factors (distance and accessibility of lakes), as fish biomass was higher in lakes that were distant from the main river and from the main city in the region. Managers should thus consider strategic selection of the geographic locations of managed sites, even in remote areas. However, the fish biomass sampled in lakes was more related to region than to the lakes’ geographical location. Therefore, co-management has at least partially contributed to increased fish abundance and fishing yields in the studied region, through the protection of an important fish habitat (lakes). We provide empirical evidence that co-management can contribute to the maintenance of fish abundance, sustainability of fisheries, and food security in large tropical rivers impacted by damming.

Optimising hydrological conditions to sustain wintering waterbird populations in Poyang Lake National Natural Reserve: implications for dam operations

Summary Poyang Lake is the largest freshwater lake in China and is of global importance for the conservation of migratory waterbirds of the East Asian – Australasian Flyway. Recent dam construction on the Yangtze River and its tributaries for agriculture and hydroelectric power has affected the hydrological regimes in downstream lakes. The Three Gorges Dam changed the hydrological regime of downstream lakes by reducing wet season flooding and expanding water storage in the dry season. Despite the critical role of Poyang Lake in regional and global biodiversity conservation and the potential adverse ecological impacts of the Three Gorges Dam on downstream lakes, there have been few studies of the hydrological requirements of wintering waterbirds in the middle Yangtze floodplains. We assembled a predictor matrix including three hydrological variables (annual inflow, maximum water level in high water season or MaxWL and minimum water level in low water season or MinWL) and two climatic variables (annual rainfall and biological cumulative temperature or BioT). Using the predictor matrix and annual waterbird census, we built group‐specific generalised additive models (GAM) to investigate how waterbird population variations were related to climatic and hydrological factors in the Poyang Lake National Natural Reserve. We then used the modelled predictor–response curves to identify the optimal lake water levels for each waterbird group. The community‐level model selected group and the group‐varying‐coefficient term of BioT, Inflow and MaxWL as explanatory variables. At group level, tuber eaters and sedge foragers responded positively to BioT and MinWL. Seed eaters, invertebrate eaters and fish eaters responded positively to Inflow and negatively to MaxWL and MinWL. Based on the modelled predictor–response curves, we propose the following optimal water level ranges for Poyang Lake wintering waterbird conservation: a) maximum high water season level should be less than 17.4 m; and b) minimum low water level should be between 8.2 m and 8.8 m.