Academic literature on the topic 'Large Tropical River'

Abstract. We assess the role of riverine inputs of N, Si, Fe, organic and inorganic C in the tropical Atlantic Ocean using a global ocean biogeochemistry model. We use two sensitivity tests to investigate the role of the western (South American Rivers) and eastern (African Rivers) riverine nutrient inputs on the tropical Atlantic Ocean biogeochemistry (between 20° S–20° N and 70° W–20°). Increased nutrient availability from river inputs in this area (compared to an extreme scenario with no river nutrients) leads to an increase in 14 % (0.7 Pg C a−1) in open ocean primary production (PP), and 21 % (0.2 Pg C a−1) in coastal ocean PP. We estimate very modest increases in open and coastal ocean export production and sea-air CO2 fluxes. Results suggest that in the tropical Atlantic Ocean, the large riverine nutrient inputs on the western side have a larger impact on primary production and sea-air CO2 exchanges. On the other hand, African river inputs, although smaller than South American inputs, have larger impact on the coastal and open tropical Atlantic Ocean export production. This is probably due to a combination of nutrient trapping in upwelling areas off the Congo River outflow, and differences in delivered nutrient ratios leading to alleviation in limitation conditions mainly for diatoms.

Abstract. Large rivers transport considerable amounts of terrestrial dissolved organic matter (DOM) to the ocean. However, downstream gradients and temporal variability in DOM fluxes and characteristics are poorly studied at the scale of large river basins, especially in tropical areas. Here, we report longitudinal patterns in DOM content and composition based on absorbance and fluorescence measurements along the Zambezi River and its main tributary, the Kafue River, during two hydrological seasons. During high-flow periods, a greater proportion of aromatic and humic DOM was mobilized along rivers due to the hydrological connectivity with wetlands, while low-flow periods were characterized by lower DOM content of less aromaticity resulting from loss of connectivity with wetlands, more efficient degradation of terrestrial DOM and enhanced autochthonous productivity. Changes in water residence time due to contrasting water discharge were found to modulate the fate of DOM along the river continuum. Thus, high water discharge promotes the transport of terrestrial DOM downstream relative to its degradation, while low water discharge enhances the degradation of DOM during its transport. The longitudinal evolution of DOM was also strongly impacted by a hydrological buffering effect in large reservoirs in which the seasonal variability of DOM fluxes and composition was strongly reduced.

Abstract. We assess the role of riverine inputs of N, Si, Fe, organic and inorganic C in the tropical Atlantic Ocean using a global ocean biogeochemistry model. We use a standard model scenario and three sensitivity tests to investigate the role of total river nutrient and carbon inputs, as well as the western (South American) and eastern (African) river inputs on the tropical Atlantic Ocean biogeochemistry, between 20° S–20° N and 70° W–20° E. Increased nutrient availability from river inputs in this area (compared to a sensitivity scenario without river nutrient inputs, NO_RIVER) leads to an increase in primary production (PP) and export production (EP), mainly in the coastal ocean area (modeled ocean area with bathymetry <200 m). Model results suggest an enhanced N-fixation by diazotrophs on the tropical Atlantic mainly in open ocean areas. The increased rate of N-fixation in the TODAY scenario is proportional to the increase in PP and EP relative to the NO_RIVER scenario, and may support up to 14% of the coastal ocean export production. Inputs from South American rivers have an impact in coastal PP and EP two times higher than those from African rivers. On the other hand, results suggest that the contribution of African and South American rivers to the total increase in open ocean PP and EP is similar. Considering the amount of delivered nutrients (2–3 times less nutrients and carbon inputs by African rivers) one concludes that African riverine inputs may have a larger impact on the whole tropical Atlantic Ocean biogeochemistry. This is probably due to a combination of nutrient trapping in upwelling areas off the large rivers' outflows and shallow mixed layers in the eastern tropical Atlantic, concomitantly to the differences in delivered nutrient ratios leading to alleviation in limitation conditions, mainly for diatoms. When river inputs are added to the model, we estimate a modest decrease in open ocean sea-air CO2 fluxes (−5.2 Tg C a−1) and an increase in coastal ocean CO2 fluxes, mainly provoked by the remineralization of riverine organic matter delivered by the South American rivers.

Floodplain sedimentation removes particles from fluvial transport and constructs stratigraphic records of flooding, biogeochemical sequestration and other aspects of the environmental history of river basins—insight that is enhanced by accurate geochronology. The natural fallout radionuclide 210 Pb, often employed to date lacustrine and marine sediments, has previously been used to determine floodplain accumulation rates over decadal-to-century time scales using the assumption that both input concentration and sediment accumulation rates are constant. We test this model in approximately 110 cores of pristine floodplains along approximately 2000 km of the Rios Beni and Mamore in northern Bolivia; over 95 per cent of the 210 Pb profiles depict individual episodic deposition events, not steady-state accumulation, requiring a revised geochronological methodology. Discrete measurements of down-core, clay-normalized adsorbed excess 210 Pb activity are coupled with a new conceptual model of 210 Pb input during floods: constant initial reach clay activity, unknown sedimentation (CIRCAUS). This enhanced methodology yields 210 Pb dates that correspond well with (i) dates determined from meteoric caps, (ii) observed dates of river bar formation, (iii) known flood dates, and (iv) dates from nearby cores along the same transect. Similar results have been found for other large rivers. The CIRCAUS method for geochronology therefore offers a flexible and accurate method for dating both episodic (decadal recurrence frequency) and constant (annual recurrence) sediment accumulation on floodplains.

Ecological processes in large rivers are controlled by their flow variability. However, it is difficult to find measures of hydrological variability that characterize groups of rivers and can also be used to generate hypotheses about their ecology. Multivariate analyses of the hydrographs of 52 rivers worldwide revealed distinctive patterns of flow variability that were often correlated with climate. For example, there were groups of rivers that corresponded broadly with ‘tropical’ and ‘dryland’ climates. However, some rivers from continental climates occupy both extremes of this range, illustrating the limitations of simple classification. Individual rivers and groups of rivers may also have different hydrographic ‘signatures’, and attempts to combine measures of hydrological variability into indices mask biologically significant information. This paper identifies 11 relatively independent measures of hydrological variability that help categorize river types and are each associated with aspects of fish biology. Ways are suggested by which the Flood Pulse Concept can be expanded to encompass hydrological variability and accommodate differences among groups of rivers from different climatic regions. Such recognition of the complex role of hydrological variability enhances the value of the concept for river conservation, management and restoration.

Permanent waterholes in intermittent rivers of northern Australia support a diverse piscifauna and are popular areas for customary and recreational fishing. The present preliminary study explored the perception that fishing reduces the abundance of targeted, large-bodied species that become restricted to disconnected waterholes during the distinct dry season. River sites in the Fitzroy River catchment, Western Australia, could be clearly classified as experiencing either high or low fishing pressure by using metrics of human ‘accessibility’. The abundance of Hephaestus jenkinsi and Lates calcarifer, targeted by both recreational and customary fishers was highly correlated with accessibility and showed a negative relationship with fishing pressure. Non-target species showed no discernible trend. We estimated that 38% of river length remains subject to relatively low fishing pressure. These preliminary relationships suggest that fish harvest can potentially alter the structure of fish assemblages in disconnected habitats. The potential impact of fishing on the sustainability of fish populations is, most likely, greatest for non-diadromous species and will become more apparent with increasing distance from recolonisation sources. Combining management techniques that maintain recolonisation and recruitment potential with traditional fisheries management strategies (e.g. bag and size limits) presents a suitable approach to mitigate the effects of fish harvesting from tropical intermittent rivers.

Sedimentation is a natural phenomenon of rivers that is enhanced by modification of the river basin. The presence of dams delays the exchange of sediments, nutrients, and organisms between the terrestrial and aquatic environments. This article assesses the impact of the Selangor dam on the sediment grain size distribution and its association with river velocity and discharge. The fieldwork for sampling is conducted in the normal and rainy seasons. The samples were analyzed through a sieve analysis procedure to determine the particle size of the sediments. After the sieve analysis technique, GRADISTAT analysis was performed on the output. The GRADISTAT analysis classifies the sediments between sandy gravel and sand, and the median grain size (D50) ranges from 4.00 to 0.18 mm. The spatial distribution of the D50 shows that the bed-load sediments of the upper Selangor River are becoming fine-grained downstream. The skewness of the sediments differs from 0.86 to 8.44, which indicates that the sediments are poorly to moderately well sorted. The Spearman's correlation of the D50 and river velocity and discharge determine no association of the D50 with river velocity and discharge. The stations near Selangor Dam have high slopes and receive "sediment hungry" water that washes small-sized sediments; therefore, the upper stations have a more significant amount of gravel and large sand. Doi: 10.28991/CEJ-SP2023-09-02 Full Text: PDF

Background and aims – Biomonitoring is an important tool for assessing river water quality, but is not routinely applied in tropical rivers. Marked hydrological changes can occur between wet and dry season conditions in the tropics. Thus, a prerequisite for ecological assessment is that the influence of ‘natural’ hydrological change on biota can be distinguished from variability driven by water quality parameters of interest. Here we aimed to (a) assess seasonal changes in water quality, diatoms and algal assemblages from river phytoplankton and artificial substrates through the dry-wet season transition (February–July 2018) in the Red River close to Hanoi and (b) evaluate the potential for microscopic counts and high-performance liquid chromatography (HPLC) analysis of chlorophyll and carotenoid pigments for biomonitoring in large tropical rivers. Methods – River water (phytoplankton) and biofilms grown on artificial glass substrates were sampled monthly through the dry (February–April) to wet (May–August) season transition and analysed via microscopic and HPLC techniques. Key results – All phototrophic communities shifted markedly between the dry and wet seasons. Phytoplankton concentrations were low (c. thousands of cells/mL) and declined as the wet season progressed. The dominant phytoplankton taxa were centric diatoms (Aulacoseira granulata and Aulacoseira distans) and chlorophytes (Scenedesmus and Pediastrum spp.), with chlorophytes becoming more dominant in the wet season. Biofilm diatoms were dominated by Melosira varians, and areal densities declined in the wet season when fast-growing pioneer diatom taxa (e.g. Achnanthidium minutissimum, Planothidium lanceolatum) and non-degraded Chlorophyll a concentrations increased, suggesting active phytobenthos growth in response to scour damage. Otherwise, a-phorbins were very abundant in river seston and biofilms indicating in situ Chlorophyll a degradation which may be typical of tropical river environments. The very large range of total suspended solids (reaching > 120 mg/L) and turbidity appears to be a key driver of photoautotrophs through control of light availability. Conclusions – Hydrological change and associated turbidity conditions exceed nutrient influences on photoautotrophs at inter-seasonal scales in this part of the Red River. Inter-seasonal differences might be a useful measure for biomonitoring to help track how changes in suspended solids, a major water quality issue in tropical rivers, interact with other variables of interest.

The dynamic interplay between physical, chemical and biological factors in the development and persistence of cyanobacterial blooms in impounded rivers is an important topic. Over a 3-year study period, variable climatic conditions were recorded in the Fitzroy River, Queensland, Australia, which is a typical, impounded lowland tropical river. Post-flood turbidity reduced the available light in the well-mixed water column to levels insufficient for cyanobacterial growth. Only when the water column stratified and the slowly sinking particles dropped from the surface layer did the ratio of surface mixed layer depth to euphotic depth approach 1, allowing cyanobacterial growth. By the time the light climate became favorable, most of the dissolved nutrients had been scavenged from the water column by settling particles or sequestered by fringing macrophytes and other biogeochemical processes. Cyanobacterial blooms dominated by Cylindrospermopsis raciborskii persisted for several months until the next flood flushed the system. The cyanobacterial species dominating that environment were very small and had high specific phosphorus uptake rates. Their nutrient requirement was met by transfer across the oxycline driven by regular high wind mixing events, entraining nutrient-rich bottom waters. Nutrient fluxes from the sediments into the anoxic bottom layer were sufficient to replace the bottom nutrients lost to the surface layer.

Freshwater fishes are often characterized by extensive population genetic subdivision and low genetic diversity and are ideal subjects for investigating contemporary patterns of dispersal and subsequent gene flow. In lotic systems, different riverine architecture, variable hydrology and species biology influence genetic diversity and population structure in resident species. Stream-dwelling species often display greater levels of gene flow within drainages or catchments or sub-catchments than between them due to complexity of stream order and the isolating nature of these systems by land or sea. However, the relative importance of these attributes in driving population structure at spatial scales remains poorly understood for many freshwater species. Study on the effects of riverscape in shaping population structure is very important to identify management or conservation units and to undertake habitat restoration measures. The Daly River is one of the largest river networks in the wet-dry tropics of Northern Australia and shows variability in hydrology. This river has a complex arrangement of habitats and heterogeneous landscape features (e.g. slope, elevation) across the catchment area. There are also instream physical barriers like waterfalls, cliffs, road crossings etc. that may hinder dispersal and subsequent gene flow.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Mining communities in more than 70 developing countries, mostly in the tropical regions, still practise artisanal and small scale gold mining (ASGM). ASGM commonly operates along rivers and streams for easy access to process water and as receptacles for mine water discharges. A largely unregulated industry, ASGM employs rudimentary mining and processing methods including the use of mercury amalgamation, and is often found near to larger scale and modern mining (LSM) operations. The substantial use of mercury by ASGM has drawn the attention of agencies and researchers but so has its persistent economic role in providing much needed rural employment. Mercury toxicity to human and environmental health has attracted much of researches, however ASGM impacts on riverine ecology, particularly at biota community levels, remains understudied. This study investigated the impacts of ASGM on the ecology of the Surow River and that of an LSM (the Ahafo mine) on the Subri River between February 2013 and April 2014. Both the Surow and Subri rivers are ephemeral tributaries of the Tano River, in Brong Ahafo, Ghana. The Ahafo mine, currently operated by Newmont Ghana Gold Limited (NGGL), has been operating on the Subri River catchment since December 2006, whilst ASGM started operations along the Surow River in 2007. Major ASGM operations ceased in May 2013 although smaller operators and processors remained. Specifically, the study aimed to determine whether and how ASGM and LSM impacted the respective river’s water and sediment quality, macroinvertebrate and microbial (Archaea and Bacteria) community structures and resulted in mercury biomagnification in fish. ASGM impact on river water and sediment quality was determined using a reversed BACI (Before/After and Control/Impact pairing) experimental design, whilst that of LSM used a conventional BACI design. Impacts on macroinvertebrate community structure were determined by comparing multiple control and impact sites sampled multiple times. The sequencing of 16S rRNA of Archaea and Bacteria was based on a one-off sampling and comparison between multiple control and impact sites on both rivers. The biomagnification of mercury in fish was tested via analysis of correlations between mercury concentrations in fish tissue and fish trophic level, fish length (proxy for age) and fish weight. The study demonstrated that gold mining, regardless of size and methods, significantly impacts the river ecosystems studied. Sediment particulates and minerals naturally available in the rock formation but exposed to the environment by mining activities were the most significant pollutants in the affected riverine ecosystems. The study area is in the tropic and experiences intensive rainfall. This, results in excess water which may come into contact with exposed rocks and wastes in the mining areas that eventually runs into or is discharged into the Surow and Subri rivers. Changes in the sediment and water quality due to mining were reflected in the macroinvertebrate communities of both rivers, while the sediment microbial communities tended to respond to differences in water quality. The study, however, strongly indicated that the types, magnitudes and effects of the environmental impacts of ASGM were different from that of LSM. The use, or the lack of, environmental management systems to mitigate impacts appeared to be the most important differentiating factor. The study also witnessed significant improvements in both water and sediment quality in the Surow River with the cessation of major ASGM in the area. Mercury, which was used in the ASGM (in relatively small quantities in Ghana compared to other countries) was detected in the Surow River sediment (despite naturally low concentrations of Hg in the local soils), but was largely undetectable in the waters. However, it posed health risks to humans and biota. This study found mercury biomagnified in fish from both the Surow and Subri rivers as well as the Tano River, indicating the presence of mercury in the rivers. The source of Hg, however, could not be clearly established but may have been from artisanal amalgamation processes and from smelting. Although mercury remains a concern in ASGM impacted rivers, it is not the only contaminant of concern. Sedimentation and particulate bound elements such as Al, As, Cu, Fe, Hg, and Pb were the main river pollutants resulting from ASGM operations. Elevated concentrations of metals in the turbid water due to the lack of sediment controls exceeded the Ghanaian and US EPA standards for the protection of aquatic life as well as that of Ghanaian raw water to be processed as drinking water. ASGM also significantly elevated the concentrations of salt ions and sulfate in river water particularly due to discharges of water from mine dewatering. During the active ASGM period, concentrations of Cu, Cr, Hg and Ni in the Surow River’s sediment exceeded the threshold effect level / TEL, lowest effect level / LEL, Australian effect low range /ERL and threshold effect level for Hylella azteca 28-day test or TEL HA28. Increased sediment load and decreased sediment quality in the Surow River were reflected in the macroinvertebrate community structure that was dominated by sediment-tolerant taxa but with only a few pollutant-sensitive taxa including Ephemeroptera and Trichoptera families. In the Subri River affected by the Ahafo gold mine, the impacts of mining were ameliorated by sediment control measures applied by the mine. The sediment control measures on the Subri River included the use of environmental control dams (ECD), one on a major tributary stream to the river, the other on a minor tributary. The ECDs reduced not only turbidity and total suspended solids, but also electrical conductivity, concentrations of most salt ions, nitrates and sulfate, and most metals both as total and dissolved forms from in the mine water being discharged into the environment. The improved water quality in downstream Subri River compared to that of the mine site and upstream was also reflected in the sediment quality, which had lower concentrations of most pollutants than that of the Surow River. The mine affected area in downstream Subri River also had more sensitive taxa including Ephemeroptera families than the Surow River. Nevertheless, mine discharge in downstream Subri appeared to alter the ecosystem compared to upstream control sections. Cessation of mine discharges at closure could see downstream sections of the river return to conditions more consistent with upstream. The exploratory microbial community study, a relatively novel study in the region, showed that the composition and diversity of the Archaea and Bacteria communities found in the Surow and Subri Rivers were comparable to those found in other studies including in the temperate regions. We also observed that microbial composition spatial variability within was greater than between rivers and that the variability was unrelated to riverine sediment chemistry but significantly related to water chemistry, particularly turbidity and concentrations of sulfate, Fe and FRP. The study also demonstrated a shift in sediment microbial community composition due to mine dewatering, particularly in the Surow River reaches affected by ASGM dewatering discharges. Given the one-off sampling nature of the sediment microbiology study, however, further study with repeated sampling regime is recommended. Sedimentation at ASGM sites dramatically altered the river morphology and biota. Further, metals carried by the sediments were deposited along the river downstream during the dry season and remobilised during the rainy seasons. The use of simple small scale ECD equivalents would substantially sediment based pollution. Discharges from mine dewatering from ASGM activities increased conductivity of the river and under full scale operations would have been problematic for biota and water quality. Although discharges from the LSM were of higher quality, they were also in high quantity and substantially altered downstream water quality and biota. Although these changes resulted in increased sensitive taxa, the long-term sustainability of these discharges is unknown. This study demonstrated that impact assessment of ASGM or LSM on rivers should not be limited to the physical and chemical properties of water and sediment, but also include its riverine biota. This study supports the use of macroinvertebrate and potentially microbes as indicators of impact of ASGM and mining in tropical rivers. Moreover, an understanding of the ecological impacts of mining large and small can assist in the

Freshwater ecosystem degradation in the Amazon and Orinoco river basins is increasing due to rising human population numbers, and large water development projects. Therefore, monitoring ecosystem condition in these rivers of high biodiversity is of global conservation importance. This dissertation evaluated the potential of using river dolphins as indicators of ecosystem condition in large tropical rivers of South America. First, population estimates of river dolphins were obtained by line-strip transect surveys and mark-recapture methods on photo-identifications. Using this information, I identified critical habitat, hotspots, and areas of concern for river dolphins, as well as the relationship between dolphin density and group size estimates with ecological features. Second, I evaluated the relationship between dolphin estimates and human stressors. Higher densities of dolphins occurred in rivers with low indices of overall freshwater degradation, such as rivers with high water quality and the lowest human population numbers. Thus, dolphin density estimates seem to be good indicators of freshwater ecosystem degradation in the Amazon and Orinoco basins. These top predators not only are indicator species, but also have the potential to act as flagship and sentinel species, indicating freshwater ecosystem degradation and stimulating conservation action. This dissertation highlights the large changes in the Amazon and Orinoco that are approaching fast. Indicator, flagship and sentinel species can become science-based conservation tools not to only document freshwater ecosystem degradation, but to raise awareness about broader implications of human stressors on biodiversity and river systems.

An orbitally induced increase in summer insolation during the last glacial-interglacial transition enhanced the thermal contrast between land and sea, with land masses heating up compared to the adjacent ocean surface. In North Africa, warmer land surfaces created a low-pressure zone, driving the northward penetration of monsoonal rains originating from the Atlantic Ocean. As a consequence, regions today among the driest of the world were covered by permanent and deep freshwater lakes, some of them being exceptionally large, such as the “Mega” Lake Chad, which covered some 400 000 square kilometers. A dense network of rivers developed.What were the consequences of this climate change on plant distribution and biodiversity? Pollen grains that accumulated over time in lake sediments are useful tools to reconstruct past vegetation assemblages since they are extremely resistant to decay and are produced in great quantities. In addition, their morphological character allows the determination of most plant families and genera.In response to the postglacial humidity increase, tropical taxa that survived as strongly reduced populations during the last glacial period spread widely, shifting latitudes or elevations, expanding population size, or both. In the Saharan desert, pollen of tropical trees (e.g., Celtis) were found in sites located at up to 25°N in southern Libya. In the Equatorial mountains, trees (e.g., Olea and Podocarpus) migrated to higher elevations to form the present-day Afro-montane forests. Patterns of migration were individualistic, with the entire range of some taxa displaced to higher latitudes or shifted from one elevation belt to another. New combinations of climate/environmental conditions allowed the cooccurrences of taxa growing today in separate regions. Such migrational processes and species-overlapping ranges led to a tremendous increase in biodiversity, particularly in the Saharan desert, where more humid-adapted taxa expanded along water courses, lakes, and wetlands, whereas xerophytic populations persisted in drier areas.At the end of the Holocene era, some 2,500 to 4,500 years ago, the majority of sites in tropical Africa recorded a shift to drier conditions, with many lakes and wetlands drying out. The vegetation response to this shift was the overall disruption of the forests and the wide expansion of open landscapes (wooded grasslands, grasslands, and steppes). This environmental crisis created favorable conditions for further plant exploitation and cereal cultivation in the Congo Basin.

AbstractCritical or extreme atmospheric conditions which could result in flood disasters are important output for numerical weather forecast. This research applied thermodynamic variables to investigate the environment of two flood scenarios in West Africa as captured by the Tropical Rainfall Measurement Mission (TRMM) satellite. Results from the two case studies of flood events, in (i) Burkina Faso and (ii) Nigeria savannah, investigated in this research work, indicated that the September 1st 2009 flood, which was as a result of a single volumetric rainfall event of 408,070.60 ((mm/h)*km2) with 65% convective region in Burkina Faso, was initiated by interactions between extremely large lower tropospheric wind shear and cold pool dynamics. The case of the Nigeria savannah floods between July and September, 2012, was triggered by both continuous rainfall and release of water from the lagdo dam in Cameroon, which affected most of the communities in the river Benue axis. The continuous rainfalls were found to be as a result of extremely high convergence of moisture in the river Benue axis at different locations and periods. One of such rainfall events, as captured by TRMM satellite during September 29, 2012 in the Nigeria rainforest zone, indicated that the volumetric rainfall is 351,310.9 ((mm/h)*km2) with only 34% convective portion. From these results, it can be deduced that a combination of thermodynamic environmental variables, volume rainfall, and other satellite-derived convective parameters could provide important information for flood forecasting.

<em>Abstract.</em>—A large river, in relation to wood dynamics, has a width several times greater than the height of the trees in its riparian area. Large rivers undergo particular physical and biological processes related to wood that vary according to their condition (pristine or managed) and their locations in the landscape (upland area or downstream, tropical or temperate climates).

Smectitic soils of the tropics are medium- to fine-textured alluvial soils containing moderate to large amounts (20% or more) of smectite, a shrinking and swelling clay mineral, in the clay fraction. Small to moderate amounts of other layer silicate minerals, such as illite, chlorite, vermiculite, and kaolinite, are also present in the clay fraction. Smectitic soils have moderate to high values of CEC (10-50 cmol/kg of soil), high base saturation, and high water-retention capacity. These soils are usually developed on alluvial materials rich in basic cations, especially Mg. Smectitic soils commonly occur on alluvial plains in river valleys and deltas as well as in inland depressions. In the wetter tropics, large areas of smectitic soils are found in tropical Asia, especially Vietnam, Thailand, and Myanmar (Burma). These young alluvial soils are rich in nutrient-bearing weatherable minerals, such as micas, feldspars, and hornblende. Smectitic soils on the alluvial plains and inland valleys have a shallow groundwater table, and some soils are flooded during the rainy season. Thus, they are best suited for rice cultivation. For example, in the flood plains along the Mekong and Chao Phraya rivers of the Indo- China peninsula, mineral-rich deposits from annual flooding are able to maintain relatively high rice yields with little or no additional nutrient inputs. Smectitic soils occurring in seasonally flooded coastal mangrove swamps are known as acid sulfate soils. These soils are used for cultivation of swamp rice and floating rice during the rainy season, depending upon the depth of flooding by fresh water. In drier regions, clayey smectitic soils (mainly Vertisols) often exhibit large cracks during the dry season and become very sticky and difficult to work with during the rainy season. In the drier tropics, large areas of clayey smectitic soils are found in central India, central Sudan, southern Ghana, and in the Lake Chad region of central Africa. Clayey smectitic soils are usually found in the inland depressions scattered throughout the drier regions of West, East and Central Africa. Because of their high chemical fertility, these soils are important soils for cropping and grazing in the drier tropics.

With rapid ecological assessments, we diagnose the conservation status of large mammals in the localities Rio Encanto, San Jacinto Las Palmas, Sacha Llanganates, Cabeceras del Anzu, Boayaku, and Flor de Bosque, located within the Llanganates Sangay Ecological Corridor (CELS) and the upper subbasin of the Anzu River, in the eastern foothills of the tropical Andes, sub-Andean and tropical ecosystems in one of the most biologically diverse regions of Ecuador. Camera traps, 5 km linear transect walks, and interviews with local inhabitants recorded 35 species of macro mammals, in 8 Orders and 21 Families, including the Andean bear (Tremarctos ornatus), Andean tapir (Tapirus pinchaque), Amazonian tapir (Tapirus terrestris), puma (Puma concolor), and chorongo monkey (Lagothrix lagotricha), mammals considered as flagship species, highly endangered. The continuity of natural habitat along the subbasins of the Encanto, Topo, Zuñag, Tigre, and Anzu rivers, as well as the mountain ranges toward the highlands, provide favorable conditions for the flow of individuals, from adjacent areas of the Llanganates and Sangay National Parks to partially protected forest areas, such as the private reserves of Fundation Ecominga, Sumak Kawsay in Situ, community reserves of Boayaku and Flor de Bosque. The protection of the area is a priority.

The Amazon, like smaller rivers, is the daughter of its drainage basin. Local climate and interactions over time with the template of topography, geology, and vegetation determine the size and flow of rivers. Likewise, the compositions of the particulate and dissolved materials carried by rivers result from initially similar rainwaters that have been uniquely imprinted by contact with almost every plant, animal, and mineral in the catchment. Rivers thus provide a continuously flowing signal, recorded by isotopes, ions and molecules, of the cumulative effects of drainage basin processes such as weathering, oxidation/reduction, gas exchange, photosynthesis, biodegradation, and partitioning. This recording is complementary to more classical methods of remote sensing based on electromagnetic radiation, but is composited over a wider range of time and space scales and includes effects of subcanopy and subsurface processes. The Amazon River is similar to other rivers in this regard, but is unusual in the size and extent of different environments its waters touch. The Amazon River is the world’s largest river and drains the world’s largest single catchment (∼6,000,000 km2). It discharges an average of about 200,000 m3 of water per second to the Atlantic Ocean. This volume is about 5 times more than the Congo, the second largest river. The Amazon has 1100 major tributaries, three of which are nearly as large as the Congo. From its origins at about 5200 m in the Andes about 200 km from the Pacific Ocean, the Amazon goes through at least 10 name changes as it snakes its way 6500 km eastward to the Atlantic Ocean (Schreider and Schreider 1970). The flooded areas along the lower mainstem are important sources of greenhouse gases such as methane (Bartlett and Harriss 1993, Devol et al. 1994) and the latent heat release from convective precipitation in the basin is sufficient to influence global climate. The Amazon drainage basin contains 40% of the world’s tropical rain forest (dos Santos, 1987) and is home to countless species of plants and animals. The river itself contains some 2000 described species of fish.

Most of South America lies within the tropics, and lowland tropical ecosystems make up the majority of its landscapes. Although there is great concern for the Amazon ecosystem, the largest of the world’s tropical forests, there are many other fascinating and in some cases more endangered types of lowland forest. Such forests may be defined as lying below 1,000 m above sea level, although it is difficult to set arbitrary limits (Hartshorn, 2001). The two main lowland moist evergreen forests are the Hylea (a term coined by Alexander von Humboldt to denote rain forests of the Amazon Basin) and the much smaller Chocó forest on the Pacific coast between Panama and Ecuador. Two related yet distinctive types of forest are the Mata Atlântica or Atlantic moist evergreen forest and the Mata Decidua or dry deciduous forest, including the caatinga woodland, which is both deciduous and xerophytic (Rizzini et al., 1988). The latter two formations are among the most threatened of all South American forests. Lowland forests vary from dense and multilayered to open and single-layered, from evergreen to deciduous, and from flooded or semi-aquatic to near-arid. Tree heights range from 30 to 40 m with emergent trees reaching over 50 m, to forests where the tallest trees barely attain 20 m (Harcourt and Sayer, 1996; Solorzano, 2001). However, because of its extent and importance, Amazonia will form the principal focus of this chapter. Amazonia covers a vast area (>6 × 106 km2) and contains some 60% of the world’s remaining tropical forest. The Amazon and Orinoco basins influence not only regional climates and air masses, but also atmospheric circulation patterns both north and south of the Equator. The sheer size and diversity of Amazonia exhausts a normal repertoire of grandiose adjectives. The Amazon may or may not be the longest river in the world but it is by far the greatest in terms of discharge, sending around one fifth of the world’s fresh water carried by rivers to the oceans(see chapter 5; Eden, 1990; Sioli, 1984). The drainage basin is twice as large as any other of the world’s catchments.

Freshwater Fisheries. Be it conservation concerns associated with overfishing, food production of large fisheries, or the economic potential of a nation’s fisheries, marine fisheries dominate the political and scientific discussion. However, freshwater fisheries are the most important for food security and employment in areas around tropical river and lake systems. It is estimated that the potential yield from freshwater fisheries is comparable to marine fisheries, but data on catch are poor. What we do know is that in many tropical countries, freshwater fisheries are very important but, generally, they are poorly regulated and studied. Major threats to freshwater fisheries include dam construction, pollution, and introduction of exotic species.

Measurements of trace metals in rivers are of substantial interest for researchers examining basic scientific questions related to geochemical weathering and transport and to scientists involved in pollution control evaluation. Trace metals in natural waters include essential elements such as cobalt, copper, zinc, manganese, iron, molybdenum, nickel, which may also be toxic at higher concentrations, and nonessential elements, which are toxic, such as cadmium, mercury and lead. Recent findings indicate that iron and, to a lesser extent, zinc and manganese play an important role in regulating the growth and ecology of phytoplankton (Martin et al. 1991), while in contrast, cadmium, arsenic, and mercury have long been recognized as poisonous to living organisms (see Pfeiffer et al. 1993, for a description of mercury problem in the Amazon basin). The release of potentially large quantities of these toxic metals, particularly in the river systems of industrialized countries, but also in tropical rivers, is an acute problem of great environmental concern. An understanding of the weathering and transport processes controlling the fate and flux of trace metals in pristine environments is important in evaluating the capacity of receiving waters to accommodate wastes without detrimental effects. The Amazon River system, which is relatively free of industrial and agricultural interference, represents an ideal case for the investigation of the origin and transport of trace metals. This understanding may also provide a scientific basis for the anticipated development of the Amazon basin. With regard to trace metals, Amazon River is still poorly documented. Martin and Meybeck (1979) and Martin and Gordeev (1986) presented a global tabulation of trace metal concentrations in particulate matter of major rivers including the Amazon, and Palmer and Edmond (1992) measured dissolved Fe, Al, and Sr concentrations in the Amazon mainstream and a number of its tributaries. Boyle et al. (1982) and Gordeev et al. (1990) published some data on Cu, Ni, Cd, and Ag dissolved concentrations at the mouth of the Amazon River and in its oceanic plume. Konhauser et al. (1994) reported the trace and rare earth elemental composition of sediments, soils and waters, mainly in the region of Manaus.

The Amazon region is of particular interest because it represents a large source of heat in the tropics and has been shown to have a significant impact on extratropical circulation, and it is Earth’s largest and most intense land-based convective center. During the Southern Hemisphere summer when convection is best developed, the Amazon basin is one of the wettest regions on Earth. Amazonia is of course not isolated from the rest of the world, and a global perspective is needed to understand the nature and causes of climatological anomalies in Amazonia and how they feed back to influence the global climate system. The Amazon River system is the single, largest source of freshwater on Earth. The flow regime of this river system is relatively unimpacted by humans (Vörösmarty et al. 1997 a, b) and is subject to interannual variability in tropical precipitation that ultimately is translated into large variations in downstream hydrographs (Marengo et al. 1998a, Vörösmarty et al. 1996, Richey et al. 1989a, b). The recycling of local evaporation and precipitation by the forest accounts for a sizable portion of the regional water budget (Nobre et al. 1991, Eltahir 1996), and as large areas of the basin are subject to active deforestation there is grave concern about how such land surface disruptions may affect the water cycle in the tropics (see reviews in Lean et al. 1996). Previous studies have emphasized either how large-scale atmospheric circulation or land surface conditions can directly control the seasonal changes in rainfall producing mechanisms. Studies invoking controls of convection and rainfall by large-scale circulation emphasize the relationship between the establishment of upper-tropospheric circulation over Bolivia and moisture transport from the Atlantic ocean for initiation of the wet season and its intensity (see reviews in Marengo et al. 1999). On the other hand, Eltahir and Pal (1996) have shown that Amazon convection is closely related to land surface humidity and temperature, while Fu et al. (1999) indicate that the wet season in the Amazon basin is controlled by both changes in land surface temperature and the sea surface temperature (SST) in the adjacent oceans, depending if the region is north-equatorial or southern Amazonia.

Shallow water mooring and riser systems for permanently turret moored FPSOs present significant design challenges. Many FPSOs, in particular in the South-East Asia region, are required to remain on-station in 100-year return period tropical revolving storm (typhoon) conditions. Extreme sea states combined with the restricted height of the water column generate large mooring loads and make it difficult to accommodate conventional riser configurations. Metocean conditions in such areas can be highly directional. This directionality can be exploited by undertaking an integrated mooring and riser design analysis. The critical interface between the mooring and riser systems is the turret offset and the associated turret heave. The conventional approach is to identify a single offset envelope for each design case, comprising the mooring system (intact or damaged) and FPSO condition (loaded or ballasted), which is then used in riser design. This paper presents a more developed approach, the integrated approach, which is based on conducting the mooring and riser analyses simultaneously for a common set of design cases. To exploit the directionality of the metocean conditions, an offset envelope for each governing metocean condition is calculated from time domain mooring simulations, followed by a parameterisation scheme. As a result, multiple turret offsets and associated metocean conditions and FPSO headings are identified which form a family of offsets for each compass octant of the environment. The integrated approach is applied to an example FPSO with an external turret supporting seven risers arranged in double wave tethered configuration. The drivers and advantages for selecting a particular riser configuration are discussed. It is shown how application of an integrated analysis approach leads to less conservative combinations for use in the riser design, and enables the development of a feasible riser system. An optimal mooring pattern, both leg make-up and orientation for riser layout, is also developed.

Urban form in special geographical conditions: a case study in Kenting National Park. Chih-Hung Chen¹, Chun-Ya Chuang¹ ¹Department of Urban Planning, National Cheng Kung University E-mail: chihhungchen@mail.ncku.edu.tw Keywords: Kenting National Park, special geographical conditions, Historico-Geographical approach, morphotope Conference topics and scale: City transformations Since the land surface is heterogeneous, the natural landscape as an essential element in contemporary morphological studies becomes the initial factor in the formation of a settlement. Moreover, the interaction with natural landscape, built form and the boundary matrix can illuminate ecological perspective on the form of the city. (Scheer, 2016) To understand the urban form under special geographical conditions, a case study is conducted in Kenting National Park, which is a tropical area with rich landscape such as moutains, lakes and rivers, plains, basins, and surrounded by seas. An analytical approach based on Historico-Geographical approach (Kropf, 2009; Oliveira, 2016) is applied in this paper. After identifying the scope of 42 settlements, there are three outer shape types such as compact, scattered, linear. Then, three kinds of morphotopes (Conzen, 1988) can mainly be figured out by comparing the combination between streets, buildings and plots: i) Detached, duplex houses on small plots along the access road; ii) Attached buildings on small plots along the main road; iii) Villas or hotels on large plots along the main road. Finally, the relationship between the larger plan units (Conzen, 1960) and the geographical conditions shows that the homogeneous configuration of plan units corresponds to the certain landscape. On the other hand, this article seeks to find out the impacts and changes caused by special geographical conditions in consequence of the landscape affects not only the formation of urban form but the evolution because its influence on socio-economic conditions. References Conzen, M. R. G. (1960) Alnwick, Northumberland: A study in Town-plan Analysis (Institute of British Geographers, London). Conzen, M.R.G. (1988) ‘Morphogenesis, morphological regions, and secular human agency in the historic townscape, as exemplified by Ludlow’, in Urban Historical Geography. Recent progress in Britain and Germany, 253-272. Kropf, K. (2009) ‘Aspects of urban form’, Urban morphology 13(2), 105-20. Oliveira, V. (2016) Urban Morphology (Springer International Publishing, Switzerland), 102-111. Scheer, B. C. (2016) ‘The epistemology of urban morphology’, Urban Morphology 20, 5-17.