Guayas River Basin Research Articles

Hydrological modeling for the discharge production in an experimental area of the Guayas river basin, Ecuador

Hydrological simulation is a vital issue within the comprehensive management of hydrographic basins, with estimates being an input for decision-making by territorial managers. The objective of the current study is to conduct the hydrological modeling of an experimental basin of the Guayas River, where the discharge of the Baba River will be simulated using the HEC-HMS hydrological modeler. Hereby, the morphometric and hydrological modeling of the basin was performed from a global DEM (ASTER GDEM) in an environment of Geographic Information Systems (GIS) complemented with the analysis of thematic coverage of land types and uses as well as of precipitation data for the sector. The simulation of the discharge of the experimental basin determined that twenty percent of the precipitation that fell in the time window of analysis generated direct runoff and the residual eighty percent is attributed to abstractions. This is a condition that is given by the presence of agricultural crops corresponding to seventy percent forest masses, native forest and shrubby vegetation, as well as by the interception processes as well as water catchment systems in the urban area. The adequate results obtained in the application of the HEC - HMS model are based on the previous work of physical and hydrological characterization of the basin expressed through the physiographic structure of the basin and the valorization of the parameters that characterize the hydrological processes. This research tends to be useful for small hydrographic basins in Ecuador that play an important role in the ecosystem and lack of hydrometeorological information.

Bayesian belief networks for the analysis of the controversial role of hydropower development in the antagonistic agrofood-fisheries nexus: A potential approach supporting sustainable development in the Guayas river basin (Ecuador)

Increasing anthropogenic activities are affecting water quality and related ecosystem services in river basins worldwide. There is a need to identify and act on synergies between the water-energy-food (WEF) elements and the other Sustainable Development Goals (SDGs) while mediating trade-offs. The Guayas river basin (GRB), one of the major watersheds in Ecuador, is being affected by increasing urbanization, agricultural and industrial activities. In this perspective paper, we indicate the WEF interactions in the GRB linked to the SDGs. A major challenge is the geographical distance between pressures and impacts, for which environmental and agricultural governance are key to support the needed change towards sustainable development. In particular, the realization of measures to reduce the pollutant input in upstream systems will need both legislative and financial means to solve downstream water quality problems. A Bayesian belief network (BBN) framework was developed in order to support sustainable decision making in the GRB. The discussed concepts can be applied to other river basins worldwide since, in many basins, very similar food production challenges need to be addressed.

Impacts of Climate Change on the Precipitation and Streamflow Regimes in Equatorial Regions: Guayas River Basin

The effects of climate change projected for 2050 to 2079 relative to the 1968–2014 reference period were evaluated using 39 CMIP5 models under the RCP8.5 emissions scenario in the Guayas River basin. The monthly normalized precipitation index (SPI) was used in this study to assess the impact of climate change for wet events and droughts from a meteorological perspective. The GR2M model was used to project changes in the streamflow of the Daule River. The climate projection was based on the four rigorously selected models to represent the climate of the study area. On average, an increase in temperature (~2 °C) and precipitation (~6%) is expected. A 7% increase in precipitation would result in a 10% increase in streamflow for flood periods, while an 8% decrease in precipitation could result in approximately a 60% reduction in flow for dry periods. The analysis of droughts shows that they will be more frequent and prolonged in the highlands (Andes) and the middle part of the basin. In the future, wet periods will be less frequent but of greater duration and intensity on the Ecuadorian coast. These results point to future problems such as water deficit in the dry season but also increased streamflow for floods during the wet season. This information should be taken into account in designing strategies for adaptation to climate change.

From Mangrove to Fork: Metal Presence in the Guayas Estuary (Ecuador) and Commercial Mangrove Crabs.

Mangrove wetlands provide essential ecosystem services such as coastal protection and fisheries. Metal pollution due to industrial and agricultural activities represents an issue of growing concern for the Guayas River Basin and related mangroves in Ecuador. Fisheries and the related human consumption of mangrove crabs are in need of scientific support. In order to protect human health and aid river management, we analyzed several elements in the Guayas Estuary. Zn, Cu, Ni, Cr, As, Pb, Cd, and Hg accumulation were assessed in different compartments of the commercial red mangrove crab Ucides occidentalis (hepatopancreas, carapax, and white meat) and the environment (sediment, leaves, and water), sampled at fifteen sites over five stations. Consistent spatial distribution of metals in the Guayas estuary was found. Nickel levels in the sediment warn for ecological caution. The presence of As in the crabs generated potential concerns on the consumers’ health, and a maximum intake of eight crabs per month for adults is advised. The research outcomes are of global importance for at least nine Sustainable Development Goals (SDGs). The results presented can support raising awareness about the ongoing contamination of food and their related ecosystems and the corresponding consequences for environmental and human health worldwide.

From field to plate: Agricultural pesticide presence in the guayas estuary (Ecuador) and commercial mangrove crabs

Mangroves are unique coastal ecosystems, located in tropical and subtropical regions. Yet, the functioning of these essential ecosystems is threatened by the presence of pollutants, including pesticides originating from agricultural activities. We investigated pesticide residues in the Guayas estuarine environment, since agricultural activities rapidly increased in the Guayas river basin over the past decades. A multi-residue analysis involving a selection of 88 pesticides was performed on the white meat and the hepatopancreas of the red mangrove crab (Ucides Occidentalis) at 15 sampling sites within the Guayas estuary along with water, sediment, and leaves samples. We found that 35 active compounds were present in the Guayas estuary, of which pyrimethanil was most commonly detected and had the highest concentrations in almost all compartments. Also, cadusafos was present in all studied compartments of the Guayas mangrove system and several prohibited pesticides (including carbendazim, carbofuran, and parathion) were detected. An ecotoxicological and probabilistic consumer risk assessment pointed out that current butachlor, carbendazim, and fludioxonil concentrations can cause adverse effects in aquatic organisms in the long term. Moreover, high potential acute and chronic risks of cadusafos residues on aquatic invertebrates and of diuron on algae in the Guayas wetlands were observed. Still, the exposure results indicated that the health risk for the consumers of the commercial red mangrove crab is low concerning cadusafos, chlorpyrifos, diuron, linuron, and pyrimethanil residues in crab tissues. The findings presented in this research can provide a useful basis for local water managers and environmental conservation groups to act and reduce the usage of pesticides, to avoid threatening aquatic and human health.

Interannual variations in the hydrodynamics of a tropical river-wetland system: a case study for the Abras de Mantequilla wetland, Ecuador

Wetlands are sensitive to hydrological conditions and human influence. The Abras de Mantequilla wetland (AdM) located at the centre of the Guayas River Basin (Western Ecuador), was declared a Ramsar site (2000) due to its important role in the conservation of bird fauna diversity. The wetland also supports significant populations of fish, including endemic species. The area exhibits two seasons: (i) a wet season (January–May); and (ii) a dry season (June–December). For the area of interest data is scarce, and a hydrodynamic model did not exist. In order to evaluate the interannual hydrodynamics and inundation patterns variability of this wetland system, a 2D hydrodynamic model was developed using the Delft3D software suite. Local knowledge was combined with field observations and expert elicitation to construct an appropriate model for the area. Results show that the Abras de Mantequilla is a river-wetland system that experiences extreme variations in hydrodynamic conditions from low water depths and almost stagnant conditions during the dry season, to a very dynamic behaviour during the rainy season. The inundation area ranges between 5 to 27 km2, water depths vary from 0.4 to 9 m and flow velocities from 0.0 up to 0.9 m/s. The “Nuevo River” is the main inflow to the wetland, with an overall contribution of about 85–90%, with peak discharges during February and March. A numerical tracer analysis indicated that the wetland can be divided into three main areas (upper, middle and low), with higher residence times found in the middle area. Overall, based on numerical hydrodynamic simulations it was possible to obtain adequate indications of the relative importance of the different river inflow conditions, as well as spatial and temporal inundation patterns, velocities and residence times under hydrological conditions varying from dry to extremely wet years. Furthermore, the hydrodynamic model provides a basis for other studies such as water quality assessment and primary production dynamics, as well as for determining the habitat suitability for fish.

Bayesian Belief Network models as trade-off tools of ecosystem services in the Guayas River Basin in Ecuador

Food production often leads to environmental degradation. Consequently, insights into ecosystem functioning in relation to exploitation are needed as a basis for socioeconomically acceptable mitigation of these impacts. A Bayesian Belief Network (BBN) model is developed to link three major ecosystem services (ES), i.e. food production, water provision and ecotourism, and determine the effect of local agricultural practices and management on the ES in the Guayas Basin (Ecuador). Several data sources were integrated into the BBN model, including processed spatial data from primary and secondary sources, sampling and survey data, and expert knowledge. The model suggests that banana and sugar cane generate the highest yield but provide low ecotourism benefits. In contrast, cacao produces the lowest yields but contributes to better water quality. Scenario analyses suggest that environmental gains are possible by optimising the land use (LU) based on the edaphoclimatic requirements of crops. Moreover, the integration of LU optimisation with upscaling and farming intensification can allow for additional advantages in water provision and ecotourism while mitigating productivity losses. The BBN development approach can serve as a reference for other case studies, where data scarcity plays a limiting factor in the assessment of interactions between key ES.

Using the Soil and Water Assessment Tool to Simulate the Pesticide Dynamics in the Data Scarce Guayas River Basin, Ecuador

Agricultural intensification has stimulated the economy in the Guayas River basin in Ecuador, but also affected several ecosystems. The increased use of pesticides poses a serious threat to the freshwater ecosystem, which urgently calls for an improved knowledge about the impact of pesticide practices in this study area. Several studies have shown that models can be appropriate tools to simulate pesticide dynamics in order to obtain this knowledge. This study tested the suitability of the Soil and Water Assessment Tool (SWAT) to simulate the dynamics of two different pesticides in the data scarce Guayas River basin. First, we set up, calibrated and validated the model using the streamflow data. Subsequently, we set up the model for the simulation of the selected pesticides (i.e., pendimethalin and fenpropimorph). While the hydrology was represented soundly by the model considering the data scare conditions, the simulation of the pesticides should be taken with care due to uncertainties behind essential drivers, e.g., application rates. Among the insights obtained from the pesticide simulations are the identification of critical zones for prioritisation, the dominant areas of pesticide sources and the impact of the different land uses. SWAT has been evaluated to be a suitable tool to investigate the impact of pesticide use under data scarcity in the Guayas River basin. The strengths of SWAT are its semi-distributed structure, availability of extensive online documentation, internal pesticide databases and user support while the limitations are high data requirements, time-intensive model development and challenging streamflow calibration. The results can also be helpful to design future water quality monitoring strategies. However, for future studies, we highly recommend extended monitoring of pesticide concentrations and sediment loads. Moreover, to substantially improve the model performance, the availability of better input data is needed such as higher resolution soil maps, more accurate pesticide application rate and actual land management programs. Provided that key suggestions for further improvement are considered, the model is valuable for applications in river ecosystem management of the Guayas River basin.

Denominación de origen de cacao ecuatoriano: ¿Un aporte de marketing global?

La presente investigación radica en la importancia del cacao fino de aroma ecuatoriano que simboliza el 60% del mercado a nivel mundial. A través de un estudio descriptivo- correlacional, multivariado e instrumentos de recolección aplicados como entrevistas se evidenció las características del cacao ecuatoriano, cotizado por sus excelentes notas florales base para la elaboración de subproductos en Europa, Norteamérica y Asia. Con la intención de incentivar el comercio internacional, el Instituto Ecuatoriano de Propiedad Intelectual (IEPI), prescribió la denominación de origen “Cacao Arriba” que permitió su certificación para todo el cacao fino de aroma que procediera del territorio nacional. Entre los resultados hallados se identificó que en el caso de Ecuador la “zona arriba”, reconocida desde la época de la colonia, representa a la Cuenca baja del rio Guayas que conforman las provincias de Los Ríos y Guayas, la cual posee características particulares por la influencia climática, la corriente de Humboldt y El Niño. Sin embargo la denominación de origen en el Ecuador se expone con la finalidad de promoción como un fruto con garantía de procedencia que contradice las características propias de discriminación geográfica que son específicas de una zona estrictamente delimitada, su impacto entre los agricultores no trascendió, mientras que para el mercado internacional no es una evidencia de características organolépticas que garanticen el origen, características y calidad específico del producto; por lo tantobajo esos parametros no representa una estrategia de marketing global.

Impact assessment of local land use on ecological water quality of the Guayas river basin (Ecuador)

Extensive anthropogenic activities including land conversion have been taking place in the Guayas river basin (Ecuador) due to increasing population growth. Land use changes are considered one of the key sources affecting the ecological water quality of the Guayas river basin. Therefore, we investigated the effect of land use on the ecological water quality both within direct vicinity and within a distance of 200 m from the sampling sites. We investigated which of three land use assessment methods (i.e. data retrieved from field protocols, from aerial pictures (Google maps) and from GIS data) is most suitable to quantify the impact of local land use on the ecological water quality and which key environmental variables influence the ecological water quality. To do so, we collected data on macroinvertebrates and environmental variables from 120 sampling sites throughout the river basin during an integrated sampling campaign. The Biological Monitoring Working Party adapted for Colombia (BMWP-Col) was calculated and used to assess the ecological water quality status of the river basin, based on macroinvertebrates. The relation between the BMWP-Col, local land use and other environmental variables was investigated using generalized linear models (GLMs) and sensitivity analyses. Based on multi-model comparison, the ecological water quality was best associated with the land use close to the sampling sites (field protocol, R2 = 0.93, p < 0.05). Models involving land use assessed using aerial pictures, field protocols and GIS data were associated mainly with hydromorphological variables. However, the models incorporating land use evaluated on a larger spatial scale (i.e. Google maps and GIS maps) were also associated with physical-chemical variables. Although, the land use assessment based on aerial pictures using Google maps” had the best outcome, a combined approach using field observation and aerial pictures can provide comprehensive land use data to the water management and provides the most complete information to define local land use of the sampling sites.

Threshold Responses of Macroinvertebrate Communities to Stream Velocity in Relation to Hydropower Dam: A Case Study from The Guayas River Basin (Ecuador)

The Guayas River basin is one of the most important water resources in Ecuador, but the expansion of human activities has led to a degraded water quality. The purpose of this study was (1) to explore the importance of physical-chemical variables in structuring the macroinvertebrate communities and (2) to determine if the thresholds in stream velocity related to macroinvertebrate community composition could be identified in the Guayas River basin. Thus, macroinvertebrates and physical–chemical water quality variables were sampled at 120 locations during the dry season of 2013 in the Guayas River basin. Canonical correspondence analysis (CCA) was performed to identify relevant physical–chemical characteristics of the river influencing the distribution of the macroinvertebrate communities. Threshold indicator taxa analysis (TITAN) was used to discriminate between the macroinvertebrate community related to stagnant waters (Daule–Peripa reservoir) and to running waters. CCA indicates that the most important environmental factors influencing the distribution of macroinvertebrate communities were stream velocity, chlorophyll concentration, conductivity, temperature and elevation. Tipping points for the macroinvertebrate community were defined by stream velocity at 0.03 m/s and 0.4 m/s, i.e., stagnant-water (including dam-related reservoirs) taxa start to quickly decrease in abundance and frequency at 0.03 m/s while running-water taxa start to quickly increase in abundance and frequency at 0.03 m/s until a stream velocity of 0.4 m/s. The results provide essential information to define environmental flows to further support water management plans of the Guayas River basin. Information obtained will be useful for management of similar rivers in South America, as well as the rest of the world.

Agricultural development in Ecuador: A compromise between water and food security?

Ecuador is facing several threats to its food and water security, with over a tenth of its population currently undernourished and living in poverty. As a response, its government is incorporating new patterns of land use and developing regional water infrastructure to cope with the related challenges. In this study, we assess to what point these efforts contribute to integrated water and food security in the country. We investigated the period 2004–2013 in the most productive agricultural region - the Guayas river basin district (GRBD) - and analysed the impacts of different scenarios of agricultural change on local water security. Our approach integrates MuSIASEM (Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism) with the hydrological SWAT model. Freshwater allocation is evaluated within all the water cycle from its source (natural systems) to the final users (societal systems). Water security is assessed spatiotemporally in terms of water stress for the population living in poverty. Water productivity is obtained in relation to agricultural production and nutrition. The multi-scale analysis shows that whereas at river basin district level the median annual streamflow has a similar magnitude than rainfall stored in soil, these two parameters differ spatiotemporally at subbasin level. The study finds the greatest challenge in achieving water security is the south-east and central part of the GRBD, due to water scarcity and a larger population living in poverty. However, these areas are also simultaneously, where the greatest crop water productivity is found. We conclude that food production for both domestic consumption and market-oriented exports can be increased while meeting ecosystem water demands in all the GRBD regions except for the east. Our integration of methods provides a better approach to inform integrated land and water management and is relevant for academics, practitioners and policymakers alike.

Distribution of agricultural pesticides in the freshwater environment of the Guayas river basin (Ecuador)

The rapid increase and transition to more intensive agricultural activities in developing nations are often leading to misuse and overuse of pesticides, making their environment vulnerable for pesticide accumulation. In the present study, the Guayas river basin was taken as a representative case study to evaluate pesticide contamination of the Ecuadorean freshwater environment. Pesticide contamination was determined at 181 sampling sites by a multi-residue method using solid phase extraction (SPE) and pesticide residues were linked with agricultural land use activities to identify the main pollution sources. Moreover, the biological water quality status based on macroinvertebrate communities was determined at every location and the relation with the occurrence of pesticide residues was further investigated. Results showed that pesticide contamination of the freshwater environment was widely present in the Guayas river basin with detections at 108 sampling sites (60%). A total of 26 pesticide products were identified. Most frequently detected pesticides included cadusafos (62 locations), butachlor (21 locations) and pendimethalin (21 locations), with concentrations up to 0.081, 2.006 and 0.557 μg·L−1 respectively. Pesticide residues detected in this study did not significantly influence the biological water quality (p = 0.69), but were observed to be positively correlated with ammonium concentrations, supporting the assumed combined application of chemical fertilizers and pesticides in agriculture. These pesticide residues were also associated with one or more agricultural crops, with in particular the banana and rice industries identified as major pollution sources. Both high consumption rates and non-specific application methods, such as aerial spraying of banana plantations and application directly into the water layer of irrigated rice fields, may attribute to pesticide contamination of the freshwater environment of the Guayas river basin. It is therefore suggested that measures, e.g. legal regulations and awareness campaigns, taken to prevent environmental pollution and accumulation of pesticides primarily focus on these industries.

English

Common bean is very important in the daily diet of Ecuadorians. Web blight (Rhizoctonia solani (Kuhn) is the major constraint faced by common bean farmers in Ecuador and everywhere in the world, causing high losses of yield grain every year. A constant selection of genotypes with excellent productive and resilience to disease features in each region is presented as a potential solution to these problems. The present study aimed to evaluate the phenology, web blight resilience and grain yield production of 17 common bean genotypes in field conditions, in the Guayas River Basin, Ecuador. Three commercial varieties (two belonging to determined feature and one to undetermined feature) and 14 more promising genotypes were evaluated. Day period for phenological stage R6 (full bloom) and R9 (flowering maturity), web blight resilience, number of harvested pods, number of grains per pod per plant, 1000-seed weight, grain yield and later yield per hectare were measured. Scott Knott test (p ≤ 0.05) was executed for mean comparisons and principal component analysis (PCA) statistical test was performed using the productive and agronomical variables, successfully distinguishing two group of genotypes according to their types of growth (determined and undetermined), highlighting the genotypes EVG-6-103, EVG-6, CAL-96, INIAP-473, AFR-619, INIAP-474, AFR-298, SER-29, SER-35, EVG-16-08 which showed the higher agronomic, sanitary, and productively averages in approximately all the studied variables. Key words: Phaseolus vulgaris L., Rhizoctonia solani (Kuhn), yield.

Cathorops festae (Boulenger 1898) (Siluriformes; Ariidae), a valid species from Ecuador and Peru.

Over the past decade, the Sea Catfish (Ariidae) genus Cathorops has been the focus of a major taxonomic review, which has resulted in the revalidation of five synonymized nominal species, and the recognition of seven new species. With 21 valid species, Cathorops is currently the most species-rich genus of Ariidae in the New World. The principal lacuna in the taxonomic knowledge of genus species is the uncertain status of Arius festae Boulenger, 1898, described from Naranjal, in the Guayas River basin of Ecuador. In the present study Cathorops festae is redescribed as a valid species based on morphological and molecular data.

Assessment of groundwater vulnerability in the Daule aquifer, Ecuador, using the susceptibility index method

The Guayas region in Ecuador is economically very important, producing 68% of the national crops. The main agricultural activities threaten the groundwater therein with nitrate contamination given the large fertiliser and water needs. The present work tests the applicability of the susceptibility index assessment method in evaluating the impact of agricultural activities on groundwater quality, using as a case study an aquifer of the Guayas river basin in Ecuador. The index adapts four parameters of the DRASTIC method and incorporated a new land use parameter. Results show that the areas highly vulnerable to contamination are located in irrigation perimeters of dominant paddy fields associated with the high recharge rates in the alluvial deposits. Respectively, moderately vulnerable and low-vulnerability areas correspond to aquatic environments and forests, semi-natural zones and water bodies. One of the main contributions of the Daule aquifer vulnerability is likely its wide, flat topography. A great part of the aquifer is at high risk of contamination by nitrates if a code of good agricultural practices is not applied. Therefore the implementation of a monitoring network to control the nitrates concentrations is the first step to assure groundwater quality for drinking purposes.

Generalized Linear Models to Identify Key Hydromorphological and Chemical Variables Determining the Occurrence of Macroinvertebrates in the Guayas River Basin (Ecuador)

The biotic integrity of the Guayas River basin in Ecuador is at environmental risk due to extensive anthropogenic activities. We investigated the potential impacts of hydromorphological and chemical variables on biotic integrity using macroinvertebrate-based bioassessments. The bioassessment methods utilized included the Biological Monitoring Working Party adapted for Colombia (BMWP-Col) and the average score per taxon (ASPT), via an extensive sampling campaign that was completed throughout the river basin at 120 sampling sites. The BMWP-Col classification ranged from very bad to good, and from probable severe pollution to clean water based on the ASPT scores. Generalized linear models (GLMs) and sensitivity analysis were used to relate the bioassessment index to hydromorphological and chemical variables. It was found that elevation, nitrate-N, sediment angularity, logs, presence of macrophytes, flow velocity, turbidity, bank shape, land use and chlorophyll were the key environmental variables affecting the BMWP-Col. From the analyses, it was observed that the rivers at the upstream higher elevations of the river basin were in better condition compared to lowland systems and that a higher flow velocity was linked to a better BMWP-Col score. The nitrate concentrations were very low in the entire river basin and did not relate to a negative impact on the macroinvertebrate communities. Although the results of the models provided insights into the ecosystem, cross fold model development and validation also showed that there was a level of uncertainty in the outcomes. However, the results of the models and sensitivity analysis can support water management actions to determine and focus on alterable variables, such as the land use at different elevations, monitoring of nitrate and chlorophyll concentrations, macrophyte presence, sediment transport and bank stability.

Ecological water quality analysis of the Guayas river basin (Ecuador) based on macroinvertebrates indices

The Guayas river basin is one of the major watersheds in Ecuador, where increasing human activities are affecting water quality and related ecosystem services. The aims of this study were (1) to assess the ecological water quality based on macroinvertebrate indices and (2) to determine the major environmental variables affecting these macroinvertebrate indices. To do so, we performed an integrated water quality assessment at 120 locations within the river basin. Biological and physical–chemical data were collected to analyze the water quality. Two biotic indices were calculated to assess the water quality with an ecological approach: the Biological Monitoring Working Party Colombia (BMWP-Col) and the Neotropical Low-land Stream Multimetric Index (NLSMI). Both the BMWP-Col and NLSMI indicated good water quality at the (upstream) forested locations, lower water quality for sites situated at arable land and bad water quality at residential areas. Both indices gave relevant assessment outcomes and can be considered valuable for supporting the local water management. A correspondence analysis (CA) applied on both indices suggested that flow velocity, chlorophyll concentration, conductivity, land use, sludge layer and sediment type were the major environmental variables determining the ecological water quality. We also suggested that nutrient and pesticide measurements are important to study water quality in the area where intensive agriculture activities take place. The nutrient levels detected in agricultural areas were relatively low and illustrated that the types of crops and the current cultivation methods were not leading to eutrophication. The applied methods and results of this study can be used to support the future water management of the Guayas river basin and similar basins situated in the tropics.

Habitat suitability of the invasive water hyacinth and its relation to water quality and macroinvertebrate diversity in a tropical reservoir

In this study, we assessed the relationship between the occurrence of the invasive water hyacinth ( Eichhornia crassipes ) and water quality properties as well as macroinvertebrate diversity in a tropical reservoir, situated in western Ecuador. Macroinvertebrates and physico-chemical water quality variables were sampled at 32 locations (during the dry season of 2013) in both sites covered and non-covered by water hyacinth in the Daule-Peripa reservoir. The results indicated that, in terms of water quality, only turbidity was significantly different between sampling sites with and without water hyacinth (Mann–Whitney U -test, p < 0.01). The habitat suitability model showed that water hyacinth was present at sites with a low turbidity. The percentage water hyacinth cover increased with decreasing turbidity. The Biological Monitoring Working Party-Colombia score and the Margalef diversity index were significantly higher (Mann–Whitney U -test, p < 0.01) at sampling sites where water hyacinth was present compared to water hyacinth absent sites. However, there were no significant differences in the Shannon–Wiener index, Evenness index and Simpson index between the sampling sites with and without water hyacinth. Our results suggest that water hyacinth cover was an important variable affecting the diversity of macroinvertebrates in the Daule-Peripa reservoir, with intermediate levels of water hyacinth cover having a positive effect on the diversity of macroinvertebrates. Information on the habitat suitability of water hyacinth and its effect on the physico-chemical water quality and the macroinvertebrate community are essential to develop conservation and management programs for large tropical reservoirs such as the Daule-Peripa reservoir and the Guayas river basin, where water resources are being at high risk due to expansion of agricultural and industrial development activities.

Relationships between aquatic biotic communities and water quality in a tropical river–wetland system (Ecuador)

Abstract Many tropical wetlands threatened by land use changes, or modifications in hydrological regime require effective management policies and implementation to protect them. The Abras de Mantequilla wetland, located in the Guayas River Basin in Ecuador, is subject to two major environmental disturbances, i.e., short-term agriculture (rice, maize) on the land around the wetland and the effects of planned infrastructure works of the Baba dam in the upper catchment. Both activities are expected to be the main constraints for the future wetland health. The objective of this study was to provide an initial characterization of the biotic communities of the river and wetland habitats before the dam starts operating. Plankton, macroinvertebrates, fishes and associated physical and chemical variables were sampled at 12 sites during the wet season (February 2011). Biotic metrics (abundance, taxa richness, diversity and evenness) were computed for the aquatic communities in the wetland and the river. A biotic index (Biological Monitoring Working Party-Colombia/adaptation) was applied to the macroinvertebrate community. Relationships between biotic and abiotic variables indicated nutrients, velocity and sediment type as main drivers. Cluster analysis grouped physico-chemical variables according to river or wetland sites. Similarities regarding the taxa composition among sites were explored with non-metric multidimensional scaling method (NMDS), showing clusters for ichthyoplankton and macroinvertebrates. Higher densities of organisms were recorded in the wetland compared with the river. The wetland is an important area of breeding and reproduction for fish communities, with its lentic habitats promoting the development of high densities of ichthyoplankton. In order to achieve sustainable solutions for integrated river–wetland systems, management options should focus on maintaining natural variation in hydrodynamic conditions throughout the entire catchment, as well as implement good practices in agriculture and reforestation using native species. Local and national authorities should support continuous monitoring programmes, taking account of seasonal variation and of future impacts from flow reduction and nutrient enrichment.