Magdalena River Research Articles

Identification, Abundance, and Distribution of Microplastics in Surface Water Collected from Luruaco Lake, Low Basin Magdalena River, Colombia

There are few studies on microplastic (MP) contamination in Colombia, and little is known about its impacts on continental aquatic ecosystems. This study evaluated, for the first time, the identification, abundance, and distribution of MP particles in the surface water of Luruaco Lake, in the low basin of the Magdalena River, Colombia, included in national programs in marine sciences and hydrobiological resources. Six stations and four samplings were established in the dry and rainy seasons. A total of 72 water samples were collected for microplastic extraction using hydrogen peroxide (H2O2) digestion, density separation with sodium chloride solution (NaCl), and filtration. The abundance of MPs ranged from 0 to 3.83 MPs·L−1, with an average of 1.90 MPs·L−1 in the rainy season and 0.25 MPs·L−1 in the dry season. According to the calculated coefficient of microplastics impact, the contamination in the surface water of Luruaco Lake is “maximum” to “extreme” for fibers with an average length of 2.05 mm and “minimum” to “average” for fragments that are 0.35 mm in size on average. Polyester (PES, 57.9%), polystyrene (PS, 47.0%), and polyethylene terephthalate (PET, 35.3%) polymers were more abundant in surface water. The temporal variation of the MPs indicates contamination related to the discharges of the tributary streams to the lake in the rainy season.

Strategies for the economic and territorial regeneration of the Magdalena River: the case of the city of Girardot, Colombia

Strategies for the economic and territorial regeneration of the Magdalena River: the case of the city of Girardot, Colombia

Trees form factor in Tropical Dry Forest in north of Tolima – Colombia

The high biodiversity can make it difficult to select dendrometric models for each ecosystem. In order to contribute to these models, a relict tropical dry forest of approximately 100 hectares was selected in the valley of the Magdalena River, located in the central region of Colombia. This forest relict is in the municipality of Venadillo, department of Tolima. A sample of 36 trees of different species with a normal diameter greater than 10 centimeters were randomly selected. All trees were measured using a non-destructive method. Diameters with bark were measured on the trunks of the standing trees at different heights from the base of the tree to its commercial height using Field Map equipment and technology. With the information collected, a tree form factor was determined to be used as a forestry decision tool or as an element of comparison with similar ecosystems. The form factor for the calculated commercial volume was 0.8.

A Preliminary Approximation to Microbiological Beach Sand Quality along the Coast of the Department of Atlántico (Caribbean Sea of Colombia): Influence of the Magdalena River

Beaches represent important economic resources linked to “Sun, Sea and Sand” tourism and, therefore, their water quality constitutes an issue of great relevance especially in developing countries. The main objective of this work was to determine the microbial quality of beach sediments along the Caribbean coast of the Department of Atlántico (Colombia) and its relationships with the existence of local sources of contamination (e.g., streams containing wastewaters), beach exposition to waves, the quantity of beach visitors—which is reflected by beach typology (e.g., urban, rural, etc.), the presence of tourist activities/infrastructures and the beach sand sedimentological characteristics. Along the study area, samples of beach sediments were gathered in beach face and backshore areas at 11 sectors and the microbiological counts of three faecal indicator bacteria, i.e., Escherichia coli, Enterococcus spp. and Clostridium perfringens, were determined. A homogeneous distribution was recorded along the coast of Escherichia coli and Clostridium perfringens in both beach face and backshore sediments, in the order of 5 and 2 log CFU/100 mL, respectively; Enterococcus spp. was, at places, not observed in backshore sediments. No relationships existed between, on one side, the counts of the faecal indicator bacteria considered and, on the other side, the presence of streams and tourist activities/infrastructures, beach typology, exposition to waves and the sedimentological characteristics of beach sands. Such results suggest a chronic contamination of beach face and backshore sediments linked to the heavily polluted sedimentological load of the Magdalena River.

Environmental crisis, food crisis and resisting fisherpersons. The case of the Magdalena River, Colombia

The Magdalena River basin is the main source of food in Colombia. 70% of agricultural output and 40% of inland fishing are produced in its basin. However, the River is facing a complex environmental crisis that affects both the fisheries and fishermen’s territoriality. The river as a source of food is declining. This article aims to present the relation between the environmental crisis of the river and food security at the local and national level, through the situation of the artisanal fisheries and fisherpersons in the Magdalena River. The methodology of the research combines quantitative and qualitative approaches, through descriptive statistics of population and productive surveys, and in-deep interviews with fisherpersons and other strategic actors in different parts of Magdalena’s basin.

A socio-ecological assessment of land-based contamination and pollution: The Magdalena delta, Colombia

River mouth systems, such as estuaries and deltas are important earth system transitional zones linking the land and coastal marine systems. They funnel anthropogenic contaminants and pollutants from the activities in the river catchment into the marine environment. The present study is focused on the Magdalena River-mouth at Bocas de Ceniza where land-based contamination and pollution are important issues. These were subsequently analysed using an expanded DPSIR framework (Drivers Pressures, State, Impacts Responses). Based on export coefficients and secondary information, the loads of BOD, TSS, Nutrients and solid waste from different sources were identified and compared to prioritize their management within the study area. Findings suggest that contaminants generated in the study area may be insignificant compared to the inputs from the Magdalena River, but they can have a significant impact on the state of local ecosystems. Of all the sources analysed, agriculture and livestock are theoretically the largest contributors of nitrogen (i.e., 14.84 t d-1 and 48.99 t d-1) and phosphorus (i.e., 5.90 t d-1 and 19.46 t d-1) in the basin ‘Direct to the Caribbean’ and ‘Cienaga de Mallorquín’ (that altogether are identified as DtC+) and the ‘Western bank of the lower Magdalena’ (DtM-LM), respectively. In the case of BOD, domestic and industrial wastewaters contribute about 5.10 t d-1 and 98.43 t d-1 in the same basins. Contributions of faecal coliforms were more than 4 orders of magnitude higher in untreated wastewater, being 4.86 x1016 NMP d-1 and 1.78 x1016 NMP d-1 in the lower Magdalena and Caribbean catchments, respectively. Inadequately managed waste and plastic represent a serious problem for the Caribbean Basin. Solid waste generated within the study area and coming from the Magdalena basin and the Caribbean Sea, reaches the coast and deteriorates its visual quality, affects mangrove ecosystems, and generates impacts on coastal populations. By basin, the DtM-LM is where the greatest pollutant loads are generated. However, in terms of impact on human well-being, it is the DtC+ that bears the brunt where pressures are translated in impacts such as increased maintenance and cleaning cost of beaches, reduction or loss of tourism revenue, adverse health effects to vulnerable groups, reduce protection against natural hazards, increased living costs and loss of cultural values.

Rarity and conservation status of the Colombian Speckled Tree Rat, Pattonomys semivillosus (I. Geoffroy, 1838)

Abstract The Colombian Speckled Tree Rat, Pattonomys semivillosus, is a little-known rodent endemic to the Lower Magdalena River basin at the Caribbean Coast of Colombia. To date it is the only species of Pattonomys documented in the country. We provide information on the rarity, and conservation status of P. semivillosus based on the current and potential distribution, population density and size using information from the literature, new records, and museum vouchers. We confirmed 66 occurrences that belong to 25 localities in six departments (Atlántico, Bolívar, Cesar, La Guajira, Magdalena, Santander, and Sucre) in northern Colombia, including 18 new localities not previously reported in the literature, mostly in the highly threatened Tropical Dry Forest ecosystem. The population density in three sites of Department of Cesar was 5.4 ind/km2, 5.9 ind/km2, and 32.4 ind/km2. The species matches with the Category D of rarity, and we suggest an update to the threatened assessment (from Least Concern to Near Threatened). This information will contribute to update the current IUCN assessment of the species.

The effect of waves in hydrodynamics, stratification, and salt wedge intrusion in a microtidal estuary

Waves have been found to modulate circulation, stratification, and sediment dynamics in several estuaries, mainly near the mouth. This study analyzes the effects of waves on the hydrodynamics, stratification process, and dynamics of the salt wedge in an estuary with a microtidal range, high fluvial and sediment discharges, and dominated by waves: the Magdalena River estuary (MRE). It is, under low flow conditions, a highly stratified, salt wedge type. Field measurements and the MOHID 3D modeling system, 2D coupled with the SWAN model, were used for this purpose. The low flow seasons of 2018 (February-March) and 2020 (March) were taken as case studies. Results show that when considering wave effects in the numerical simulations, more realistic conditions are reproduced in the circulation patterns and salinity distribution in the outer estuary. Variations in velocity patterns and salinity distribution are found between the mouth and 2 km upstream of the mouth when comparing the simulations with and without waves, especially in the mixing layer. These variations in hydrodynamics and stratification may be associated with increased wave-induced bed shear stress, variations in barotropic and baroclinic acceleration, and increased vertical mixing. At 2 km into the river channel, the reduction in wave height energy of 95% and changes in salinity distribution are already lower than 2%. In addition, it was observed that waves do not generate significant changes in the dynamics of the salt wedge, which is mainly affected by the diurnal tidal cycle, presenting variations in the length of the intrusion of up to 1 km, and in the magnitude of the longitudinal salinity gradient at the salt front, presenting low salinities at high tide when the wedge enters, and high salinities at low tide, in its retreat.

Distribution of Miathyria marcella larvae (Odonata: Libellulidae) and water quality of wetlands in Northern Colombia

This study aims to assess the physicochemical characteristics regulating the distribution and abundance of M. marcella larvae in six wetlands in the northern Colombia. Standardized techniques for collecting invertebrate and physicochemical data were used in 29 sampling points in an intraannual period. Mean pH and temperature oscillated in narrow ranges within wetlands (7.7 ± 0.09–8.6 ± 0.07; 28.1 ± 0.29–32.8 ± 0.17 °C, respectively), whereas ammonium concentrations and conductivity exhibited a wide variation (0.2 ± 0.03–2.8 ± 0.54 mg NH4 L−1; 861 ± 30.7–19254 ± 1706 µS cm−1, respectively). A total of 2586 individual M. marcella larvae were collected. Abundance was greater in wetlands influenced by the Magdalena River, with 19.4 ± 1.7 and 9.3 ± 1.4 individuals; followed by wetlands hydrologically influenced by seasonal runoff, with 8.1 ± 0.4 and 6.4 ± 0.4 individuals; and lowest in wetlands with influence of the Caribbean Sea, with 3.9 ± 0.3 and 0.3 ± 0.1 individuals. Abundances of M. marcella larvae exhibited similar variations at different months during the sampling period. Abundance and distribution of M. marcella larvae in wetlands of northern Colombia is strongly dependent on water conductivity, transparency and alkalinity. This study evidence that Odonata larvae are a valuable tool as bioindicators for wetland assessment and monitoring.

Seasonal and deep groundwater‐surface water interactions in the tropical Middle Magdalena River basin of Colombia

AbstractThis study is an attempt to understand flow patterns in the Middle Magdalena Valley River basin (MMV), a tropical lowland humid forest. For this purpose, we used δ2H and δ18O water stable isotopes measured in different surface and groundwater sources collected in the area both during the dry and the wet seasons. Two hundred and forty‐five water samples were collected in rainfall, springs, rivers, swamps, and wells (from 10 to 350 m depth). Thus, we were able to establish three tendencies that suggest the existence of surface‐groundwater interactions or preferential groundwater fluxes in the MMV: (i) samples with an isotopic enrichment from the wet to the dry season (groundwater samples following the rainfall isotopic variability), (ii) groundwater samples with an isotopic depletion from the wet to the dry season (opposite to the rainfall isotopic signal), and (iii) groundwater samples whose isotopic composition did not change significantly among seasons. However, none of these tendencies could be related to geology or the type of sampled site, which suggests that some not fully understood processes must be taking place in the hydrological system of the MMV. Both, surface, and groundwater samples are grouped close to the Colombian meteoric line, with exception of some swamp samples collected during the dry period, which displayed the expected evaporation trend line tendency. This may be an indicator of the connection/disconnection of swamps with the river during the hydrological year. Finally, this study aims to fulfil the gap in water‐stable isotope data in Colombia and provide insights about the hydrological setup of a lowland tropical basin.

Drivers for the artisanal fisheries production in the Magdalena River

We review knowledge on the Magdalena River in Colombia and its fish to identify those drivers that influence the artisanal fisheries production. We identify eight direct drivers (four natural and four anthropogenic) and at least four indirect drivers. Those drivers modify conditions in the fluvial network that promote fish movements, reproduction, and their larvae survivor. Landscape, rains, floods, connectivity of the fluvial net as land cover change, water pollution, hydropower, and alien species are the natural and anthropogenic direct drivers described in this article. The river–lake interaction dynamics in the Magdalena River are determined by two rainy cycles per year. Two seasonal flooding periods induce two cycles in the biological productivity of floodplains because water and sediment inputs. The most visible consequences in these hydrological cycles are the migrations of potamodromous fish and the periodic increase in the artisanal fishery production. Major floodplains are reducing their storage capacity by trapping ∼10%–40% of upstream sediment production. This process induces many research questions about rates of biomass production, carbon fluxes in the basin, impacts of human-induced erosion, and increasing rates of sediment load on floodplain connectivity, but still there is not enough data to answer them. Finally, we make some suggestions toward the sustainability of the Magdalena floodplains. The well-being of the floodplain ecosystems and their connectivity with the main river are the main tools to preserve and manage the ecosystem services of the Magdalena River and its floodplains lakes.

SYNTHESIS MODEL FOR THE CONCEPTUAL DESIGN OF INLAND CARGO VESSELS TO OPERATE ON THE MAGDALENA RIVER

Inland waterways are presented both as a need and an opportunity for developing an intermodal transport system to boost Colombian economic growth. Riverine transportation as part of an intermodal system represents conveying a significant amount of cargo at a low cost and therefore reducing greenhouse gas emissions. To competitively include this cargo transportation alternative in an intermodal context, the development of effective container vessels is required. Most of the Colombian rivers present sedimentary, high flow, and low depth nature. Then, the design of riverine cargo vessels capable of navigating in shallow waters with less brake power requirements is needed. A synthesis model: an automatic and integrated design procedure, has been programmed to generate and evaluate feasible vessel dimensions at a conceptual design stage. Through systematic variations of the main dimensions, this procedure allows evaluating a design space in which the most effective concept-vessel solution is selected. At the end of this procedure, the main characteristics for container vessels in the Magdalena River at a conceptual design stage, are defined. Validation of the synthesis model with a riverine logistic support ship is provided.

From the Editor

From the Editor

Chimichagua and the Musical Ecosystem of the Tambora in the Depresión Momposina

AbstractThe tambora is a traditional celebration geographically dispersed across the Depresión Momposina—a vast area along the Magdalena River Basin in northern Colombia—and one of the well-known bailes cantaos, as the sung dances of this region are commonly known. Few in-depth studies into this celebration have been conducted so far, and none of them have devoted particular attention to the tambora of the town of Chimichagua. In this study, the results of the fieldwork carried out in Chimichagua reveal peculiar characteristics of this tambora, which clearly distinguish it from others in the area. Its musical and choreographic specificities make it possible to speak of a complex musical ecosystem in the region, whose diversity is threatened by several factors that will be discussed in this article.

Distribution and conservation of vanilla crop wild relatives: the value of local community engagement for biodiversity research

Natural vanilla is a high-value crop with demand increasing globally. Crop wild relatives (CWR) represent valuable agrobiodiversity and are prioritized in the Global Strategy for Plant Conservation. Vanilla species are naturally rare with historically infrequent botanical collections. Despite their importance as CWR, fewer than 10% of Vanilla species have been evaluated for the IUCN Red List. Colombia is a diversity center for Vanilla species, yet many remote regions are lacking detailed floristic characterization. We show that the participation of rural communities in scientific endeavor enhances capacity to register biodiversity. We report two Vanilla species in the under-explored region of the Serranía de las Quinchas in the mid–Magdalena River valley in Colombia, including the first report for Colombia of Vanilla karen-christianae. For this, and the second species, Vanilla dressleri, we present descriptions with photographic botanical illustrations, updated distribution maps, and preliminary conservation status assessment. Both species are of elevated conservation concern, categorized as Endangered – EN: B2a,b(ii,iii,iv,v) following IUCN criteria. Within Colombia, all recorded occurrences for both species fall outside protected areas. Vanilla crop wild relatives in Colombia have urgent conservation needs. The Serranía de las Quinchas is a priority for further botanical exploration for Vanilla, as well as other protected areas with appropriate habitat. In situ conservation should be complemented with ex situ actions. Community participation in biodiversity research is recommended in this and other remote regions as an integral step towards enhancing biodiversity research and community-based conservation.

A NEW PREY ITEM FOR THE COLOMBIAN RAINBOW BOA, Epicrates maurus (GRAY, 1849) (SQUAMATA, SERPENTES, BOIDAE): THE SHORT-TAILED CANE MOUSE Zygodontomys brevicauda (J. A. ALLEN & F. M. CHAPMAN, 1893)

During field surveys conducted in 2021 in the Middle Magdalena River Valley, Colombia, we recorded a new dietary item for the snake Epicrates maurus, consisting of the rodent species Zygodontomys brevicauda. When photographed, the snake regurgitated the partially digested mouse, which was identified from its dental and cranial characters. The present record contributes to the knowledge about the dietary spectrum of E. maurus in northern South America.

Mixing mechanisms at the strongly-stratified Magdalena River's estuary and plume

This study analyzed the hydrodynamic structure of the estuary and plume of a large, tropical, and strongly-stratified river, the Magdalena. The Magdalena River is the largest source of fresh water and sediment of the Caribbean Sea and drastically impacts the morphodynamics and ecosystems along the Colombian coast. The analyses are based on the results of a calibrated and validated numerical model. Three scenarios of low, mid, and high freshwater discharge were analyzed to consider the seasonal variability of the mixing processes. The relative importance of three mixing mechanisms in the system is investigated, and the estuary and plume are subdivided into sectors depending on the dominant hydrodynamic processes at each sector. The results show that mixing in this system is mainly controlled by turbulence at the pycnocline, especially at the lift-off point in the transition between the estuary and the plume's near-field. A hydraulic jump occurs in the transition between the near- and mid-fields of the plume, but the mixing produced here is comparatively low since the plume has been mostly diluted already in the estuary and the near-field. During low and mid discharge scenarios, saline intrusion in the river channel forms a strongly stratified estuary where bottom propagated turbulence generates instabilities producing minor mixing. Meanwhile, the saltwater is flushed out of the river during the high discharge scenario, and pycnocline instabilities produce mixing at least one order of magnitude larger than during low discharge conditions. Coriolis acceleration does not seem to be a relevant driver of the plume behavior, despite the larger extension of the plume during high discharges, given the low latitude of the system.

Feeding strategy of fish that colonize reservoirs in the Magdalena river basin

Construction of dams for hydropower in Andean rivers of Colombia is increasing loss of species of the region. Fish species that persist in these artificial ecosystems are those which find favorable the new conditions for their recruitment. Because feeding is one of the fish life strategies that influence their persistence in reservoirs, we analyzed the stomach contents of the species present in two cascade reservoirs in the Magdalena river basin. The objectives were to describe the diet, to determine their feeding strategies and to evaluate if the rainy season or spatial distribution affects the diet of the fish species. Our results indicate that the fish species Brycon henni and Astyanax microlepis that feed on a wide range of resources that the system offers and adopt a generalist strategy. Also, opportunistic species such as Roeboides dayi and Hoplosternum magdalenae occupied these environments. Climatic seasonality does not influence the feeding habits of the fish species inhabiting the study reservoirs. Knowledge of the feeding habits of fish species is a priority for strengthening the environmental management of aquatic resources of the Andes.

Fine scale population structure of Acropora palmata and Acropora cervicornis in the Colombian Caribbean.

Using a standardized SNP array, we identified two populations of Acropora cervicornis and one population of A. palmata in the Caribbean coast of Colombia. San Andrés was the most genetically differentiated location for both species. An average pairwise FST value of 0.131 and 0.050 between San Andrés and neighboring collection sites was estimated, for A. cervicornis and A. palmata, respectively. Based on population patterns of both acroporid species, we inferred that Magdalena River is not a barrier of genetic connectivity among Colombian populations. Genetic comparisons between the Colombian coast of Caribbean with other Caribbean locations agree with previous studies for both species, where four populations were identified in A. cervicornis and three in A. palmata. Our results support published bio-physical model predictions and highlight the Panama-Colombia gyre as a possible isolating mechanism within the western Caribbean. However, the genetic diversity in both species was about half (mean HE per site = 0.321 in A. palmata and 0.369 in A. cervicornis) than previous estimates in acroporid populations in the Caribbean. The lower genetic diversity as well their relative isolation and high levels of reef degradation may be of particular conservation concern that may require species-specific management coupled with science-based restoration efforts.

Contribution to the knowledge of non-native fishes in reservoirs in the Magdalena River basin: the study case Piedras blancas reservoir

ABSTRACT The habitat fragmentation caused by reservoir construction in different aquatic systems in the Magdalena River basin is a latent threat to the diversity of fishes and aquatic environments in the Andean region of Colombia. Contributing to the knowledge about how fish assemblages are formed in these scenarios is fundamental for the management and decision-making on the aquatic resources of the basin. In this communication, we describe the results of a fish characterization in the area of influence of the Piedras Blancas reservoir, a high Andean reservoir built for hydroelectric power generation. Only three species of fish that make up the evaluated assemblage were captured, and two of them, Cyprinus carpio and Xiphophorus maculatus, are not native to the basin. Possibly, with a greater sampling effort, more species can be found. The native species Hemibrycon sp. is distributed mainly in a creek, while in the reservoir, the introduced species dominate. The environmental variables were in optimal ranges for the development of life in the evaluated environments. It is important to advance the knowledge about the distribution of the introduced and native species in the basin to generate recommendations that contribute to the management of these species in the aquatic systems of Colombian Andes.