Low Current Velocity Research Articles

Design and tests of a marine current turbine in low flow velocity

Marine current energy is recognized a promising energy source due to its inherent stability and high predictability. In the past decade, several milestones have been achieved in marine current turbine (MCT) research such as MeyGen and O2. However, compared with high-velocity currents, low velocity currents are more commonly distributed worldwide, which presents new challenges. The demand for low starting velocity and high efficiency necessitates some novel structure in the design of blade, power transmission, etc. To address these issues, taking a 50W MCT as research object, this paper firstly presents the MCT design of a new fan-shaped rotor configuration, a compact non-contact magnetic coupling, a low inertial power train and hollow-cup DC generator for easier starting. Furthermore, to realize the maximum power point tracking (MPPT) and sustainable power supply, the electrical system and its control strategy were designed. The hydrodynamic performance of the fan-shaped rotor was simulated and analyzed using CFD, and a simulation model of the electrical and control systems was constructed and tested to verify the performance. Finally, the tank and sea tests were respectively conducted to validate the performance of proposed MCT. The results indicate that the proposed MCT is capable of starting at velocities around 0.2 m/s and achieving a power coefficient (Cp) exceeding 0.4, making it well-suited for providing a continuous and stable power supply in areas with low flow velocities.

Mass occurrence of planktic dendroid graptolite synrhabdosomes (Calyxdendrum) from the Early Ordovician Fezouata biota of Morocco

The genus Calyxdendrum is here revised to include planktic dendroid graptolites from the Ordovician (Tremadocian to Sandbian). The mass occurrence of Calyxdendrum amicabilis n. sp. from the Fezouata biota represents one of the few occurrences of synrhabdosomes of dendroid morphology that have ever been discovered. Composite structures, formed from about four to six slender, conical tubaria of the species appear as umbrella-shaped synrhabdosomes. In these, the individual tubaria are connected by their short nemata forming an irregularly shaped proximal membrane. The species is found in the late Tremadocian Sagenograptus murrayi Biozone of the Bou Izargane section in the Ternata plain north of Zagora, Morocco. The mass occurrence is interpreted to represent planktic dendroid colonies transported by low velocity currents or moving actively into different water regions on a wide shallow shelf region. They settled in the “soupy” soft sediment, where they were subsequently compacted in the now lithified mudstone. Planktic dendroids of the genus Calyxdendrum are so far known exclusively from the peri-Gondwana region, but may prove to show a wider biogeographical distribution when better known.

Experimental Study on the Effect of Single Flow Disturber on the Performance of the Straight-Bladed Hydrokinetic Turbine at Low Current Speed

Indonesian Marine Energy Association 2014 provided the results of ratifying the potential of ocean current energy in Indonesia of 17,989 MW. The amount is quite large for the results of several potential points in the territory of Indonesia. However, the potential of ocean currents in Indonesia has not been utilized optimally, even though the current turbine technology is developing rapidly in the world. The existing turbine technology that is already available worldwide cannot be applied directly in Indonesia. This is because the water condition in Indonesia is classified as low-speed current, unlike some countries in the world which are classified as high-speed current. Therefore, a turbine that can work in the condition of the territorial waters in Indonesia, in general, with a low current speed is needed. The turbine technology used in this study consists of turbine A (without a flow disturber) and turbine B (with a single flow disturber). The purpose of this study was to determine the increase in turbine performance at low current speeds. The method used in this study was an in-situ experiment because it was closer to the actual conditions. The results obtained from this study indicated that the addition of a single flow disturber could increase turbine performance at all variations of current speed, namely 0.4, 0.88, and 1 m/s. The most exciting result was that under the low current speed of 0.4 m/s, adding a single flow disturber could increase the ability to self-start from 0 rpm to 7.180 rpm and efficiency from 0 to 4%. In addition, at a current speed of 0.88 m/s with the addition of a single flow disturber, it could increase efficiency from 10.8% to 11.1%. At a current speed of 1 m/s with the addition of a single flow disturber, it could increase efficiency from 16.6% to 18%. That is, turbine B (with a single flow disturber) is very suitable to be applied in the territorial waters of Indonesia, which tend to have low current velocity.

A hydrothermal plume on the Southwest Indian Ridge revealed by a multi-proxy approach: Impact on iron and manganese distributions (GEOTRACES GS02)

Iron (Fe) and manganese (Mn) are crucial micronutrients that limit oceanic primary productivity in the Southern Ocean. It has been recently suggested that hydrothermal activity may be an important source of oceanic dissolved iron, yet, this contribution is still not fully understood and only one active hydrothermal site has been reported on the Southwest Indian Ridge (SWIR), south of 40°S.Using a multi-proxy approach, this study demonstrates the occurrence of hydrothermal venting on the SWIR in the near vicinity of the location 44°51.690 S, 36°10.460 E, which is likely to be a low or moderately high temperature fluid. Indeed, we report high values of dissolved methane to manganese ratios (up to 11.1 ± 1.2 mol mol−1), low particulate iron (pFe) and manganese (pMn) concentrations (with maximum values of 0.7 nmol L−1 and 0.06 nmol L−1, respectively) associated with the presence of few oxyhydroxides, as well as high 223Radium (Ra) and 224Ra activities near the seafloor. The Fe and Mn data revealed a significant enrichment at depths influenced by hydrothermal circulation on the seafloor, within the Upper Circumpolar Deep Water. Dissolved Fe (dFe) and dissolved Mn (dMn) concentrations were enriched by 3- and 7-fold, respectively, and pFe and pMn by 2- and 1.5-fold, respectively, compared to a reference station located outside the SWIR. They were however lower than concentrations reported so far near high temperature vents, suggesting a weaker influence of this hydrothermal system on deep Fe and Mn reservoirs. We show that a large fraction of the dFe could be stabilized by organic complexation with humic substances (eHS, estimated 27–60% of dFe). High prokaryotic abundance related to the proximity of the hydrothermal vent suggests that other Fe-complexing ligands of biological origin might also stabilize Fe in its dissolved form. Collectively, these measurements integrated within the concept of a “multi-proxy approach”, helped painting a more detailed picture of the complex interactions and processes in this region of the SWIR. Although the system is a source of both dFe and dMn to the deep ocean, the low current velocities and the bathymetry likely limit the fertilization of surface water by dFe and dMn along this section of the SWIR.

Coupling Effects of a Top-Hinged Buoyancy Can on the Vortex-Induced Vibration of a Riser Model in Currents and Waves

In order to investigate the effects of the top-end dynamic boundary of risers caused by floater motions on their vortex-induced vibration (VIV) characteristics, a combined model comprising a buoyancy can with a relatively simple structural form and a riser is taken as the research object in the present study. The aspect ratios of the buoyancy can and the riser model are 5.37 and 250, respectively. A set of experimental devices is designed to support the VIV test of the riser with a dynamic boundary stimulating the vortex-induced motion (VIM) of the buoyancy can under different uniform flow and regular wave conditions. Several data processing methods are applied in the model test, i.e., mode superposition, Euler angle conversion, band pass filter, fast Fourier transform, and wavelet transform. Based on the testing results, the effect of low-frequency VIM on the high-frequency VIV of the riser is discussed in relation to a single current, a single wave, and a combined wave and current. It is found that the coupling effect of VIM on the riser VIV presents certain orthogonal features at low current velocities. The effect of the cross-flow VIM component on VIV is far more prominent than that of its counterpart, the in-line VIM, with increasing flow velocity. The VIM in the combined wave–current condition significantly enhances the modulation of vibration amplitude and frequency, resulting in larger fluctuation peaks of vibration response and further increasing the risk of VIV fatigue.

Exploring invasiveness and versatility of used microhabitats of the globally invasive Gambusia holbrooki

Non-native species can lead to severe impacts on invaded ecosystems, including the decline of ecosystem function through deleterious impacts on species diversity. The successful establishment of non-native species in new environments is the first barrier a species must overcome, ultimately depending on its ability to either cope with or adapt to local site-specific conditions. Despite the widespread distribution and ecological consequences of many freshwater invaders, site-specific and climatic preferences are often unknown. This is also the case of the Eastern mosquitofish Gambusia holbrooki, a global invader considered as a pervasive threat to endemic species. Here, we determined the ecological features and preferred site-specific conditions of G. holbrooki in Türkiye, which spans a wide range of diverse biogeographically distinct ecosystems by surveying populations from 130 localities in 2016 and 2017. Gambusia holbrooki were detected by hand-net in 48 of these sites (19 lotic, 29 lentic). It showed a preference for shallow waters with medium sized rocks, and abundances differed spatially across a latitudinal gradient and was influenced predominantly by variations in pH. The only other factors predicting its presence were low current velocities and gravel substrate, highlighting its ecological versatility in utilising a wide range of microhabitats. Bioclimatic models suggest that G. holbrooki is found in areas with a wide average annual temperature ranging from 10 to 20 °C, but with temperature not being a limiting factor to its invasion. Gambusia holbrooki shows a preference for xeric freshwater ecosystems and endorheic basins, as well as temperate coastal rivers, temperate upland rivers, temperate floodplain rivers and wetlands, and tropical and subtropical coastal rivers. These results, particularly the wide occurrence with only few limiting factors, emphasise the invasion potential of mosquitofish and should substantiate the need for localised invasive species management and conservation efforts, particularly in smaller or insular areas where mosquitofish and endemic fish species co-exist.

Design and control of a parallel-axis twin-rotor counter-rotating marine current turbine for the shallow sea conditions

The ocean contains a large amount of marine current energy which is considered to be one of the most promising renewable energy sources for commercialization. In contrast to the high-velocity currents in straits close to the mainland or islands, the velocities of the currents in most of the sea are low. The exploitation of low-velocity currents is of great significance to the regions with such energy sources. Although the technology for harvesting marine current energy is developing rapidly, the exploitation of low-velocity current energy is often neglected due to its low power density. When the existing marine current turbine (MCT) technology developed for high-velocity currents is used for low-velocity currents, it will result in large rotor diameters and low performance of starting current velocities, which is subject to the water depth and the levelized cost of energy. To solve those problems, a direct-drive parallel-axis twin-rotor marine current turbine (TRMCT) was developed in this research, with a focus on the design of the transmission and generator of the MCT, as well as the improvement of the control strategy. Firstly, the structure of the TRMCT and its characteristics were given. Secondly, the improved optimal torque control strategies for the TRMCT were designed. Finally, to verify the feasibility of the TRMCT and its control strategy, the mathematical model was built and simulated, and the starting performance and operating performance were analyzed. The results show that the proposed TRMCT can start to work at about 0.2 m/s and the conversion efficiency of the whole system can reach about 25%. Compared to the scheme using two identical single-rotor MCTs, the TRMCT's output power can increase by up to 26%. Besides, the torque imbalance caused by the difference in the current velocities on the two rotors can be well coped with.

Vertical sediment distribution mechanism in tidal flats -A case study in Zhoushan Archipelago

Tidal flats connect terrestrial and oceanic environments, and play an important role in the evolution of coastal ecosystems and geomorphology. Taking tidal flat on Zhairuoshan Island (ZRS) as an example, we studied the dynamic characteristics of suspended sediment concentration (SSC), sediment resuspension, and transportation in tidal flats. The field data of the waves, currents, and sediments were obtained from the tidal flat on the east of ZRS Island. The results show that current-induced bed shear stress is dominant. Under the combined action of waves, tides, and currents, SSC has two main periods (12.2 h, 6.2 h, 60−80%) and three minor periods (23.5 h, 8.2 h, and 5.1 h, 20−40%). Advection transport is dominant, at approximately 2–3 times the sediment resuspension, and the net sediment flux is onshore. Turbulent intermittent events play an important role in sediment resuspension, and their probability is affected by velocity. The vertical instantaneous transport of sediment depends on wave height. The vertical profile of SSC shows that, at high current velocity, the sedimentation formula that considers flocculation better fits the vertical profile of suspended sediment using the Rouse formula. The settling velocity of a single particle fits better at low current velocities, indicating that the flocculation of sediment is weak at low velocities. This study improves our understanding on near-bottom sediment characteristics and controlling mechanism in tidal flat in muddy coasts.

Analysis of the German tidal energy resource


 
 
 A transformation of the energy sector towards a low-emission power generation is needed to mitigate global warming and fight the current climate crisis. In recent years, tidal energy technology has matured and shows potential to balance Europe’s future power grid. While reviews of the tidal energy resource exist for a number of European countries, the potential of tidal energy along the German North Sea coast is overlooked so far. This review closes this gap and provides a first analysis of the German tidal energy resource. Germany’s North Sea coast is characterised by comparatively low current velocities and shallow waters. Using available data from the EasyGSH-DB North Sea Model, Germany’s practical tidal energy resource is estimated at 66.6 GWHy−1, under strong restrictions, excluding the most energetic sites in the estuaries of Elbe, Weser, and Ems. Based on the results, future work for a more detailed analysis is suggested.
 
 

Low-flow ocean current turbine diffuser shroud concentrated and accelerated flow technical research

Ocean current energy is the kinetic energy of seawater flow and is a low-cost, low-carbon, clean, and renewable energy source. Ocean current energy is mainly captured by the Ocean Current Turbine (OCT). However, as the depth of the water increases, the flow rate of the water decreases significantly. The main purpose of this paper is to study the low efficiency of current turbine capture due to low current velocities, with the main objective of achieving the effect of gathering and increasing the speed of low current energy. Firstly, this paper investigates the mechanism and mathematical model of the concentrated and accelerated flow of the diffuser shroud. Secondly, the velocity and pressure flow fields of the basic diffuser shroud are simulated and analyzed under different low flow velocity conditions (flow velocity below 1.0 m/s), different aspect ratios, and different diffusion opening angles. This paper further investigates the effect of speed increase for four different airfoil sections of diffuser shroud. Finally, measurements and verification are carried out with Particle Image Velocimetry (PIV) circular water hole experiments. The experimental results demonstrate the concentrated and accelerated results of the diffuser shroud. The basic diffuser shroud has a 39% increase in flow field velocity. The airfoil section diffuser shroud has a better velocity increase on the flow field than the basic diffuser shroud. The flow field flow rate increased to 58%. The optimum location for the speed increase is near the inlet and less than 0.5 times the inlet diameter. Compared to the simulation results, the experimental results of the PIV circulating water hole show an average error of less than 4%. The results of this paper provide a research basis for the efficient capture of current energy in deep-sea low-flow waters and a theoretical basis for the design of low-flow current energy turbines.

Environmental Parameters And Phytoplankton Community Quality: Implications For Food Safety In Coastal Communities

This study aimed to evaluate environmental parameters and phytoplankton quality as well as the implications for the food safety of seafood-consuming coastal communities. The study was conducted in coastal waters of South Sulawesi, Indonesia at four sites (three stations/site): Pangkep (PK), Kuri (KR), Maros (MR), and Tallo (TL) during June, August, and October 2020. Observations formed three spatial clusters: MR1, PK; MR2, MR3, TL; KR (92.5 % similarity), and two temporal clusters: June 2020; August and October 2020 (87.9 % similarity). PCA showed parameters most strongly characterizing TL, KR, and MR (except MR1) were high levels of salinity, nitrate, nitrite, ammonium, silicate, temperature, pH, and abundance of both phytoplankton that can form harmful algal blooms (HABs) and non-HAB forming phytoplankton (non-HABs), with low current velocity. PK was characterized by high current velocity, non-HABs, orthophosphate, ammonium, nitrite, and turbidity with low nitrate and HABs. Main characterizing parameters in the temporal PCA were high current velocity and HABs with low orthophosphate in June 2020; high nitrate, ammonium, orthophosphate, and non-HABs with even lower HABs in August 2020; high turbidity, temperature, and salinity with low pH, nitrite, silicate, and HABs in October 2020. Current velocity (low at TL, KR, MR and high at PK) influenced both non-HABs and HABs. The results indicate that faster currents may have impeded HABs development so that the phytoplankton quality was still good. Therefore, the fish from these waters can be considered safe for human consumption, thereby contributing to maintaining the health of coastal communities.

Numerical study on residual rate of fluidized solidified slurry in pumping for scour repair around monopile

A new scour countermeasure for monopile foundation using solidified slurry have been proposed recently. The fluidized solidified slurry is pumped to the seabed area around pile for scour protection or into the developed scour holes for scour repair as the fluidized material solidifies gradually. During this complex process with pumping and solidification, the flow and diffusion of solidified slurry can result in the material loss and deterioration. However, there is still not a comprehensive and reasonable analysis on the state of retention of the fluidized solidified slurry in this process. Thus, the effect of scour protection can't be evaluated effectively. The current work focuses on the residual rate of fluidized solidified slurry during the pumping operation, which is the ratio between volume of the solidified slurry remaining in the scour pit and that pumped into. A series of multiphase flow (the ambient seawater and the solidified slurry) numerical simulations using a computational fluid dynamics (CFD) approach were conducted to investigate the effects of pumping location, current velocity, pumping velocity and material property of solidified slurry on the residual rate of fluidized solidified slurry. It was found that the pumping location near and at the downstream of the monopile with a lower pumping pipe nozzle is optimal for a higher residual rate of fluidized solidified slurry. Solidified slurry with smaller slump flow value pumped at a lower current velocity and higher pumping velocity contributes to a higher residual rate. Based on a comprehensive parametric study, an empirical formula is established to calculate the final residual rate of the solidified slurry for theoretical reference and practical application. This work provides an important insight in understanding the residual rate of solidified slurry in application to scour protection of monopile.

Hybridized Vertical-Axis Underwater Current Power Turbine System Suitable for Low Underwater Current Velocities: A Report of Its Application and Potential in Imo River, Nigeria

Abstract A novel vertical axis underwater current power dual turbine that extracts power from flowing water bodies of low velocities (0.5 m/s or less) is presented. It has now a further innovation of a dual turbine and hybrid system that provides a solar panel roof over the underwater current power turbine (UCPT) platform to enable the system to extract power from both solar and underwater current. The hull of the UCPT was built using Glass-Fiber Reinforced (GFR) instead of steel material. The use of GFR reduced the hull's weight by 50% compared to the steel made. The installation of the UCPT in Imo River in Nigeria demonstrated that the UCPT has 99% efficiency in converting the water flow hydraulic power to mechanical power. The model was scaled to a product of 5.7 kW underwater power generating platform that provides addition integrate-able solar power of 25kW capacity. It is further demonstrated that satellite model development of the UCPT can be made to generate 150 kW and more depending on the number of the installed UCPT.

The Benefit Using a Circular Flow Disturbance on the Darrieus Turbine Performance

Darrieus is a vertical-axis type turbine with difficulty rotating at low current velocity. Adding a circular flow disturbance in front of the Darrieus turbine can improve the self-start capability. This study has aimed to improve the turbine's performance by identifying the configuration and diameter ratio of flow disturbance. Numerical modelling in transient conditions has been done by using Computational Fluid Dynamics (CFD) software with a sliding mesh technique. There are four diameter ratios ds/D 0.1, 0.3, 0.5, and 0.7 and three variations of cylinder position. Each combination variation has been simulated at current velocity of 0.3, 0.4, 0.5, and 0.6 m/s. As a result, depending on where the cylinder installation is located, the circular flow disturbance has an effect that might hinder or enhance the performance of the turbine. The best result is at the flow disturbance position of -60o with a diameter ratio of ds/D 0.5 at TSR 1.43. The maximum coefficient of power (Cp) value has increased by 38%. Furthermore, at overall current velocities with a range of 0.3–0.6 m/s, the average Cp has increased of 30% with the best diameter ratio usage of ds/D 0.5.

Trait–environment relationships of hydroids (Cnidaria: Hydrozoa) across large spatial and environmental gradients in the Atlantic Ocean

AbstractAimThe aim was to test trait–environment relationships in hydroids across large spatial and environmental gradients and to evaluate associations between traits, environmental variables, space and phylogeny.LocationAtlantic Ocean and adjacent polar seas.Time periodPresent day.Major taxa studiedHydrozoa.MethodsTrait–environment relationships and their spatial and phylogenetic contexts were assessed in hydroids by using a combination of a fourth‐corner test and extended‐RLQ approach, in a multivariate ordination method that uses five matrices: (1) species across sites, (2) environmental data across sites, (3) traits across species, (4) latitude and longitude for each site, and (5) phylogenetic distance among species. We based our analyses on 3680 records of 431 species distributed at 1440 sites, 16 species traits, nine environmental variables and a phylogenetic tree of the studied species.ResultsHydroid traits are significantly correlated with environmental variables and geographical space, and hydroid phylogeny is correlated with the environment and geographical space. More evidently, we observed an increased presence of larger species (taller, more branched, with greater base diameter and polysiphonic) at sites richer in nitrate and silicate, with higher dissolved oxygen, lower temperatures, lower salinities and lower current velocities. The observation of phylogenetically related species with similar traits and distributions corroborates that historical processes interact with the environment in determining community assembly and explaining patterns of distribution of species traits.Main conclusionsSeveral environmental variables combined affect the distribution of hydroid traits, which are also influenced by spatial and historical factors. In the first analysis of its kind for hydrozoans, we have provided an overview of how hydroids are distributed across environments according to their traits and revealed the spatial and phylogenetic components of these trait–environment relationships.

Experimental and multiphase modeling of small vertical-axis hydrokinetic turbine with free-surface variations

Vertical-axis hydrokinetic turbines are promising option to harness the low velocity currents. However, limited investigations have been carried out considering the interactions between the turbine rotor and the channel section, including the free-surface. Thus, a vertical-axis turbine model has been designed and manufactured, to be tested in an open channel. Also, a three-dimensional multiphase simulation has been carried out, using the volume of fluid (VOF) model, to capture the air–water interface and to investigate the free-surface variations effects on the turbine output. Experimentally, the turbine model has been characterized under different flow conditions and free-surface levels. The peak power coefficients are found to increase with the upstream velocity. This effect is directly linked to the blockage ratio and the Froude number. A reasonably good match has been found between the experimental and the numerical results. The VOF model is able to simulate the free-surface longitudinal variations, and the effect of the turbine blockage of the channel. The velocity field and the pressure coefficient distribution, around the turbine rotor, have been studied and correlated with the free-surface variations from upstream to downstream of the turbine. Finally, the vortex street generated by the blade–plate interaction has been analyzed.

Prototyping of a tethered undersea kite to harvest energy from low velocity currents

The global energy consumption has been on the rise since the last industrial revolution and continues to be. So far the demand could be satisfied by a mixture of conventional and renewable energies. With the global effort to eliminate conventional energies to stop the anthropological climate change, the demand for reliable and predictable renewable energies is growing. Under these circumstances, more attention is drawn towards the development of non-intermittent ocean energy systems. Apart from waves, thermal and salinity gradients, currents are an abundant and reliable ocean energy source. Inspired by state-of-the-art technology, a unique system for current energy, the Current Kite, is presented in the following paper. This tethered undersea kite (TUSK) consist of a wing to which a turbine is attached. The wing drags the turbine through the water in a certain trajectory, sweeping a large area at a relative speed that is several times the actual speed of the underwater current. In the following paper we present the general setup and design of our first and second prototype. The first prototype was build as a prove of concept. It was equipped with active steering and several on board sensors. With the second prototype the aim was to build a more sophisticated system, which would make the active steering redundant and use more efficient, circular flight paths. A wing which would adjust itself in the current and follow the predefined circular path, was designed using numerical simulations. To achieve this circular flight movement without twisting the electrical cable, a swivel and a stress reducer were designed and built to connect the TUSK as well as transfer electrical power to land. In addition the tracking-system was redesigned, communicating by modulation over the power line. This provides a fully autonomous ocean current power plant, which communicates in real time data and has a promising outlook in efficiency, regarding to the state of art. Due to Covid-19 regulations it was not possible to test the prototype. Therefore the paper mainly focuses on the design and construction process, up to the production of the TUSK.

Numerical simulation of cross-flow Savonius turbine for locations with low current velocity in Indonesia

Numerical simulation of cross-flow Savonius turbine for locations with low current velocity in Indonesia

IN-SITU EXPERIMENT OF CROSS-FLOW SAVONIUS HYDROKINETIC TURBINE WITH A DEFLECTOR

The crossflow type Savonius turbine is capable to rotate at low current velocity conditions. The drawback of this turbine lies on its efficiency. This study aims to test its performance before implementation in the field. The research method used is an in-situ experimental study in Umbulan, Pasuruan. Turbine model T1 AR 1.145 without deflector is used, when TSR reaches a value of 0.824, it gets a CQ value of 0.327 and a CP value of 0.269. In the same model with deflector, when TSR reaches a value of 1.1, the CQ value is 0.251, and the CP value is 0.276. It can be concluded that this turbine is suitable for area with low current velocity.

English

The current anarchic exploitation of Marcusenius fish in the Malebo Pool located in the Congo River stands as a threat of extinction to certain species, while the ecology of most of them are hardly known. This study aims at evaluating the impact of environmental factors on the distribution of Marcusenius fish caught in six fishing stations in the Malebo Pool. Canonical correspondence analysis of environmental factors classified the stations into two groups, which differ in vegetation formation, bottom substrates, water current velocity, pH, suspended particles and in dissolved oxygen. Thus, the five stations located upstream and in the middle of the pool are characterized by low water current velocity, slightly acidic pH, bottom substrates composed of silt, plant debris, clay, silt and sand. The predominant Echinocloa and Eichhornia plant formations found in these sites provide shelter, food sources and impact on the distribution and abundance of seven Marcusenius species in Malebo pool. The rocky substrate of Kinsuka station associated with the plant formation dominated by Ledermanniella and Pennisetum, and a high-water current constitute a habitat that is not favourable for Marcusenius species.   Key words: Abundance, ecology, flora, Marcusenius, fishing, substrate, Malebo Pool.