Riverine Habitats Research Articles

Integrating Large Wood Jams into Hydraulic Models: Evaluating a Porous Plate Modeling Method

AbstractLarge wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two‐dimensional hydraulic modeling of porous LW jams using the open‐source modeling software Delft3D‐FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer‐generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error‐prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.

Extreme temperature combined with hypoxia, affects swimming performance in brown trout (Salmo trutta).

Climate change is predicted to impact freshwater aquatic environments through changes to water temperature (Twater), river flow and eutrophication. Riverine habitats contain many economically and ecologically important fishes. One such group is the migratory salmonids, which are sensitive to warm Twater and low O2 (hypoxia). While several studies have investigated the independent effects of Twater and hypoxia on fish physiology, the combined effects of these stressors is less well known. Furthermore, no study has investigated the effects of Twater and O2 saturation levels within the range currently experienced by a salmonid species. Thus, the aim of this study was to investigate the simultaneous effects of Twater and O2 saturation level on the energetics and kinematics of steady-state swimming in brown trout, Salmo trutta. No effect of O2 saturation level (70 and 100% air saturation) on tail-beat kinematics was detected. Conversely, Twater (10, 14, 18 and 22°C) did affect tail-beat kinematics, but a trade-off between frequency (ftail) and amplitude (A, maximum tail excursion) maintained the Strouhal number (St = ftail• A/U, where U is swimming speed) within the theoretically most mechanically efficient range. Swimming oxygen consumption rate (n}{}{dot{M}}_{{mathsf{O}}_{mathsf{2}}}) and cost of transport increased with both U and Twater. The only effect of O2 saturation level was observed at the highest Twater (22°C) and fastest swimming speed (two speeds were used—0.6 and 0.8 m s−1). As the extremes of this study are consistent with current summer conditions in parts of UK waterways, our findings may indicate that S. trutta will be negatively impacted by the increased Twater and reduced O2 levels likely presented by anthropogenic climate change.

A compendium of ecological knowledge for restoration of freshwater fishes in Australia

Many freshwater fishes are imperilled globally, and there is a need for easily accessible, contemporary ecological knowledge to guide management. This compendium contains knowledge collated from over 600 publications and 27 expert workshops to support the restoration of 9 priority native freshwater fish species, representative of the range of life-history strategies and values in south-eastern Australia’s Murray–Darling Basin. To help prioritise future research investment and restoration actions, ecological knowledge and threats were assessed for each species and life stage. There is considerable new knowledge (80% of publications used were from the past 20 years), but this varied among species and life stages, with most known about adults, then egg, juvenile and larval stages (in that order). The biggest knowledge gaps concerned early life stage requirements, survival, recruitment, growth rates, condition and movements. Key threats include reduced longitudinal and lateral connectivity, altered flows, loss of refugia, reductions in both flowing (lotic) and slackwater riverine habitats, degradation of wetland habitats, alien species interactions and loss of aquatic vegetation. Examples and case studies illustrating the application of this knowledge to underpin effective restoration management are provided. This extensive ecological evidence base for multiple species is presented in a tabular format to assist a range of readers.

Compromised thermal tolerance of cardiovascular capacity in upstream migrating Arctic char and brown trout-are hot summers threatening migrating salmonids?

Heat waves are threatening fish around the world, leading sometimes to mass mortality events. One crucial function of fish failing in high temperatures is oxygen delivery capacity, i.e. cardiovascular function. For anadromous salmonids, increased temperature could be especially detrimental during upstream migration since they need efficiently working oxygen delivery system in order to cross the river rapids to reach upstream areas. The migration also occurs during summer and early autumn exposing salmonids to peak water temperatures, and in shallow rivers there is little availability for thermal refuges as compared to thermally stratified coastal and lake habitats. In order to shed light on the mechanisms underpinning the capacity of migrating fish to face high environmental temperatures, we applied a physiological and molecular approach measuring cardiovascular capacities of migrating and resident Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in Northern Norway. The maximum cardiovascular capacity of migrating fish was significantly lower compared to the resident conspecifics. The onset of cardiac impairment started only 2°C higher than river temperature, meaning that even a small increase in water temperature may already compromise cardiac function. The migrating fish were also under significant cellular stress, expressing increased level of cardiac heat shock proteins. We consider these findings highly valuable when addressing climate change effect on migrating fish and encourage taking action in riverine habitat conservation policies. The significant differences in upper thermal tolerance of resident and migrating fish could also lead changes in population dynamics, which should be taken into account in future conservation plans.

The “Habitat Provision” Index for Assessing Floodplain Biodiversity and Restoration Potential as an Ecosystem Service—Method and Application

River floodplains provide a large number of ecosystem services (ESSs) for human societies. However, human manipulations of rivers and floodplains have led to the loss of many ESSs, including the provision of habitats for typical floodplain flora and fauna. To quantify such losses, we present a new index, which incorporates the functional and structural quality of riverine and alluvial habitats and their communities. The assessment is based on publicly available biotic and abiotic data at a local scale (e.g., type mapping, species data). The new evaluation method consists of three steps: First, an evaluation at type level is done by using well-established assessment criteria (e.g., groundwater dependence, legal protection status, regenerability). Secondly, the individual habitats are assessed based on specific quality characteristics (e.g., presence of protected birds or backwater influence). Finally, these values are aggregated within 1-km floodplain compartments weighted by their spatial expansion. The uses a five-step value to describe the importance of a floodplain area for typical species and habitats from very high (=5) to very low (=1). The aim of this habitat provision index is to provide a tool for planners and decision makers to compare and analyze the effects of past or future measures. The methodical approach is tested for two rivers: the Nahe and the Rhine. The performance of the is analyzed by comparing the current conditions (status quo) against two different scenarios. The is validated and shown to be sensitive to different water management scenarios (river restoration and technical polder scenario for flood risk enhancement), with both scenarios showing an improvement in the provision value.

Argulus from the Pascagoula River, MS, USA, with an Emphasis on Those of the Threatened Gulf Sturgeon, Acipenser oxyrinchus desotoi

Species of Argulus (Branchiura Thorell, 1864) are common ectoparasites of freshwater, estuarine, and marine fishes. Argulid identification and taxonomy is often confusing because many species are reported to parasitize multiple host species, have similar morphological characters, and come from various salinity regimes. Gulf sturgeon is an anadromous fish natal to drainages in the north-central Gulf of Mexico, and as with many endangered species, has a poorly documented parasite community. During Gulf sturgeon tagging and monitoring studies (2016–2019) in the Pascagoula River, MS, USA, species of Argulus were collected from Gulf sturgeon as well as other incidentally captured fishes. Argulus flavescens Wilson, 1916 was found on Gulf sturgeon and flathead catfish, Argulus americanus Wilson, 1902 on bowfin, and Argulus bicolor Bere, 1936 on Atlantic stingray. We provide morphological details and measurements for these species as well as the first confirmed 28S rDNA molecular data. Argulus flavescens was more abundant and prevalent on larger Gulf sturgeon and on sturgeon captured in freshwater rather than estuarine habitats. Our results indicate that A. flacescens may not tolerate estuarine salinities and that the anadromous life-history pattern of Gulf sturgeon could help rid them of A. flavescens when they emigrate from their riverine habitats.

Impact of cyclone Fani on the breeding success of sandbar-nesting birds along the Mahanadi River in Odisha, India

Cyclonic storms have detrimental effect on birds particularly those inhabit and breed in open and exposed areas like sea and riverine habitats. This note reports the effect of ‘Fani’, one of the severe cyclones that affected Odisha in May 2019 on sandbar- nesting birds along the Mahanadi River. The study found significant relative decline in population, complete failure of nests and survival of chicks. As tropical cyclones are expected to be more frequent in future, it may emerge as new threats for survival of sandbar-nesting birds.

Fine-scale population structure and ecotypes of anadromous Hilsa shad (Tenualosa ilisha) across complex aquatic ecosystems revealed by NextRAD genotyping

The anadromous Hilsa shad (Tenualosa ilisha) live in the Bay of Bengal and migrate to the estuaries and freshwater rivers for spawning and nursing of the juveniles. This has led to two pertinent questions: (i) do all Hilsa shad that migrate from marine to freshwater rivers come from the same population? and (ii) is there any relationship between adults and juveniles of a particular habitat? To address these questions, NextRAD sequencing was applied to genotype 31,276 single nucleotide polymorphism (SNP) loci for 180 individuals collected from six strategic locations of riverine, estuarine and marine habitats. FST OutFLANK approach identified 14,815 SNP loci as putatively neutral and 79 SNP loci as putatively adaptive. We observed that divergent local adaptations in differing environmental habitats have divided Hilsa shad into three genetically structured ecotypes: turbid freshwater (Western Riverine), clear freshwater (Eastern Riverine) and brackish-saline (Southern Estuarine-Marine). Our results also revealed that genes involved in neuronal activity may have facilitated the juveniles’ Hilsa shad in returning to their respective natal rivers for spawning. This study emphasized the application of fundamental population genomics information in strategizing conservation and management of anadromous fish such as Hilsa shad that intersect diverse ecotypes during their life-history stages.

Patterns of Species Richness and Abundance in Badingilo National Park in South Sudan

The study was carried out to determine patterns of birds’ species richness, alpha and beta diversities; and abundance in Badingilo national park using a 10 m fixed-radius point count method. A total of 2670 individuals were recorded from 182 points in the park. The highest expected number of species (Jack1 estimator) was observed in the Riverine habitat and least was in the Agriculture and Human settlement habitat type. The total number of species observed in the park was 63; however Jack1 estimator indicated that there were 68 species in the park. The majority of the birds observed during the study were resident species, few migratory and Palaearctic bird species. Few birds observed in the park were abundant. The most abundant species was the village weaver (381 individuals), and the rarest species were black-bellied bustard, barn owl, black scimitar bill and tree pipit (one individual each).

A Suitable Method for Assessing Invasibility of Habitats in the Ramsar Sites - an Example of the Southern Part of the Pannonian Plain

Considering the great importance of Ramsar Site for biodiversity, we measured the invasibility - the habitat characteristic that refers to the susceptibility to invasions, in six Ramsar Sites of the southern part of the Pannonian Plain. We selected 18 invasive neophytes of different life forms, due to their different habitat preferences, to cover as many habitat types as possible. We made 669 plots during the period 2011-2015, in which at least one target invasive taxa was present. We determined habitat types in each plot, using the EUNIS habitat classification. The invasibility of different habitats in Ramsar Sites was determined taking into account the coverage index (D%) of all selected invasive species. Our analyses showed that habitat invasibility was highest in different forest, and in riverine shrub habitats, while the smallest invasibility was registered in sedge and reed beds, without free-standing water. Previous research based on some other methods coincides with our results and supports the suitability of using the coverage index method when estimating the habitat’s invasibility. As wetlands are one of the most endangered ecosystems in the world, determination of habitat invasibility has great importance for management and should be one of the main preventive steps in their protection.

Report of five interesting avian species from Durgapur ecoregion, West Bengal, India by citizen science effort

This study aimed to report a few lesser known species from Durgapur ecoregion, West Bengal, India. In spite of the anthropogenic pressure, Durgapur supports a high avian diversity. So far, 257 avian species belonging to 59 families were recorded with a citizen science effort during a period of more than five years (2013–present). Out of these, five species discussed here, are either not recorded previously or have few records: Hume’s Lark and Graceful Prinia were recorded from riverine habitat; and Lesser Racket-tailed Drongo, White-rumped Shama, and Indian Blue-Robin were recorded from woodland habitat. More extensive exploration of this region with involvement of citizen scientists in this study will enrich our knowledge about bird diversity, their migration and distribution pattern in this region.

Changes to freshwater mussel assemblages after 25 years of impoundment and river habitat fragmentation

Abstract The Tennessee–Tombigbee Waterway is among the largest and most expensive environmental engineering projects of the 20th century. The waterway accommodates barge navigation between the Tennessee River Drainage and Mobile River Basin through a series of locks, dams, canals, and dredged and diverted streams. These structures have altered riverine habitat and fragmented lotic habitats resulting in isolated freshwater mussel populations in patches of streams such as the East Fork Tombigbee River, where 42 species were known historically. The first post‐waterway mussel surveys in 1987 and 1988 reported 31 taxa. During 2010 and 2011 surveys, 70 sites were sampled using both timed searches and quadrats and detected 29 extant mussel species. Between 1988 and 2010–2011 the relative abundance of nine mussel taxa decreased, whereas the abundance of 11 taxa increased. The populations of three federally listed species were detected at levels below the detection limits in 1988 as well as three non‐native unionids that appear to have colonized the East Fork Tombigbee River via the Tennessee–Tombigbee Waterway River. Although mussel abundance and total species richness were relatively unchanged, assemblage composition shifted toward animals typical of smaller streams rather than large rivers. This shift suggests that present‐day East Fork Tombigbee River habitats favour smaller‐bodied, thinner shelled taxa that are laterally compressed and lack shell sculpture. These taxa are likely to be better adapted to hydrologically and hydraulically variable habitats than are thick‐shelled, large bodied, and sculptured mussels. The results suggest that mussel assemblages are dynamic and may exhibit predictable responses to changes in hydrology, physical habitat conditions, and stream connectivity. However, examinations over broad (20+ yr) temporal scales are needed to observe these shifts. The data demonstrate the value of regular monitoring of diverse mussel assemblages and the importance of stream connectivity and flow modifications to this long‐lived group of benthic invertebrates.

Population Size and Habitat Utilization of Menelik’s Bushbuck (Tragelaphus scriptus Meneliki Neumann, 1902) in Abasheba-Demero Controlled Hunting Area, Southeastern Ethiopia

Background : Despite Ethiopia is among few African countries with high wild animal species diversity, its mammalian resource is highly degrading. Hence, assessing the demography and ecology of the wild animals is indispensable to provide information on the current status of animal, which helps for better wildlife conservation and management purpose. Thus, an investigation on the population size and habitat utilization of endemic Menelik’s bushbuck ( Tragelaphus scriptus Meneliki Neumann, 1902 ) in Abasheba-Demero controlled hunting area was done for one year during both dry and wet seasons of the year, 2019. Objective : The objective of investigation was to gather baseline data on population size, structure and habitat utilization of Menelik’s bushbuck in Abasheba- Demero CHA. Methodology : To reach the objective, quantitative data was collected using18 representative random sampling of line-transects covering sample area of 18km 2 . For field survey, the total area of the controlled hunting area was systematically clustered into four sample units based on the major habitats of the study area (Montane forest habitat, woodland, riverine and seasonal grass-wetland) habitat. Data Analysis : SPSS computer software version 20, descriptive statistics and chi-square test were used to analyze the data. Result : The projected population of Menelik’s bushbuck was 519.36±individuals. From the total population, Male bushbuck covered38.27%females were 50.62%and young’s were 11.1%. The sex ratio of male to female was found to be 1:1.32. Age structure was dominated by adults, which constituted 55.5% of the total population. Although, the bushbucks were evenly distributed in all the four habitat types in both seasons, its frequency was higher in the riverine forest habitat (3.33 individuals per km 2 ). The most commonly observed group types throughout the study period were single (solitary) bushbuck. Conclusion : Based on the current study result the population of Menelik’s bushbuck was not in immediate danger. However, negative attitude of local people towards the CHA and anthropogenic pressures are major underlying problem that needs appropriate correction measure. Keywords : Abasheba-Demero, Controlled hunting area, Menelik’s bushbuck DOI : 10.7176/ALST/76-03 Publication date :September 30 th 2019

Water velocity regulates macro‐consumer herbivory on the benthic macrophyte Podostemum ceratophyllum Michx.

Abstract Macrophytes influence aquatic ecosystems by increasing habitat complexity and providing trophic resources for aquatic fauna. While herbivory on freshwater macrophytes is widely documented in lakes and low‐velocity riverine habitats, the influence of herbivory on macrophytes in higher‐velocity habitats has rarely been examined. We investigated the hypothesis that water velocity can influence consumption rates of the submerged macrophyte, Podostemum ceratophyllum, an angiosperm that grows attached to stable substrates in high water velocity riverine habitats throughout eastern North America. Known macro‐consumers of Podostemum include crayfishes, turtles, and waterfowl. We estimated grazing pressure by conducting short‐term (up to 77‐day) transplant and consumer‐exclosure experiments, and quantified changes in Podostemum stem length when the plant was exposed to low (<0.5 m/s) and higher velocities in two Piedmont rivers in Georgia (USA). Podostemum transplanted into low‐velocity habitats rapidly lost stem length unless macro‐consumers were excluded from accessing the plant. In contrast, Podostemum transplanted into high‐velocity habitats showed little change or gained stem length. We estimated that 85% (67–98%; 95% credible interval) of the daily stem growth (0.026 cm cm−1 day−1) in Podostemum was consumed during a 77‐day paired consumer‐access versus exclosure experiment conducted in mean water velocities of 0.35–0.5 m/s. We also found a positive relation (R2 = 0.58) between Podostemum biomass and water velocity (ranging between c. 0.1 and 1.3 m/s) in benthic samples collected over a 2‐month period. We conclude that high water velocity reduces herbivory on Podostemum, and that water velocity can thus control the accrual of benthic plant biomass and the movement of plant‐derived materials through benthic food webs. Our research has implications for estimating resource storage and flux in lotic food webs and illuminates a mechanism by which flow regulation and management may affect basal resources in rivers.

Detection of full and limited amphidromous migratory dynamics of fish in Caribbean rivers

AbstractAll native fishes living in the Caribbean island rivers are considered diadromous but few species have been validated as diadromous. In Guadeloupe (Lesser Antilles) as well as in the other tropical islands, the riverine habitats are subject to strong anthropogenic pressure due to resource modifications or dams. The management of fish biodiversity requires knowledge concerning their life history traits and behaviour that are still unknown for most species at a local scale and at the whole distribution area of the species. In a Guadeloupe river, we inferred the migratory patterns of four freshwater fishes common to Caribbean rivers by the analysis of otolith microchemistry. We found two species Eleotris perniger (Eleotridae) and Sicydium plumieri (Gobiidae) to be completely amphidromous with a marine larval phase and a freshwater adult phase. Agonostomus monticola (Mugilidae) was also found to be amphidromous in this system. The fourth species Gobiesox cephalus (Gobiesocidae) showed elemental ratios suggesting an estuarine larval phase and was defined as “limited amphidromous”. The identification of such life history traits, with limited dispersion abilities, argues for specific management measures in tropical island rivers at a basin scale for the conservation of biodiversity.

Two new species of miniature psammophilic sarcoglanidine catfishes of the genus Microcambeva from the Atlantic Forest of eastern Brazil (Siluriformes: Trichomycteridae)

ABSTRACTTrichomycterid catfishes of the Sarcoglanidinae, which includes small-sized species living in sandy river substratum, have been poorly represented in collections. We herein describe two new species of the sarcoglanidine genus Microcambeva, endemic to river basins draining the Brazilian Atlantic Forest. The presence of a distal widening on the posterior process of the autopalatine and a rudimentary anterior autopalatine ossification shared by the two new species, M. mucuriensis sp. nov. from the Rio Mucuri and M. jucuensis sp. nov. from the Rio Jucu basin, and M. draco from the Rio Jucuruçu basin indicates that these three species are more closely related to each other than to other congeners. Microcambeva mucuriensis seems to be more closely related to M. draco than to M. jucuensis in that the first two species share the presence of a well-developed anterior process of the interopercle. The two new species are also distinguished from congeners by the number of opercular odontodes and premaxillary teeth, and the relative size of the sesamoid supraorbital. Available evidence taken from this study and previous reports indicates that different sarcoglanidine lineages have adapted to live in distinct riverine habitats, with species of Atlantic Forest Microcambeva inhabiting clearwater streams and Amazonian sarcoglanidines found in tea-stained acidic-water streams.http://www.zoobank.org/urn:lsid:zoobank.org:pub:8CFF9C88-1CEC-44AF-AD26-1D4A56F3D946

Zooplankton dynamics in a Great Lakes connecting channel: Exploring the seasonal composition within the St. Clair-Detroit River System

The connecting channels linking the Laurentian Great Lakes provide important migration routes, spawning grounds, and nursery habitat for fish, but their role as conduits between lakes for zooplankton is less understood. To address this knowledge gap in the St. Clair–Detroit River System (SCDRS), a comprehensive survey of crustacean zooplankton was performed in both riverine and lacustrine habitats from spring to fall 2014, providing the first system-wide assessment of zooplankton in the SCDRS. Zooplankton density and biomass were greatest in northern reaches of the system (southern Lake Huron and the St. Clair River) and decreased downstream towards Lake Erie. The composition of zooplankton also changed moving downstream, transitioning from a community dominated by calanoid copepods, to more cyclopoids and cladocerans in the Detroit River, and to cladocerans dominant in western Lake Erie. Coincidentally, species richness increased as sampling progressed downstream, and we estimated that our single-year sampling regime identified ~88% of potential taxa. Other species assemblages have responded positively to recent water quality and habitat restoration efforts in the SCDRS, and this survey of the zooplankton community provides benchmark information necessary to assess its response to continued recovery. In addition, information regarding the lower trophic levels of the system is integral to understanding recruitment of ecologically and economically valuable fish species targeted for recovery in the SCDRS.

Ecology, threats and conservation status of Carex buekii (Cyperaceae) in Central Europe

Carex buekii is a tall sedge, forming large stands in wetlands, particularly in river floodplains across Central Europe and thus on many sites determining the typical appearance of riverine habitats. Our paper aims at increasing the knowledge on ecology of C. buekii and its role in the wetlands. Field data were collected in Poland, the Czech Republic, Slovakia, Hungary, and Italy. Carex buekii usually occurs in nutrient rich habitats, but is also capable of colonising relatively nutrient-poor ones; it grows on both acidic and alkaline soils (pH 3.3–7.4) with diverse concentrations of assimilable elements (Ca, Mg, P, K). One of the most important ecological characteristics of C. buekii is its relationship to the floodplains of watercourses. It seems to be dependent on, or at least very tolerant to regular disturbances by streaming, floods and transport of sediments. Carex buekii usually forms relatively uniform stands of its own association, Caricetum buekii. The species most frequently accompanying C. buekii are Urtica dioica, Calystegia sepium, Galium aparine, Rubus caesius, Phalaris arundinacea, and Cirsium arvense. The sedge also occurs in the understorey of forests with e.g. Alnus glutinosa, Salix fragilis, Padus avium, and Quercus robur. Carex buekii is able to colonise man-made or man-changed habitats such as railway embankments and roadsides or regulated river banks. Taking into account the IUCN Red List Criteria we propose to regard C. buekii as a least-concern (LC).

Riverine turtles select habitats maintained by natural discharge regimes in an unimpounded large river

AbstractTurtle populations are imperiled worldwide, but limited ecological information from unaltered systems hampers science‐based management and conservation of some species, especially riverine turtles such as the spiny softshell (Apalone spinifera). We therefore investigated movements and spatial habitat selection of 54 A. spinifera in 633 river kilometres (rkm) of the least‐altered river in the conterminous United States—the Yellowstone River in Montana—from 2005 to 2009. Movement rates and home ranges were smaller than in fragmented, altered river systems because nesting and overwintering habitats were common and in close proximity. Habitat selection also differed. A. spinifera in the Yellowstone River overwintered in unaltered bluff pools and summered in complex reaches with side channels, islands, and diverse habitats. However, those in the highly altered Missouri River used deep alluvial pools for overwintering and flooded, inundated, or backwatered tributary mouths in spring and summer. Importantly, selected habitats in both rivers were functionally similar, including complex river reaches (with multiple channels, islands, and diverse habitats) and natural pool types. Unfortunately, these are the very habitats that are limited in rivers affected by dams, bank stabilization, and channelization. Therefore, preservation of natural and diverse riverine habitats—and the fluvial dynamics that maintain them—may enhance conservation of A. spinifera in large rivers.

Seed dispersal by proboscis monkeys: the case of Nauclea spp.

Frugivorous vertebrates such as primates are important dispersal agents in tropical forests, although the role of folivorous colobines is generally not considered. However, recent studies reported seed dispersal by endo- and epizoochory in colobine primates, including the proboscis monkey (Nasalis larvatus), suggesting that the role colobines play in seed dispersal might have been underestimated. In the Lower Kinabatangan Floodplain in Sabah, Malaysian Borneo, we investigated whether seeds were still able to germinate after being ingested by proboscis monkeys. Faecal samples (n = 201) from proboscis monkeys were collected between 2015 and 2017. Intact seeds belonging to eight plant species were found in 77% of the faecal samples. Nauclea spp. were the most abundant plant species, accounting for 98% of all intact seeds. This study is the first to conduct germination trials on seeds defecated by proboscis monkeys. Higher germination success was recorded in ingested Nauclea spp. seeds than in control seeds, from both ripe and unripe Nauclea orientalis fruits (P < 0.001). Therefore, we suggest that proboscis monkeys play a role in seed dispersal by enhancing the germination success of defecated seeds for at least some plant species. Similar to other colobines, although proboscis monkeys may provide a lower contribution to seed dispersal (low seed diversity over short distances) than other sympatric frugivores, this study emphasises that proboscis monkeys do contribute to the dispersal of intact seeds, such as Nauclea spp., in potentially suitable riverine habitats.