Floodplain Lakes Research Articles

Divergent sensitivity of primary producers and benthic invertebrates to hydrological alteration in floodplain lakes

Floodplain lake ecosystems are hydrologically dynamic and biologically important. Their ecosystem functioning is complex due to the concurrent influence of multiple anthropogenic stressors. Paleolimnological studies focused on a single biotic proxy might lead to biased results, as multiple trophic levels may show different responses to the same driver. In this study, multiple proxies including chlorophyll and carotenoid pigments (indicators of phytoplankton) and chironomids (indicators of invertebrates) were analyzed in a 210Pb dated sediment core from Luhu Lake (Yangtze floodplain, China). Using these indicators, we investigated how different trophic levels respond to external driving forces (i.e., hydrological alteration represented by K/Al ratios and nutrient influxes indicated by TP) in floodplain lakes. Sedimentary pigments showed that algal production increased in Luhu Lake after the 2000s. The chironomid community shifted from a fauna dominated by Microchironomus tener-type to an assemblage characterized by macrophyte-dwelling taxa (e.g., Tanytarsus, Paratanytarsus, Paratanytarsus penicillatus-type) after the 1970s. Finally, nutrient-tolerant taxa (e.g., Microchironomus tabarui-type) increased in abundance after the 1990s. Redundancy analysis and hierarchical partitioning analysis showed that the increases in algal production were mainly correlated with anthropogenic nutrient influxes, followed by hydrological alteration. In contrast, the transition in the chironomid communities were mainly associated with hydrological alteration, followed by food sources. Our study revealed asynchronous responses of phototrophs and benthic invertebrates to hydrological alteration, highlighting the necessity of analyzing multiple trophic levels to obtain a sophisticate understanding of long-term ecosystem evolution in lotic floodplain lakes which are influenced by multiple stressors. These findings will provide valuable information for the sustainable development, as well as the conservation and restoration of floodplain lakes.

Evolution and Prospects of Freshwater Fish Species and Aquaculture in Colombia: A Historical Perspective

Since the 1970s Colombia has been aware of the importance of aquaculture and inland fisheries in the future of its economy due to the constant increase of a population that is increasingly in need of protein of animal origin. In 1972, a joint project between the Government of Colombia and the Food and Agriculture Organization of the United Nations was approved and aimed at studying inland fishing and developing aquaculture in the country. The work of the project is described, as are the fish culture and fisheries research activities starting with the situation in the 1970s but comparing it with recent findings. A list of the main capture and culture fish species is given. Colombian fishing production has had great variations, but first inland water fishing was more important than marine. For instance, in 1972 total fish catch was 104,390 tons and 79% of that originated from inland waters. After the continental fisheries went down, the marine fisheries accounted in 2019 already 78 per cent of the total catch of the country. Mean standing fish crop estimates in 1975‒76 from the bay, open water and vegetation habitats in four floodplain lakes were 118, 12 and 251 kg/ha indicating clearly that the fish productivity on the Magdalena floodplain was relatively low. The aquaculture sector has been growing rapidly, reflecting global trends, and producing more than capture fisheries. Aquaculture produced 88,000 tons in 2013, which was a three-fold increase from the mid-1990s. Again twofold increase took place before 2020 when the production was almost 180,000 tons. Future development prospects of inland fisheries and aquaculture are discussed and a mention is made of the present situation of ornamental fish cultivation and trade in Colombia.

Taxonomic and functional response of fish assemblages to flood-triggered water level fluctuations in a large floodplain lake along the Yangtze River

Taxonomic and functional response of fish assemblages to flood-triggered water level fluctuations in a large floodplain lake along the Yangtze River

Łączność hydrologiczna, strukturalna i ekologiczna funkcjonalność meandrującego ekosystemu delty Dunaju

The pressure control of the climate change and anthropogenic factors have consequences on the ecological systems, generating structural changes. The abiotic (i.e., water hydrology and hydraulics, sediment load, water physic-chemistry) and biotic (i.e., biodiversity, structure and functionality of food webs) characteristics of river-channels-lakes from deltas depend on several factors; however, the main driver of these characteristics is represented by the hydrologic connectivity with the main stem of the river. Floodplain lakes can be permanently, temporarily or disconnected with the main stem of the river producing interruptions in the transfer of fresh water and thus affecting benthic macroinvertebrates, by decrease in their population, diversity and even loss of sensitive taxa. Multidisciplinary investigations (hydrodynamics, sedimentological and ecological measurements and analyses) were made to investigate a river-channel-lake site type situated on the St. George branch formed by a cutoff meander (Mahmudia meander), a connective channel (Uzlina Canal) and a lake (Uzlina Lake) to observe how much the fresh water and sediment input to the delta depressions is affected by the structural changes of the meander physiography. The Mahmudia meander was rectified 40 years ago and the response of the channel consisted in a very fast silting of the former meander, currently receiving less than 5% of the upstream water and sediment discharge. The lateral connectivity with the deltaic depressions thought the lateral canals is compromised.

Floodplain Lake Water Level Prediction with Strong River-Lake Interaction Using the Ensemble Learning LightGBM

Floodplain Lake Water Level Prediction with Strong River-Lake Interaction Using the Ensemble Learning LightGBM

Unravelling groundwater budget in the Poyang floodplain system under intensifying seasonal lake inundation

Study regionPoyang Lake Plain at the south bank of the middle Yangtze River Study focusThe dynamics of the groundwater budget, prominently driven by the surface water-groundwater interaction, present significant challenges for water resources and the eco-environment in extensive river-lake-floodplain systems. This research utilizes a groundwater flow model through the application of the MODFLOW-NWT numerical simulator, aiming to explore the patterns of exchange between surface water and groundwater due to intensive seasonal lake inundation, and its consequential impact on the annual and seasonal groundwater storage within the vast Poyang Lake floodplain, China. New hydrological insights for the regionSimulation results indicate that the change in groundwater storage during the dry year (i.e., –24.96×107 m3/yr in 2022) has decreased by 186.35×107 m3 compared to the wet year (i.e., 161.38×107 m3/yr in 2020). The contribution of surface water infiltration is approximately 45 % of the regional groundwater budget during wet seasons, and groundwater discharge into surface waterbodies accounts for over 60 % of the groundwater budget during dry seasons. The lake infiltration during wet years is approximately 3 times that in dry years, and the flow of infiltrated lake water into plain aquifers is approximately 5 times that in dry years. The present study contributes significant knowledge regarding the impact of intensifying seasonal inundation on variations in regional groundwater budget in large lake-aquifer system.

Different effects of natural siltation, damming and pollution on two adjacent lakes of Dongting Lake Wetland: Evidence from paleolimnology

Evaluating the influences of hydrology on lotic floodplain lakes has been difficult due to concurrent effects of different human activities in the catchment. This study aims to explore the responses of floodplain lakes to natural siltation and damming by studying grain size and geochemical elements in 210Pb-dated sediment cores from two adjacent lakes with different hydrological conditions in the same catchment, including a hydrologically-isolated lake (Donghu Lake) and a hydrologically-connected lake (East Dongting Lake) in the middle Yangtze floodplain. The results showed that the riverine sediment supply declined in Donghu Lake after its isolation from the Yangtze River due to natural siltation in the 1910s. In East Dongting Lake, the riverine sediment supply remained relatively stable before the operation of the Three Gorges Dam (TGD) in 2003 CE, and then declined rapidly in response to a decrease in riverine sediment supply. Total phosphorus and total organic carbon in Donghu Lake increased after the “reform and opening-up” in the late 1970s, whereas they remained at low concentrations in East Dongting Lake before the TGD operation in 2003 CE. Hydrological isolation from the Yangtze River reduced the influxes of riverine sediments, but promoted nutrient enrichment and primary production in East Dongting Lake through extending water residence times. Stable element composition in Donghu Lake after 2003 CE suggested that the TGD operation had minor effects on hydrologically-isolated lakes. The comparison between hydrologically-closed and hydrologically-free lakes within the same catchment provides an effective method to identify different effects of natural siltation, damming and environmental pollution.

The overlooked carbon cache: Unveiling organic carbon storage in small floodplain lake sediments under humid continental climate changes

Small floodplain lakes (SFLs), characterized by their diminutive size (<10,000 m2), have been consistently overlooked in assessments of organic carbon (C) stock and the impacts of climate changes. This study aims to ascertain both the quantity and quality of carbon stored within the sediments of SFLs. Furthermore, we endeavour to evaluate the influence of ongoing climate change on the floodplain lake structure within the continental humid climate zone on the example of the Vistula River valley and estimate the CO2 emission from dry floodplain lakes. The sedimentary organic carbon content (TOC) ranged from 2.3–64 g kg−1, averaging at 3.4 g kg−1. Consequently, the sediments in the analysed SFLs of the river section potentially harbour up to 5,785 Mg TOC. Notably, the abundance of easily soluble carbon fractions (humic and fulvic acids) was relatively low (∼15 %), implying a stable immobilization of organic C compounds and minimal impact of sediments on water quality. Satellite imagery analysis for the years 2017–2020 revealed a 31 % reduction in the total lake surface area within a 100-km-long segment of the Vistula River. The decreasing surface area of floodplain lakes and rising mean air temperatures increase CO2 emissions and have an additional impact on climate warming. Our research underscores that investigating lake C storage concerning climate change demands a nuanced approach. While higher temperatures stimulate primary production, the reduction in lake surface area and the escalating role of small lakes, such as SFLs, in C storage should be paramount considerations.

Occurrence and Spread of the Alien Thermocyclopis taihokuensis (Harada, 1931) (Crustacea: Cyclopoidae) across Floodplain Lakes of the Khoper State Reserve in Voronezh Oblast in 2021–2022

Occurrence and Spread of the Alien Thermocyclopis taihokuensis (Harada, 1931) (Crustacea: Cyclopoidae) across Floodplain Lakes of the Khoper State Reserve in Voronezh Oblast in 2021–2022

Linking hydrological connectivity with the richness and composition of aquatic invertebrates across the Paraná River floodplain, Argentina

Lateral hydrological connectivity can affect the community characteristics by promoting dispersal of organisms between the river and its floodplain. We investigated the species richness, specific diversity, and relative abundance of microcrustaceans transported by the flood and the macroinvertebrates retained by Pontederia crassipes Mart. roots in five floodplain lakes with different connectivity within the RAMSAR Site Humedales Chaco. Due to differences in the slopes of the floodplain studied, the connectivity was determined by the topographic location of each lake, rather than by the distance from the river. During the hydrological connection, there was a transverse gradient in the physical and chemical characteristics of the water, with an increase in the electrical conductivity and a decrease in dissolved oxygen and suspended solids in the more isolated sites. A total of 62 species of microcrustaceans (48 cladocerans and 14 copepods) and 63 taxa of macroinvertebrates were identified. The microcrustaceans had high species richness in the three most connected lakes, whereas the macroinvertebrates had a peak in taxa richness in the lakes with intermediate connectivity. The low beta diversity (βw) for both microcrustaceans (14.63 %) and macroinvertebrates (16.9 %) indicated that taxa richness varied little between sites with different hydrological connectivity. In both assemblages, cluster analysis based on the similarity of the relative abundance grouped the three sites more connected and separated from the less connected sites. Our results suggest that species richness followed different patterns in different assemblages across the lateral gradient and that the hydrological connectivity was more related to the relative abundance of microcrustaceans and macroinvertebrates than to the classical measures of βw. Species diversity indices did not vary between sites. The high total species richness of invertebrates is mainly a result of the spatial arrangement of the different floodplain lakes.

Effects of different hydrological conditions on the taxonomic structure and functional traits of mollusk communities in a large floodplain wetland.

Floodplain wetlands are critical to the conservation of aquatic biodiversity and the ecological integrity of river networks. However, increasing drought severity and frequency caused by climate change can reduce floodplain wetlands' resistance and recovery capacities. Mollusks, which are common inhabitants of floodplain wetlands, are among the most vulnerable species to drought. However, the response of mollusk communities to drought has received little attention. Here, we investigated how the structure and functional traits of mollusk communities changed in response to varying hydrological conditions, including a flash drought (FD) in the Poyang Lake floodplain wetland. Our findings showed that FD strongly reduced mollusk abundance and biomass, decreased both α- and β-diversity, and resulted in the extinction of bivalve taxa. A sudden shift in community trait structure was discovered due to the extinction of many species. These traits, which include deposit feeding, crawling, scraping, aerial respiration, and dormancy, help mollusks survive in FD and tolerate completely dry out of their Changhuchi habitat. Finally, we discovered that dissolved oxygen was an important controlling variable for mollusk communities during drought. Our findings provide a scientific basis for the management and conservation of floodplain wetland biodiversity in the context of increasing drought frequency and intensity.

Mercury Bioconcentration and Translocation in Rooted Macrophytes (Paspalum repens Berg.) from Floodplain Lakes in the Araguaia River Watershed, Brazilian Savanna

Macrophytes are fundamental photosynthetic organisms for functioning freshwater ecosystems, identified as potential bioindicators of mercury (Hg) in the environment. We quantified the concentrations of total Hg (THg) in water and macrophytes (Paspalum repens Berg.) from 17 lakes on the Araguaia River floodplain, aiming to compare the bioconcentration factor (BCF) in the aerial tissues and roots; evaluate the translocation factor (TF) between plant tissues; and assess the influence of environmental factors and land use on THg concentrations in water and macrophytes. The BCF was significantly higher in roots (1.29 ± 0.32) than in aerial tissues (0.41 ± 0.34), with low TF between plant tissues (0.14 ± 0.06). The highest concentrations of THg in water were determined in lakes with higher land use intensity and a pH close to neutral, indicating the transport of particulate-bound Hg and the immobilization in the water column. In contrast, wetlands were priority areas for the bioconcentration of THg in macrophytes, associated with sulfate, dissolved oxygen, and oxidation–reduction potential in the water. Thus, although P. repens is not a suitable bioindicator of Hg mobilization by anthropogenic land use in our study area, our results suggest the potential of macrophytes as bioindicators of sites that are favorable to Hg methylation.

Niche partitioning and seasonality may mediate coexistence of piranha species in Amazonian floodplain lakes

Niche partitioning and seasonality may mediate coexistence of piranha species in Amazonian floodplain lakes

Effects of constant high water levels in winter on waterbird diversity in Caizi Lakes: A functional perspective

The middle and lower Yangtze River floodplain lakes are important stopover and wintering sites for migratory birds on the East Asian–Australasian Flyway. The periodic water level fluctuation of the lakes plays a critical role in the aggregation of waterbirds. However, the construction of a series of gates and dams has impeded the hydrological connectivity between rivers and lakes and disrupted the natural water level fluctuation patterns of lakes. The water level status of lakes influences habitat utilization by waterbirds. In recent years, Caizi Lakes, the gate-controlled lakes connected to the Yangtze River due to the need for water level regulation requirements, has experienced sustained high water levels in winter, which can reduce habitat quality and in turn influence waterbirds activity. In the present study, wintering waterbirds in Caizi Lakes were surveyed during the 2021–2022 (W1) and 2022–2023 (W2) wintering periods. Moreover, we explored the effects of constant high water levels in winter on waterbird assemblages by comparing species richness, abundance, and functional alpha and beta diversity. Correlation analyses were then performed to elucidate the relationship between habitat factors and water level changes during the wintering period of migratory waterbirds and between changes in various habitat factors and wintering waterbird assemblages under different hydrological conditions. The results showed that functional beta diversity was more sensitive to changes in waterbird assemblages in Caizi Lakes than functional alpha diversity. Moreover, constant high water levels in the mid-wintering period decreased suitable habitats for wintering waterbirds, increased functional turnover among waterbird assemblages, increased total dissimilarity among assemblages significantly, and decreased the level of functional nestedness significantly. Additionally, the areas of the three wetland habitats in Caizi Lakes were significantly correlated with water level changes during W1 and relatively less affected by water level changes under constant high water level conditions during W2. The changes in habitat area were influenced primarily by anthropogenic activities, with an increase in meadow area favorable for species richness and abundance, as well as functionally nested components. Water level regulation should take into consideration the natural hydrological rhythms of the declining water level to ensure that adequate and suitable habitats are provided for wintering waterbirds.

Assessment of environmental water strategies for improving fringing vegetation health by modelling vegetation condition in a connected floodplain lakes system

AbstractAcross the globe, environmental water has been allocated with the purpose of preserving the health and vitality of floodplain vegetation. However, the influences of environmental water volume and environmental water delivery strategies have not been studied widely because of shortage of on‐ground monitoring data. Remotely sensed data can bridge this gap by providing long‐term and continuous information; Landsat imagery from 1988 to 2020 was used in this research. We used the normalized difference vegetation index (NDVI) as an indicator of physiological condition of lake‐fringing trees on the Hattah Lakes floodplain, south‐east Australia. We employed the random forest (RF) regression method to model the relationship between NDVI and various climate and hydrological factors, such as the volume of water delivered to the connected lakes system as environmental water allocations or natural floods. The RF models performed well overall, with a mean R2 value of 0.73. The analysis identified the monthly total of environmental water delivered 3 months prior to the Landsat image date as a more crucial factor than natural floods over the same period for driving vegetation condition. Environmental water from 3 months previously exerts a positive influence on NDVI until the volume reaches a specific threshold. We have observed significant improvements in floodplain vegetation through the current environmental water strategy, particularly since the construction of pumping infrastructure in 2013. We suggest that managers aim to inundate the lake fringing area every 3 years, specifically from August to September, by delivering environmental water up to the modelled threshold volume. Finally, the use of infrastructure has proven to be an effective and efficient method for irrigating floodplain lakes, leading to improvements in vegetation condition while conserving water resources.

Distribution of selenium: A case study of the Drava, Danube and associated aquatic biotopes

This paper presents the results of the research on the overall distribution of selenium (Se) in various aquatic compartments (water, sediment, plankton and macrophytes) at six selected sites of the Croatian part of the Drava and Danube rivers, the connected floodplain lake and the melioration channel system carried out in two sampling periods (flooding in June and the drought period in September). In addition, the physicochemical water properties, plankton composition and biomass were analysed. Our study revealed low mean Se contents in sediments and water, indicating Se deficiency in the studied freshwater systems. The physicochemical environment, including Se distribution, was primarily influenced by hydrology rather than site-specific biogeochemical and morphological characteristics. The flooding period was characterised by higher Se content in water and higher transparency, nitrate and total nitrogen concentrations than drought conditions. At the river sites, sediment Se content was the highest during the flood period, while at all other sites, higher concentrations were found during the drought, reaching the maximum in the lake. Although Se concentrations were below the threshold for aquatic ecotoxicity, they increased in the following order: water (0.021–0.187 μg Se L−1) < sediments (0.005–0.352 mg Se kg−1) < macrophytes (0.010–0.413 mg Se kg−1) < plankton (0.044–0.518 mg Se kg−1) indicating its possible biomagnification at the bottom of the food chain. Species known for high Se accumulation potential dominated the biomass of the main plankton groups and the composition of the macrophyte community, which may provide a more sensitive and accurate steady-state compartment monitor for Se assessment in freshwater biotopes.

Interrelationship between limnological parameters of a floodplain lake in Dwarkeshwar river basin and their impact on fish biodiversity

Interrelationship between limnological parameters of a floodplain lake in Dwarkeshwar river basin and their impact on fish biodiversity

Vegetation types and flood water level are dominant factors controlling the carbon sequestration potential in Dongting Lake floodplain, China

Wetlands are important carbon sinks. However, the carbon sequestration potential of flooded wetlands may be weakened owing to water regime changes induced by anthropogenic disturbances. Using the eddy covariance technique, this study quantified the effects of the water level and vegetation types on the net ecosystem CO2 exchange (NEE), gross primary production (GPP), and ecosystem respiration (Reco) from a reed marsh (Miscanthus sacchariflorus) and a sedge meadow (Carex spp.) in the Dongting Lake floodplain from 2014 to 2016. Our results indicated that the sedge meadow (−89.49 to −186.47 g C m−2 y−1) and reed marsh (−246.12 to −513.94 g C m−2 y−1) were carbon sinks on the interannual timescale. However, the sedge meadow changed from a carbon sink to a carbon source during the flooding season. The effect of flooding on the carbon sink function in the reed marsh was dependent on the water level. The carbon sink function of the reed marsh was enhanced by moderate flooding (water level under 30.5 m in Chenglingji) owing to the inhibition of Reco, but was weakened by extremely high-water levels (over 33 m in Chenglingji) during the flooding season. Seasonal variations in NEE, GPP, and Reco were closely related to photosynthetic photon flux density, soil water content, water level, soil temperature, and air temperature. We can conclude that the increase in reed area combined with the decrease in flooding days in the sedge meadow can potentially enhance the carbon sink function of the Dongting Lake floodplain.

Tracing Water Recharge and Transport in the Root-Zone Soil of Different Vegetation Types in the Poyang Lake Floodplain Wetland (China) Using Stable Isotopes

Background: root-zone water transport is crucial in the water transformation from precipitation to groundwater, directly influencing soil moisture distribution and resource acquisition for wetland plants. Methods: This study investigated the movement mechanism of root-zone (0–80 cm) soil water in the Poyang Lake wetland, China, during a dry year. Hydrological observation and stable isotopes (δ18O and δD) were utilized. Results: The root-zone soil water content was low (2.9–12.6%) at the high site covered by Artemisia capillaris, while it remained high (25.2–30.2%) at the median and low sites covered by Phragmites australis and Carex cinerascens, respectively. The isotopic values of shallow soil water (0–40 cm) in the A. capillaris site followed the seasonal pattern of rainfall isotopes, indicating predominantly rainfall recharge. Rainfall was primarily transported by piston flow, with an infiltration depth of approximately 60 cm. Conversely, depleted water isotopes measured at certain depths in P. australis and C. cinerascens sites closely resembled those of rainfall, suggesting that preferential flow dominated. The average groundwater contribution proportions in root-zone soil water were 65.5% and 57.4% in P. australis and C. cinerascens sites, respectively, while no contribution was detected in A. capillaris site. Conclusions: Preferential flow and groundwater recharge occurred in the P. australis and C. cinerascens sites. They enhance the hydrological connection at the profile scale and are useful for maintaining a favorable root-zone moisture environment for wetland ecosystems in dry years. However, the hydrological connectivity between root-zone soil and groundwater was found to be obstructed in the A. capillaris site. This might be the main reason for vegetation degradation at high elevations in the Poyang Lake wetland.

Peculiarities of the structure of zooplankton communities in floodplain water bodies of the Middle Ob

The zooplankton of the caught floodplain lakes of the Middle Ob, located at various distances from the main riverbeds, was studied. It is shown that the development of the summer complex of zooplankton in floodplain lakes begins simultaneously with the passage of the flood; a significant diversity of species and the largest biomass increase in them in the summer months. The more often the floodplain lakes is filled with hollow waters, the higher the species diversity and the calculated indicators of plankton are in it. The factors that register the signs of zooplankton development in the caught lakes are revealed: the frequency of flooding, water temperature, the content of consumption for a number of taxa — the gas regime. Studies have shown that that the zooplankton of the caught reservoirs is subject to increased impact of the communities of the special territory of rivers and lakes of the above-floodplain terrace of the distribution of faunal diversity, increased species richness and specific species structure.