Reed Beds Research Articles

Characterization of haemosporidian infections in warblers and sparrows at south-western European reed beds

The prevalence and intensity of avian haemosporian infections (genera Haemoproteus and Plasmodium) were investigated using molecular techniques and microscopy in nine passerine species at three Portuguese reed beds along a small latitudinal gradient. The effect of age, sex, season, site and year in the infection prevalence was evaluated for some of these host species. Of the sampled birds, 34.5% were infected, all with low level parasitemias. Haemoproteus spp. was only present in migrant species and was not locally transmitted, while Plasmodium spp. infected more species and reached a higher overall prevalence. Prevalence differed among bird species and was affected by different variables for each species: it was associated with age in the Reed Warbler Acrocephalus scirpaceus, with season in the Cetti’s Warbler Cettia cetti and with year in the House Sparrow Passer domesticus. Site did not influence prevalence for any species at this small geographical scale. Reed Warbler adults had already migrated to Africa and contacted with two different parasite faunas, whereas juveniles had not, thereby explaining the importance of age to explain parasitemia in this species. For the resident Cetti’s Warbler, prevalence varied significantly with season, perhaps due to lower food availability in autumn and winter, making birds weaker and more prone to infection.

Dewatering mechanisms in pilot-scale Sludge Drying Reed Beds: Effect of design and operational parameters

Eleven pilot-scale Sludge Drying Reed Beds (SDRBs) have been constructed, and operated treating municipal activated sludge. Quantification of the dewatering mechanisms in these systems (i.e., evapotranspiration and draining) is attempted here, and the effects of different parameters, i.e., the level of sludge loading, the presence of reeds, the gradation of substrate materials etc., on these mechanisms are presented. Results reveal that evapotranspiration is the major dewatering process that takes place in SDRB systems, accounting for 58–84% of total water losses, depending on unit characteristics, sludge loading, season and other parameters. Draining follows in significance, with respective values varying from 13% to 41% of total water losses, while 1% to 4% of water remains in the sludge layer. The presence of reeds was found necessary, since it improved the dewatering efficiency. Precipitation and temperature were also found to affect the dewatering process under temperate climate conditions.

Greenhouse Gas Fluxes from Dutch Peatland Water Bodies: Importance of the Surrounding Landscape

Methane and carbon dioxide fluxes were quantified for 14 ditches and larger water bodies in Dutch peatlands, surrounded by different habitat types, using concentration changes in floating flux chambers. Average fluxes from these waters were 11 ± 2 (mean ± SE) mg CH4 m−2 h−1 (n = 66) and 86 ± 21 mg CO2 m−2 h−1 (n = 55). Variability among water bodies was substantial in both gases and could be explained by water depth and surrounding habitat. Ditches in intensively used dairy land or rough pastures had significantly higher CH4 emission rates (17 ± 6 and 18 ± 8 mg CH4 m−2 h−1) than those in reed and sedge beds or open water (7 ± 1 and 5 ± 2 mg CH4 m−2 h−1). Bubbles contributed between 34 and 69% to the total CH4 flux, with higher proportions observed in ditches sheltered by tall vegetation. Observed day-time CO2 fluxes were either positive (shaded ditches in reed and sedge stands or rough pasture; 120–150 mg CO2 m−2 h−1) or did not differ from zero (open water, ditches in intensively managed pasture). Since these peatlands have substantial areas of permanent surface water (6–43%), landscape-scale carbon flux estimates are improved by incorporating specific flux estimates for these waters.

Micro-tidal coastal reed beds: Hydro-morphological insights and observations on wave transformation from the southern Baltic Sea

This paper investigates the hydro-morphological controls on incident wind-generated waves at, and the transformation of such waves within, two Phragmites australis reed beds in the southern Baltic Sea. Meteorological conditions in combination with geomorphological controls result, over short (<2 km) distances, in significant differences in water level and wave climate to which fringing reed beds are exposed. Significant wave height attenuation reached a maximum of 2.6% m −1 and 11.8% m −1 at the transition from open water into the reed vegetation at the sheltered and exposed sites respectively. Wave attenuation through the emergent reed vegetation was significantly lower in greater water depths, suggesting (1) a reduced influence of bed friction by small shoots/roots and/or (2) drag reduction due to flexing of plants when the wave motion is impacting stems at a greater height above the bed. For a given water depth, wave dissipation increased with increasing incident wave height, however, suggesting that, despite their ability to flex, reed stems may be rigid enough to cause increased drag under greater wave forcing. The higher frequency part of the wave spectrum (>0.5 Hz) was preferentially reduced at the reed margin, confirming the theoretical wave frequency dependence of bottom friction. The possibility of physiological adaptation (differences in reed stem diameter) to water depth and wave exposure differences is discussed. The results have implications for the possible impact of environmental changes, both acute (e.g. storm surges) or chronic (e.g. sea level rise) in character, and for the appropriate management of reed bed sites and delivery of ecological goods and services.

Removal capacity and pathways of phenolic endocrine disruptors in an estuarine wetland of natural reed bed

Phenolic compounds are partly known as endocrine disruptors with various harmful effects including feminization and carcinogenesis at very low concentrations. Consequently, the pathways and removal of these compounds in natural and artificial sewage treatment systems such as wetlands have received wide concern. In this paper, a natural reed bed wetland with an area of 695 ha located in the Liaohe River estuary in Northeast China was employed as a demonstration site to study the retention and removal efficiency of phenolic compounds including 4-nonylphenol (4-NP), bisphenol A (BPA), 4- t-octylphenol (4-t-OP), and 2,4-dichlorophenol (DCP), and to evaluate their purification capacity via water and mass balance analyses during an irrigation period from May 9 to September 8, 2009. The results showed that the phenolic compounds could be retained in the wetland system and removed through various processes. On average, 27.5% of phenolic compounds could be retained by the wetland substrate during the initial three-day irrigation period with a retention capacity order of 4-t-OP > 4-NP > BPA > DCP. During the following 120 d irrigation period, the phenolic compounds could be efficiently removed with an average percentage of 91.6%. It is estimated that 1.76 kg d −1 of phenolic compounds could be removed by the Liaohe River estuarine wetland (∼8 × 10 4 ha). The reed bed wetland system therefore provides a feasible mitigation option for phenolic pollutants in sewage and wastewater.

Natural and economic factors of shrinkage of lakes of the Wielkopolska Lakeland

Natural and economic factors of shrinkage of lakes of the Wielkopolska LakelandThe paper discusses the issue of plant overgrowth in the littoral zone of lakes. It presents the plant encroachment process and its environmental and economic consequences based on the example of selected lakes of the Wielkopolska Lakeland. In order to estimate changes of quantity in the riparian vegetation structure, historical records of changes of reed bed areas were compared with their present areas. Historical data included bathymetric plans from the 1960's created by the Institute of Inland Fisheries and information obtained from interviews with the inhabitants of settlements located in the vicinity of the studied lakes. Present-day boundaries of reed bed zones were identified using orthophotos, aerial photographs and in situ inspections. In the course of the field research, identification of plant species and estimates of plant condition in the studied stands were carried out. Obtained data combined with data on local hydrological-meteorological conditions, water quality and land use in the direct vicinity of lakes allowed the authors to determine the conditioning factors of riparian vegetation encroachment. The collected evidence allowed the authors to establish that in the last five decades, the area of reed beds around the studied lakes increased by an average of 15-20%. This process was usually accompanied by the encroachment of hydrophytic plants consequently leading to the shrinkage of supralittoral zones. In the last 20 years, these two phenomena intensified considerably, particularly during two low water periods noted during this period. However, the encroachment of riparian vegetation proceeded differently in the case of each lake and it was most protrusive in highly eutrophicated reservoirs and those with a history of permanent or long-term lowering of the water table. The qualitative structure of the studied plant communities was conditioned mostly by nutrient inflow and the type of growing medium. In large clean lakes and in zones of sandy lake bottom, the reed beds were dominated by the common reed (Phragmitetum australis). In smaller, polluted lakes and shielded bays of larger lakes with stagnant water, beside multi-species reed beds, floating-leaf hydrophytic macrophyte plants of the genus Nymphaea, tall stands of sedges and helophytes were observed.

Lead, mercury and cadmium content in bottom sediments, reed (Phragmites australis) beds and great pond snails (Lymnaea stagnalis) in fishponds and the role of littoral zones in their accumulation

We studied the contents of cadmium (Cd), lead (Pb) and mercury (Hg) in common reed (Phragmites australis), great pond snails (Lymnaea stagnalis), and in littoral bottom sediments in 18 fishponds in two regions of the Czech Republic. We also assessed the impact of environmental factors on heavy metal accumulation in these three components of littoral ecosystem. Cadmium and lead values were significantly higher in bottom sediments (median values 0.70 and 13.4 mg·kg-1) than in reed (0.014 and 0.51 mg·kg-1) and snails (0.074 and 0.81 mg·kg-1). Cadmium values in reed stems positively correlated with Cd values in great pond snails (Spearman’s rank correlation, rS = 0.62; p &lt; 0.05). Cadmium and lead contents in reed stems positively correlated with each other (rS = 0.56; p &lt; 0.05). The mercury values in snails (0.043 mg·kg-1) were higher than in sediments (0.040 mg·kg-1) and these were higher than in reed stems (0.010 mg·kg-1). We also found higher mercury contents in reed stems and higher cadmium contents in great pond snails in eastern compared to western parts of investigated ponds. Based on the principal component analysis (PCA) performed on heavy metal values, relative reed beds rate in the pond perimeter was negatively correlated with the sample scores on the first PCA axis and the orientation of sampling site and fish stock density negatively correlated with the second PCA axis. Our results proved the important role of littoral sediments in Cd, Pb and Hg accumulation, and the suitability of great pond snails for mercury stress biomonitoring in fishponds. In conclusion, littoral reed beds play a very important role in toxic element uptake in fishponds. The results contribute to the understanding of heavy metal cycles and their accumulation in fishponds under semi-natural conditions and in less affected landscape, and can be used as reference values for comparison with more damaged sites.

Distribution and diversity of littoral macroinvertebrates within extensive reed beds of a lowland pond

Although habitats of hard emergent macrophyte beds, including reed beds (Phragmites australis), are very common in the littoral zones of stagnant waters in central Europe, research investigating their macroinvertebrate communities is still lacking. In this study, the spatial distribution of macroinvertebrates was studied within large reed beds in the littoral zone of a lowland fishpond (Nesyt, SE Moravia, Czech Republic). Using a hand net, horizontal line transects in the reed bed leading from the marginal area with the open water towards the shore were sampled. The results of NMDS ordination and PERMANOVA test proved that the taxonomic composition of the macroinvertebrate assemblage changed significantly along the investigated horizontal transect from the open water towards the shore, together with gradual changes in some environmental factors. The taxa diversity was found to be the highest in the areas closest to the shore. In the reed bed areas near open water, corixids, aquatic insects larvae, leeches, water mites, some naidids and tubificids, which represented free-swimming invertebrates with tracheal gill breathing, ectoparasites, gatherers/collectors and taxa preferring pelal and inorganic substrates, were more abundant compared with the interiors of reed beds. On the other side, in the shallow dense interior of reed beds close to the shore, gastropods, water slaters, some naidids and enchytraeids, aquatic beetles and dipteran larvae were characteristic taxa, which belonged especially to grazers and scrapers, shredders and invertebrates preferring phytal and POM (particulate organic matter) microhabitats. Different predators were recorded in areas near open water and near the shore. This invertebrate spatial distribution probably reflects changes in microhabitat and environmental conditions along the investigated horizontal transect. The results of this study proved that extensive reed beds serve as refuges for many groups of aquatic macroinvertebrates within lowland fishpond ecosystems.

Movements of radio-tracked American mink (Neovison vison) in extensive wetland in the UK, and the implications for threatened prey species such as the water vole (Arvicola amphibius)

In a number of countries around the world, introduced American mink are acknowledged to have had a negative effect on a number of native species, many of which are of particular conservation concern. In the UK, there has been an observed correlation between the spread of mink and the decline of the, once common and widespread, water vole. Large wetlands, such as extensive reed bed, appear to mitigate the impact of mink predation on water voles and some bird species. The present study was carried out to test the hypothesis that the observed refuge effect of reed beds arises from the way mink forage in this type of wetland. The results suggest that the interior of reed bed offers a spatial refuge for water voles, and other species, from predation by mink, because more than 60% of mink foraging activity occurred within 10 m of a main (>10 m wide) channel. Where mink ventured within the reed bed itself, they associated closely with scrub. The implication is that easily navigable channels and areas of scrub probably compromise the refuge effect of reed beds. This can be used to inform management recommendations at these sites.

Treatment of Dairy Farm Effluents Using a Settling Tank and Reed Beds: Performance Analysis of a Farm-Scale System

Effluents from intensive dairy farming should be treated to prevent water pollution. A full-scale integrated treatment system was developed at Poisy in the French Alps. The treatment system consists of an aerated settling tank followed by vertical-flow reed beds planted with common reed. Recirculation of reed bed effluent to the settling tank was used to reduce the concentrations of pollutants within the system. Dairy farm effluents included dairy manure, milk house wash water, manure storage runoff, and at times small amounts of waste milk. Mean inflow rate for milk house wastewater was 5,000 L d-1 (+50 L of waste milk). During periods of heavy rainfall, inflow rates of up to 35,000 L d-1 were observed due to runoff from yard areas. To improve treatment performance, an aeration system was installed in the settling tank in May 2006. Mass removals increased by more than 10% for organic pollutants due mainly to aeration. Mean load removals ranged from 82% to 96% for organic and solid pollutants. Mean total nitrogen and phosphorus removals were 76% and 19%, respectively. Sludge accumulation on the reed beds was 2.2 cm year-1. Sludge quality conformed to French land application regulations.

Ecological Benefits of Bioremediation of Oil Contaminated Water in Rich Savannah of Palogue, Upper Nile Area-Southern Sudan

Plants and their associated microbes can be used in the cleanup and prevention of environmental pollution. This growing technol ogy uses natural processes to break down, stabilize, or accumulate pollutants. It is well established that most crude oils are biod egradable to a great extent, especially components as short linear alkanes or simple aromatic hydrocarbons. However, the heavy fraction, made of long-chain saturated and polyaromatic hydrocarbons and a considerable fraction of asphaltenes and resins, is generally recalcit rant to degradation. Based upon fi eldwork conducted during February 2010, bioremediation of oil contaminated water is investigated in Palogue oil fi elds in the rich savannah of Upper Nile area in southern Sudan. The paper reviews the ecological bene fi ts of bioremediation to pro- duce a clean environment of oil pollutants there, and how far it could be bene fi t for the Sudan, supported from some world experiences. The main fi ndings suggested valuable results by the Reed Bed ‘’Phragmites australis’’ (Figure 1) which breaks down the hydrocarbons sequence to produce free water of contaminants, now suitable for forestry development and recovery of natural fauna after decad es of military con fl ict. The paper concluded that community awareness is essentially imperative and a national strategy is needed for further adaptive methods for the environment conservation.

The treatment of run-off from a fertiliser plant for nitrification, denitrification and phosphorus removal by use of constructed wetlands: a demonstration study

The paper describes an evaluation carried out on demonstration scale to show that it was possible to use a Hybrid Reed Bed System comprising a Horizontal flow and a Vertical Flow Bed for treating the high strength run-off from a fertiliser packaging plant. The site is located close to an estuary which is sensitive to nutrients. The environmental regulators were therefore concerned that excessive mass flows of nitrate, ammoniacal nitrogen and phosphate, potentially arising from the site run-off, were not discharged into the estuary. The fertiliser manufacturing company required a simple, low maintenance system for removing nitrogen and phosphorus. A series of experimental runs were carried out to characterise the performance of the Hybrid System, establishing the effluent quality that could be achieved and the mass removal rate which was appropriate for acceptable treatment. These tests showed that it was possible to achieve a reduction of 79% in Total N whilst using molasses as a carbon source for denitrification. When using a 4:1 recycle ratio this produced an effluent with concentrations of 14 mg NH(4)-N/litre and 18 mg NO(3)-N/litre from treating site run-off containing concentrations in the order of 75 mg/litre of both NH(3)N and NO(3)-N. Chemical dosing with an iron salt brought the P concentration down to around 0.5 mg PO(4)-P/litre.

Treatment performance of artificial floating reed beds in an experimental mesocosm to improve the water quality of river Kshipra

The discharge of untreated wastewater in River Kshipra had brought annual average of BOD, TKN and TS levels up to 39 mg/l, 38 mg/l and 781 mg/l respectively in the study area. Treatment performance by Artificial Floating Reed Beds (AFRB) was evaluated for removal efficiency of TS, NH4-N, NO3-N, TKN and BOD from river water, initially, under a pilot scale by an AFRB of size 200 m2 planted with local reed grass, Phragmites karka, in the part of River Kshipra at the confluence with meeting point of a wastewater stream. The system performance was recorded as 43% reduction in TS, 38% reduction in TKN and 39% BOD reduction. The experimental AFRBs were buoyant structure planted with reed grass, each unit had a rectangular size and covered an effective surface area of 2 m2. The experiment with the mesocosms with treatment of River water resulted that AFRB was reducing pollution load by 55-60% of TS, 45-55% of NH4-N, 33-45% of NO3-N, 45-50% of TKN and 40-50% of BOD. AFRB may be recommended as an in-situ, eco-friendly river water treatment structures for small shallow, slow flowing (or slightly stagnant) water bodies.

Influence of fish-farming management on duck breeding in French fish pond systems

Fish ponds host a relatively important share of the breeding population of waterfowl in Europe. The objective of this study was to investigate the influence of fish-farming management on the distribution of dabbling and diving duck breeding, in 103 fishponds from four regions important for duck breeding in France. Duck breeding in fish ponds was apparently influenced by food resource and nesting site availability. Dabbling duck pair density was generally higher when invertebrates were abundant in macrophytes beds and when competition for food with carps Cyprinus carpio was potentially decreased by lower fish stock biomass. Diving duck pair abundance seemed to be negatively influenced by low invertebrates biomasses in pond sediment and by the absence of large reed beds at the edge of waterbodies. The difference between dabbling and diving ducks was also confirmed by a study of the variation in brood numbers standardized by pair numbers. This brood:pair ratio corresponded to a measure of nesting success and the possible attraction of fish ponds for some broods hatched in neighbouring waterbodies. Dabbling duck brood:pair ratio was lower in one of the study regions where most of meadow areas surrounding fish ponds have been transformed into cereal crops in the past few decades. Diving duck brood:pair ratio was positively linked to pond fertilization due to fish farming. Fish farming, therefore, influenced duck breeding by an interaction between carp density and fertilization. We hypothesize that fertilization increases zooplankton density, thereby decreasing the competition between carps and waterfowl for benthic prey.

Does the zooplankton prey availability limit the larval habitats of pike in the Baltic Sea?

The objectives of this study were to (1) investigate whether the availability of suitable zooplankton prey limits the distribution of the coastal larval areas of pike ( Esox lucius) in two archipelago areas of the northern Baltic Sea and (2) compare the availability of zooplankton prey in spring between different types of coastal littoral habitat. According to the results, reed belt habitats formed by Phragmites australis constitute hot spots for zooplankton prey in the coastal ecosystem. During the spring, reed-covered shores of the inner archipelago maintained more than 10 times higher densities of copepods and cladocerans, the preferred prey for larval pike, compared to the other studied shores. Temperature conditions were also most favourable in the reed belt habitat. Thus, the reed belts of the inner and middle archipelago were shown to form the best habitat for larval pike in the coastal area of the northern Baltic Sea, and this was also the only habitat where pike larvae were found. Our results suggest that the poor survival and recruitment of pike in the outer archipelago, however, cannot exclusively be explained by sub-optimal feeding conditions of the larvae. There are also other important factors, presumably connected to the exposure to the open sea, that affect the distribution of the pike larvae. Our results, however, highlight the importance of sheltered coastal reed belt shores as reproduction habitat for spring-spawning fish in the northern Baltic Sea. Further, this study disproves the assumption that the seaweed bladder wrack ( Fucus vesiculosus) forms a reproduction habitat for pike in the coastal area.

Treatment of domestic wastewater in a pilot-scale HSFCW in West Iran

This research investigated the feasibility of using constructed wetland system with a second-stage processing, included duckweed lagoon as a polishing stage, as an appropriate technology for treating the domestic wastewater generated by small communities in the economical underdeveloped cold regions. The reed bed pilot included four basins, of which two were used to plant reed and the two others as witness. The duckweed pilot was set up near the reed beds. The pilot plant was tested with six different BOD, COD, TN, TP, TSS and TDS loadings. The test results showed the artificial reed bed with subsurface flow capable of removing TSS by 92%, BOD by 89% and COD by 78%. Moreover it is possible to remove phosphorus and nitrogen containing compounds by 29% and 35%, respectively. The reed bed effluents were discharged into duckweed lagoon and the removal ratios of the above parameters were once again studied. The results showed reductions of 20% in BOD, 10% in COD, 24% in TSS, 8% in TN and 29% in TP. Based on these studies, the use of artificial reed beds for treating household wastewater in small communities is a sound technical and economical solution, while duckweed can be used as a complementary post-treatment process during the warm seasons.

Comparative pilot study of the performances of two constructed wetland wastewater treatment hybrid systems

For small settlements sanitation, constructed wetland systems offer a suitable social economic alternative to the classic wastewater treatment plants. In order to study the treatment mechanisms occurring in the soil–plant system, we set up a small-scale pilot wastewater treatment plant composed by a settler/digester followed by two trains combining two different types of subsurface flow constructed wetlands called ‘hybrid systems’. The first train represents a combination of a vertical flow reed (Phragmites australis) bed followed by a horizontal bed, planted with Typha, whereas in the second one, the combination is reversed.The hybrid systems are fed intermittently with a hydraulic load of 0.2 m per day given in two sequences of one hour separated by a six-hour rest period. We followed the quality of the effluent at the outlet of the beds. The two hybrid systems present satisfactory performances: yields higher than 90% in organic matter removal are registered.For the first system we could obtain a substantial nitrification but uncompleted denitrification whereas for the second system we observed that the total nitrogen (NTK) reduction was achieved by denitrification and nitrification remains almost complete. The pathogenic bacteria abatement is satisfactory for the two systems but more remarkable for the second (2 u log).

Short-term water content analysis for the optimization of sludge dewatering in dedicated constructed wetlands (reed bed systems)

The performance of reed bed systems is usually presented following a long-term evaluation of case studies. However, short-term water content analyses may be useful to better understand the dynamics of the dewatering process and hence to rationally describe the system, with the ultimate aim of improving the system overall. In this study we performed daily water content analyses in the interval between subsequent sludge loadings in a real-scale reed bed system situated in Pisa (central Italy). Water content analyses were performed at different periods of the year: in winter, drainage quickly led to a maximum of about 8% dry matter while in summer the dewatering process significantly continued after the first week thanks to evapotranspiration. A comparative analysis of planted and unplanted beds confirmed that the mechanical function of plants is essential in the winter, when the unplanted bed did not present any dewatering capability. A semi-empirical equation describing the dynamics of the dewatering process is then proposed and calibrated. This equation forms the basis for the technical and economical optimization of the resting time in terms of required surface area and drying efficiency. An optimum of 11 days resting time was finally evaluated in the presented case study.

A comparative study on the treatment performance of a conventional septic tank system and reed bed-soil absorption system receiving domestic effluent

In Ireland, the most prevalent domestic wastewater treatment application in unsewered areas is the conventional septic tank system comprising of septic tank and soil absorption system, the latter more commonly referred to as a percolation area in Ireland. Recent concern has been expressed over the discharge of on-site effluent to highly permeable soils which, although permitted in current Irish EPA guidelines, has generated debate as to whether an insufficient level of treatment in the subsoil’s vadose zone is being achieved. In situations where a septic tank installation is considered unsuitable according to a rigorous site assessment, a secondary treatment system such as a horizontal subsurface-flow reed bed can be installed to improve the effluent quality before discharge to the subsoil. On-site research was thus carried out to assess and compare the treatment capabilities of freely-draining subsoils receiving both septic tank and secondary effluents in tandem with a treatment assessment of a horizontal subsurface-flow reed bed. Results over an 18-month period have shown the HF reed bed to perform poorly with removal of only 52% of the organic load. An impressive 1.9 log-unit removal in E. coli was nevertheless achieved. The majority of nitrification is seen to occur in the first 0.35m of subsoil for all sets of percolation trenches and, while coupled with poor denitrification throughout the subsoil, has compromised groundwater quality in the form of nitrate infiltration. The research also shows that in general the septic tank effluent has received a comparable quality to the secondary effluent in terms of N-loading and E. coli occurrence by the time the point of potential discharge to groundwater is reached in the subsoil.

Ecological studies on medaka in a remained habitat in Qinhuangdao, Hebei, China

Ecological studies were carried out in the remaining habitat for medaka (Oryzias latipes), a marsh in the suburbs of Qinhuangdao City, Hebei Province, China. Sewage released from villages increases the nutrient levels in open water areas of the marsh, while in cattail (Typha angustifolia) and reed (Phragmites communis) beds the nutrient levels are decreased. There are fewer zooplanktons in the cattail and reed beds than in the open water areas. Sampling fishes with trap nets showed that medaka lived in dense populations in the cattail and reed beds, while the other three fish species, wild goldfish (Carassius auratus), topmouth gudgeon (Pseudorasbora parva), and mud loach (Misgurnus bipartitus), occupied the open water areas in the marsh. A little amount of paradise fish (Macropodus chinensis) was also found in the marsh. Japanese fresh-water shrimps (Macrobrachium nipponense) were found only in the influx canal from waterworks. Indoor aquarium experiments showed that the wild medaka in this marsh was easily cultured with commercial feed similar to domesticated strains. Some ecological aspects of the medaka were discussed based on the observations of the fish in the marsh.