Densities Of Oligochaetes Research Articles

Long-term changes in the density and composition of profundal macrobenthos in Lake Biwa from 1966 to 2000

Lake Biwa, the largest lake in Japan, has been affected by eutrophication and climate warming since the 20th century. To examine the effects of these environmental changes on dominant macrobenthos species in Lake Biwa, the density and composition of these organisms were determined monthly from 1966 to 2000 at an offshore station in the lake, and analyzed in terms of various physicochemical factors. Annual mean bottom temperatures at the site generally remained stable (6.1–8.0°C) until 1985, increased from 1985 (6.5°C) to 1990 (8.3°C), and remained high thereafter (7.4–8.3°C). Branchiura sowerbyi dominated the oligochaete community in terms of density and biomass until 1985. Oligochaete density increased after 1986, dominated by B. sowerbyi, Limnodrilus spp., and Tubifex tubifex. Although the increase in macrobenthic density after 1986 was mainly explained by an increase in T. tubifex density (3811–8076 individuals m–2), total macrobenthos biomass was mainly controlled by B. sowerbyi (1.9–9.5 g m–2). Notably, the increase in T. tubifex density roughly coincided with density decreases in the benthic gobid fish Gymnogobius isaza (from 567 tons to undetectable) and the shrimp Palaemon paucidens (from 758 to 142 tons). Jesogammarus annandalei density increased from 1985, roughly coinciding with the decrease in gobid fish. These findings demonstrate the importance of biological interactions such as predation in the succession of dominant macrobenthos species in Lake Biwa.

Macroinvertebrate Response to Internal Nutrient Loading Increases in Shallow Eutrophic Lakes.

In eutrophic lakes, even if external loading is controlled, internal nutrient loading delays the recovery of lake eutrophication. When the input of external pollutants is reduced, the dissolved oxygen environment at the sediment interface improves in a season without algal blooms. As an important part of lake ecosystems, macroinvertebrates are sensitive to hypoxia caused by eutrophication; however, how this change affects macroinvertebrates is still unknown. In this study, we analysed the monitoring data of northern Lake Taihu from 2007 to 2019. After 2007, the external loading of Lake Taihu was relatively stable, but eutrophication began to intensify after 2013, and the nutrients in the sediments also began to decline, which was related to the efficient use of nutrients by algal blooms. The community structure and population density of macroinvertebrates showed different responses in different stages. In particular, the density of oligochaetes and the Shannon-Wiener index showed significant differences in their response to different stages, and their sensitivity to eutrophication was significantly reduced. Under eutrophication conditions dominated by internal loading, frequent hypoxia occurs at the sediment interface only when an algal bloom erupts. When there is no bloom, the probability of sediment hypoxia is significantly reduced under the disturbance of wind. Our results indicate that the current method for evaluating lake eutrophication based on oligochaetes and the Shannon-Wiener diversity index may lose its sensitivity.

What Are the Relationships between Plankton and Macroinvertebrates in Reservoir Systems?

Macroinvertebrates and plankton play crucial roles in reservoir food webs; however, their relationships have received limited attention. This study investigates the associations between plankton and macroinvertebrates in fifty selected reservoirs. During the spring season, significant concordances were observed in species richness between phytoplankton and zooplankton, as well as between zooplankton and macroinvertebrates. In contrast, during the summer season, the concordance in species richness between phytoplankton and macroinvertebrates was higher compared to other assemblages. Although macroinvertebrates showed a strong connection with phytoplankton in terms of species richness in both seasons, the congruencies were not statistically significant. Partial least squares regression (PLSR) analysis revealed that the densities of phytoplankton, Chlorophyta, Cyanophyta, and protozoans significantly influenced the total macroinvertebrate density in both seasons. Additionally, the densities of mollusks and aquatic insects were affected by the densities of Chlorophyta and Cyanophyta, while the density of oligochaetes was influenced by the density of Chlorophyta. These findings indicated that phytoplankton and zooplankton serve as primary food sources for macroinvertebrates, highlighting the close relationship between plankton and macroinvertebrates in reservoir systems. Moreover, the results of formative measurement models indicated a strong association between zooplankton and macroinvertebrates during the spring, whereas phytoplankton and macroinvertebrates exhibited a close association during the summer. The substantial concordance in density between phytoplankton and zooplankton revealed by the formative measurement models confirmed that assemblages with similar body sizes exhibit stronger concordance compared to those with significant differences in body size.

Benthic infaunal spatial biodiversity, coexistence, and availability for shorebird communities in the Jakarta Coastal Wetlands, Indonesia

Abstract. Wibowo AA, Basukriadi A, Nurdin E, Nasution NS. 2022. Benthic infaunal spatial biodiversity, coexistence, and availability for shorebird communities in the Jakarta Coastal Wetlands, Indonesia. Intl J Bonorowo Wetlands 12: 23-32. Wetlands on the Jakarta Coast, Indonesia, is one of the important habitats for shorebirds. In the wetland ecosystem, benthic infauna is an important food source for the shorebird community. This study aims to assess the benthic infaunal spatial biodiversity and its availability for the shorebird community in the wetlands covering an ecotourism area and the west and east parts of a protected mangrove forest. The bird diversity was assessed using visual encounter surveys and 10 x 10 m plots for mangroves. The K-means clustering method measured the benthic infaunal coexistence and availability for shorebirds. Based on the result, benthic infauna was available as a food resource for shorebirds in the following order: Oligochaeta > Polychaeta > Gastropod > Crustacea, with the density of oligochaetes reaching 376.66 inds/100 m2. The Shannon-Wiener biodiversity index (H’) ranges for benthic infauna were 1.306-1.573. Gastropods were available to Ciconiidae and Anhingidae; oligochaetes and polychaetes were available to Anatidae, Scolopacidae, and Phalacrocoracidae. In contrast, crustaceans were not available to any shorebird species. As confirmed in this study, shorebird species were associated with the presence of benthic infaunal communities and it recommends conserving the wetlands to ensure the availability of benthic infauna.

Non-native Dreissena associated with increased native benthic community abundance with greater lake depth

Although the typical interaction between non-native invasive species and native species is considered to be negative, in some cases, non-native species may facilitate native species. Zebra and quagga mussels (Dreissena spp.) are aggressive invaders in freshwater systems, and they can alter energy flow by diverting nutrients from pelagic to benthic food-webs. In the last two decades, quagga mussels have largely replaced zebra mussels in shallow regions of the Laurentian Great Lakes and colonized deeper waters previously devoid of all dreissenids. Here, we aim to characterize potential positive effects of dreissenids in relation to depth on the benthic community in lakes Michigan and Huron. For this study, we used benthic survey data collected from Lake Michigan in 2015 and Lake Huron in 2017 and annual U.S. EPA Great Lakes National Program Office Long-term Biology Monitoring Program data for both lakes from 1998 to 2019. Benthic species richness and abundance (excluding dreissenids) in both lakes were almost three-fold higher in the nearshore (<70 m) compared to offshore (>70 m) communities. We found that, even though abundance of benthic invertebrates decreased with increased depth, total benthos density and biomass were higher in the presence than in the absence of quagga mussels in both lakes. Moreover, increased quagga mussel density and biomass with depth offset the lower benthos density and biomass at deeper depths, and samples with dreissenids had high densities of oligochaetes in both nearshore and offshore communities. These patterns are consistent with facilitative effects of quagga mussels on both shallow and deep-water benthic communities.

The enemy of my enemy is my friend: Consumption of parasite infectious stages benefits hosts and predators depending on transmission mode.

Research Highlight: Hobart, B. K., Moss, W. E., McDevitt-Galles, T., Stewart Merrill, T. E., Johnson, P. T. J. (2021). It's a worm-eat-worm world: Consumption of parasite free-living stages protects hosts and benefits predators. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13591 Many parasites and pathogens have infectious stages that are vulnerable to consumption by non-host organisms. This consumption can benefit both the predators that consume this unusual food resource and the hosts which are less likely to encounter infectious propagules. Yet the importance of these benefits may also depend on parasite transmission, which can influence consumer opportunities to feed upon free-living infectious stages. Hobart et al. (2021) report that freshwater snails with high densities of symbiotic oligochaetes are less likely to be parasitized by trematodes (Platyhelminthes) with an 'active' versus 'passive' (motile or stationary, respectively) mode of transmission, supporting a protective effect via oligochaete predation upon infectious propagules. However, these predators benefit from snails harbouring passively acquired infections, and likely achieve their higher abundance from easy access to prey in the form of a second infectious stage emerging from these hosts. Consumption of free-living infectious stages is thus beneficial to hosts and predators, but varies with parasite life history and ecology.

Macrozoobenthos assemblage patterns in European carp (Cyprinus carpio) ponds − the importance of emersed macrophyte beds

Qualitative and quantitative differences in benthic macrozoobenthos distribution in carp pond littoral zones (macrophyte areas; LM) and pelagic zones (macrophyte-free areas; MF) were assessed in four commercial carp (Cyprinus carpio) grow-out ponds in the Czech Republic (semi-intensive management) and Austria (organic management) monthly over the growing season (June-September) of 2016 and 2017. While differences in environmental parameters and granulometric composition between LM and MF were statistically non-significant (p&gt; 0.05), organic matter content was significantly higher (p&lt; 0.05) in LM. Average macrozoobenthos density and biomass in LM (mean 431 ind.m−2and 6.78 g.m−2) was usually significantly higher (p&gt; 0.05) than MF (371 ind.m−2and 3.17 g.m−2). A similar trend was observed for zoobenthos diversity, with LM having a higher diversity (76 taxa) than MF (47 taxa). At the start of the growing season, chironomid density was higher (p&lt; 0.05) in muddy MF zones, regardless of management type, while oligochaete density was higher in muddy LM. The density of both groups later declined, such that density was significantly higher (p&gt; 0.05) in sandy substrates, regardless of habitat or management type. Our data suggest a significant drop in macrozoobenthos density and biomass compared with historical data, mainly due to new management techniques (fertilisation, supplementary feeding) and intensification (higher stock densities), suggesting that pond management is crucial as regards benthic invertebrate development and diversity. Our results indicate that emersed LM beds positively influence macrozoobenthos performance in carp ponds, potentially making them biodiversity hotspots. Further, LM beds can be regarded as invertebrate harbours, and hence should be protected and encouraged.

ФАУНА МАКРОБЕСПОЗВОНОЧНЫХ ОЗЕРА НЕРО

The taxonomic composition of macrobenthos of Lake Nero and the mouth area of the river Sarah are shown. The main part of the benthos in the summer in the lake is formed by larvae of amphibiotic insects – chironomids, biting midges and mayflies. The macrobenthos of the lake and the mouth of the Sara River can be characterized as chironomid species complex. Relative to the results of previous studies, changes occurred in the dominant complex, a decrease in the total biomass of macroinvertebrates was noted. Together with a decrease in the species diversity, the only one dominant species (Chironomus f.l. plumosus) indicates a decrease in the homogeneity of the structure of benthic communities and its simplification. A decrease in the species richness, occurrence and density of oligochaetes was observed in comparison with the data of other studies. In contrast benthic communities, aquatic plants biotopes can be characterized as more favorable for both benthic and fitophilic invertebrates. The large number of invertebrate species makes it possible to evaluate the thicket as a biotope with very favorable environmental conditions. Rheophilic, limnophilic and obligate benthic species occurring here can coexist, rising from the bottom into thickets with a favorable oxygen regime, which allows them to survive in conditions of oxygen deficiency.

Effect Thresholds of Metals in Stream Sediments Based on In Situ Oligochaete Communities

Aquatic oligochaetes, comprising a large number of species showing various degrees of resistance to chemical pollution, are recognized as valuable bioindicators of sediments’ quality. In the Geneva area (Switzerland), oligochaete tools were previously tested for assessing the biological quality of stream sediments, and effect thresholds of combined metals (quotients) in sediments were defined. The aims of the present study were to update this previous work with new data acquired in different cantons of Switzerland and to establish effect thresholds on oligochaete communities for individual metals and for combined metals. The oligochaete metrics “Oligochaete index of sediment bioindication (IOBS)”, “oligochaete density” and “percentage of tubificids without hair setae” proved pertinent for assessing the effects of metals and organic matter in sediments. We established a threshold effect level (TELoligo) and probable effect level (PELoligo) for eight metals in sediments (Cr, Ni, Zn, Cu, Pb, Cd, Hg and As) as well as a probable effect level for these metals combined (mPELoligo-Q). These thresholds could be used directly to screen for alteration of in situ communities restricted to sediments and/or for establishing sediment quality standards based on a combination of different biological and ecotoxicological tools.

Urbanization alters belowground invertebrate community structure in semi-arid regions: A comparison of lawns, biofilters and sage scrub

As the proportion of the human population living in cities continues to increase, understanding the factors affecting urban biodiversity is crucial to enhancing conservation efforts, urban ecosystem function, and human wellbeing. Here we present the results of the first comparative study of belowground invertebrate communities in urban soils (lawns and biofilters) and remnant patches of native coastal sage scrub (CSS) in a semi-arid urban environment. Among 12 sites sampled in La Jolla, California, USA, invertebrate community composition was most homogeneous among lawns, which differed significantly in composition from both biofilters and CSS. In almost all other aspects of invertebrate community diversity metrics (richness, evenness, diversity) as well as environmental factors (moisture, organic matter, plant cover and richness), lawns differed significantly from native CSS habitats, but biofilters were intermediate and not significantly different from other habitat types. Lawn soil invertebrate evenness and diversity were significantly lower, but density was highest in lawns, with higher densities of oligochaetes (Megadrilacea, Enchytraeidae), fly larvae (Sciaridae, Chironomidae), mites (Oribatida, Mesostigmata), and springtails (Poduromorpha, Symphypleona) in lawns relative to CSS. Differences in soil moisture, organic matter, and plant, tree, and building cover explained 40–62% of the variability in invertebrate density, richness, diversity, and evenness among sites. These findings suggest a shift in belowground invertebrate community structure that may be common among urbanizing semi-arid environments. The amendment of urban dryland soils with organic matter and moisture alters the presence and population density of several invertebrate taxa, and may cause a transition toward dominance by desiccation-intolerant litter transformers.

Simultaneous preservation of the DNA quality, the community composition and the density of freshwater oligochaetes for the development of genetically based biological indices.

IntroductionOligochaetes are recognized as valuable bioindicators of sediment quality in streams and lakes. The development of an oligochaete index based on the identification of specimens using DNA barcodes requires a method for simultaneously preserving the DNA quality and information on the specimen density and oligochaete community composition. Absolute ethanol optimally preserves DNA but fixation of freshwater oligochaetes with this medium can cause disintegration and fragmentation of specimens. Here, we investigated the possibility to preserve oligochaete specimens in low-pH formalin and in neutral buffered formalin for up to four weeks before genetic analyses and tested if the addition of absolute ethanol to formalin-fixed oligochaetes resulted in a loss of specimens and/or species.MethodsWe performed guanidine extraction and polymerase chain reaction (PCR) amplification/sequencing of a fragment of the cytochrome c oxidase I (COI) gene on tissue fragments preserved in low-pH formalin for up to 3 weeks and in neutral buffered formalin for up to 4 weeks. In addition, we compared the density and taxonomic composition of formalin-fixed oligochaetes of several sieved sediment samples before and after the addition of absolute ethanol.ResultsThe COI fragment of all oligochaete specimens preserved in neutral buffered formalin for up to 28 days was successfully amplified by PCR and obtained sequences were complete and of high quality. The amplification success rate for low-pH formalin fixed specimens declined after 7 days of storage. The addition of absolute ethanol to formalin-fixed oligochaete communities did not alter density or diversity estimates.DiscussionOur results indicate that sediment samples can be stored in neutral buffered formalin for up to 4 weeks and the sieved material can then be transferred to absolute ethanol, without affecting DNA quality, density and community composition of oligochaetes. Based on these results, a protocol for preserving freshwater oligochaetes, describing all the steps from collection of sediments to preservation of the biological material in absolute ethanol, is proposed. This method of fixation/preservation is of relevance for establishing DNA barcode reference databases, inventories of genetic diversity and developing genetically based biological indices.

Change of macrobenthic communities in the 1930s, 1970s and 2015 in the mesotrophic Lake Nojiri, Central Japan

We documented the current status of the macrobenthic community of Lake Nojiri (surface area: 4.56 km2; maximum depth: 38.5 m; altitude: 654 m above sea level; mesotrophic lake), and examined changes over time in the densities of chironomids and oligochaetes, by comparison with previous quantitative data of the lake reported in 1931 and 1973. We discussed the succession of benthic macroinvertebrates in relation to changes in the lake bottom environment, as evidence of lake eutrophication. On March 10, 2015, a bathymetrical sampling survey was carried out using a standard Ekman grab at each of the 5 stations (min. ca. 6 m – max. ca. 27 m) in Lake Nojiri. The average densities of the benthic communities for all the stations were ca. 5000m-2, comprised principally of oligochaetes ca. 2800 m-2 (57%) and chironomids ca. 2100 m-2 (43%), whereas their benthic biomass averaged ca. 9.7 g m-2, chironomids ca. 7.6 g m-2 (77%) and oligochaetes ca. 2.3 g m-2 (23%). In the shallower stations, the dominant species was Heterotrissocladius sp., but Chironomus nipponensis Tokunaga was the dominant species in the deeper stations. The densities of C. nipponensis was ca. 14 times higher than those reported by Miyadi in 1931 and 4 times higher than reported by Kitagawa in 1973a. In recent years the density of the oligochaete Tubifex tubifex, has tended to increase and the anoxic- and anaerobic-layer have thickened, especially in deeper regions where they are widely distributed. Moreover, we found differences in the C. nipponensis larval growth rate with water depth, i.e., small IV-instar larvae that dominated at the deepest Station 5. At this station, we suggest that low dissolved oxygen concentration and low water temperature during summer-fall suppresses growth of C. nipponensis. Large environmental changes must have affected chironomid and oligochaete densities and growth rate of C. nipponensis, especially in the deeper regions with low dissolved oxygen concentrations, low water temperature and high organic matter (ignition loss; 15.0% in St. 4 and 13.9% in St. 5) in the sediments. This is a strong evidence that the eutrophication of this lake is continuing.

Geographical variation in oligochaete density and biomass in subtropical mangrove wetlands of China

Oligochaetes play an important role in nutrient cycling and energy flow in benthic food webs as well as in mangrove wetlands. However, they have not been as extensively studied as other macrofaunal groups such as polychaetes, gastropods, bivalves, and crustaceans. Under the assumption that oligochaete density and biomass obey specific geographical distribution patterns in subtropical mangrove wetlands of China, we investigated these two parameters in the Luoyang Estuary of Quanzhou Bay, Zhangjiang Estuary and Gaoqiao mangrove wetlands. A geographical gradient in oligochaete density was present in Aegiceras corniculatum and Kandelia obovata habitats, whereby it decreased from lower latitudes to higher latitudes. Further, ANOVA tests on oligochaete distribution revealed that both oligochaete density and biomass were significantly influenced by region, season and region × season at the A. corniculatum and K. obovata habitats. The annual average oligochaete density and biomass at the A. corniculatum habitat were higher than that at the K. obovata habitat, in both the Luoyang and Zhangjiang estuaries. There were significant correlations between oligochaete density and biomass and sediment particle size parameters, confirming that sand, silt, and clay contents were the key environmental factors affecting oligochaete distribution.

Invasive red swamp crayfish (Procambarus clarkii) and native noble crayfish (Astacus astacus) similarly reduce oligochaetes, epipelic algae, and meiofauna biomass: a microcosm study

AbstractHuman activities have led to the decline of native crayfish and promoted dispersion of invasive species in European freshwater ecosystems. Crayfish are well-known predators of benthic macroinvertebrates, but benthic communities in aquatic ecosystems also include an abundant and functionally important meiofaunal component. For these organisms, the effects of invasive and native crayfish species are poorly understood. In this study, the effects of predation by the invasive red swamp crayfish (Procambarus clarkii) and the native noble crayfish (Astacus astacus) on the density, biomass, and secondary production of meiofaunal assemblages were compared in a model ecosystem experiment. Both crayfish species reduced the overall density of oligochaetes; the biomasses of total meiofauna, oligochaetes, and microcrustaceans; and secondary production by total meiofauna and oligochaetes. Nematodes and rotifers were unaffected by either crayfish species. An analysis of the gut contents of P. clarkii and A. astac...

The effect of sediment characteristics on bioturbation-mediated transfer of lead, in freshwater laboratory microcosms with Lumbriculus variegatus.

While it has been well established that sediment bioturbators can affect the fate of metals in aquatic systems and that the fate of metals there can depend on sediment characteristics, the interaction between these influences is not well known. The present study therefore investigated whether the influence of a sediment bioturbator on the fate of metals is affected by sediment characteristics. This was investigated using two laboratory microcosm experiments with lead-contaminated sediment and the oligochaete Lumbriculus variegatus. The first experiment used sediment collected from five Toledo Bend reservoir sites that differed in sediment characteristics, and analyses looked at the influence of sediment organic matter, sediment silt/clay content, sediment pH, and pore-water pH. In the second experiment, organic matter and silt/clay content of Toledo Bend reservoir sediment were varied experimentally using alpha-cellulose and clay, and Pb transfer to the water column and bioaccumulation were again quantified. Both experiments were conducted with sediment spiked with Pb to a concentration of 100 µg/g, at an oligochaete density of 6279 ind./m². In the first experiment, the Pb concentrations in the water column and those in the worms at the end of the 14-day experiment differed among sediment-collection sites. Silt/clay content and sediment pH were the two most important variables influencing Pb transfer from sediment to the water column. A multiple regression model with these variables explained 58% of the variability in this lead transfer. For Pb accumulation by the worms, sediment organic matter and pore-water pH were the two most important variables. This regression model explained 85% of the variability in tissue Pb levels. In the second experiment, where the individual effects of the organic matter and silt/clay content on Pb transport and distribution were assessed, the use of sediment with more organic matter resulted in a reduction in both the Pb transfer to the water column and the accumulation in worms. The increase in the sediment's silt/clay content resulted in a reduction in Pb bioaccumulation only. Overall, the results of the present study demonstrate that sediment pH, pore-water pH, organic matter, and silt/clay content influence the bioturbation-mediated transfer and the environmental distribution of Pb.

Landscape Visual Quality and Meiofauna Biodiversity on Sandy Beaches.

Sandy beaches are central economic assets, attracting more recreational users than other coastal ecosystems. However, urbanization and landscape modification can compromise both the functional integrity and the attractiveness of beach ecosystems. Our study aimed at investigating the relationship between sandy beach artificialization and the landscape perception by the users, and between sandy beach visual attractiveness and biodiversity. We conducted visual and biodiversity assessments of urbanized and semiurbanized sandy beaches in Brazil and Uruguay. We specifically examined meiofauna as an indicator of biodiversity. We hypothesized that urbanization of sandy beaches results in a higher number of landscape detractors that negatively affect user evaluation, and that lower-rated beach units support lower levels of biodiversity. We found that urbanized beach units were rated lower than semiurbanized units, indicating that visual quality was sensitive to human interventions. Our expectations regarding the relationship between landscape perception and biodiversity were only partially met; only few structural and functional descriptors of meiofauna assemblages differed among classes of visual quality. However, lower-rated beach units exhibited signs of lower environmental quality, indicated by higher oligochaete densities and significant differences in meiofauna structure. We conclude that managing sandy beaches needs to advance beyond assessment of aesthetic parameters to also include the structure and function of beach ecosystems. Use of such supporting tools for managing sandy beaches is particularly important in view of sea level rise and increasing coastal development.

Influence of the ornamental red cherry shrimp Neocaridina davidi (Bouvier, 1904) on freshwater meiofaunal assemblages

Meiofauna serves as a link between microbial production and higher trophic levels, such as macroinvertebrates and juvenile fish. However, the role of meiofauna in the freshwater food web has not been accurately evaluated, and the influence of shrimp predation on freshwater meiofaunal assemblages is unknown. In this study, the predation effects of Neocaridina davidi , an ornamental freshwater shrimp native to inland water bodies in Asia, on meiofaunal density, biomass, structure, and secondary production were examined using model ecosystems (microcosms) that were sampled repeatedly over 42 days. Shrimp predation altered the structure of the meiofaunal community over the course of the experiment, in particular the density, biomass, and secondary production of nematodes, microcrustaceans, and oligochaetes. An analysis of the stomach contents of N. davidi indicated a high degree of omnivory and the frequent consumption of meiofaunal organisms. The results indicated that predation by the freshwater shrimp N. davidi depresses the overall abundance, biomass, and secondary production of meiofaunal assemblages. Moreover, they also provide insights into food-web ecology and the first evidence of freshwater shrimp predation on meiofaunal assemblages.

Assessing the diversity of the benthic oligochaete communities in urban and woodland ponds in an industrial landscape (Upper Silesia, southern Poland)

Studies were carried out in two mining pond complexes in an industrial landscape. The first complex (consisting of six ponds) was located in an urban area and the second one (consisting of six ponds) in a woodland area. The aims of the study were to assess the diversity of benthic oligochaetes and to evaluate which environmental variables are most important in determining variations in the community structure in ponds of varying location. In total, 21 oligochaete species were recorded (7–11 in the urban ponds, 11–15 in the woodland ponds). Aulodrilus pluriseta, Aulodrilus japonicus and Ophidonais serpentina were only found in the woodland ponds, while Potamothrix bavaricus only occurred in the urban ponds. Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Chaetogaster diaphanus and Ophidonais serpentina dominated in the woodland ponds, whereas Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Potamothrix bavaricus and Tubifex tubifex prevailed in the urban ponds. The total density of oligochaetes was higher in the urban ponds thought the values of the diversity indices were higher in the woodland ponds. The local diversity of the ponds was high, while the among-site diversity made only a small contribution to the regional diversity. Nonetheless, a cluster analysis divided all of the ponds into two distinct groups depending on their location. CCA analysis showed that conductivity, pH, total hardness, alkalinity, the concentration of chlorides and the content of organic matter in the bottom sediments were most associated with the distribution of some oligochaete species among the ponds studied.

Macrozoobenthic community structure and bioassessment of water quality in Lake Dongting, China

2014年4个季度对洞庭湖大型底栖动物进行调查,共记录底栖动物4 门7纲58种,其中寡毛类7种,软体动物28种,水生昆虫19种,线虫1种,蛭类2种,钩虾1种.洞庭湖底栖动物平均密度为187.4 ind./m²,软体动物是最主要的类群,平均密度为88.7 ind./m²,占总密度的47.3%,寡毛类和水生昆虫的密度分别为24.1和27.8 ind./m²,分别占总密度的12.9%和14.9%.河蚬(Corbicula fluminea)、铜锈环棱螺(Bellamya aeruginosa)、苏氏尾鳃蚓(Branchiura sowerbyi)、指突隐摇蚊(Cryptochironomus digitatus)和钩虾(Gammaridae sp.)为洞庭湖的优势种.典范对应分析表明,水温和溶解氧是影响洞庭湖底栖动物分布的关键环境因子.采用Shannon-Wiener多样性指数和BI生物指数对洞庭湖各样点的水质状况进行评价,总体上评价结果分别为轻污染和良好,结果表明二者具有一定的差异,结合洞庭湖各样点的综合营养状态指数可以看出,BI指数的评价更加适合洞庭湖水质评价.;Macrozoobenthos were quarterly investigated in Lake Dongting in 2014, a total of 58 species belonging to 4 Phylums and 7 Classes were recorded, including 7 Oligochaeta, 28 Mollusca, 19 Insecta,1 Nematoda, 2 Hirudinea and 1 Gammaridae. The average density of macrozoobenthos was 187.4 ind./m²,of which mainly represented by mollusks. The density of mollusks, oligochaetes and aquatic insects was 88.7, 24.1 and 27.8 ind./m²,accounted for 47.3%, 12.9% and 14.9% of total density, respectively.The dominant species were Corbicula fluminea, Bellamya aeruginosa, Branchiura sowerbyi, Cryptochironomus digitatus and Gammaridae sp.. Canonical correspondence analysis showed water temperature and dissolved oxygen were highly correlated with macrozoobenthic community structure.Shannon-Wiener diversity index and Hilsenhoff's Biotic Index (BI)were calculated to assess the water quality of Lake Dongting,the evaluation result was light pollution and good respectively.The results of two indices were different to a certain extent, combined with ∑TLI, BI methods was more suitable for bioassessment in Lake Dongting.

The effects of predation by juvenile fish on the meiobenthic community structure in a natural pond

Summary Benthic communities in aquatic ecosystems include an abundant and functionally important meiofaunal component. The effects of predation by fish on zooplankton, macroinvertebrates and periphyton in freshwater habitats have been clearly demonstrated, whereas impacts on meiofaunal assemblages are poorly understood. In this study, the predation effects of benthivorous juvenile carp (Cyprinus carpio) on the abundance, biomass, secondary production, size classes and community structure of meiofaunal assemblages and on nematode diversity in the littoral zone of a natural freshwater pond were examined over 125 days using field enclosures and exclosures. Fish predation altered the abundance, biomass and secondary production of nematodes, oligochaetes and microcrustaceans (cyclopoids, harpacticoids, ostracods and cladocerans) but not of rotifers. These changes were consistent with top‐down control of the freshwater meiofaunal assemblages in the natural pond over time. By contrast, small‐bodied meiofauna were more abundant in the presence of fish, suggesting indirect facilitation. Both species richness and species composition but not the diversity of the nematode community were affected by fish predation. Removal of the fish from the enclosures resulted in the thorough recovery of the density, biomass and secondary production of nematodes, oligochaetes and microcrustaceans within 45 days. The results indicate that predation by juvenile freshwater fish depresses the overall abundance, biomass and secondary production of meiofaunal assemblages, except in the case of rotifers, and alters the size structure of the meiofaunal community. Our study provides insight into the food‐web ecology of lakes and the first evidence of freshwater fish predation effects on meiofaunal assemblages in a natural habitat.