Some ecological aspects of aquatic oligochaetes in the Lower Pearl River (People's Republic of China)

Densities of the 8 most important species or genera of the 15 taxa found at a series of stations along the Guangzhou Reach of the Pearl River are given. Shannon-Weaver diversity index values were low throughout the area studied. No clear correlations were found between oligochaetes and NH₃-N or a combination of 6 chemical factors (COD, NH₃-N, NO₃-N, Cr, Pb, Hg). However, when the main groups of the benthos, including the oligochaetes, were taken together, and a BPI (Biological Pollution Index) approach used, a correlation between the macroinvertebrate community and the combined chemical factors was noted.     

Distribution patterns of aquatic oligochaetes inhabiting watercourses in the Northwestern Iberian Peninsula

Distribution patterns of aquatic oligochaete assemblages, inhabiting largely unpolluted watercourses, in the Northwestern Iberian Peninsula, and their relationships with chemical and physiographical characteristics were analyzed by means of multivariate analyses. Qualitative and quantitative samples from 47 stations were obtained seasonally during 1983/84 and 1988/90. The variables included in this study were altitude, order number, distance from the origin, mean width, mean depth, substrate, current velocity, oxygen content, pH, conductivity, alkalinity and concentration of different ions.From a chemical point of view, major changes in the structure of oligochaete assemblages were related to water mineralization. The correlation between faunal distribution and environmental variables showed a great increase when physiographic parameters were included in the analyses. Substrate type and current velocity are the principal variables explaining the community structure.     

Oligochaetes and water pollution in two deep Norwegian lakes

Analyses of the oligochaete fauna of two of the deepest lakes in Scandinavia — the Norwegian lakes Mjösa (450 m) and Tyrifjorden (295 m), revealed a totally different species composition in the deep profundal compared with the upper profundal - in contact with the nutrient-enriched epilimnion. In both lakes a pronounced thermal stratification develops in the summer, thus the epilimnion receiving gross organic pollution behaves differently from the profundal. The lakes are each effectively divided into two bodies of water with limited water exchange between them, i.e. one major oligotrophic body and one minor more nutrient-rich. Since the 1950s both lakes have been exposed to heavy pollution of various kinds. In Lake Mjösa in 1975 and 1976 unpleasant algal blooms of the blue-green alga Oscillatoria bornetii fa. tenuis occurred. Bottom samples obtained at the same time revealed that the deep central bottoms of the lake were totally dominated by oligotrophic oligochaete indicators, i.e. by Stylodrilus heringianus and Spirosperma ferox, while the fauna of the upper profundal in the vicinity of domestic and agricultural sewage outfalls, wood processing industries, etc. was dominated by Limnodrilus hoffmeisteri and Tubifex tubifex in great abundance, indicating enriched conditions. Several other species indicative of eutrophy, were absent, most of them belonging to the genus Potamothrix. A fairly similar situation exists in Lake Tyrifjorden, where, for instance, in the shallow bay of Steinsfjorden — heavily eutrophied by agricultural wastes — blooms of blue-green algae have caused problems from time to time. The same oligochaete communities as in Lake Mjösa distinguish the central oligotrophic bottoms from the regionally more enriched upper profundal. The likely reasons for an intact profundal oligochaete fauna are great volumes of oxygen-rich hypolimnic water of low temperature and a high bottom/lake surface area ratio.     

水生双翅目昆虫监测水体重金属污染的研究

水生双翅目昆虫是监测水体重金属污染的理想对象。文章归纳用于监测重金属污染的水生双翅目昆虫的种类,重点介绍水生双翅目昆虫在重金属污染下外部形态、内部结构、生化及分子水平的变化,以及相关生物标志物的研究,为水生双翅目昆虫用于水体重金属污染的生物监测提供科学依据。     

The occurrence of oligochaetes in lake chains receiving pulp mill waste and their relation to eutrophication on the trophic scale

Earlier conceptions of oligochaetes as indicators of trophy were somewhat enlarged to include more littoral, meiofaunal and naidid species. The amplitudes of different species on the oligotrophy-eutrophy axis seem to be generally large. Certain species which probably originally occur mainly in very humic environments seem also to be able to endure very strong organic loading caused by pulp mills. Species of this kind seem to be Dero digitata, Specaria josinae, Slavina appendiculata and Aulodrilus pluriseta. Chaetogaster langi and Arcteonais lomondi are also species which live in areas receiving pulp mill wastes. A. lomondi and D. digitata seem to be species living in greater depths than the naidids generally. Tubifex tubifex densities as high as 600000 ind · m^-2 were found near a pulp mill when the meiofauna method was used. A third of the T. tubifex were found deeper than 5 cm from the sediment surface. S. josinae and S. appendiculata may be found down to depths between 5 and 10 cm.     

Lacustrine,profundal meiobenthic oligochaetes as indicators of trophy and organic loading

Meiobenthic and macrobenthic oligochaetes were collected from two depths in Lake Päjänne and examined together with environmental data in which two environmental gradients can be seen. Numbers of Piguetiella blanci, Aeolosoma quaternarium and Aeolosoma hemprichi were positively correlated with oxygen saturation and negatively correlated with total phosphorus and COD suggesting that these species are indicators of oligotrophic conditions. Numbers of Amphichaeta leydigii, Specaria josinae and Vejdovskyella comata were positively correlated with total phosphorus which implies that these species prefer eutrophic conditions. The last three species and Dero digitata showed positive correlations with COD and organic sedimentation, which suggests that they also indicate organic loading. A decrease in aeolosomatid biomass was seen with increasing phosphorus and organic loading. The average body size of detritus-feeding naidids in the upper part of the profundal zone was reduced by organic loading, and more clearly eutrophication, which emphasizes the importance of including meiobenthic oligochaetes in pollution investigations. Of the naidid and aeolosomatid species, Chaetogaster langi preferred the greatest depths of the profundal zone while most of the other species were more abundant at 20 m rather than at the maximum depth. Clustering of the oligochaete taxa supported these observations and clustering of sampling stations based on oligochaete variables generally corresponded to clustering based on environmental data.     

New records of aquatic Oligochaeta from Texas,with observations on their ecological characteristics

Twenty-six species of aquatic oligochaetes are reported from Texas, including 18 Naididae, seven Tubificidae, and one Glossoscolecidae. Illustrations are provided for ten species recorded for the first time from the state: Chaetogaster cristallinus, Nais elinguis, Nais pardalis, Pristina acuminata, Pristina sima, Stylaria lacustris, Aulodrilus limnobius, Ilyodrilus templetoni, Limnodrilus claparedianus, and Sparganophilus tamesis. Species accounts include presently known distributions in Texas and ecological and morphological characteristics.     

The use of fish parasites as bioindicators of heavy metals in aquatic ecosystems: a review

Parasites are attracting increasing interest from parasite ecologists as potential indicators of environmental quality due to the variety of ways in which they respond to anthropogenic pollution. In environmental impact studies certain organisms provide valuable information about the chemical state of their environment not through their presence or absence but instead through their ability to concentrate environmental toxins within their tissues. Free living invertebrates, notably bivalve molluscs, are commonly employed in this role as `sentinel organisms' to monitor the concentrations of bioavailable metals in aquatic ecosystems. Also certain parasites, particularly intestinal acanthocephalans of fish, can accumulate heavy metals to concentrations orders of magnitude higher than those in the host tissues or the environment. The comparison of metal accumulation capacities between acanthocephalans and established free living sentinel organisms revealed significantly higher concentrations of several elements in Acanthocephalus lucii (Müller) than in the Zebra mussel Dreissena polymorpha (Pallas) which is a commonly used bioindicating organism in Europe. In contrast to the high heavy metal concentrations recorded in adult acanthocephalans, the larval stages in their respective crustacean intermediate hosts show little tendency to accumulate metals. A number of experimental studies demonstrate a clear time dependent accumulation of lead for acanthocephalans in their final hosts. These investigations provide evidence that the extremely high metal concentrations in intestinal acanthocephalans of fish are not the result of a slow process of accumulation but instead a relatively rapid uptake to a steady-state level. Thus, metal concentrations in adult acanthocephalans respond rapidly to changes in environmental exposure of their hosts. The value of parasites for environmental monitoring will be discussed in detail in the present article.     

Superficial and hyporheic oligochaete communities as indicators of pollution and water exchange in the River Moselle, France

Benthic oligochaetes were sampled on three occasions (June, August and October 1992) in the upper (0–10 cm) and hyporheic (35–45 cm depths) sediments at five sites of the River Moselle, from upstream of the town of Epinal to Velle-sur-Moselle. The first site (upstream from Epinal) is considered as unpolluted and the four remaining sites are polluted by industrial effluents. The most polluted stations were generally dominated by the pollution tolerant taxon Limnodrilus. Numbers of individuals of this taxon decreased at the less polluted last site in recovery zone, and were also scarce in the first unpolluted site. It is noteworthy that these tendencies were observed in both superficial and hyporheic substrates and to the greatest degree in hyporheic ones. At the unpolluted site, the hyporheic habitat is dominated by the groundwater species Propappus volki, Pristina spp., Pristinella spp. At the less polluted site (last site), the deep sediments are dominated by groundwater species and the Tubificidae without hair setae decrease from June to October. As a result of water exchange between superficial and subterranean waters, superficial substrates of the first and the last stations tend to be colonised by a high proportion of hyporheic species that suggests that flow is primarily from subterranean to superficial waters. The contrary is the case at other polluted stations which are characterised by the invasion of hyporheic substrates by the pollution tolerant superficial taxa Limnodrilus. This suggests that water flows from the river to the deeper groundwater. These two stations are located near drinking water plants which utilise groundwater, thus increasing the vulnerability of groundwater to surface contaminants.     

Assessment of pollution impact on aquatic microbial communities based on DNA hybridization and protozoan identification: preliminary method development and comparison

Common methods of assessing the biological impact of point source discharge involve a census of organisms above and below the discharge. The identification and enumeration of organisms necessary for this approach can be time consuming and costly. When microbial communities are used, identification and enumeration are often impossible because the majority of species are identifiable only when cultured and most native species cannot be cultured. As such, little is known about the response of nonculturable aquatic microbial communities to anthropogenic changes. We isolated aquatic microbial DNA from colonized artificial substrates in two streams receiving industrial waste. DNA was isolated from the microbial communities upstream and downstream of the discharges and the similarity of these communities were compared by DNA-DNA hybridization. These novel estimates of impact were compared to more conventional estimates based on a component of the microbial communities that could be readily identified, the protozoans. Protozoan species were identified and similarity between upstream and downstream stations was assessed using Jaccard's similarity index.In the Roanoke River, protozoan species richness was significantly lower at the downstream station. Both Jaccard's coefficients and DNA hybridizations indicated that upstream communities were more similar to each other than with the downstream site. However, these differences were not significant. Estimates of community similarity from Jaccard's coefficients and DNA hybridizations were not correlated. In Peak Creek, protozoan species richness was significantly lower at the downstream station. Jaccard's coefficients and DNA hybridizations were not significantly higher within upstream stations than between upstream and downstream stations. The two similarity measures were not correlated. Problems in this preliminary study included small sample sizes and highly variable background on hybridization membranes resulting from the use of nonradioactive DNA probe label and detection methods. Alternative approaches using radioisotopes or COT curves may be more viable means of making molecular methods a useful tool in impact assessment.     

The effect of organic pollution on the abundance and distribution of aquatic oligochaetes in an urban water basin, Taiwan

Aquatic oligochaetes are abundant in polluted areas and are, therefore, commonly used as bioindicators to study organic pollution in rivers and streams. In order to develop a species-level oligochaete biotic index to reflect the River Pollution Index (RPI) in the Taichung Water Basin in Taiwan, we conducted a systematic sampling scheme to collect aquatic oligochaetes from the sediment samples of watercourses in the Taichung Water Basin, Taiwan. We evaluated the relationships between aquatic oligochaetes and the sewage pollution using statistical methods. The distribution of aquatic oligochaetes in relation to environmental variables, such as water quality and sediment characteristics of the regional urban contaminated streams was expressed by Canonical Correspondence Analysis (CCA). We identified 17 species of aquatic oligochaetes (Annelida, Clitellata) including 3 species of Tubificidae, 13 species of Naididae, and 1 species of Enchytraeidae from the watercourses of an urban region in the Taichung Water Basin in Taiwan, during the summer and winter of 2005 and 2006. A positive correlation was found between the total abundance of aquatic oligochaetes and the RPI (r = 0.58, P < 0.05). However, only population density of the most abundant tubificid, Limnodrilus hoffmeisteri, increased with increasing RPI values and a significantly negative correlation was found between the population density of the naidid, Nais communis, and RPI values. The results of CCA indicated that certain naidids, such as Aulophorus furcatus and Allonais gwaliorensis also tolerated extremely polluted environments in upper stream or stony habitats, implying that tubificids should not be the sole representation of simple biotic indices but should also include pollution-tolerant naidids. We found that the community structure of aquatic oligochaetes was influenced by short-term variations in microhabitat rather than according to seasonal factors in our study region. The results proved that aquatic oligochaetes were sensitive enough to provide a supplement for the regional urban pollution assessment applications for biotic indicators at the species-level.     

An ecological study of a small New Zealand stream with particular reference to the Oligochaeta

The composition, temporal and spatial distribution, and productivity of profundal benthos were investigated in a Colorado Front Range reservoir which impounds water diverted from the Western Slope of the Rocky Mountains. Horsetooth Reservoir, 10.6 km × 1.0 km, consists of three basins with depths greater than 50 m connected by two equalizing channels ca. 30 m deep. Water quality parameters did not vary significantly between sites, but temperature, pH, and dissolved oxygen varied seasonally. The composition and organic content of sediment exhibited a gradient from inlet to outlet which significantly influenced faunal density and distribution patterns. Although 28 genera of macroinvertebrates were collected, the oligochaetes Tubifex tubifex (Müller) and Limnodrilus hoffmeisteri Claparède comprised 97.6% of the total organisms. Chironomids comprised 2.2%. The relative contribution of chironomids to total biomass decreased with increasing depth; the reverse was true for oligochaetes. Mean annual density ranged from 3,827 to 51,901 total organisms/m² for six sampling sites. Mean annual biomass varied from 0.16 to 2.3 g ash-free dry wt/m². Annual turnover ratios ranged from 3.6 to 4.5. Annual production estimates varied from 7.2 to 82.8 kg/ha ash-free dry weight, averaging 39.3 kg/ha or 26.9 kcal/m².     

Meiobenthic naidid and aeolosomatid oligochaetes from the profundal zone,and relations of species to eutrophication

Oligochaetes were sampled using meiobenthos methods from depths of between 20 and 94 m in Lake Päijänne in 1986. Individuals belonging to several species of the Naididae and Aeolosomatidae, which are generally considered to include mainly littoral or lotic species, were found more or less regularly at these profundal depths. The naidid species Chaetogaster langi and Amphichaeta leydigii were more abundant in the deepest areas than at 20 m. Species also appeared to react differently to water quality. The naidid species Chaetogaster langi and the aeolosomatid species Aeolosoma quaternarium, A. hemprichi and Rheomorpha neiswestnovae were most abundant on average at oligotrophic, unpolluted stations, naidid species Amphichaeta leydigii, Specaria josinae and Vejdovskyella comata were more abundant at eutrophicated stations and Dero digitata was more abundant in organically loaded areas. The observations of Amphichaeta leydigii, Chaetogaster setosus and Rheomorpha neiswestnovae were new for Finland.     

Environmental concentrations of polyhydroxyalkanoates and their potential as bioindicators of pollution

A quick and inexpensive protocol based on gas chromatography was used to identify and measure environmental concentrations of microbial polyhydroxyalkanoates, PHAs. Samples taken from apparently unpolluted sites characterised by agricultural land or native vegetation possessed concentrations ranging from 0.12 to 0.40 mg PHA per g sample. In contrast, environments impacted by anthropogenic activity displayed concentrations 14 to 40 times higher. The results support the suggestion that PHAs could be used as pollution bioindicators in preliminary assessments of environmental health.     

Oligochaete respiration as a measure of sediment toxicity in Puget Sound,Washington

Respiration rate measurements were conducted with the marine oligochaete Monopylephorus cuticulatus Baker and Brinkhurst to determine the sublethal toxicity of sediments collected from Puget Sound, Washington. Worms were exposed to elutriates prepared from centrifuged sediment slurries. Standard respiration rates were measured at high dissolved oxygen levels for each sample tested and were compared with control and other test results. A total of 97 sediment samples were tested; 40 samples demonstrated significant respiration effects (elevation or depression). Comparison with results of other tests conducted at the same stations or geographic locations (genotoxicity to fish cells, lethality to sensitive species, reproductive impairment tests) indicated very good agreement on broad scale toxicity patterns at different geographical areas, and that respiration measurements effectively determined sublethal toxicity of sediments. This study represents the first application of respiration measurements as a sublethal toxicity test for field-collected sediments.     

Anatomy and ultrastructure of the marine oligochaete Tubificoides benedii (Tubificidae), with emphasis on its epidermis-cuticle-complex

Although Tubificoides benedii (d'Udekem, 1855) (= Peloscolex benedeni) is a ubiquitous form in eutrophicated or polluted coastal muds and is characterized by an exceptional viability in sulphide sediments, almost nothing is known about its anatomy and the structure of its conspicuously papillate body surface. As a part of a research project on sulphide annelids, done by our group, we investigated the body structure of this common and still extraordinary marine tubificid using light, scanning and transmission electron microscopy.While the internal structures correspond to the general pattern of marine tubificids (Giere, 1983), the epidermis-cuticle-complex is unusual. The epidermis cells, which are much interdigitated, contain numerous extremely long and irregularly shaped mitochondria. At the tip of the body, many sensory cells, embedded in the normal epidermis cell layer, end with ciliary tufts at the body surface. Long epidermal microvilli traverse the thick cuticular layer which only in the anterior- and posterior-most segments is studded by epicuticular projections. From most parts of the body these surficial rodlets, so far held typical for all Oligochaeta, are absent. Instead, here the cuticle forms numerous high, almost leaf-life papillae between which a viscous mucus layer regularly harbours many bacteria.This distinct papillate body armature may serve for stabilization of the mucus layer with its associated bacteria. It is well conceivable that the mucus, beside its usual role of reducting friction in the burrowing process, attracts bacteria. That their settlement may be more than an accidental association and involve some regulative interaction is indicated by the specific attachment of gram-negative bacterial threads often populating the posterior end of T. benedii (Dubilier, 1986). The significance of possible stress exerted by the sulfide-environment on the worm, as evidenced by an unusually high concentration of lysosomal structures and abnormally formed mitochondria in the epidermis, has to be verified in further studies.     

Measuring the responses of macroinvertebrate communities to water pollution: a comparison of multivariate approaches, biotic and diversity indices

The responses of macroinvertebrate communities to pollution by sewage effluent in the River Trent system (UK) were investigated using a variety of multivariate approaches, biotic indices and diversity indices. It was found that multivariate analyses clearly illuminated the change of community structure along the pollution gradient. CY Dissimilarity Measure (CYD)-based Non-Metric Multidimensional Scaling (NMDS) appeared to perform better than DCA and clustering. Species richness, the BMWP, BMWP-ASPT, the Chandler Score, Chandler-ASPT could detect the effects of major pollution. However, these indices showed varying sensitivity to different ranges of pollution, for example, Chandler-ASPT and BMWP-ASPT are more sensitive to the change in clean/slightly polluted range than in the moderate/very polluted range. The diversity indices were the least informative. The advantages and disadvantages of the various approaches were discussed.     

Differences in endozoochorous dispersal between aquatic plant species, with reference to plant population persistence in rivers

Summary 1. In river ecosystems, populations are continuously subjected to unidirectional downstream currents resulting in a downstream movement of populations. To ensure long-term population persistence in rivers, organisms must have a mechanism for upstream dispersal, which allows them to re-colonise upstream areas.
2. In this study we assessed differences in the potential for endozoochorous seed dispersal of Sparganium emersum and Sagittaria sagittifolia , two aquatic plant species with different seed morphologies, by mallard ( Anas platyrhynchos ) and teal ( Anas crecca ), two duck species with different body weights.
3. We found no significant differences in seed retrieval (the proportion of ingested seeds retrieved after gut passage) and seed retention time (time between seed ingestion and retrieval), between mallard and teal, despite the difference in body weights. We did find a significantly higher germination (%) over retention time of S. emersum seeds retrieved from teal compared with mallard, most likely related to a more efficient removal of the seed coat during passage through the gut of teal.
4. There were large differences between S. emersum versus S. sagittifolia in: (i) seed retrieval (22.65 ± 20.8% versus 1.60 ± 2.4%, respectively); (ii) seed retention time in duck gut, with a maximum of 60 h versus 12 h; (iii) the effect of gut passage on seed germination, with an increase of approximately 35% versus a decrease of 25%; and (iv) the effect of gut passage on seed germination rate, with an acceleration of 10 days versus a delay of 3 days on average. The results show that S. emersum has a higher potential for endozoochorous dispersal by ducks and postdispersal establishment than S. sagittifolia .
5. We propose that, in rivers, bird-mediated seed dispersal may promote re-colonisation of upstream areas, enabling long-term plant population persistence.     

环境汞污染对藻类的毒性效应及其影响因素

综述了汞污染对藻类的毒性效应及影响因素。水环境中汞主要以元素汞、无机汞和有机汞3种形式存在。藻类吸附汞主要分为胞外的快速吸附和胞内的缓慢富集,在安全浓度内,金属汞对藻生长有一定的促进作用,随着浓度增大,抑制藻生长或致死。汞进入藻体细胞后,藻类为了存活会产生一系列保护机制。藻类对汞的排斥和排出作用可能就是对汞耐性的一种重要机制。藻类也可以通过多种方式减少汞进入藻类细胞,以及通过与其他物质结合汞使其排出胞外。温度、pH、生物学因素等影响重金属对藻类的毒性作用。并就藻类对汞耐性和适应机理、利用藻类修复和监测重金属污染、藻类响应汞胁迫的信号转导途径及其保护机制等未来研究领域进行了展望。     

The gutless oligochaete Phallodrilus leukodermatus Giere,a tubificid of structural,ecological and physiological relevance

Phallodrilus leukodermatus is not only characterized by the complete absence of mouth, gut, anus and nephridia, but also by an exceptional dermal ultrastructure which is associated with gram-negative bacteria. The vertical distribution of the worms from Bermudian carbonate sands is also unusual in attaining population maximum at oligoxic or anoxic depths around the redox discontinuity (RPD) layer, where extremely high concentrations of amino acids and sugars are to be recorded. Based on results from current ecophysiological and ultrastructural studies, an interpretation of the unique biology of the worms is attempted.