The biology of Oligochaeta from Dorset chalk streams (original) (raw)
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Micro-distribution of oligochaetes in a soft-bottomed lowland stream (Elsbeek; The Netherlands)
Aquatic Oligochaetes, 1999
This study focuses on a low-gradient, soft-bottomed stream which shows strong fluctuations in discharge, partly natural (i.e. due to rainfall) and partly due to agricultural land-use. This dynamic discharge pattern causes silt deposition between discharge peaks which in turn cause the silt to be washed out. This process occurs independently from the height of the peak. The main substrate in the stream is quite homogeneous fine sand. Twenty-three species of oligochaetes were found. Their distribution and abundance varied with season and substrate. Mature tubificids and Lumbriculus variegatus occurred throughout the year. Stylodrilus heringianus occurred in winter and spring. Different naidids occur in different seasons, though half of the species can be collected all year. The micro-habitat of three tubificids, one lumbriculid and eight naidids were be identified. A high number of oligochaete species coexisted in a small stretch of the stream due to a separation in micro-habitat in space and time. The temporal variation in distribution was due to season. Particle size, the mineral and organic component of the substrate, and position in the stream bed influenced the spatial distribution of species. Temporal and spatial distribution of oligochaetes can not be separated.
Springer eBooks, 2001
In most soft-bottomed, lowland streams in the Netherlands discharge regimes largely follow the precipitation pattern. Winter discharges are higher and much more dynamic then summer discharges, although rain storms throughout the year cause unexpected peak flows. Minimal precipitation, reduced stream flow and droughts can occur during the summer months. Lowland stream habitat, particularly in The Netherlands, is hydrologically dynamic, with substrates frequently moved or disturbed. Differences in discharge patterns in Dutch soft-bottomed lowland streams are expected to affect distribution patterns of macroinvertebrates and thus oligochaetes. Ten small to medium sized lowland streams, differing from one another in hydrological regime, were studied. Five major habitats in each stream were assessed on three occasions over a 15-month period. Each habitat sampled with a micro-macrofauna shovel; during each sampling period, several environmental parameters, especially hydrological and substrate parameters, were measured. Ordination (CANOCO) (Ter Braak, 1989) and statistical tests (chisquared test) (Lindgren & McElrath, 1970) were used to determine the major oligochaete distribution patterns between streams as well as between habitats within each stream. Each stream was characterized by its oligochaete assemblage; general distribution patterns and individual oligochaete-substratum relationships were documented. Hydro-morphological parameters together explained the differences in major distribution patterns. Preferences of oligochaetes for specific structural habitats are discussed.
The effect of drought on Oligochaeta communities in small woodland streams
Oligochaeta communities were studied in four streams inflowing Lękuk Wielki lake and from the outflow of this lake (NE Poland) during 1997-1999. Twenty five taxa of oligochaetes were identified, representing aquatic (Tubificidae, Lumbriculidae), semi-aquatic (some Enchytraeidae and Lumbricidae) and soil (Lumbricidae, some Enchytraeidae) families. The occurrence of Naididae was limited to the outflow of the lake. After a drought period the densities of oligochaetes were the highest, diminishing during the permanent flow period. The composition of the oligochaete fauna in the studied small, drying streams depends on fauna composition in the lake and surrounding soil as well as the inflow from shallow subterranean waters, therefore species with different ecological requirements appear simultaneously.
The Enchytraeidae (Oligochaeta) of streams of Southern England
Annales de Limnologie, 1989
The authors present a list of aquatic Enchytraeidae for the streams of Southern England. They examine the distribution of the species. Les Enchytraeidae (Oligochaeta) des eaux courantes du sud de l'Angleterre. Mots clés : Enchytraeidae aquatiques, Angleterre. Les auteurs dressent un inventaire de la faune des Enchytraeidae aquatiques du sud de l'Angleterre. lis envisagent la répartition des espèces.
Acta Limnologica Brasiliensia, 2011
Aim: This study evaluated the use of oligochaetes at different levels of taxonomic resolution as environmental indicators in Argentine lowland streams affected by different land uses. Methods: Sampling sites were grouped based on the physicochemical and habitat characteristics (low-, moderate-, and high-impact disturbance). Collection of the oligochaetes samples was carried out seasonally in sediment and vegetation habitats. Results: The increases in nutrients and organic matter produced elevated densities of the Oligochaeta, but when the disturbance also involved changes in the physical habitat or enhancements in toxic substances, the abundance decreased significantly to values even lower than those of non-impacted environments. The responses of Naidinae and Tubificinae were similar. The density of the Pristininae decreased with increasing impact, but those of the Enchytraeidae and Rhyacodrilinae increased at the most highly impacted sites. The Opistocystidae were not recorded in high-impact sites. Species richness and diversity (H') were lower in high-impact sites and even lower in sediments. Some species presented no restrictions in the habitat type or with the contamination level: Limnodrilus hoffmeisteri, Dero furcatus, D. digitata, D. pectinata, Pristina longiseta, and P. aequiseta. Moreover, Trieminentia corderoi, Slavina appendiculata, and Aulodrilus pigueti exhibited the highest abundances at low-impact sites and were not registered in high-impact sites. Conclusions: The Oligochaeta show a relatively wide ecological valence through their extensive number of species. Although lower taxonomic levels can give information about environmental status, test-species' sensitivities to different types and degrees of contamination will be of utmost relevance to the evaluation of ecological quality.
1999
The lack of any reliable method for assessing the age of individuals collected in the field has often been considered a major obstacle for population studies in aquatic oligochaetes. One possible solution could be the adoption of other variables, such as weight or stage, for the definition of the population structure; this approach would be useful if allowed good predictions about population growth. We measured, under laboratory conditions, the effect of age, size and life stage on survival, growth and fecundity of Limnodrilus hoffmeisteri Claparède. The results are used to establish four matrix population models, based respectively on the classification of the individuals by age, weight and stage and on a mixed classification. Matrix population models make the assumptions that the individuals in a population can be arranged in a number of discrete classes and that time is a discrete variable. In these models, the population is represented by a vector (each element in the vector is the number of individuals in a class) and the demographic coefficients (survival, growth and fecundity) are collected in a square matrix. The estimate of λ, the potential long term population growth rate and its confidence interval were taken from the four models using the jackknife method. The width of the confidence interval is a measure of the effectiveness of the models and thus of the classification of the individuals. The results suggest that weight is inefficient as a criterion for the definition of population structure of L. hoffmeisteri in comparison to age and stage.
Canadian Journal of Fisheries and Aquatic Sciences, 2001
Most tubificid worms are classified in the same functional group by their similar bioturbation and feeding activities in fine sediments of lakes. The objective of this study was to test the functional redundancy of two genera of tubificids (Limnodrilus and Tubifex) at two densities in coarse sediments using slow filtration columns. We measured the effects of the worms on particle redistribution, organic matter processing, nutrient fluxes, and microbial characteristics. The results showed that Limnodrilus and Tubifex created the same stimulation of aerobic and anaerobic microbial activities in the sediment. However, 50 Tubifex had a greater effect than 50 Limnodrilus on microbial processes. Furthermore, at a density of 100 oligochaetes per column, only Tubifex significantly increased particle redistribution and oxygen consumption in the first centimetre of the sediment. In contrast, Limnodrilus more often modified microbial activity in the deeper layers of the columns. The functional redundancy of the two genera of tubificid worms was validated by most measured processes. However, the variability within functional groups cannot be neglected because each genus had its functional peculiarity in the ecosystem. Résumé : En raison de leur mode de déplacement et d'alimentation dans les sédiments fins des lacs, la plupart des oligochètes tubificidés sont classés dans le même groupe fonctionnel. L'objectif de cette étude est de tester la redondance fonctionnelle entre deux genres de tubificidés (Limnodrilus et Tubifex) pour deux densités en organismes dans des sédiments grossiers en utilisant des colonnes infiltrantes. L'effet des vers est mesuré sur la redistribution des particules, la décomposition de la matière organique, les flux de nutriments et plusieurs paramètres microbiens. Les résultats indiquent que Limnodrilus et Tubifex produisent une stimulation des activités microbiennes aérobie et anaérobie dans le sédiment. Cependant, 50 Tubifex ont un effet plus important sur l'activité microbienne que 50 Limnodrilus. A une densité de 100 individus par colonne, seul Tubifex augmente significativement la redistribution des particules et la consommation en oxygène dans les premiers cm de sédiment. Au contraire, Limnodrilus semble être plus actif que Tubifex en profondeur. La redondance des deux genres de vers est validée par la plupart des processus mesurés. Cependant, la variabilité à l'intérieur des groupes fonctionnels ne peut être négligée car chaque genre a sa spécificité dans le fonctionnement de l'écosystème. Mermillod-Blondin et al. 1759
Acta Limnologica …, 2008
The water quality of an urban stream in southeast Brazil was evaluated using species of Tubificidae (Annelida: Oligochaeta) as biological indicators. From May 2005 to April 2006, a total of 75,746 specimens were collected, from which six species (Aulodrilus limnobius, Bothrioneurum sp., B. vejdovskyanum, L. hoffmeisteri, L. udekemianus, Tubifex tubifex) were found. In the majority of the sampling sites, the Tubificidae species were found at high densities (>5,000 ind.m -2 ). Limnodrilus hoffmeisteri, which is widely used as an indicator of organic pollution, composed more than 75% of collected fauna. Using some biotic indices such as density of Tubificidae, percentage of L. hoffmneisteri and Modified Howmiller and Scott Environmental Index, it was possible to verify that São Pedro stream receives large amounts of organic pollutants. These findings confirm Tubificidae as an effective biological indicator of stream conditions. Resumo : Utilizando espécies da família Tubificidae (Annelida:Oligochaeta) avaliou-se a qualidade da água de um córrego urbano, no sudeste do Brasil. De maio de 2005 a abril de 2006, foram coletadas seis espécies (Aulodrilus limnobius, Bothrioneurum sp., B. vejdovskyanum, L. hoffmeisteri, L. udekemianus, Tubifex tubifex) num total de 75.746 espécimes. Em todos os pontos de coleta, com exceção do ponto I, os tubificideos ocorreram em elevada densidade (>5.000 ind.m -2 ), sendo Limnodrilus hoffmeisteri, espécie amplamente reconhecida como indicadora de poluição orgânica, compôs mais de 75% da fauna coletada. Através da utilização dos seguintes índices bióticos, como a densidade de Tubificidae, porcentagem de L. hoffmneisteri e Índice Ambiental Modificado de Howmiller and Scott foi possível constatar que o córrego estudado recebe elevada carga de material orgânico oriundo de atividades humanas, confirmando o potencial dos oligoquetos tubificideos na avaliação da qualidade de ambientes aquáticos.
Man and River Systems, 1999
This study had a purpose to validate different tools based on the oligochaetes for the evaluation of the biological quality of sediments within a surveillance network. Biological data (IOBS index, percentage of Tubificidae with and without hair setae, worm densities), physical data (granulometrics) and chemical data (Cd, Cu, Cr, Hg, Ni, Pb, Zn, PCBs, PAHs) have been studied with co-inertia analysis. These analyses show an opposition between IOBS index and metals, a correlation between metals and percentage of Tubificidae without hair setae, and an association between PAHs, low index values, high densities and high percentage of Tubificidae with hair setae. For 24 sites, biological and chemical data gave similar information. In 11 cases on 36 they are conflicting. The use of metal speciations, according to the method of Teissier et al. (1979), show that the organic matter content seems to have an important role by sorbing metals leading to lower availability. Macrophyte cover could also explain some conflicting results. Granulometrics does not play a determinating role in the present case. As a conclusion, a table allowing the classification of river sediments is proposed for monitoring assessment. This table takes into account IOBS index values, the worm densities and the percentage of Tubificidae without hair setae.
Fundamental and Applied Limnology / Archiv für Hydrobiologie, 2009
The taxonomic and functional structure of oligochaete and chironomid communities in a stony-bottomed river reach was investigated with respect to substrate and hydraulic conditions. Combined oligochaete and chironomid data were analyzed to search for main gradients and the separate data sets were analyzed to identify the most important variables determining the structure of the communities. Preferences for particular hydraulic conditions, expressed as Froude number, were calculated for 29 most abundant taxa. The results of Correspondence Analysis (CA) indicated that the main gradient in the data could be explained by hydraulic conditions and, inversely, by the amount of sedimented particulate organic matter (POM). The second CA axis probably refl ected the quantity of the available food and space resources. Canonical Correspondence Analysis (CCA) showed the amount of sedimented POM as the most important variable explaining 21 and 24 % of the variance in the oligochaete and chironomid data, respectively. Among the other variables, the occurrence of aquatic vegetation, variability of near-bottom current velocity and substrate roughness were the most important. In the case of chironomids, the proportions of functional feeding strategies changed along the gradient of hydraulic conditions: the proportions of predators, active fi lterfeeders and collectors/gatherers decreased with the increasing hydraulic stress, while the proportion of grazers/ scrapers increased. Nevertheless, in the case of oligochaetes, the proportions of functional feeding strategies did not follow the gradient of hydraulic conditions. Although the total abundance of both oligochaetes and chironomids was independent of hydraulic conditions, only few oligochaete taxa were able to succeed in hydraulically rough conditions and most oligochaete taxa were found only in pools. On the other hand, chironomids showed high taxa richness, which seemed to be limited by the quantity of the available food and space resources rather than hydraulic stress.