11. Communities in aquatic habitats

11.1. Ephemeral water bodies

In temporary habitats there is only a short period of time in which the water body is filled with (some) wa - Tubifex tubifex ter. In these habitats only the oligochaetes with a rapid reproduction (R-strategy) are able to survive and variegatus Dero digitata Nais elinguis establish a population. These species reproduce asexually by means of parthenogenesis ( ), architomy ( ) or paratomy ( , ). Cocoon-forming sexually

reproducing species are not capable to reproduce in just a short period2 of time. So in these habitats the di - versity is low, but the abundance may reach over 100,000 ind./m . These ephemeral water bodies are not only small puddles or forest-tracks filled with rainwater but also flooded pools in meadows, river banks after high water or the tidal area of the river delta. In these water bodies not only aquatic oligochaetes may Typical species: Dero digitata Tubifex tubifex Varichaetadrilus be found, but also limnic . harmani , , and probably also 11.2. .Ground water, springs

In ground water and springs the temperature is one of the key factors. A few species of aquatic oligochaetes, especially within the Lumbriculidae and the subfamily Rhyacodrilinae (tubificids), are characteristic for ground water influenced water bodies. Probably all of these species can freely migrate between ground water and surface waters. These migratory species are called AED-species or Active Exchange Describers (Lafont & Vivier 2006). AED-species are mainly found in the ground water itself, but dependent on the sea - son and the temperature, these can occasionally be found in the surface waters. In early spring, when the Trichodrilus temperature of the surface waters are low and the ground water level is high, these AED-species are able and Rhyacodrilus to migrate to the surface waters. That is why ground water species like spec. (Lumbriculidae) spec. (tubificids) are most often found in spring (April-May). In summer and autumn, when the temperature of the surface water is higher and the groundwater level is lower, ground water Typical species Lumbriculus variegatus Trichodrilus Hap- related species, are less often found in surface waters. lotaxis gordioides Bichaeta sanguinea Rhya- : All Lumbriculidae except (e.g. , ssp.), codrilus coccineus Rhyacodrilus falciformis Rhyacodrilus subterraneus Embolocephalus velutinus Pro- , , all the Rhyacodrilinae and Phallodrilinae species, including pappus volki Pristina , , and , , 11.3. Ditches, andssp. ponds

In our area these smaller permanent water bodies are mostly eutrophic with usually an abundance of silt Elodea nutallii Ceratophyllum demersum and or Potamogeton pectinatus and organic material. When the saprobic level is not that high, there can also be an abundant growth of waterweeds, with , as the most common ones. The ditches are usually less than 60 cm deep, not more than 6 meters width and stagnant. Limnodrilus hoffmeisteri L. claparedianus and Ilyo- The banks are either natural but most of all protected by wooden piling. In ditches the number of species drilus templetoni are usually low, often with only 2-3 species present i.e. , . Depending on the type of bank and the development of waterweeds there may be more species present. Also size matters. In small, shallow ditches there are in general less species present than in larger, deeper ditches, thus the size of the water body matters. The densities however, may be higher in smaller water bodies. Typical species: Lumbriculus variegatus limosella Chaetogaster limnaei Dero digitata Nais pardalis Nais communis Nais variabilis Ophidonais serpentina Slavina appendiculata Stylaria lacustris , , , , , , , , , ,

254 Limnodrilus claparedianus Limnodrilus hoffmeisteri Tubifex tubifex Ilyodrilus templetoni Potamothrix heuscheri Psammoryctides barbatus Quistadrilus multisetosus , , , , 11.4. Canals, and lakes , .

Although the morphology of lakes and canals are quite different, there is a resemblance in oligochaet com- munity. The water bodies are large with more or less turbulent water, and (in our faunal area) mostly eu- trophic. The diversity and species composition depends on organic contamination, oxygen depletion, and dynamics. Organic contamination in conditions of low water dynamics can result in the absence of Oli- gochaeta caused by oxygen depletion. Dynamic water movement can stimulate the mass development of in organically polluted areas. Low water mobility near the bottom, which leads to the accumu- lation of organic matter in sediments, and the formation of sapropel, can also be limiting to oligochaetes. The distribution of oligochaetes in lakes depends on many different factors, most of them regulated by hy- drodynamics. Thus, the structure and development of oligochaete communities is directly related to water movement. Exsessive dynamic action and stagnation are equally detrimental to these (Slepukhina Spirosperma ferox Tubifex tubifex Stylodrilus heringianus and Psammoryctides barbatus 1996). In Swedish lakes Milbrink et al. (2002) recognized several oligochaete communities: oligotrophic lakes with , , , and a Potamothrix hammoniensis subdivision dependant on the presence or abundance of a particular species, mesotrophic lakes with mix- Potamothrix heuscheri Tubifex tubifex and Limnodrilus hoffmeisteri ture of species, and eutrophic lakes with a variety of tolerant species such as , , . In our faunal area oligotrophic lakes Typical species: Rhynchelmis limosella, Nais bretscheri Ophidonais serpentina Ripistes parasita Aulodri- are scarce. lus limnobius Aulodrilus pluriseta Branchiura sowerbyi Ilyodrilus templetoni Limnodrilus claparedianus , , , Limnodrilus hoffmeisteri Limnodrilus udekemianus Potamothrix hammoniensis Potamothrix heuscheri , , , , , Potamothrix moldaviensis Psammoryctides albicola Psammoryctides barbatus, Psammoryctides moravicus , , , , Quistadrilus multisetosus, Rhyacodrilus coccineus Spirosperma ferox Tubifex tubifex , , , 11.5. Brooks , , .

Brooks are small, flowing water bodies. The brooks are usually located in sandy areas, like the pleistocene eastern part of The Netherlands and the dune area. Brooks are either meandering through the landscape with natural banks, but may also be normalized with banks of wooden piling. In both types, one should keep in mind that the bottom may have a more or less heterogenous composition of substrates and conse - quently a local difference in species composition. Sandy and silty substrates both have their correspond - Typical species: Lumbriculus variegatus Stylodrilus heringianus, Trichodrilus Dero dorsalis Nais alpina ing species. Nais behningi Nais bretscheri Nais elinguis Nais pseudobtusa Piguetiella blanci Specaria josinae Uncinais , , , , uncinata Aulodrilus japonicus Bothrioneurum vejdovskyanum Haber speciosus Limnodrilus claparedianus , , , , , , Limnodrilus hoffmeisteri Limnodrilus udekemianus, Psammoryctides albicola Psammoryctides barbatus , , , , , Rhyacodrilus coccineus Spirosperma ferox Lophochaeta ignota Tubifex tubifex Propappus volki , , , 11.6. Acidic waters, (fens, moorland, pools) , , .

Acidic waters are characterized by a low pH, a certain instability of the water level, and a deficiency of available food. These waters are usually dystrophic. These water bodies are mostly located in the sandy areas in the pleistocene eastern part and the dune area. In these water bodies the oligochaete fauna is Typical species: Lumbriculus variegatus Dero obtusa Ripistes parasita Vejdovskyella comata impoverished, and only a few species are adapted to this habitat. , (?), , .

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