geomorphological factors are the major determinants of species
composition in water mite communities.
5. The complex, fully aquatic, life cycle and multilevel biocoenotic interactions
make water mites well suited for the detection of physical and chemical
disturbances to lotic ecosystems.
6. Future research should address the distribution, biology, autecology,
community dynamics and ecological interactions of lotic water mites.
Водотоки: низшие ракообразные.
Volume 44 Issue 1 Page 63 - May 2000
The biology and ecology of lotic microcrustaceans
M. -J. Dole-Olivier*, D. M. P. Galassi, P. Marmonier and M. Creuze Des Chatelliers*
1. Copepoda, Ostracoda and Cladocera are important meiobenthic Crustacea
which can be both numerically abundant and species rich in running waters.
Harpacticoids and ostracods are well adapted to benthic life because they
are typical crawlers, walkers, and burrowers. Many cladocerans are
substratum dwellers, but most benthic species among these can also swim.
Cyclopoids which are generally good swimmers are nevertheless often
bottom frequenters and actively colonise sediment interstices (the hyporheic
2. The subclass Copepoda includes 10 orders. With 53 families, the order Harpacticoida dominates the benthos. Only five of these families are represented in fresh waters (ca. 1 000 species and subspecies). The order Cyclopoida includes 12 families of which the Cyclopidae is well represented in freshwater habitats with 900 species and subspecies. Freshwater Ostracods belong to the order Podocopida (5 000 species) with three superfamilies occurring in running fresh waters. The group Cladocera contains four orders, 12 families, more than 80 genera, and 450-600 freshwater species. Most of the benthic species are found in the families Chydoridae (39 genera), Macrothricidae, Ilyocryptidae and Sididae.
3. For each of the three major taxa, morphological characteristics are presented, specimen collection and preparation are described and references to available taxonomical keys are provided.
4. Biological characteristics are extremely diverse among and within the three
taxa, resulting in a great variety of strategies in meiobenthic crustaceans.
Characteristics of reproduction, sexual dimorphism, cyclomorphosis and
population parameters (i.e. clutch size, lifespan, growth, moulting) are
provided for some of the most common species.
5. Important differences between the three main taxa were found at the species
level. Ecological requirements such as hydraulic microhabitats and
geomorphologic features of the streambed are the major determinants of
species diversity and abundance for benthic microcrustacea of lotic
Putting the meio- into stream ecology: current findings and future
directions for lotic meiofaunal research
A. L. Robertson*,S. D. Rundle and J. M. Schmid-Araya
1. There is a paucity of research on epigean freshwater lotic meiofauna. This
may result from a previous emphasis on interstitial (groundwater and
hyporheic) meiofauna and/or a reliance on sampling methodologies in lotic
systems which are inappropriate for meiofauna.
2. Meiofauna contribute much to the diversity of lotic ecosystems. Species
lists for seven streams reveal that meiofauna contribute 58-82% of total
species numbers, with rotifers and chironomids dominating most systems.
The absence of taxonomic keys for most meiofaunal taxa in large areas of
the world precludes a wider analysis of their contribution to lotic diversity
and an assessment of biogeographical patterns and processes.
3. The trophic and functional role of meiofauna in lotic ecosystems is unclear.
There are few estimates of meiofaunal production in freshwaters and
biomass spectra have produced conflicting results for lotic meiofauna.
Present static estimates suggest that the contribution of meiofauna to lotic
productivity and biomass is small to moderate, but further studies
incorporating a temporal component may provide a more realistic picture of
the total contribution of meiofauna to biomass size spectra.
4. Meiofauna differ from macroinvertebrates in several respects apart from
size and conceptual models for lotic ecosystems should include all
metazoans if they are to be truly representative.
5. Information on the basic ecology of certain lotic meiofauna (i.e. nematodes,
tardigrades, microturbellarians) is urgently required. For those groups
whose distributional patterns are better understood (e.g. microcrustaceans),
the mechanisms underpinning these patterns should be explored. It is
essential that the importance of meiofauna is recognised by lotic ecologists;
the only realistic way forward is for greater collaboration among meiofaunal
ecologists and taxonomists and other lotic scientists.
Водотоки с бобровыми прудами
Расселение, пограничные явления и трофические взаимодействия в речках с бобровыми прудами.
Dispersal, Boundary Processes, and Trophic-Level Interactions in Streams Adjacent to Beaver Ponds
ECOLOGY 1995, Vol 76, Iss 3, pp 908-925
I combined long-term (10 yr) descriptive and short-term experimental studies in a headwater stream in northern Minnesota to assess: (1) the effect of annual variation in stream discharge and spatial proximity of beaver (Castor canadensis) ponds on lotic fish abundance and (2) the subsequent influence of discharge and fish predation on lotic invertebrate
colonization. Considerable annual variation in fish density occurred in the stream over the 10-yr period, particularly in pool habitats. Increased fish density was associated with increased stream discharge and creation of beaver ponds downstream from the study site. Weir traps used to monitor directional (upstream vs. downstream) fish movement during the last 4 yr of the study indicated annual changes in fish density were associated with the amount of fish dispersal occurring along the stream segment. Downstream fish movement, out of an upstream beaver pond occurred primarily during periods of elevated stream discharge. Upstream movement, out of a downstream beaver pond, occurred over a broader range of discharge conditions. A controlled, ''split-stream,'' experiment examining the effect of very low vs. elevated discharge on upstream fish movement indicated, however, that upstream movement of fish out of beaver ponds was also reduced by very low discharge conditions. Movement data for individual fish species revealed considerable variation among the taxa in the tendency for downstream vs. upstream movement, due to variation in the morphology of upstream vs. downstream beaver ponds and its subsequent effect on the composition of fish dispersing from these source areas. Most fish movement occurred over relatively brief time periods, suggesting life history and developmental processes were critical in influencing the timing of dispersal. Size structure of fishes captured in the stream indicated predominantly older age classes (>age I) of fish were dispersing along the stream. However, based on the occurrence of age 0 individuals only 1 of 12 species, the creek chub (Semotilus atromaculatus), routinely reproduced in the stream.
Experiments conducted in an artificial stream located below one of the beaver ponds indicated discharge and fish predation have potentially strong and interactive effects on invertebrate colonization in stream ecosystems. Differences in colonization of riffles and pools under low vs. elevated discharge and fish vs. no-fish treatments suggested, however, that the interactive effect of these factors on invertebrate colonization was variable over even small spatial scales. Elevated discharge increased invertebrate colonization in riffles but decreased invertebrate colonization in pools. Contrary to intuitive expectations, fish predation reduced invertebrate colonization more under elevated than low discharge conditions, particularly in pool habitats.
Taken together, these results suggest: (1) beaver ponds act as reproductive ''sources'' for fish on the landscape, while adjacent stream environments act as potential reproductive ''sinks,'' (2) large-scale spatial relationships between beaver ponds and streams, along with the influence of discharge on the permeability of the boundaries between these habitats, are critical in controlling fish dispersal between ponds and streams and the subsequent abundance and composition of fish in lotic ecosystems, and (3) fish predation and discharge have potentially cascading effects on invertebrate colonization in lotic ecosystems.