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Мейобентос водотоков.

Водотоки: донные коловратки.


Freshwater Biology

Volume 39 Issue 1 Page 25 - February 1998

Small-sized invertebrates in a gravel stream: community structure and

variability of benthic rotifers

J. M. Schmid-Araya

1. The Rotifera assemblage inhabiting the streambed surface and the hyporheic

zone of a gravel stream was investigated between October 1991 and October 1992.

Forty-two species of Monogononta and 27 of Bdelloidea were identified. Within

these two classes, dominant species differed between the surface and the hyporheic

zone. At the streambed surface, the abundance of monogonont rotifers showed a

seasonal pattern with significantly higher densities in pools, whereas bdelloids

showed no clear temporal trend and did not differ significantly among sites. In the

hyporheic zone, the depth distribution differed among the two rotifer groups,

bdelloids occurred in highest densities between 0 and 30cm sediment depth, while

monogononts were most abundant at greater depths.

2. Species composition differed greatly between successive sampling dates (min. 5

to max. 26days) at both the streambed surface and the hyporheos. At the

streambed surface and in the shallow hyporheos a significantly higher percentage of

species was replaced in riffles than in pools.

3. Few measured hydrophysical variables were associated with the Rotifera

assemblage structure. At the streambed surface, species richness was negatively

correlated with water temperature and substratum heterogeneity, and Monogononta

rotifer densities declined with water depth and substratum roughness.

4. Permutation tests carried out on temporal serial correlations showed that, at riffle

sites at the streambed surface, bdelloid rotifer densities, rotifer species richness and

diversity did not differ significantly from a temporal, near-random pattern. The

hyporheic rotifer assemblage followed similar near-random patterns.

Водотоки: мейобентос


Freshwater Biology

Volume 44 Issue 1 Page 1 - May 2000

An introduction to a special issue on lotic meiofauna

A. L. Robertson*,S. D. Rundle and J. M. Schmid-Araya

Summary

1. This special issue focuses on the meiofauna of lotic freshwater systems,



providing a review of the biology and ecology of this relatively poorly

studied constituent of the benthos in running waters.

2. Six papers review the biology and ecology of the major groups of lotic

meiofauna: microturbellarians; rotifers and gastrotrichs; nematodes; water

mites; microcrustaceans and tardigrades.

3 Current knowledge of the ecology of lotic meiofauna is presented further in

six papers that also highlight important future directions for research.

Водотоки: турбеллярии


Freshwater Biology

Volume 44 Issue 1 Page 5 - May 2000


The biology and ecology of lotic microturbellarians


Jurek Kolasa

Summary


1. More than 200 known species of Microturbellaria occur in running waters

world-wide but discovery of many more is likely. Their population density

varies greatly as a function of substratum, productivity, phenology and

hydrology. The density may exceed 7 000 individuals m-2. The number of

species in a single small sample may reach 20.

2. Many species appear to have microhabitat or stream section specialisation

but community patterns are obscured to a certain extent by common and

eurytopic species. The specialisation is particularly evident in the smaller,

lower-order streams.

3. Some of this habitat specialisation is attributable to the ecological origin of

species that may include terrestrial, underground, marine and lentic species

pools.


4. Feeding habits of Microturbellaria range from omnivory to specialised

predation.

5. Quantitative field studies require extraction and examination of live specimens

from samples. Such samples pose transportation and storage problems and

must be processed within hours of collection.

6. Taxonomy is well resolved for the Northern Hemisphere but is likely to be a

major challenge in other parts of the world. In any region, however, new

species may demand caution while using current keys to their identification.



Водотоки: коловратки и гастротрихи.

Freshwater Biology

Volume 44 Issue 1 Page 15 - May 2000


The biology and ecology of lotic rotifers and gastrotrichs


Claudia Ricci* and Maria Balsamo

Summary


1. The occurrence of Rotifera and Gastrotricha in the meiobenthos of lotic

habitats is reviewed. About 150 rotifer and 30 gastrotrich species are

reported in such habitats worldwide.

2. The two phyla share some morphological and biological features that might

account for their presence in the meiofauna. Small-size, a soft and elongate

body, adhesive glands on the posterior body end, movement through cilia,

relatively short life cycles, parthenogenesis and dormant stages are common

characteristics.

3. Most species of both taxa inhabiting the superficial sediments in streams

and rivers may move downward into the hyporheos in response to both

biotic (predation) and abiotic (spates, erosion, desiccation) disturbances.


Водотоки: нематоды.

Freshwater Biology

Volume 44 Issue 1 Page 29 - May 2000


The biology and ecology of lotic nematodes


Walter Traunspurger

Summary


1. Morphological structures for identifying freshwater nematodes, e.g. buccal

cavity, sensory receptors, oesophagus, reproductive organs and tail are

described.

2. Most freshwater nematodes belong to the Adenophorea and are

characterised by the presence of setae, adhesive glands and conspicuous

amphids.

3. Methods for collecting nematodes from the sediments of running water

(e.g. corer, pumps), within plants and aufwuchs are listed. Methods for

fixation, extracting and preparing nematodes for identification are

described.

4. Life history parameters (e.g. generation time, eggs per female) are not

available for lotic nematodes but are summarised for free-living nematodes

in soil, lakes and seas. Field studies indicate that, in contrast to laboratory

experiments with nematode cultures, many species will have a generation

time of several months.

5. Abundance and species diversity of nematodes of lotic habitats are

provided; more than 100 nematode species inhabit lotic habitats and

densities can reach 230 individuals per ml.

6. Links between meiobenthic nematodes and the micro- and macrobenthos

are unclear at present. Evidence such as the increased bacterial activity due

to nematode grazing suggests that such interactions may be significant.

Водотоки: клещи.

Freshwater Biology

Volume 44 Issue 1 Page 47 - May 2000



The biology and ecology of lotic water mites (Hydrachnidia)

A. di Sabatino * R. GereckeAND P. Martin

Summary

1. The Hydrachnidia (water mites, Hydracarina) are the most diversified group



of the Acari in freshwaters and are abundant and speciose in lotic habitats.

Lower-order streams may contain up to 50 species (including benthic and

hyporheic forms) and small springs up to 20 crenobiont species.

2. Water mites are grouped into 8 superfamilies, 50 families, 300 genera

containing more than 5 000 species. Representatives of all superfamilies

(about 3 000 species worldwide) occur in lotic ecosystems, although most

lotic species belong to the Hydryphantoidea, Lebertioidea and

Hygrobatoidea. Identification of water mite families, genera and subgenera,

throughout the world, is possible using taxonomic publications. Keys to

species level are also available but mainly for local faunas. Descriptions of

larvae and deutonymphs are rare.

3. The life cycle of the Hydrachnidia is unique among the Acari and is similar

to that of holometabolous insects, with a heteromorphic parasitic/phoretic

larva and two pupa-like resting stages. The larva parasitises mainly insect

hosts with apparently no strict host-specificity. Deutonymphs and adults

are voracious predators feeding mainly on insect eggs, insect larvae and

microcrustaceans. In some cases, water mite parasitism and predation may

substantially affect the structure of lotic communities.

4. Most species show a high degree of habitat/microhabitat specialization.

Temperature, current-speed, substratum type, physiographic and

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.

Freshwater Biology

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*

Summary


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

zone).


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

habitats. Many studies on the ecology of these communities are limited by a

lack of knowledge of the life history characterisitics of lotic (especially

interstitial) crustacean populations.



Водотоки: тихоходки.

Freshwater Biology

Volume 44 Issue 1 Page 93 - May 2000


The biology and ecology of lotic Tardigrada


Diane R. Nelson* and Nigel J. Marley

Summary


1 Tardigrades comprise a micrometazoan phylum that is a sister group of the

arthropods.

2 They are components of the meiobenthos in lotic habitats, and 50-70

species have been reported in such habitats world-wide. Approximately 800

species have been identified from all marine, freshwater, and terrestrial

habitats.

3 Taxonomy is based primarily on the morphology of the claws, buccal-

pharyngeal apparatus, cuticle and eggs.

4 Reproductive modes include sexual reproduction (amphimixis) and

parthenogenesis. The sexual condition of individuals may be either

gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout

the life of the tardigrade.

5 Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis,

osmobiosis and anhydrobiosis) enable tardigrades to withstand

unfavourable environmental conditions.

6 Population densities, life histories, dissemination and biogeography of

freshwater species are poorly known.

Водотоки: факторы микрораспределения мейобентоса.

Freshwater Biology

Volume 44 Issue 1 Page 109 - May 2000


What drives small-scale spatial patterns in lotic meiofauna communities?


Christopher M. Swanand Margaret A. Palmer

1. Lotic meiofaunal communities demonstrate extremely variable dynamics,

especially when viewed at small spatial scales ( metres). Given the limited

amount of research on lotic meiofauna, we chose to organise our

discussion of their small-scale spatial patterns around the dominant factors

we believe drive their spatial distributions in streams. We separate scale-

dependent effects that structure lotic meiofauna into biotic factors (e.g.

predation, food quantity/quality, dispersal) and abiotic factors (e.g. local

flow dynamics and substratum characteristics).

2. The impact of predation on the distribution of meiofauna varies with the

scale over which predators forage (e.g. fish predation influences meiofauna

in different ways and at broader spatial scales than do invertebrate

predators), the type of streambed substrata in which the predator-prey

interactions occur, and the dispersal ability of different meiofauna. The

latter is greatly influenced by predator and prey (meiofauna) interactions

with the flow environment.

3. Organic matter influences the small-scale distribution of meiofauna in

streams. Both its quality as food (as indicated by C:N content, ATP

content, or microbial biomass) and its spatial distribution on the streambed,

influence meiofauna patchiness, community structure and life history

characteristics. As a habitat, the structure that organic matter provides (e.g.

wood or leaves) can influence predator-prey interactions, offer materials for

case-building and offer refugia during disturbance events - all of which

influence the small-scale spatial distribution of meiofauna.

4. Stream flow influences the distribution of meiofauna at broad scales (10s-

100s of metres), primarily because of the high susceptibility of meiofauna to

passive drift; small-scale interactions between flow and substrata are also

important, however, particularly at more localised ( metre) scales. At both

scales, substratum particle size is important to interstitial-dwelling fauna,

influencing the probability of passive drift by meiofauna as well as local

microhabitat conditions (e.g. dissolved oxygen; upwelling/downwelling in

the hyporheic zone) and, thus, the small-scale distribution among

microhabitats.

5. In general, the processes governing the distribution of meiofauna at small

scales cannot be separated entirely from those processes working at larger

scales. A conceptual diagram is presented illustrating the relative importance

of various factors in influencing the spatial patterns of meiofauna and over

what scales these factors act.



Водотоки: региональное распределение мейобентоса.

Freshwater Biology Volume 44 Issue 1 Page 123-134 - May 2000

Global and regional patterns in lotic meiofauna

Simon D. Rundle*, David T. Bilton* and Dennis K. Shiozawa

1. Parsimony analysis of endemicity (PAE) was used to assess patterns in the

distribution of harpacticoid copepods (all freshwater species and stream

species only) at global and regional scales. These analyses provided a

focus for reviewing large scale patterns and processes in freshwater

meiofauna.

2. On a global scale, PAE suggested that large-scale biogeographical events

have been most important in shaping present-day distributions in the

Canthocamptidae. A small proportion (4%) of canthocamptid species were

widespread (i.e. occurred in more than one biogegraphical region),

suggesting that dispersal may also play a role in determining distribution at

the species level. Global distribution patterns for other meiofauna suggest

varying roles for dispersal and vicariant events. No consistent latitudinal

trends in species diversity were evident, although a lack of distributional

data for many regions, and uncertainty over the status of many

cosmopolitan species, precludes more robust analyses. Molecular

techniques should prove useful in identifying truly cosmopolitan taxa.

3. On a regional scale, a PAE within Western Europe demonstrated a clear link

between the distribution of canthocamptid species and the extent of the

Last (Wiechselian) glaciation. Northern and southern areas of Europe

contain distinctive harpacticoid faunas and the recolonisation of northern

Europe appears to have been from the Balkans rather than other

Mediterranean peninsulae. The high harpacticoid diversity in southern

Europe, may reflect a lack of glacial disruption of groundwater habitats.

4. A PAE of lotic data for harpacticoid copepods within the Holarctic

reflected the global PAE for freshwater harpacticoids as a whole, but not

the regional PAE. A high proportion of stream-dwelling harpacticoids are

widespread species, but only one (Bryocamptus zschokkei) was found in

streams across the Holarctic. Other cosmopolites were restricted to streams

in Europe or North America, suggesting that species niche requirements

might differ among regions. There appeared to be some convergence in the

composition of lotic copepod communities in terms of the number of

species within genera.

5. We conclude that large-scale processes inevitably have a major influence on

the local composition of lotic meiofaunal communities, but that the relative

importance of small scale vs. large scale processes is unclear at present,



largely due to a paucity of suitable data.

Водотоки: динамика сообществ мейобентоса.

Freshwater Biology Volume 44 Issue 1 Page 135 - May 2000
Lotic meiofaunal community dynamics: colonisation, resilience and persistence in a spatially and temporally heterogeneous environment
Anne L. Robertson
1.The spatial and temporal dynamics of lotic meiofaunal communities were
examined with a focus on colonisation, maintenance of populations in lotic
environments and persistence of meiofaunal communities.
2.Lotic meiofaunal colonisation of new habitats may take place via a number of
mechanisms and is rapid at both the patch scale (within hours-days) and the
drainage basin scale (within 20years). Successional patterns in lotic meiofaunal
communities are evident although data are extremely limited.
3.Lotic meiofaunal communities appear to be resilient to high flow disturbances.
Resilience is moderated by the availability of in-stream refugia and habitat
hydrology. Lotic meiofauna may also adopt a refuge as habitat approach to such
disturbances.
4.Lotic cyclopoid copepods possess a common suite of life history characteristics
that confers resilience to disturbances. Compared to pelagic planktonic species they
have short generation times, many descendants per reproductive cycle and long
lifespans. Females in source populations are likely to survive disturbances and so
could continuously reproduce over a long period of time producing large numbers
of offspring which develop rapidly and recolonise sink areas of the stream.
5.Persistence of lotic meiofaunal communities is highly variable. Meiofaunal
persistence does not increase with increasing proportions of in-stream flow refugia.

Водотоки: трофическая роль мейобентоса.

Freshwater Biology

Volume 44 Issue 1 Page 149 - May 2000

Trophic relationships: integrating meiofauna into a realistic benthic food web

J. M. Schmid-Araya and P. E. Schmid

Summary

1 This paper summarises the most important contributions on trophic

relationships of lotic meiofauna. In contrast to marine research, the few

quantitative studies of the freshwater meiobenthos have shown that these

invertebrates not only take up particulate/fine organic matter, but also

dissolved organic substances attached to organic particles. In lotic

ecosystems, further estimates of grazing rate and bacterial/algal ingestion

rate are needed, particularly in situ measurements.

2 The effects of macroinvertebrate predators upon meiofauna are still under

debate. Depending on the type of experiments (laboratory vs. field) it seems

that macrofauna may or may not affect meiofauna. Field samples and

analyses of gut contents of larval tanypod chironomids have shown that the

impact upon meiofauna was low and larvae were nonselective predators.

Predation amounted to 2.2% of the combined prey density and prey

consumption averaged 1.3 individuals per predator individual per year.

3 Adding taxonomic resolution by including the meiofaunal component within

lotic food webs distinctly increases the number of total species and, as a

consequence, changes food web statistics. Webs that included meiofauna

revealed that these metazoans contributed substantially to the percentage of

intermediate species (species with predators and prey). The resolution of

dietary analyses of major consumers of macro- and meiobenthos showed

that many stream invertebrates feed on meiofauna.

Водотоки: роль мейобентоса.

Freshwater Biology

Volume 44 Issue 1 Page 165 - May 2000

The importance of meiofauna to lotic ecosystem functioning


Christine C. Hakenkamp*andAntoine Morin

1. Although meiofauna occur in large numbers in many streams, almost

nothing is known about their functional role.

2. In other systems, meiofauna influence microbial and organic matter

dynamics through consumption and bioturbation. Given that these are

important processes in streams, meiofauna have the potential to influence

lotic function by changing the quality and availability of organic matter as

well as the number and biotic activity of benthic microbes. Selective feeding

by meiofauna has the potential to alter the availability of nutrients and

organic carbon.

3. Meiofauna generally contribute only a small amount to metazoan production

and biomass in streams, although exceptions occur. Within a stream, the

relative importance of meiofauna may reflect whether the temporary or

permanent meiofauna dominate the meiobenthos as well as the season when

samples are collected.

4. We suggest stream conditions (small sediment grain size, restricted

interstitial flow) under which meiofauna have the greatest likelihood of

influencing stream ecosystem function.

5. Important areas for future research include addressing whether meiofauna

feed selectively, whether meiofauna are links or sinks for carbon in streams,

and whether bioturbation by meiofauna influences stream ecosystem

processes in a predictable manner.


Водотоки: перспективы изучения мейофауны.

Freshwater Biology Volume 44 Issue 1 Page 177-183 - May 2000



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

Authors: Schlosser-IJ



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

Abstract:

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.



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