Продольные изменения экосистем водотоков

Продольные изменения в водотоках.

Volume 47 Issue 1 Page 129 - January 2002

Трофическая сеть беспозвоночных в градиенте ресурсов водотока.

Invertebrate food webs along a stream resource gradient

space and time. The river continuum concept (RCC) provides a useful framework

for predicting variability in the biota and food availability along streams. We

estimated the flow of organic matter (gm2year1) through food webs, arrayed along a

stream, that had different resource inputs. Four sites were sampled along the Little

Tennessee River, North Carolina, U.S.A.: two fifth order sites, one sixth and one

seventh order site. The dominant resource is leaf detritus in the upstream reach (the

upstream fifth order site), algae in the mid-reaches (the downstream fifth and sixth

order sites), and suspended material downstream (seventh order site).

2.Eleven genera, contributing from 50 to 66 of the total macroinvertebrate

secondary production of each site, were studied. We estimated organic matter flow

from resource to consumer by combining previously measured rates of invertebrate

secondary production with gut content analyses and assimilation efficiencies.

3.Organic matter flow through food webs increased in a downstream direction,

while the structure of the food webs remained constant. The total food consumed

by the taxa analysed increased from 34gm2year1 at the upstream site to 730gm2year1

at the most downstream site. We estimate that the organic matter consumed by the

entire macroinvertebrate community ranged from 66 to 1164gm2year1. These results

indicate that there is variation in the magnitude of organic matter flow through the

food webs along this river continuum.

4.The dominant food resource consumed also changed along the gradient. Leaf

detritus consumption decreased from 58 of the total consumption upstream to 6

downstream, whereas consumption of amorphous detritus increased from 18 to 64.

The proportion of animal material consumed also increased from 3 to 27. The total

consumption of autochthonous resources (diatoms and filamentous algae)

increased along the continuum (from 6.41 to 34.05gm2year1). We conclude that

these results are related to variation in resource availability, dietary shifts and

invertebrate secondary production. These results link resource availability to energy

flow, a relationship originally suggested by the RCC.

Влияние размера водотока.

Gore J A. Hamilton S W.

Comparison of flow-related habitat evaluations downstream of low-head

weirs on small and large fluvial ecosystems.

Regulated Rivers-Research & Management 12(4-5). 1996. 459-469.

of instream habitat structures to enhance the capture of organic detritus

and aufwuchs, as well as, colonization by macroinvertebrate and fish

species. Structural design is based upon the assumption that these habitat

requirements can be controlled through the design of structures that

produce preferred physical and chemical conditions in relation to flow

conditions. Restoration scientists are assuming that hydraulic conditions

are one primary template that govern the distribution of lotic organisms.

For benthic macroinvertebrates, substrate composition is the most easily

manipulated habitat characteristic. The most common structures for fish

habitat enhancement have been current deflectors, overpour structures

(dams and weirs) and instream cover, especially for juveniles. These

instream structures also modify local hydraulic conditions to present

preferred habitat to benthic invertebrates. The physical habitat

simulation (PHABSIM), a software package used in the instream flow

incremental methodology, was used to evaluate stream enhancement

activities on a low-order stream, with the placement of a series of

three-log weirs on Brushy Branch, a second-order stream in Tennessee, and

compared with published results of a hydraulically similar concrete

structure on a large-order system used to re-regulate flows downstream of

peaking hydropower facility on the Cumberland River, Tennessee. On Brushy

Branch, the simulation demonstrated that benthic macroinvertebrate habitat

can be dramatically increased at low flows (up to five times higher) after

placement of structures that improve hydraulic conditions to sustain

maximum diversity of the benthic community. In this case, then, the

structures acted to augment habitat under low flow conditions.

Reregulation dams, on large rivers, modify the water surface elevation and

dampen high velocities, which enhances habitat for juvenile and adult

salmonids when subject to the high discharge surges of peaking generation.

Thus, these low-head structures augment habitat under high flow

conditions. Hydraulic habitat models, then, can be a useful tool to

evaluate the benefit of certain restoration activities and, in the case of

weir-like structures, indicate that similar structures impart similar

benefit, regardless of scale of application.

Продольное изменение сообществ.

Freshwater Biology Volume 46 Issue 12 Page 1705 - December 2001

macroinvertebrate community distributions were examined in an alpine glacial

stream (Roseg River, Switzerland).

2.Physico-chemical parameters reflected seasonal changes in glacial influence via

shifts in water sources and flowpaths (glacial meltwater versus ground water), and

were best described by turbidity, particulate phosphorus and specific conductance.

High nitrogen concentrations indicated snowmelt was the main water source in June.

3.Macroinvertebrate densities and taxon richness were highest during spring (4526m

2 and 16 taxa, all sites combined) and late autumn/early winter (8676-13398m2 with

16-18 taxa), indicating these periods may be more favourable for these animals than

summer when glacial melting is maximal. Diamesa spp. (Chironomidae) dominated

the fauna at the upper three sites (>95 of zoobenthos) and were abundant at all

locations. Other common taxa at lower sites (1.2-10.6km downstream of the glacier

terminus) included other chironomids (Orthocladiinae, Tanytarsini), the mayflies

Baetis alpinus and Rhithrogena spp., the stoneflies Leuctra spp. and

Protonemura spp., blackflies (Simulium spp., Prosimulium spp.), and

Oligochaeta.

4.Co-inertia analysis revealed a strong relationship between environmental

conditions and benthic macroinvertebrate assemblages. Furthermore, it elucidated

temporal variability in longitudinal response patterns, as well as a similarity in

temporal patterns among individual sites.

5.Our results suggest that zoobenthic gradients are not solely related to temperature

and channel stability. Seasonal shifts in sources and pathways of water (i.e. extent

of glacial influence), and periods of favourable environmental conditions (in spring

and late autumn/early winter) also strongly influenced zoobenthic distributions.
Продольное изменение сообществ.

Freshwater Biology Volume 46 Issue 12 Page 1737 - December 2001

Gisli M. Gislason, Hakon Adalsteinsson, Iris Hansen, Jon S. Olafsson & Kristin Svavarsdottir

originating from the Hofsjokull Ice Cap in central Iceland at an altitude of 860m.

Sampling sites were distributed from the source to 45km downstream at 160m a.s.l.

Comparative studies were carried out on non-glacial rivers and tributaries in the

area, at similar altitudes and distances from the glacial source.

2.Detrended correspondence analysis (DCA) demonstrated that species

composition of benthic macroinvertebrates was related to the distance from the

glacier. Assemblages at sampling sites furthest from the glacier were similar in

species composition to sites in non-glacial rivers. Temporal variation was small

compared with longitudinal zonation.

3.Based on canonical correspondence analysis (CCA) of data from the main glacial

river, distance from the glacier, altitude, bryophyte biomass and the Pfankuch Index

of channel stability were the measured explanatory variables having a significant

effect on the structure of macroinvertebrate assemblages, accounting for 31 of the

total variation in the data set. When data from all the rivers were analysed, altitude,

bryophyte biomass, channel slope, suspended sediment concentration and

maximum water temperature explained 21 of the variance.

4.Macroinvertebrate communities were in general agreement with the predictions of

the conceptual model of Milner & Petts (1994) for the upstream reaches. The

assemblages consisted mainly of Orthocladiinae and Diamesinae (Chironomidae),

although other taxa such as Simuliidae, Plecoptera and Trichoptera were also found

in low numbers. Shredders were lacking from the benthic communities, apparently

because of continued glacial influence in the river even 45km downstream from the

glacier and lack of allochthononus inputs from riparian vegetation.

Freshwater Biology

Volume 46 Issue 12 Page 1765 - December 2001

Longitudinal distribution of macroinvertebrates in two glacier-fed New Zealand rivers

Alexander M. Milner, Russell C. Taylor & Michael J. Winterbourn

examined from September 1999 to January 2000 (austral summer) along two

glacier-fed rivers in South Island, New Zealand.

2.The rivers were characterized by high flow variability, high turbidity and

physically disturbed beds. Water temperature ranged from <1°C near the glacier

margin to 10°C further downstream.

3.Epilithic algal biomass was very low (<0.1mgm2) in months characterized by

heavy rainfall, but ranged from 1.1 to 14.4mgm2 following an extended period with

negligible precipitation.

4.Abundance and diversity of invertebrates in both rivers was low. Dominant taxa

were Chironomidae (Orthocladiinae, Podonominae, Diamesinae), although mayfly

species (Deleatidium: Leptophlebiidae) also occurred at most sites. A species of

Eukiefferiella (Orthocladiinae) was collected at all sites and was the most abundant

invertebrate close to the glacier margins. No meiofauna were found in either river.

5.Faunal diversity increased at the lowermost stations where species of Plecoptera,

Trichoptera, Coleoptera and non-chironomid Diptera also occurred.

6.The faunas of the two New Zealand rivers conformed to the conceptual model of

Milner & Petts (1994) in that taxon richness increased downstream with water

temperature. However, invertebrate abundance increased downstream in only one of

the two rivers. Also in contrast to the model predictions, Leptophlebiidae and

Orthocladiinae, rather than Diamesinae, dominated the fauna at the coldest sites.
Водотоки: продольное изменение условий.

Freshwater Biology Volume 42 Issue 2 Page 345 - September 1999

Changes in agricultural intensity and river health along a river continuum

JoN. S. Harding, Roger G. Young, JohN. W. Hayes, Karen A. Shearer and JohN. D. Stark
1.The impact of agricultural activities on waterways is a global issue, but the

magnitude of the problem is often not clearly recognized by landowners, and land

and water management agencies.

2.The Pomahaka River in southern New Zealand represents a typical lowland

catchment with a long history of agricultural development. Fifteen sites were

sampled along a 119-km stretch of the river. Headwater sites were surrounded by

low-intensity sheep farming, with high-intensity pasture and dairying occurring in the mid-reach and lower reaches.

3.Water clarity decreased significantly from about 6m in the headwaters to less than

2m in the lower reaches. Benthic sediment levels increased significantly downriver,

peaking at 35mgm2 below several tributaries with high-intensity agriculture in their

catchments. Periphyton levels were also significantly greater in the lower reaches

than the headwaters, and coincided with increased nitrogen (DIN) and phosphorus

(SRP) concentrations.

4.Macro-invertebrate species richness did not change significantly throughout the

river, but species composition did with Ephemeroptera, and to a lesser extent,

Plecoptera and Trichoptera dominating the headwater sites (where there was high

water clarity, and low nutrient and periphyton levels). Downriver these assemblages

were replaced by molluscs, oligochaetes and chironomids.

5.Canonical correspondence analysis indicated that agricultural intensity and

physical conditions associated with agriculture activity (e.g. impacted waters, high

turbidity and temperature) were strongly associated with the composition of benthic

assemblages at differing reaches down the Pomahaka River.

6.The present results indicate that quantifying agricultural intensity within a

catchment, particularly relative livestock densities, may provide a useful tool for

identifying threshold levels above which river health declines.
Продольные изменения: колонизация бентоса.

Johnson S L. Vaughn C C.

A hierarchical study of macroinvertebrate recolonization of disturbed

patches along a longitudinal gradient in a prairie river.

Freshwater Biology 34(3). 1995. 531-539.

1. Macroinvertebrate densities and community composition were examined at three spatial scales after substratum disturbance; among reaches along a longitudinal gradient, within reaches and within plots. Reaches consisted of sandstone outcrops that were separated by approximately 2 km of highly mobile sandy silt substratum.

2. Substrata were disturbed by scraping sandstone plots (0.3 times 0.3 m). Body-sized depressions created by Trichoptera in the sandstone were removed along with the upper 5 mm of sandstone, resulting in areas of newly exposed, smooth sandstone.

3. The spatial scale of examination determined whether patterns of macroinvertebrate distribution and densities were discernible. Initially there were no significant differences in community composition or total densities among reaches or among upstream/downstream locations within reaches. Following substratum disturbance and 30 days recolonization, total macroinvertebrate densities did not differ significantly between undisturbed plots and disturbed plots. However, densities of Petrophilia (Pyralidae: Lepidoptera) differed along the longitudinal gradient and the Simuliidae had its highest density in the upstream reach. Significant differences were found in total macroinvertebrate densities between the upstream and the downstream halves of disturbed plots, with higher densities occurring in the downstream portions.

4. Recolonized plots had similar macroinvertebrate densities and community composition to undisturbed plots, suggesting that the stream community was highly resilient.

Продольное распределение макроводорослей в реках, Бразилия.

Necchi O Jr. Moreira J C L.

Longitudinal distribution of macroalgae in two tropical lotic ecosystems

from southeastern Brazil.

Archiv Fuer Hydrobiologie 135(1). 1995. 113-128.

Macroalgal species richness and diversity were analysed along a

longitudinal profile in small and large scales during Spring, Fall and

Winter, respectively in a small stream and a mid size river in the

northwest region of Sao Paulo State, southeastern Brazil (20 degree 23'-20

degree 49'S, 49 degree 26'-51 degree 19'W). Longitudinal variation in

species richness and diversity in small scale was strongly associated with

incident light. Microhabitat distribution (from data taken by quadrat

technique) revealed no significant correlations. Principal coordinates

analysis (PCO) indicated no consistent groupings among sampling sites in

distinct seasons (Spring, Fall and Winter). Longitudinal analysis in large

scale revealed different patterns in the two seasons sampled (Spring and

Winter), whereas species diversity presented a consistent trend: high

upstream, low in mid reaches and higher downstream. It was associated with

type of substratum in Spring, rocky substrata presenting the highest

values for species richness and diversity. Weak correlations were observed

in Winter. Microhabitat distribution showed significant correlations

between species abundance and the following variables: positive for rocky

substrata and current velocity and negative for sandy-clayish substratum

and macrophyte-dominated substratum. PCO delineated only one consistent

grouping formed by the two headwater sites. Small scale macroalgal

distribution corroborated the longitudinal pattern predicted by the River

Continuum Concept, whereas the large scale approach showed a distribution

more associated with substratum type than to light availability. These

results showed an opposite trend in relation to the expected

distributional pattern. Longitudinal distribution in macroalgal community

structure has yet to be better documented, particularly for tropical

streams and no generalization is possible at this stage.

Продольное распределение ручейников в реке, Франция.

Guinand B. Ivol J M. Tachet H.

Longitudinal distribution of Trichoptera in the Loire River (France):

Simple ordination methods and community structure.

Hydrobiologia 317(3). 1996. 231-245.

The longitudinal distribution of Trichoptera at 37 sampling sites along

800 km of the Loire River (France) was analyzed in order to better

understand large-scale changes in community structure occurring on a

stream continuum. Different simple ordination methods - centered PCA and

Correspondence Analysis were performed to investigate these changes. Both

analyses showed that a major change occurs in the community in the upper

reaches of the Loire River between the Serre de la Fare and Vorey sampling

sites with the appearance of Hydropsyche contubernalis and H. exocellata.

Even though other changes in community structure could exist, revealed

either by Correspondence Analysis at the first sampling sites (crenal), or

by PCA at sampling sites influenced by dams, this Trichoptera community

appears to be stable enough in the latter part of the Loire River with the

addition of a few species, Hydropsyche bulgaromanorum, Ecnomus tenellus

and E. deceptor, rather than changes in species. The results are discussed

in the light of different concepts in stream ecology, and the validity of

such data analyses to describe some community patterns.

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