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Трофика экосистем водотоков



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Трофика экосистем водотоков

Трофика детритного ручья.


Tavares Cromar A F. Williams D D.

The importance of temporal resolution in food web analysis: Evidence for a

detritus-based stream.

Ecological Monographs 66(1). 1996. 91-113.


A series of time-specific food webs for the macroinvertebrate riffle

community of Duffin Creek, Ontario was constructed using dietary

information obtained from the analysis of gut contents. Trophic links were

quantified using a dietary index of relative importance. Precision of the

analysis was maintained at a high level by: (1) identifying dietary items

as accurately as possible via direct gut analysis; (2) identifying web

members to the species level, thus avoiding the taxonomic aggregation and

lumping of size classes common in food web analyses; and (3) ensuring

temporal resolution of the web by determining ontogenic variation in the

diets of dominant members of the community. The Duffin Creek webs are

heavily detritus-based with a large proportion of top-to-basal, and

intermediate-to-basal links. Top-to-basal links, proportions of top and

intermediate species, and lower connectance (0.180-0.219) varied

temporally. Trophic connectance ranged from 0.090 to 0.109, consistent

with values expected for a web consisting largely of specialist feeders.

Weak links made up the largest proportion of total links in the webs,

whereas very strong links made up the smallest proportion. Omnivory was

more common than indicated in other webs and can be attributed to

ontogenic diet switching. Comparison of the statistics for a summary web

with those generated for the time-specific webs indicated that the total

number of links per web, total number of species, number of top and

intermediate species, and linkage density were much greater for the

summary web. In view of these differences, the importance of temporal

resolution when assessing food web structure and dynamics is emphasized.

The possibility that some of the observed features in our web are common

to other detritus-based webs is considered. Future studies of this calibre

are justified.

Питание детритофагов в горных потоках.


Authors: Richardson-JS

Title: Seasonal Food Limitation of Detritivores in a Montane

Stream - An Experimental Test

Source: ECOLOGY

1991, Vol 72, Iss 3, pp 873-887

Language: English

Document type: Article

Addresses:

UNIV-BRITISH-COLUMBIA, DEPT ZOOL, ECOL GRP, VANCOUVER V6T-2A9,

BC, CANADA

Author keywords:

Demography; Detritus; Insects; Phenology; Population;

Seasonality; Shredders; Streams

Keywords Plus:

SOUTHWESTERN BRITISH-COLUMBIA; LEAF LITTER; WOODLAND STREAM;

POPULATION-DYNAMICS; GROWTH; ECOSYSTEMS; BREAKDOWN; FRESH;

INVERTEBRATES; ENVIRONMENTS

Abstract:

Many species of detritivorous invertebrates in small

streams depend almost entirely on inputs of leaf litter for

their nutritional requirements, however the concentration of

this resource varies considerably seasonally. An experiment

designed to test the hypothesis that productivity of coarse

particle detritus feeders (shredders) is seasonally food limited

was performed using replicate streamside channels that received

one of three input rates of whole leaf detritus (rates equal to

those naturally falling into montane streams, and two levels of

increased inputs).

Seven of the nine common shredder species attained

significantly higher adult mass, higher densities, or both when

food was supplemented. Larval densities of Malenka spp. and

Brillia retifinis were significantly higher when additional food

was added. Brillia retifinis densities were more than 10 x

greater in high food additions than in the ''natural''

treatment; B. retifinis apparently fills a role as a fugitive in

this system and is better able to track shifts in resource

abundance by virtue of its short generation time. Zapada

cinctipes and Z. haysi were more dense in high and intermediate

food input treatments during the last half of the summer. Other

taxa had nonsignificant trends to higher densities when extra

food was provided. Most of the change in benthic densities can

be attributed to decreased rates of emigration with increased

food supply.

Six of the eight taxa for which adult mass at emergence was

measured were significantly more massive (4-46%) when food was

added. Both sexes exhibited this increase in mass, but females

gained proportionally more in most species. There were no

detectable changes in the timing of adult emergence due to food

manipulations.

The biomass of most taxa increased in proportion to the

overall increase in biomass of the common coarse-detritus

consumers. The main exceptions to that pattern were a

disproportionate increase in the percentage of the biomass

represented by Brillia retifinis and a decrease in the

representation of Zapada cinctipes.

The responses of this community to food supplementation

demonstrate food limitation of detritivores. The exponential

increase in benthic biomass under food addition shows the scope

for productivity if food were not limiting. These coexisting

species benefitted from enhanced food supply on a spatial scale

that is relevant for population level processes. The large

seasonal variation in resource abundance under natural

conditions creates bottlenecks during periods of low food

supply, which constrain subsequent production even during

periods when food is abundant.

Бентос водотоков: вторичная продукция.


Authors: Sallenave-RM Day-KE

Title: Secondary Production of Benthic Stream Invertebrates in

Agricultural Watersheds with Different Land Management-

Practices

Source: CHEMOSPHERE

1991, Vol 23, Iss 1, pp 57-76

Language: English

Document type: Article

Addresses:

UNIV-GUELPH, DEPT ENVIRONM BIOL, GUELPH N1G-2W1, ONTARIO,

CANADA

ENVIRONM-CANADA, NATL WATER RES INST, RIVERS RES BRANCH,



BURLINGTON, ONTARIO, CANADA

Keywords Plus:

SOUTHERN ONTARIO STREAMS; LIFE-HISTORY PATTERNS; HYDROPSYCHE

TRICHOPTERA; PLANKTON COMMUNITIES; ENVIRONMENTAL FATE;

EXPERIMENTAL PONDS; HYNES METHOD; ATRAZINE; IMPACT;

MICROCOSMS

Abstract:

Annual secondary production of four coexisting caddisfly

species (Trichoptera; Hydropsychidae: Hydropsyche spp.) was

estimated in two adjacent branches of Kintore Creek, Ontario,

Canada. The west branch was located in a demonstration

watershed where conservation tillage was practiced i.e., mulch-

finishing of row crops, planting of forage and cover crops, some

no-till practices, etc. Conventional agricultural land

management occurred in the watershed which drained into the east

branch i.e., corn-wheat-alfalfa rotation with fall moldboard

ploughing. Production estimates and densities of caddisflies

were consistently higher in the watershed where conservation

tillage was practiced. For example, mean annual production of

H. slossonae was 12.02 g ash-free dry weight (AFDW)/m2 in the

west branch vs. 2.45 g AFDW/m2 in the east branch. Differing

concentrations of herbicides, insecticides and nutrients in the

two watersheds are discussed as possible explanations for this

pronounced difference in productivity.


Водотоки: биомасса и продукция бентоса.


Freshwater Biology Volume 44 Issue 2 Page 199 - June 2000

Benthic secondary production and biomass of insects emerging from

a northern German temperate stream

Rainer Poepperl

1. Secondary production and emergence of aquatic insects were examined in

the outlet of Lake Belau, Northern Germany, by means of benthic samples

and emergence traps.

2. At three stream sections annual larval secondary production varied between

4.9 and 10.8 gDM (dry mass) m-2 year-1. Insects contributed with 3.4, 8.9,

and 8.7% to the total macroinvertebrate production that varied between 56.5

and 215.1 gDM m-2 year-1. Emerged biomass was between 1.0 and 2.0 gDM

m-2 year-1. At all three stream sections Diptera dominated with a larval

production of 3.0-l6.1 gDM m-2 year-1, followed by Trichoptera with 1.0-2.1

and Ephemeroptera with up to 0.9 gDM m-2 year-1.

3. Average larval production amounted to 9.0 gDM m-2 year-1 and emerged

biomass to 1.7 gDM m-2 year-1. Larvae of insects amounted to 7.0% of total

macroinvertebrate production.

4. The ratio of annual emerged biomass to secondary production (E/P) varied

among individual taxa. At the stream sections the ratio ranged from 15.9% to

20.1% with an average of 18.3% for the stream.

5. Relative constancy of the E/P ratio suggests that the determination of

emerged biomass can be used as a method for estimating the secondary

production of aquatic insects. The composition of functional feeding groups

clearly differs between emerged biomass and total macroinvertebrate

production. Therefore, the method does not allow conclusions on the level

of production of the whole benthic community. However, composition of

functional feeding groups at emergence roughly reflects composition of

these groups in the benthic insect community.



Трофика водотоков, Англия


03.12-04А2.81. Показатели связанности пищевых сетей в экосистемах водотоков. Connectance in stream food webs / Schmid-Araya Jenny M., Schmid Peter E., Robertson Anne, Winterbottom Julie, Gjerl_Жv Charlotte, Hildrew Alan G. // J. Anim. Ecol. - 2002. - 71, № 6. - С. 1056_ѕ1062. - Англ.

Показатели связанности пищевых сетей (отношение числа реализованных трофических связей к числу теоретически возможных) проанализированы для 22 сообществ беспозвоночных животных, населяющих ручьи и мелкие реки. Выбранные для анализа сообщества описаны с высокой степенью таксономической подробности и содержат от 22 до 212 видов. Показано, что связанность пищевых сетей снижается по мере увеличения числа видов, формирующих сообщество. Это снижение может быть обусловлено высокой гетерогенностью гидрофизических условий водотоков, а также расширением диапазона размерной изменчивости организмов. Полученная оценка показателя степени в соотношении "число трофических связей _ѕ число видов" (_b=1.3) указывает на то, что для экосистем водотоков гипотезы "постоянства связанности" (_b=2) и "прямой пропорциональности" (_b=1) не подтверждаются. Великобритания, School of Biological Sci., Queen Mary, Univ. of London, London E1 4NS, UK, e-mail: J.M.Schmid-Araya@qmul.ac.uk. Ил. 3. Табл. 1. Библ. 50.


Водотоки: роль фитофагов.


Freshwater Biology Volume 43 Issue 4 Page 545 - March 2000

Фитофаги в кисловодных водотоках.

Herbivory in an acid stream

Mark E. Ledger and Alan G. Hildrew

Summary

1. Spatial and temporal variation in the distribution and feeding of non-



predatory macroinvertebrates was investigated in a first-order, acid stream

in the Ashdown Forest, southern England.

2. Stonefly (Nemouridae) and chironomid (Orthocladiinae) larvae were

abundant on the upper surfaces of mineral substrata of three sizes (small

stones, large stones, bedrock). The density of larvae in each taxonomic

group did not vary among substrata of different sizes, although strong

seasonal variation existed.

3. Nemourids and chironomids (H. marcidus) collected from the upper

surfaces of substrata exhibited generalist feeding habits, consuming algae

(diatoms, coccoid and filamentous green algae), detritus (biofilm matrix

material and fine particulate organic matter (FPOM)) and inorganic debris.

4. There was spatial variation in the gut contents of nemourids. The

proportion of algae in the guts of larvae often increased with the size of the

substratum from which they were collected. Strong temporal variation in the

composition of the diet also existed. Nemourids ingested a large quantity of

attached algae and biofilm matrix from the biofilm in spring and winter, but

consumed loose FPOM and associated microflora in summer and autumn.

5. We conclude that, in this acid stream, the trophic linkage between algae and

grazers is maintained by detritivorous stonefly and chironomid species. The

relationship between the feeding habits of these larvae and other life-history

attributes, such as mouthpart morphology and mobility, is discussed.

Водотоки: роль микроорганизмов


Freshwater Biology

Volume 40 Issue 3 Page 453-495 - November 1998

The role of micro-organisms in the ecological connectivity of running waters

M. Pusch D. Fiebig I. Brettar H. Eisenmann B. K. Ellis L. A. Kaplan M. A. Lock M. W. Naegeli W. Traunspurger

Summary

1. Riparian zones hold a central place in the hydrological cycle, owing to the



prevalence of surface and groundwater interactions. In riparian transition zones, the

quality of exfiltrating water is heavily influenced by microbial activities within the

bed sediments. This paper reviews the role of micro-organisms in biogeochemical

cycling in the riparian-hyporheic ecotone.

2. The production of organic substances, such as cellulose and lignin, by riparian

vegetation is an important factor influencing the pathways of microbial processing

in the riparian zone. For example, anaerobic sediment patches, created by

entrainment of allochthonous organic matter, are focal sites of microbial

denitrification.

3. The biophysical structure of the riparian zone largely influences in-stream

microbial transformations through the retention of organic matter. Particulate and

dissolved organic matter (POM and DOM) is retained effectively in the hyporheic

zone, which drives biofilm development and associated microbial activity.

4. The structure of the riparian zone, the mechanisms of POM retention, the

hydrological linkages to the stream and the intensity of key biogeochemical

processes vary greatly along the river continuum and in relation to the geomorphic

setting. However, the present state of knowledge of organic matter metabolism in

the hyporheic zone suggests that lateral ecological connectivity is a basic attribute

of lotic ecosystems.

5. Due to their efficiency in transforming POM into heterotrophic microbial

biomass, attached biofilms form an abundant food resource for an array of

predators and grazers in the interstitial environments of rivers and streams. The

interstitial microbial loop, and the intensity of microbial production within the bed

sediments, may be a primary driver of the celebrated high productivity and

biodiversity of the riparian zone.

6. New molecular methods based on the analysis of the low molecular weight RNA

(LMW RNA) allow unprecedented insights into the community structure of natural

bacterial assemblages and also allow identification and study of specific strains

hitherto largely unknown.

7. Research is needed on the development and evaluation of sampling methods for

interstitial micro-organisms, on the characterization of biofilm structure, on the

analysis of the biodegradable matter in the riparian-hyporheic ecotone, on the

regulation mechanisms exerted on microbiota by interstitial predators and grazers,

and on measures of microbial respiration and other key activities that influence

biogeochemical cycles in running waters.

8. Past experiences from large-scale alterations of riparian zones by humans, such

as the River Rhine in central Europe, undeniably demonstrate the detrimental

consequences of disconnecting rivers from their riparian zones. A river management

approach that uses the natural services of micro-organisms within intact riparian

zones could substantially reduce the costs of clean, sustainable water supplies for

humans.

Водотоки: утилизация внешней органики.


Freshwater Biology

Volume 41 Issue 4 Page 687 - June 1999

What happens to allochthonous material that falls into streams?

A synthesis of new and published information from Coweeta

J. R. Webster, E. F. Benfield, T. P. Ehrman*, M. A. Schaeffer, J. L. Tank, J. J. Hutchens and D. J. DAngelo

1. ,One of two things can happen to allochthonous material once it enters a stream:

it can be broken down or it can be transported downstream. The efficiency with

which allochthonous material is used is the result of these two opposing factors:

breakdown and transport.

2. ,The present synthesis of new and published studies at Coweeta Hydrologic

Laboratory compares biological use versus transport for four categories of

particulate organic material: (1) large wood (logs); (2) small wood (sticks); (3)

leaves; and (4) fine particulate organic matter (FPOM).

3. ,Over 8_years, logs showed no breakdown or movement.

4. ,The breakdown rate of sticks (3_cm diameter) ranged from 0.00017 to

0.00103_day1, while their rate of transport, although varying considerably with

discharge, ranged from 0 to 0.1_m_day1.

5. ,Based on 40 published measurements, the average rate of leaf breakdown was

0.0098_day1. The leaf transport rate depended on stream size and discharge.

6. ,The average respiration rate of FPOM was 1.4_mg_O2_g_AFDM1_day1 over a

temperature range of 6-22_°C, which implies a decomposition rate of 0.00104_day

1. Transport distances of both corn pollen and glass beads, surrogates of natural

FPOM, were short (<_10_m) except during high discharge.

7. , Estimates of transport rate were substantially larger than the breakdown rates

for sticks, leaves and FPOM. Thus, an organic particle on the stream bottom is

more likely to be transported than broken down by biological processes, although

estimates of turnover length suggest that sticks and leaves do not travel far.

However, once these larger particles are converted to refractory FPOM, either by

physical or biological processes, they may be transported long distances before

being metabolized.



Водотоки: трофические взаимосвязи.


Freshwater Biology

Volume 41 Issue 4 Page 771 - June 1999

Effects of prey dispersal on predator-prey interactions in streams

J. Dahl* and L. Greenberg

1. We studied the effect of mesh size (6 and 3mm) on interactions between brown

trout (Salmo trutta) and benthic invertebrates in enclosures placed in a stream in

southern Sweden. We also compared how different prey exchange rates affected

interactions between trout and invertebrates.

2. Trout had strong impacts on some benthic taxa, and different mesh sizes

produced different patterns. Trout affected the abundance of 10 of the 21 taxa

examined, six in enclosures with 3mm mesh and six in enclosures with 6mm mesh.

The abundance of nine of the prey taxa was lower in the presence of trout, only

leptocerids were more numerous in the presence of trout.

3. Our measurements of prey immigration/emigration, together with trout diet data,

suggest that direct consumption by trout, rather than avoidance behaviour by prey,

explains most decreases in prey abundance. There was avoidance behaviour by

only two of the twenty-one prey taxa, with trout inducing emigration of the mayflies

Baetis rhodani and Paraleptophlebia sp.

4. Trout indirectly increased periphyton biomass in both 3 and 6mm enclosures.

The effect of trout on periphyton was probably due to strong effects of trout on the

grazer, Baetis rhodani, Heptagenia sp. and Paralepthoplebia sp.

5. Our results suggest that mesh size, through its effects on exchange rates of prey,

may affect interactions between predators and prey in running waters, but that the

effects of dispersal and predation on invertebrates are taxon specific.



Водотоки: трофические взаимосвязи.


Freshwater Biology

Volume 41 Issue 3 Page 553 - May 1999

Associations between stream fish and benthos across environmental gradients

in southern Ontario, Canada

Bruce W. Kilgour* and David R. Barton

Summary


1.The relationship between fish and benthic invertebrate communities in wadeable

streams in southern Ontario, Canada, was examined using three independent and

spatially distinct data sets.

2.Associations between fish and benthos were always significant when benthos

were identified to family and often at the level of phylum. Identification to genus

improved the strength of the fish-benthos association in one case. In contrast,

identification to species did not improve the strength of the fish-benthos

association. Associations between benthos and fish were weaker for one study

utilizing a rapid bio-assessment protocol involving field sorting and identification,

and a second study which utilized winter benthic collections.

3.In two surveys, stream temperatures were important to the distributions of both

fish and benthos, while in a third survey, fish and benthos were primarily influenced

by stream size. In all three studies, fish and benthos were associated with similar

suites of environmental variables, suggesting that the fish-benthos associations in

these streams was driven by corresponding environmental tolerances.

4.Although there was significant variation in the strength of the fish-benthos

association which could be attributed to differences in sampling methodologies, the

findings from the present study confirm that stream fish and benthos are

significantly associated. Therefore, surveys of benthos can be used to make

inferences on the condition of fish community composition.



Водотоки: источники органики.


Freshwater Biology

Volume 40 Issue 1 Page 145-158 - August 1998

Primary nutrients and the biotic integrity of rivers and streams

Robert J. Miltner & And Edward T. Rankin

1. Controls to reduce loadings of primary nutrients to maintain biotic integrity in

rivers and streams have not been widely implemented because the relation between

nutrients and chlorophyll, and its consequences for higher trophic levels, is

confounded in lotic ecosystems by their openness, the variable degree of nutrient

limitation and by the effect of physical factors.

2. The relationship between primary nutrients and biotic integrity in rivers and

streams was tested using biological, physical and chemical information collected

since 1982 from similar locations in streams throughout Ohio using standard

procedures.

3. There was a negative correlation between nutrients, especially total phosphorus,

and biotic integrity. The deleterious effect of increasing nutrient concentration on

fish communities in low order streams was detectable when nutrient concentrations

exceeded background conditions (total inorganic nitrogen and phosphorus > 0.61

mg L1 and 0.06 mg L1, respectively).

4. These results suggest that the control of release of toxins and oxygendemanding

wastes to rivers is insufficient to protect aquatic life, and confirm the importance of

nonpoint sources of pollution in catchment planning as well as the combined effect

of habitat and riparian quality on nutrient assimilation.



Водотоки: влияние бентоса на фитопланктон.


Freshwater Biology

Volume 39 Issue 1 Page 9-24 February 1998

Can a community of small-bodied grazers control phytoplankton in rivers?

V. Gosselain, L. Viroux AND J. -P. Descy*

1. Phytoplankton, zooplankton and grazing were monitored throughout the growing

season for three years (1994-96) in the Belgian section of the River Meuse.

2. A size structure analysis of the algal community shows that there was a summer

shift toward larger algal units, following a decline in phytoplankton biomass. These

changes occurred after an increase in zooplankton biomass and diversity.

3. Daily filtration rates of grazers ranged from 1 to 113%day1 and maxima were

observed during the summer period. Higher rates tended to correspond with peaks

of rotifer biomass. A decline in total phytoplankton biomass within two weeks

followed the increase in zooplankton biomass and filtration rate. A rapid biomass

recovery was then observed, along with a shift of the algal community toward larger

units. When grazing activity was not sustained, due to zooplankton fluctuations, the

change in phytoplankton size structure was less marked.

4. We suggest that the composition of the phytoplankton community of large rivers

may at times be controlled by grazers. However, such biotic interactions can take

place only when physical constraints are reduced, i.e. when discharge is low, and

when increased transfer time, high temperature and availability of grazeable algae

allow high zooplankton biomass.



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