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Трофика водных экосистем.

Трофические взаимосвязи.


Freshwater Biology Volume 47 Issue 3 Page 377 - March 2002

Effects of freshwater shrimp assemblages on benthic communities along an

altitudinal gradient of a tropical island stream

JAMES G. MARCH, CATHERINE M. PRINGLE, MATT J. TOWNSEND &

AMANDA I. WILSON

1.In tropical island stream ecosystems freshwater shrimps are often the dominant

macroconsumers and can play an important role in determining benthic community

composition. However, most studies of the ecological role of shrimps are limited to

high-altitude shrimp-dominated sites where other biota (fishes and snails) are absent

or significantly less abundant than at lower altitudes.

2.We examined how effects of different shrimp assemblages on benthic

communities changed along an altitudinal gradient in a tropical island stream in

Puerto Rico. We used electroshocking and observations to quantify abundance and

taxonomic composition of shrimp assemblages at three sites (300, 90 and 10m a. s.

l) along the Rio Espiritu Santo. We also experimentally manipulated access of

shrimps to the benthic environment simultaneously at each site using electric fences

over a 35-day period.

3.At the high-altitude site, exclusion of shrimps (predominantly Atya spp. and

Xiphocariselongata) resulted in significantly greater accrual of organic and

inorganic material, chlorophyll a and algal biovolume. In the absence of shrimps,

the algal community was dominated by filamentous green algae (Chlorophyta:

Oedogonium and Rhizoclonium). Excluding shrimps did not affect total insect

biomass but significantly increased sessile chironomids (Diptera: Chironomidae).

We observed similar treatment effects at the mid-altitude site where shrimps

(primarily Macrobrachium spp. and X. elongata) occurred at lower densities. In

contrast, at the low-altitude site there were no treatment differences in organic and

inorganic material, chlorophyll a, algal biovolume, algal assemblage composition

and insects.

4.The lack of treatment differences at the low-altitude site was probably because of

very high densities of grazing snails (Thiaragranifera and Neritina spp.) which

reduced organic and inorganic resources and obscured potential shrimp effects.

5.This study demonstrates that freshwater shrimps can play an important role in

determining benthic community composition; however, their effects vary and

appear to depend on the presence of other biota. This study suggests that loss of

shrimps as a result of anthropogenic disturbances will have different effects on the

stream community depending upon location along the altitude gradient.



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.

Source


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.


Насекомые: пищевые взаимосвязи в водотоках.


Authors: Wrona-FJ Dixon-RWJ

Title: Group-Size and Predation Risk - A Field Analysis of

Encounter and Dilution Effects

Source: AMERICAN NATURALIST

1991, Vol 137, Iss 2, pp 186-201

Language: English

Document type: Article

Addresses:

UNIV-CALGARY, DEPT BIOL SCI, DIV ECOL, AQUAT GRP, CALGARY

T2N-1N4, ALBERTA, CANADA

Keywords Plus:

MARINE INSECT; SELFISH HERD; TRICHOPTERA; LARVAE; PREY;

HYDROPSYCHIDAE; AVOIDANCE; LIMNEPHILIDAE; AGGREGATIONS;

CHIRONOMIDAE

Abstract:

We propose a general fixed-constant linear-regression model

that can be used to assess empirically the potential benefits

and disadvantages of group living from the separate and combined

effects of predator encounter and numerical dilution. Using

this model, we assessed group-size-related predation risk in

pupae of the stream-dwelling trichopteran Rhyacophila vao from

the planarian predator Polycelis coronata. When considered on

its own, Rhyacophila pupal aggregation conferred an apparent

disadvantage from encounter-related effects, since both predator-

encounter probabilities and local densities increased in a

density-dependent manner with pupal group size. In contrast,

dilution effects related to the functional response of Polycelis

yielded group-size-related benefits. When their combined (i.e.,

attack-abatement) effect was considered, aggregation was found

to confer a net fitness advantage to pupae by decreasing

predation hazard, primarily from the benefits of predator

dilution not being entirely swamped by the potentially

deleterious encounter effects. Furthermore, assessment of these

relationships at different spatial scales helped elucidate some

of the underlying proximal biological mechanisms involved. This

study shows how the separate consideration of predator-encounter

and dilution effects can provide an incomplete depiction of the

effectiveness of grouping as an antipredator defense and

emphasizes the importance of assessing their combined, attack-

abatement effect.


Водотоки: влияние рыб на бентос.


Authors: Dudgeon-D

Title: An Experimental-Study of the Effects of Predatory Fish

on Macroinvertebrates in a Hong-Kong Stream

Source: FRESHWATER BIOLOGY

1991, Vol 25, Iss 2, pp 321-330

Language: English

Document type: Article

Addresses:

UNIV-HONG-KONG, DEPT ZOOL, HUI OI CHOW SCI BLDG, POKFULAM RD,

HONG-KONG, HONG-KONG

Keywords Plus:

FORAGING BEHAVIOR; PREY COMMUNITIES; DISTURBANCE;

DISTRIBUTIONS; SUBSTRATE; INVERTEBRATES; INSECTS; RIVER

Abstract:

1. Predation upon macroinvertebrates by the loach

Oreonectes platycephalus Gunther (Cobitidae) was studied using

predator inclusion/exclusion cages in a series of pools along a

Hong Kong stream. Treatments employed were predator exclusion,

medium (approximately natural) predator densities (1 fish cage-

1) and high predator densities (2 fish cage-1).

Macroinvertebrate abundance in cages was monitored after 2 and 4-

weeks exposure to predators.

2. The presence of fish was associated with significant

declines in the total numbers of macroinvertebrates colonizing

cages. However, taxa were influenced differently, with mayflies

decreasing by a factor of two while the more mobile shrimps

(Atyidae) were unaffected. Chironomid abundance (largely

Chironominae) was unaffected by predator density and increased

in week 4. Detritus acted as a confounding variable at this

time because chironomid abundance was significantly correlated

with the weight of accumulated detritus in cages.

3. While invertebrates were more abundant in cages lacking

fish, there were no fewer invertebrates in cages with 2 fish

than with 1 fish. This may indicate the presence of secure

refuges among substrates in the cages, preventing the additional

fish from depleting prey further, or a lack of precision of

methods due to natural variations in prey densities and spatial

patchiness.

4. No significant effects of predators on relative prey

abundance or species richness were detected.

5. The impact of predation on prey abundance weakened on

week 4, perhaps due to extra refuges among the accumulated

detritus. However, drying of the stream increased fish

densities in pools so that cages may have become zones of

relative safety that were colonized readily by

macroinvertebrates. This result highlights the need for year-

round investigations to quantify predation effects in Hong

Kong's seasonal tropical climate.


Питание и продукция бентоса в водотоках.


Authors: Hall-RO Likens-GE Malcom-HM

Title: Trophic Basis of Invertebrate Production in 2 Streams at

the Hubbard Brook Experimental Forest

Source: JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY

2001, Vol 20, Iss 3, pp 432-447

Many forest stream food webs have leaf litter as the

primary food resource, but instream primary production can also

be quantitatively important, in part because it is more easily

assimilated. We estimated the trophic basis of invertebrate

production in 2 streams at Hubbard Brook Experimental Forest:

Bear Brook (BB), a 2nd-order closed canopy stream, and Main

Hubbard Brook (HB), a 5th-order open-canopy stream. We combined

secondary production measurements for 1 y with gut content

analyses to estimate the fraction of total secondary production

derived from various food sources. Secondary production was low

in both streams: 4.2 g ash-free dry mass (AFDM) m(-2) y(-1) in

BB and 3.0 g AFDM m(-2) y(-1) in HB. The amount of primary

consumer secondary production derived from algae was 5% in BB

and 28% in HB, with the remainder derived from organic detritus.

Higher algal availability and lower benthic organic matter

storage resulted in a higher fraction of algal consumption in HB

relative to BB. Predators consumed similar to 72 to 92% of total

secondary production, producing high predatory losses of insect

production. Algal production was not a large food source in

either stream because of low availability, possibly caused by

shading in BB and possibly nutrient limitation in both streams.


Питание птиц в водотоках.


Authors: Ormerod-SJ Tyler-SJ

Title: Exploitation of Prey by a River Bird, the Dipper Cinclus-

Cinclus (L), Along Acidic and Circumneutral Streams in

Upland Wales

Source: FRESHWATER BIOLOGY

1991, Vol 25, Iss 1, pp 105-116

Language: English

Document type: Article

Addresses:

UNIV-WALES, COLL CARDIFF, NATL RIVERS AUTHOR, CATCHMENT RES

GRP, PENYFAI LANE, LLANELLI SA15-4EL, DYFED, WALES

ROYAL-SOC-PROTECT-BIRDS, WALES OFF, NEWTOWN SY16-1AP, POWYS,

WALES

Keywords Plus:



ASSIMILATION EFFICIENCY; NESTLING INSECTIVORES; DIET;

GROWTH; CATCHMENT; WYE; PREDATION; SIZE

Abstract:

1. The diet of the Eurasian dipper Cinclus cinclus, a

riverine bird from a globally widespread genus, was assessed

through all stages of its annual cycle using published data and

field studies from streams of contrasting chemistry. Time-

activity budgets were also compiled throughout the year and used

to estimate annual energy requirements from the stream

ecosystem.

2. The annual energy requirements for a territorial pair

ranged from 148,000 to 158,000 kJ yr-1 depending on whether one

or two broods were reared. After allowing for assimilation

efficiency, these requirements were estimated to represent 10.5-

11.0 kg dry mass of fish and invertebrates. Using

representative values for territory size (4680-11,250 m2),

annual exploitation of secondary production was estimated at

0.93-2.35 g dry mass m-2.

3. Several features combined to focus the predatory load

on certain organisms over different stages of the annual cycle.

These included the availability and selection of alternative

prey, the need to provision nestlings with large items such as

trichopteran larvae, and the use by females of calcium-rich prey

such as fish prior to egg formation.

4. Across their range of territory size, annual

exploitation (dry mass) by dippers was estimated at 0.06-0.29 g

m-2 for Plecoptera, 0.02-0.22 g m-2 for Ephemeroptera, 0.59-1.11

g m-2 for Trichoptera and 0-0.78 g m-2 for fish. Exploitation

of Ephemeroptera, Trichoptera and fish were all highest in

circumneutral streams, but exploitation of Plecoptera was

highest in acidic streams because other prey were scarce.

5. Cottids dominated the fish component of the diet.

Influences on their density could be substantial according to

available data on production in Welsh streams. Hydropsychids

and limnephilids dominated the trichopteran component, with

exploitation again representing potentially substantial amounts

of production. Contemporaneous data are required on benthic

production and exploitation by the birds.

6. The ecological role of birds in rivers particularly,

and aquatic ecosystems generally, is currently neglected but

worthy of considerable research effort.

Влияние размера поедателя на перифитон.


Authors: Steinman-AD

Title: Effects of Herbivore Size and Hunger Level on Periphyton

Communities

Source: JOURNAL OF PHYCOLOGY

1991, Vol 27, Iss 1, pp 54-59

Language: English

Document type: Article

Addresses:

OAK-RIDGE-NATL-LAB, DIV ENVIRONM SCI, POB 2008, BLDG 1504,

OAK-RIDGE, TN 37831, USA

Author keywords:

Cocconeis; Competition; Elimia; Growth Form; Herbivory;

Periphyton; Snails; Stigeoclonium; Streams

Keywords Plus:

PHYTOPLANKTON COMMUNITY; CADDISFLY POPULATION; STREAM;

COMPETITION; INSECT

Abstract:

The effects of herbivore size and hunger level were tested

on lotic periphyton community structure and ash-free dry

mass(AFDM). My hypotheses were 1) that small herbivores would

remove more periphyton per units biomass than large herbivores

of the same species because of energetic demands and 2) that

within the same size class, starved herbivores would remove more

periphyton than nonstarved herbivores. The herbivore used was

the prosobranch snail Elima clavaeformis Lea. Seven treatments

were employed: 1) no snails (control); 2) small ''starved''

snails; 3) large ''starved'' snails; 4) small and large

''starved'' snails; 5) small fed snails; 6) large fed snails;

and 7) small and large fed snails. Although snails removed

significant amounts of periphyton AFDM relative to controls,

neither snail size nor degree of starvation had a significant

effect on loss of total AFDM. Small snails removed

significantly more erect forms of Stigeoclonium tenue (C. A.

Ag.) Kutz. than large snails, but snail size had no other

significant effect. Starved snails removed significantly more

Cocconeis placentula Ehr. than fed snails, suggesting that after

the more susceptible growth forms (e.g. erect Stigeoclonium)

were removed, Cocconeis cells became more vulnerable to grazing

by hungry snails. When small and large snails were combined in

chambers, large snails gained weight over time, whereas small

snails lost weight. These results suggest that intraspecific

competition may occur within populations of Elimia.


Питание бентоса опадом в Миссисипи.


Authors: Beiser-MC Testa-S Aumen-NG

Title: Macroinvertebrate Trophic Composition and Processing of

4 Leaf Species in a Mississippi Stream

Source: JOURNAL OF FRESHWATER ECOLOGY

1991, Vol 6, Iss 1, pp 23-33

Language: English

Document type: Article

Addresses:

UNIV-MISSISSIPPI, DEPT BIOL, FRESHWATER BIOL PROGRAM,

UNIVERSITY, MS 38677, USA

Keywords Plus:

WOODLAND STREAM; LITTER DECOMPOSITION; LEAVES;

INVERTEBRATES; COLONIZATION; SHREDDERS; BREAKDOWN; INSECTS;

ECOLOGY; FRESH

Abstract:

The benthic invertebrate community associated with leaf

packs of four taxa of deciduous leaves was examined along with

changes in community composition occurring during leaf

decomposition. Dogwood leaves were processed most rapidly,

followed by tulip poplar, hickory, and oak, with average decay

coefficients (k) of 0.059, 0.046, 0.026, and 0.021 d-1,

respectively. Twenty-five taxa of macroinvertebrates were

collected from the leaf packs, and most were insects.

Trichoptera were the most commonly collected organisms and were

dominated by Lepidostoma sp. The majority of the taxa occurred

on all leaf species and in similar numbers. Among the collected

taxa were eight shredders, five collectors, nine predators, and

two scrapers. Invertebrates colonized leaf packs two days post-

introduction, suggesting that shredders did not require pre-

conditioned leaves. Attempts to correlate the number of

invertebrates with percent leaf material remaining were

unsuccessful. The greatest macroinvertebrate abundance and

diversity occurred on oak leaves. There was no discrimination

between leaf species by the majority of the colonizing

invertebrates, with over 96% of the invertebrate taxa found on

all four leaf species. The results suggest that invertebrates

in warmwater streams are able to exploit allochthonous resources

over a longer time period than invertebrates in higher latitude

streams.

Пищевые взаимосвязи.


Freshwater Biology Volume 47 Issue 7 Page 1257 - July 2002

Predation on mayfly nymph, Baetis rhodani, by native and introduced Gammarus: direct effects and the facilitation of predation by salmonids

DAVID W. KELLY, JAIMIE T. A. DICK & W. IAN MONTGOMERY

1.In a series of laboratory experiments, we assessed the predatory nature of the

native Irish amphipod, Gammarus duebeni celticus, and the introduced G. pulex,

towards the mayfly nymph Baetis rhodani. We also investigated alterations in

microhabitat use and drift behaviour of B. rhodani in the presence of Gammarus,

and indirect predatory interactions with juvenile Atlantic salmon, Salmo salar.

2.In trials with single predators and prey, B. rhodani survival was significantly

lower when Gammarus were free to interact with nymphs as than when Gammarus

were isolated from them. The invader G. pulex reduced the survival of B. rhodani

more rapidly than did the native G. d. celticus. Both Gammarus spp. were active

predators.

3.In `patch' experiments, B. rhodani survival was significantly lower both when G.

pulex and G. d. celticus were present, although the effect of the two Gammarus

species did not differ. Again, active predation of nymphs by Gammarus was

observed. Significantly more nymphs occurred on the top and sides of a tile, and

per capita drifts were significantly higher, when Gammarus were present. Baetis

rhodani per capita drift was also significantly higher in the presence of the

introduced G. pulex than with the native G. d. celticus.

4.Gammarus facilitated predation by salmon parr of B. rhodani by significantly

increasing fish-nymph encounters on exposed gravel and in the drift. There were no

differential effects of the two Gammarus spp. on fish -B. rhodani encounters or

consumption.

5.We conclude that Gammarus as a predator can have lethal, nonlethal, direct and

indirect effects in freshwaters. We stress the need for recognition of this predatory

role when assigning Gammarus spp. to a `Functional Feeding Group'.




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