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Title: The Effects of Substrate Texture, Grazing, and

Disturbance on Macroalgal Establishment in Streams

Source: ECOLOGY 1991, Vol 72, Iss 1, pp 297-309

Abstract:

Two common macroalgae, Cladophora glomerata (a filamentous

chlorophyte) and Nostoc parmeloides (a colonial cyanobacterium),

are strongly associated with rough substrates in Rattlesnake

Creek, a second-order stream in coastal Santa Barbara County,

California. To test the hypothesis that rough texture reduces

algal mortality from invertebrate grazers and from winter

storms, we conducted a series of experiments on two substrate

types (tiles) that varied only in surface heterogeneity. The

dominant grazer, the caddisfly Agapetus celatus, was excluded

from tiles using petroleum jelly barriers, and algal

establishment was compared with that on control tiles; grazing

experments were repeated during spring and autumn. In a

separate experiment, storm scouring was simulated by manually

scrubbing naturally colonized rough and smooth tiles at

different intervals (7 wk, 3 wk, and once, with an undisturbed

control) from December to June, during which algal establishment

and survival were monitored.

In the absence of Agapetus, Cladophora was found nearly

equally on rough and smooth surfaces. Grazers strongly reduced

Cladophora establishment on all surfaces (often by > 80%);

texture did not generally influence grazing effects in autumn,

but refuges (pits) greatly increased algal survival in spring

when recruitment was greater. Two other grazing insects (Baetis

spp. and Micrasema) increased on exclusion tiles, apparently due

to competitive release, but did not eliminate effects of

Agapetus. Manual disturbance at 3- and 7-wk intervals kept

Cladophora densities much lower than on control and once-scoured

tiles. Densities were higher on rough tiles, but the

interaction between disturbance and texture was not significant

for macroalgae; however, microscopic examination showed that

basal filaments, and new sporelings, were protected within

depressions.

Nostoc attained densities in autumn of almost-equal-to 50-

100 colonies/100 cm2 on rough tiles and was virtually absent

from smooth tiles. Unlike Cladophora, Nostoc was little

affected by grazing, but was greatly reduced by disturbance.

Rough texture provided minor protection, but mature Nostoc

formed basal crusts that resisted disturbance, thereby

maintaining space in the absence of severe scour.

Substrate heterogeneity provides refuges from herbivory and

disturbance for establishing macroalgae. While it increasingly

appears that herbivory plays a profound role in determining

algal dynamics in streams, herbivores and substrate texture may

also interact to modify the rate and direction of benthic

succession. By inhibiting the establishment of intermediate

taxa (e.g., Cladophora), grazers may restrict succession on

smooth substrates to an early, diatom-dominated assemblage, or

accelerate dominance by later taxa (e.g., Nostoc) on rugose

substrates.

Водотоки: влияние макрофитов.

Freshwater Biology

Volume 45 Issue 1 Page 85-95 - September 2000

Effects of aquatic plant management on stream metabolism and

oxygen balance in streams

Barbara R. Kaenel Heinrich Buehrer Urs Uehlinger

1.In unshaded, nutrient-rich streams, prolific growth of stream macrophytes often

results in flows that over-top the banks and in high primary production and

respiration that may result in extreme diel variations in dissolved oxygen.

Consequently, water protection authorities commonly remove macrophytes

periodically.

2.We investigated the effect of plant removal on stream metabolism and oxygen

balance in two Swiss streams with a high macrophyte biomass. We monitored the

concentration of dissolved oxygen before and after macrophytes were removed by

cutting and dredging, and calculated rates of gross primary production and

ecosystem respiration by means of diel oxygen curves.

3.The removal of plants, which had reached a dry biomass of 320-420 g m2

immediately before plant removal, had a different impact on stream metabolism in

the two streams. In the first (plants removed in May), neither primary production

nor ecosystem respiration were significantly affected. In the second (plants

removed in late July), gross primary production and ecosystem respiration were

reduced by about 70%. In this latter stream gross primary production increased in

the first 2 weeks after plant removal but never recovered to pre-disturbance levels.

4.The removal of plants coincided with only a moderate increase in nocturnal

oxygen concentration (+1 mg L1). This, and the rapid partial recovery of stream

metabolism in the second stream, suggests that an increase in the oxygen

concentration after plant cutting is transient in unshaded, nutrient-rich streams.

Водотоки: роль макрофитов

Freshwater Biology

Volume 40 Issue 3 Page 497 - November 1998

Development, maintenance and role of riparian vegetation in the river landscape

Eric Tabacchi David L. Correll Richard Hauer Gilles Pinay Anne-Marie Planty-Tabacchi Robert C. Wissmar

Summary

1. Riparian structure and function were considered from a longitudinal perspective

in order to identify multiscale couplings with adjacent ecosystems and to identify

research needs.

2. We characterized functional zones (with respect to vegetation development in

association with various biogeochemical processes) within geomorphological

settings using a delineation based upon erosional, transitional and depositional

properties.

3. Vegetation dynamics within the riparian corridor are clearly influenced

substantially by hydrological disturbance regimes. In turn, we suggest that

vegetation productivity and diversity may widely influence riverine biogeochemical

processes, especially as related to the consequences of changing redox conditions

occurring from upstream to downstream.

4. However, surface and groundwater linkages are the predominant controls of

landscape connectivity within riparian systems.

5. The importance of riparian zones as sources and sinks of matter and energy was

examined in context of structural and functional attributes, such as sequestering or

cycling of nutrients in sediments, retention of water in vegetation, and retention,

diffusion or dispersal of biota.

6. The consequences of interactions between different communities (e.g. animals

and plants, micro-organisms and plants) on biogeochemical processes are notably

in need of research, especially with respect to control of landscape features.

Multiscale approaches, coupling regional and local factors in all three spatial

dimensions, are needed in order to understand more synthetically and to model

biogeochemical and community processes within the river-riparian-upland

landscape of catchments.

Речная растительность, Пакистан.

Shah S S H. Chaghtai S M.

The stream vegetation of Ambela Pass, Buner, NWFP, Pakistan.

Scientific Khyber 9(1). 1996. 85-92.

The vegetation of a stream in Ambela Pass, Buner, NWFP Pakistan was

sampled both in spring and fall for four years in order to study its

composition. The area is divisible into two clear zones, Zone "A" and "B",

Zone A, the upstream part, is covered over by the seepage water only and

has a peaty soaked soil. Zone "B" the downstream part, is covered by a

perpetually flowing water body. Zone "A" supported 12 species in the

spring and 11 in the fall seasons. The spring community was dominated by

Mentha longifolia and Nasturtium officinale. In the fall again the same

two plants dominated the community but N. officinale took the lead over M.

longifolia. Zone "B" communities of both spring and the fall seasons were

dominated by a woody perennial plant, Arundo donax, while the co-dominants

were M. longifolia and N. officinale which changed their order of

dominance in the two seasons. The area is under biotic interference.

Cutting, slashing and grazing were common. Arundo donax is fastly taking

over the area on the flat topography.

Реофильные мхи, Финляндия.

Virtanen V.

Floristic composition and habitat ecology of stream bryophytes in Lohja

parish, southern Finland.

Annales Botanici Fennici 32(3). 1995. 179-192.

Bryophyte flora and community structure were studied in 8 streams around

Lake Lohjanjarvi in southern Finland. Floristic composition, cover,

frequency, and microhabitat parameters were measured, including type of

substrate, moisture, slope and aspect in stream. Aspect was used for

description of zonation pattern. The Brillouin diversity equation and

Sorensen's quotient of similarity were used for the evaluation of

community structure. The communities included 33 mosses and 5 hepatics.

One third of the species were truly aquatic and the rest were terrestrial

species occasionally occurring in a stream habitat. Most species occurred

at low frequencies. Fontinalis antipyretica Hedw. was most frequent and

adundant, and Brachythecium plumosum (Hedw.) B.S.G., Hygroamblystegium

fluviatile (Hedw.) Loeske, Racomitrium aciculare (Hedw.) Brid., and

Scapania undulata (L.) Dum. were rather common. Communities differed from

each other in floristic composition, species number, diversity, and

relative abundance of species. The highest diversity was in the stream

with a rather high species number and the most even relative abundance of

species.

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