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Identifying the scales of variability in stream macroinvertebrate abundance, functional composition and assemblage structure (2004)

Heino, Jani ; Louhi, Pauliina ; Muotka, Timo

Oxford, UK : Blackwell Science Ltd

Freshwater biology 49 (2004), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Many natural ecosystems are heterogeneous at scales ranging from microhabitats to landscapes. Running waters are no exception in this regard, and their environmental heterogeneity is reflected in the distribution and abundance of stream organisms across multiple spatial scales.2. We studied patchiness in benthic macroinvertebrate abundance and functional feeding group (FFG) composition at three spatial scales in a boreal river system. Our sampling design incorporated a set of fully nested scales, with three tributaries, two stream sections (orders) within each tributary, three riffles within each section and ten benthic samples in each riffle.3. According to nested anovas, most of the variation in total macroinvertebrate abundance, abundances of FFGs, and number of taxa was accounted for by the among-riffle and among-sample scales. Such small-scale variability reflected similar patterns of variation in in-stream variables (moss cover, particle size, current velocity and depth). Scraper abundance, however, varied most at the scale of stream sections, probably mirroring variation in canopy cover.4. Tributaries and stream sections within tributaries differed significantly in the structure and FFG composition of the macroinvertebrate assemblages. Furthermore, riffles in headwater (second order) sections were more variable than those in higher order (third order) sections.5. Stream biomonitoring programs should consider this kind of scale-dependent variability in assemblage characteristics because: (i) small-scale variability in abundance suggests that a few replicate samples are not enough to capture macroinvertebrate assemblage variability present at a site, and (ii) riffles from the same stream may support widely differing benthic assemblages.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01259.x

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The stream as a habitat templet for bryophytes: species' distributions along gradients in disturbance and substratum heterogeneity (1995)

MUOTKA, TIMO ; VIRTANEN, RISTO

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 33 (1995), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. The structure of bryophyte communities in streams in relation to habitat characteristics, especially disturbance, is described. Disturbance in rivers is quantified as movement of the stream bed, whereas in small streams water level fluctuation is used as an indicator of disturbance frequency.2. Canonical correspondence analysis differentiated frequently disturbed sites from more stable ones. The existence of a disturbance gradient was confirmed in a subset of the study sites using long-term records of discharge variation. A parallel change was detected in the species composition of bryophyte communities with low-statured, potentially fast colonizers dominating the disturbed end and large perennial species the stable end of the gradient.3. A consistent pattern of zonation of bryophyte species was found along the gradient from continually submersed to persistently dry conditions in small streams and lake outlets. An abrupt increase in species richness occurred at or just above the water line, where facultatively aquatic species tolerant of both conditions formed the bulk of the community.4. The relationship between species richness and standing crop in stream bryophyte communities was consistent with the hump-backed model of Grime (1979), especially at the within-habitat scale. Quadrats of low and very high standing crop were characterized by low species richness, while peak richness was observed at intermediate standing crops.5. A few perennial species (e.g. Fontinalis spp. and Rhynchostegium riparioides) capable of monopolizing space dominated the most stable habitats. Species composition in low biomass sites was more variable, yet only one basic growth-form (small-statured species with high allocation to spore production) seemed possible in these highly disturbed streams. In habitats of intermediate biomass, small-scale disturbances apparently allow the formation of a more varied bryophyte community.6. A habitat templet for stream bryophyte life strategies and community structure is presented. Disturbance is proposed to be the factor filtering out traits unsuitable for a given environment. The potential of stream bryophytes for testing and developing general ecological theory is emphasized.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb01156.x

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3

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Are biological classifications of headwater streams concordant across multiple taxonomic groups? (2003)

Paavola, Riku ; Muotka, Timo ; Virtanen, Risto ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 48 (2003), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Studies assessing human impacts on freshwater ecosystems are typically based on a single taxonomic group, often macroinvertebrates or fish. Unfortunately, the degree to which such macroinvertebrate or fish-based surveys can be generalised across other taxonomic groups remains largely unknown. A prerequisite for useful generalisations is that different taxonomic groups exhibit concordant patterns of community structure across sites.2. We examined the concordance among fish, benthic macroinvertebrates and bryophytes in 32 streams in a boreal catchment in Finland. Our goal was to test how consistently different taxonomic groups classify stream sites; for example, can site groupings based on macroinvertebrates be used as a surrogate for bryophyte or fish assemblage classification?3. Our results show that community classifications in headwater streams are not concordant across taxonomic groups, at least not at the within-river system scale. The lack of concordance reflected the fact that all three groups responded to different environmental factors. Macroinvertebrate community structure was mainly correlated with stream size and pH, whereas bryophytes were related to water colour, nutrient content and in-stream habitat variability. Fish community structure was best described by stream depth, substrate size and water oxygen concentration.4. Our results suggest that great care should be taken when typologies based on benthic macroinvertebrates, or any other taxonomic group, are extrapolated to other groups in creating typologies of lotic environments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01131.x

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Nocturnal drift of mayfly nymphs as a post-contact antipredator mechanism (2000)

Huhta, Arto ; Muotka, Timo ; Tikkanen, Pertti

Oxford, UK : Blackwell Science Ltd

Freshwater biology 45 (2000), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested.  2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout (Salmotrutta, a drift-feeding fish), one with alpine bullhead (Cottuspoecilopus, a benthic fish), one with both species, and two fishless streams.  3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In contrast, drift was nocturnal in streams with trout and, to a lesser extent, in the stream with bullhead. Non-dipteran prey drifted mainly nocturnally in all streams with fish, whereas Diptera larvae were less responsive to the presence of fish.  4. In laboratory experiments, bullheads were night-active, causing a much higher frequency of drift by touching Baetis at night than during the day. Thus, increased nocturnal drift may serve to avoid both visual predators (a pre-contact response) and benthic fish (a post-contact response). In streams with bottom-feeding fish, nocturnal drift should be caused by increased drift by night rather than by reduced drift by day.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2000.00615.x

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5

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Coexistence in a guild of filter feeding caddis larvae: do different instars act as different species? (1990)

Muotka, Timo

Springer

Oecologia 85 (1990), S. 281-292

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ISSN: 1432-1939

Keywords: Coexistence ; Guild structure ; Hydropsychidae ; Polycentropodidae ; Size-structured populations

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Guild structure and coexistence of filter feeding caddis larvae was studied in three lake-outlet streams in northern Finland. Natural stones were used as sampling units, and for each stone measurements of six microhabitat variables were taken. Species and species instar relationships in the multivariate microhabitat space were analyzed by a method based on Principal Components Analysis. Seven species of filtering caddis larvae were found at the study sites, but detailed analysis was restricted to the four most abundant ones (Polycentropus flavomaculatus, Hydropsyche angustipennis, H. pellucidula, H. saxonica). P. flavomaculatus was the microhabitat generalist of the guild, whereas all the hydropsychids were narrowly specialized in at least one larval instar. In all species, different instars utilized the microhabitat somewhat differentially. Moss content and Froude number were significantly different between instar microhabitats in all comparisons. Ontogenetic niche changes not only separated species instars from each other, but also profoundly changed the biotic as well as abiotic environment of the species at different phases of larval development. This may have important effects on the dynamics of interacting species and, consequently, on the guild structure. While some of the more classical models of coexistence may also be relevant for understanding coexistence in this guild of sessile stream insects, ontogenetic niche changes clearly need to be taken into consideration in future studies of guild structure and species interactions of filter feeding caddisfly larvae.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00319414

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6

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Predator detection and avoidance by lotic mayfly nymphs of different size (1994)

Tikkanen, Pertii ; Muotka, Timo ; Huhta, Arto

Springer

Oecologia 99 (1994), S. 252-259

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ISSN: 1432-1939

Keywords: Baetis ; Antipredatory responses ; Stream ; Drift ; Refuge use

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We studied antipredatory responses of lotic mayfly (Baetis) nymphs in a factorial experiment with four levels of fish presence: (1) a freely foraging fish (the European minnow,Phoxinus phoxinus), (2) a constrained fish, (3) water from a fish stream, (4) water from a fishless stream. LargeBaetis nymphs drifted mainly during night-time in treatments involving either the chemical or actual presence of fish, whereas no diel periodicity was observed when the water was not conditioned with fish odour. The response was strongest when the fish was uncaged, which suggests that visual or hydrodynamic cues are needed in addition to chemical ones for an accurate assessment of predation risk. Fish presence had no effect on the drift rates of small nymphs. Instead, they increased their refuge use in the presence of a live fish. Chemical cues alone did not have any effect on the refuge use of any of theBaetis size classes. Our results indicate active drift entry by mayfly nymphs. Because predation pressure is spatially and temporally variable, nymphs must sample the environment in order to locate predator-free areas or areas with low predation risk. Drifting should be the most energy-saving way to do this. To avoid the risk from visually feeding fish, large individuals can sample safely (i.e. enter drift) only at night-time, while the small ones can also do this safely during the day. We suggest that, contrary to some earlier assumptions, mayfly drift is not a fixed prey response. Instead,Baetis nymphs are able to assess the prevailing predation pressure, and they adjust their foraging behaviour accordingly.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00627737

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7

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Short-term recovery of benthos following disturbance from stream habitat rehabilitation (1994)

Tikkanen, Pertti ; Laasonen, Pekka ; Muotka, Timo ; [et al.]

Springer

Hydrobiologia 273 (1994), S. 121-130

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ISSN: 1573-5117

Keywords: stream rehabilitation ; benthic macroinvertebrates ; disturbance ; recovery

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The recovery of benthic macroinvertebrates after disturbance from stream rehabilitation was studied in the River Livojoki, northern Finland. The stream that had been channelized for log transport was rehabilitated on 1 July 1992 by digging holes and inserting boulders. We measured habitat characteristics and sampled benthic animals before and after rehabilitation, including an unrehabilitated control site. The immediate effect of rehabilitation was a slight decrease in the abundances of benthic insects. Recolonization occurred rapidly, within 10 days. Disturbance of the rehabilitation did not have a detectable effect on the macroinvertebrate community. Most species-level changes and community patterns reflected seasonal life history events. Timing of such rehabilitation work can be critical for the recovery rate, which depends on the colonization abilities of the species present after disturbance. We suggest that many disturbances (including minor floods and moderate rehabilitation procedures) may have only small, short-term effects on benthic communities. We emphasize the importance of considering seasonality in studies of disturbance in streams.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00006854

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