Softwater Stream Research Articles

The Shape of Water Stream Induces Differences in P300 and Alpha Oscillation.

Touching is a fundamental human behavior used to evaluate objects in the external world. Many previous studies have used tactile stimulation to conduct psychological and psychophysiological experiments. However, most of these studies used solid material, not water stream, as an experimental stimulus. To investigate water perception, or to easily control the temperature of an experimental stimulus, it is important to be able to control the water stimulus. In this study, we investigated the usability of water as an experimental stimulus for electroencephalography (EEG) experiments and report the basic EEG response to water stimulus. We developed a tactile stimulation device using a water stream to study EEG responses, with the ability to control the stimulus onset timing. As stimuli, we selected two types of water stream, normal and soft, based on a psychological experiment to confirm a difference of subjective feeling induced by these water streams. We conducted a typical oddball task using the two different water streams and recorded EEG waveforms from 64 electrodes while participants touched the water streams. We calculated P300 at the Pz electrode, alpha asymmetry at the frontal electrodes, and alpha suppression at the parietal area. As a result, we observed typical P300 differentiation based on the stimulus proportion (target 20% and standard 80%). We observed a weaker alpha suppression when participants touched the soft water stream compared to the normal shower. These results demonstrate the usability of water stream in psychophysiological studies and suggested that alpha suppression could be a candidate to evaluate comfort of water stream.

Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study

Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2–3 nm) and Fe-bearing colloids (3–1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3–6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40–1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments.

Chamaesiphon species in soft-water streams in Germany: occurrence, ecology and use for bioindication

We analyzed the records of several species of Chamaesiphon A. Braun ex Grunow 1865 collected by the water management authorities of the German federal states North RhineWestphalia (NRW) and Saxony (SN). In total, 579 sampling events from 429 different sampling sites at soft water streams and rivers of the Central German Uplands (types 5, 5.1 and 9 of the German typology for running waters) were included. Samples were collected between 2006 and 2012. Sites ranged from unimpaired, nutrient-poor to nutrient-rich sites. Twelve different species of Chamaesiphon were recorded. The epiphytic species C. confervicolus and C. incrustans and the epilithic species C. fuscus, C. polymorphus and C. starmachii were most common in both federal states. Uni- and multivariate methods were employed to describe autecological preferences of these taxa. C. fuscus and C. starmachii occur at significantly lower nutrient levels and therefore are characteristic for unimpaired sites, whereas C. confervicolus, C. incrustans and C. polymorphus prefer nutrient-rich sites. C. confervicolus and C. incrustans are different in respect of the morphological features of the sampling sites like stream width, depth and substrate. C. polonicus which occurs in the medium range regarding nutrients and geochemical properties is known to be a tolerant species. The use of Chamaesiphon species for assessment and especially their classification within the PHYLIB tool is discussed.

Relating metal exposure and chemical speciation to trace metal accumulation in aquatic insects under natural field conditions

The present study investigated to what extent measured dissolved metal concentrations, WHAM-predicted free metal ion activity and modulating water chemistry factors can predict Ni, Cu, Zn, Cd and Pb accumulation in various aquatic insects under natural field conditions. Total dissolved concentrations and accumulated metal levels in four taxa (Leuctra sp., Simuliidae, Rhithrogena sp. and Perlodidae) were determined and free metal ion activities were calculated in 36 headwater streams located in the north-west part of England. Observed invertebrate body burdens were strongly related to free metal ion activities and competition among cations for uptake in the biota. Taking into account competitive effects generally provided better fits than considering uptake as a function of total dissolved metal levels or the free ion alone. Due to the critical importance and large range in pH (4.09 to 8.33), the H+ ion activity was the most dominant factor influencing metal accumulation. Adding the influence of Na+ on Cu2+ accumulation improved the model goodness of fit for both Rhithrogena sp. and Perlodidae. Effects of hardness ions on metal accumulation were limited, indicating the minor influence of Ca2+ and Mg2+ on metal accumulation in soft-water streams (0.01 to 0.94mM Ca; 0.02 to 0.39mM Mg). DOC levels (ranging from 0.6 to 8.9mgL−1) significantly affected Cu body burdens, however not the accumulation of the other metals.Our results suggest that 1) uptake and accumulation of free metal ions are most dominantly influenced by competition of free H+ ions in low-hardness headwaters and 2) invertebrate body burdens in natural waters can be predicted based on the free metal ion activity using speciation modelling and effects of H+ competition.

Evidence of rock glacier melt impacts on water chemistry and diatoms in high mountain streams

A first study of high alpine freshwaters at Hochebenkar and Krumgampen (Oetztal Alps, Tyrol, Austria) revealed pronounced differences in the concentration of major ions, heavy metals, species composition and biodiversity of epilithic diatoms in streams emerging from two active (i.e. ice containing) rock glaciers and in adjacent unaffected reference streams. The clear-water streams impacted by active rock glaciers are characterized by high electrical conductivity (EC) values, but differ in acidity, heavy metal concentrations and by the proportion of circumneutral and acidobiontic diatoms. On the contrary, all reference streams exhibit low EC and circumneutral to slightly acidic pH values characteristic for surface waters on bedrock composed of paragneiss and micaschist, with no detectable heavy metals and a diatom composition typical for high altitude softwater streams. The high ion concentrations in streams emerging from rock glaciers are attributed to a seasonally increasing release of melt waters from active rock glaciers.

Transfer of Achnanthes decipiens to the genus Nupela

Achnanthes decipiens Reimer was described from a benthic sample collected from a small stream in South Carolina, USA. Examination of the type material with light and electron microscopy showed that this species belongs to the genus Nupela Vyverman & Compère to which it is transferred. Nupela decipiens (Reimer) Potapova is similar to N. praecipua (Reichardt) Reichardt by the size and shape of the valve and the striation pattern, but differs from it by the large central area on the raphe valve. So far, N. decipiens has been reported from a few slightly acid soft-water streams in eastern North America.

Tabellaria vetteri, a New Diatom (Bacillariophyceae: Tabellariaceae) from Pennsylvania, USA.

ABSTRACT. A new diatom species, Tabellaria vetteri, is described from North-Central Pennsylvania. Unlike other representatives of the genus Tabellaria Ehrenberg, the new species lacks rimoportulae, the central part of its valve is internally thickened, and all girdle bands are open. Other characters, such as shape of the frustule, numerous ligulate girdle bands bearing septa, uniseriate striae with small poroid areolae, large apical pore fields, and simple spines fit the current concept of this genus. The new species is found so far only in two small soft-water streams and is especially abundant on sand.

Longitudinal extent of acidification effects of plantation forest on benthic macroinvertebrate communities in soft water streams: evidence for localised impact and temporal ecological recovery

Plantation conifer forest can increase the risk of acidification in acid-sensitive catchments with consequences for macroinvertebrates and ecosystem functioning. This study compared headwater streams in forested and non-forested catchments to appraise the distance required for the acid effect on macroinvertebrates to diminish downstream. Strict criteria were followed in the selection of paired streams, including similarities in elevation, aspect, stream order, geographical proximity, geology and soil type, with no inflowing tributaries in the first 2.5 km and no major land-use other than plantation forest and moorland. Consequently two headwater streams (one forested, one non-forested) drained Ordovician sedimentary geology and two headwater streams (one forested, one non-forested) drained Old Red Sandstone (ORS) were selected. All streams drained peaty soils. Up to six sites at 500 m intervals were sampled in triplicate by multihabitat kick sampling. Ecological impact and recovery from acid effects involved the entire macroinvertebrate community, but varied between seasons. Acid-sensitive Ephemeroptera revealed marked effects of episodic acidification, with Baetis rhodani and Rhithrogena semicolorata found to be transient between seasons. The increase in acid-sensitive ephemeropteran species with increasing distance downstream indicates the finite effects of forest mediated acidification on soft water streams in Ireland. Ecological impact appears, therefore, to be localised within the catchment, with ecological recovery occurring a short distance downstream. This is the first study to have reported such results.

Mercury concentration in black flies Simulium spp. (Diptera, Simuliidae) from soft-water streams in Ontario, Canada

Total Hg in Simulium spp. (Diptera, Simuliidae) was measured in 17 soft-water streams in the District of Muskoka and Haliburton County (Ontario, Canada) during 2003 and 2004. Black flies contained 0.07–0.64 μg/g total Hg (dry weight). The methylmercury concentration was measured in 6 samples of the 17, and ranged from 58% to 93% of total Hg. The concentration of total Hg is much higher than has been found in other filter feeding insects, and represents a significant potential source of Hg to fish. Mercury concentrations in Simulium spp. at different sites were strongly positively correlated with dissolved organic carbon, and the proportion of land within each catchment that was wetland. There was also a strong negative correlation with pH. By examining Hg concentration in filter feeding insects we have found a significant entry point for Hg and MeHg into the food web.

Does competition for phosphate supply explain the invasion pattern of Elodea species?

Two invasive aquatic plants, Elodea canadensis and Elodea nuttallii, occurred in north-eastern France. In this study, we examine the influence of phosphorus availability in soft water streams to explain the invasion pattern of exotic species ( E. nuttallii and E. canadensis) compared to native plants ( Callitriche platycarpa, Ranunculus peltatus). Total phosphorus was measured in these four aquatic macrophytes. Sediment total phosphorus and water-soluble reactive phosphorus were also analysed each season in 2001. Phosphorus content in the two invasive species and in R. peltatus was higher than in C. platycarpa. Elodea species are adapted to the seasonal phosphorus fluctuations as well as R. peltatus and exhibited high phosphorus storage ability. The high fluctuation availability of resources in space or/and time favoured the spread of the invasive plants and confirms the theory of invasibility of Davis et al. [2000. Fluctuating resources in plant communities: a general theory of invasibility. J. Ecol. 88, 528–534]. The eutrophication process increases the invasibility of E. nuttallii's, while inducing competition between E. nuttallii and native macrophyte species.

Effect of pH on photo-oxidation of dissolved organic carbon by hydroxyl radicals in a coloured, softwater stream

Previous work has shown that the photo-oxidation rate of dissolved organic carbon (DOC) exposed to solar radiation was significantly enhanced in acidic stream waters and that the average photo-oxidative loss of DOC in the UVA region was more than 60%. This study examined the effect of pH on photobleaching and the photo-oxidative loss of DOC and the degree of photo-oxidative loss by hydroxyl radicals (•OH) over the pH range 4–9 in a coloured, softwater stream. Binding iron with NaF lowered the photo-oxidation rate constant by about 50% at pH 4 and by 10–20% at pH 4.6 and 4.9. Hence, iron plays an important role in the photo-oxidative loss of DOC at pH 4 with declining importance as the pH increases. The importance of •OH in photo-oxidative loss of stream DOC was evaluated by adding KI to quench •OH. After 69 hours of artificial irradiation without KI, DOC loss decreased as pH increased from pH 4 to 9 whereas the minimum loss of absorbance at 300 nm occurred at pH 7. KI significantly reduced loss of DOC at pH 4, 5 and 7 but not at pH 9 with the fraction of DOC lost by non-•OH mechanisms gradually increasing from 58% to 75% between pH 4 and 7, and 100% at pH 9. Since many northern freshwater lakes on the Precambrian Shield receive large fluxes of UV-labile humic matter from peatlands and have pH < 7.5, photo-oxidative loss of DOC by both non-•OH and •OH mechanisms is important in C dynamics in northern freshwaters but with photo-oxidative loss dominated by non-•OH mechanisms likely operating in the UVA region.

Diel changes of inorganic chemistry in a macrophyte-dominated, softwater stream

Diel fluctuations of conductivity and alkalinity were measured in a macrophyte-dominated stretch of the Piako River, a rural, lowland, softwater stream in New Zealand. Both quantities exhibited elevated levels at dawn and depressed levels in the early evening suggesting that the variations might be connected with the diel cycles of macrophyte photosynthesis and respiration. A chemical analysis was used to determine which ions induced the diel variations. For low-flow periods with minimal allochthonous inputs, the changes in conductivity were correlated with calcium, magnesium and the ionised components of total inorganic carbon (bicarbonate, HCO3–, and carbonate, CO32–). The changes in alkalinity were correlated with fluctuations of calcium and magnesium. The latter result was not anticipated based on solubility product calculations. Diel cycles of groundwater inputs explained 60% of average conductivity variations and 30% of average alkalinity variations between dusk and dawn. Other mechanisms also contribute to the observed changes and we speculate that localised calcite production and dissolution may be occurring.

Respiration and annual fungal production associated with decomposing leaf litter in two streams

Summary1. We compared fungal biomass, production and microbial respiration associated with decomposing leaves in one softwater stream (Payne Creek) and one hardwater stream (Lindsey Spring Branch).2. Both streams received similar annual leaf litter fall (478–492 g m−2), but Lindsey Spring Branch had higher average monthly standing crop of leaf litter (69 ± 24 g m−2; mean ± SE) than Payne Creek (39 ± 9 g m−2).3. Leaves sampled from Lindsey Spring Branch contained a higher mean concentration of fungal biomass (71 ± 11 mg g−1) than those from Payne Creek (54 ± 8 mg g−1). Maximum spore concentrations in the water of Lindsay Spring Branch were also higher than those in Payne Creek. These results agreed with litterbag studies of red maple (Acer rubrum) leaves, which decomposed faster (decay rate of 0.014 versus 0.004 day−1), exhibited higher maximum fungal biomass and had higher rates of fungal sporulation in Lindsey Spring Branch than in Payne Creek.4. Rates of fungal production and respiration per g leaf were similar in the two streams, although rates of fungal production and respiration per square metre were higher in Lindsey Spring Branch than in Payne Creek because of the differences in leaf litter standing crop.5. Annual fungal production was 16 ± 6 g m−2 (mean ± 95% CI) in Payne Creek and 46 ± 25 g m−2 in Lindsey Spring Branch. Measurements were taken through the autumn of 2 years to obtain an indication of inter‐year variability. Fungal production during October to January of the 2 years varied between 3 and 6 g m−2 in Payne Creek and 7–27 g m−2 in Lindsey Spring Branch.6. Partial organic matter budgets constructed for both streams indicated that 3 ± 1% of leaf litter fall went into fungal production and 7 ± 2% was lost as respiration in Payne Creek. In Lindsey Spring Branch, fungal production accounted for 10 ± 5% of leaf litter fall and microbial respiration for 13 ± 9%.

Annual production of leaf-decaying fungi in 2 streams

We determined fungal biomass and production associated with decaying leaves over an annual cycle in 2 streams that differed in water chemistry to obtain an indication of the variability of these parameters. Basin Creek is a softwater stream with a pH of 6.3 and relatively low concentrations of inorganic N (94 μg N/L) and P (3 μg P/L), whereas Hendrick Mill Branch is a hardwater stream with a pH of 8.2 and somewhat higher concentrations of inorganic N (139 μg N/L) and P (6 μg P/L). Both streams received similar annual leaf litter fall (379–422 g/m2), but the mean annual standing crop of leaf detritus was higher in Basin Creek (41.6 g/m2) than in Hendrick Mill Branch (20.0 g/m2). Concentrations of fungal spores in the water of both streams peaked in September and December. Leaves sampled in Hendrick Mill Branch generally contained higher concentrations of fungal biomass and fungi had higher rates of production/g leaf than in Basin Creek. This observation agreed with results from litter bags of red maple (Acer rubrum L.) leaves placed in the 2 streams. However, fungal biomass and production associated with leaves sampled, expressed on an areal basis, were higher in Basin Creek because of the higher standing crop of leaves in that stream than in Hendrick Mill Branch. Mean annual fungal biomass was 2.4 g/m2 in Basin Creek and 1.4 g/m2 in Hendrick Mill Branch. Annual fungal production was 31.7 g/m2 in Basin Creek and 26.6 g/m2 in Hendrick Mill Branch, with maximum production/m2 in both streams occurring in the autumn. Turnover time of fungi based on annual production to biomass ratios was shorter in Hendrick Mill Branch (18 d) than in Basin Creek (27 d). Differences in the streams (water chemistry, temperature) favored greater fungal activity in Hendrick Mill Branch, but the higher standing crop of leaf litter in Basin Creek led to slightly higher annual fungal production/m2 in this stream.

Fungal growth, production, and sporulation during leaf decomposition in two streams.

I examined the activity of fungi associated with yellow poplar (Liriodendron tulipifera) and white oak (Quercus alba) leaves in two streams that differed in pH and alkalinity (a hard water stream [pH 8.0] and a soft water stream [pH 6.7]) and contained low concentrations of dissolved nitrogen (<35 microg liter(-1)) and phosphorus (<3 microg liter(-1)). The leaves of each species decomposed faster in the hard water stream (decomposition rates, 0.010 and 0.007 day(-1) for yellow poplar and oak, respectively) than in the soft water stream (decomposition rates, 0.005 and 0.004 day(-1) for yellow poplar and oak, respectively). However, within each stream, the rates of decomposition of the leaves of the two species were not significantly different. During the decomposition of leaves, the fungal biomasses determined from ergosterol concentrations, the production rates determined from rates of incorporation of [(14)C]acetate into ergosterol, and the sporulation rates associated with leaves were dynamic, typically increasing to maxima and then declining. The maximum rates of fungal production and sporulation associated with yellow poplar leaves were greater than the corresponding rates associated with white oak leaves in the hard water stream but not in the soft water stream. The maximum rates of fungal production associated with the leaves of the two species were higher in the hard water stream (5.8 mg g(-1) day(-1) on yellow poplar leaves and 3.1 mg g(-1) day(-1) on oak leaves) than in the soft water stream (1.6 mg g(-1) day(-1) on yellow poplar leaves and 0.9 mg g(-1) day(-1) on oak leaves), suggesting that effects of water chemistry other than the N and P concentrations, such as pH or alkalinity, may be important in regulating fungal activity in streams. In contrast, the amount of fungal biomass (as determined from ergosterol concentrations) on yellow poplar leaves was greater in the soft water stream (12.8% of detrital mass) than in the hard water stream (9.6% of detrital mass). This appeared to be due to the decreased amount of fungal biomass that was converted to conidia and released from the leaf detritus in the soft water stream.

Decomposition and fungal colonization of Fontinalis antipyretica var. gracilis (Bryophyta)

The decomposition of Fontinalis antipyretica var. gracilis was studied with the litterbag technique in a softwater stream between May and October. The daily exponential decay coefficient was 0.0054. Phenolics declined exponentially from an initial value of 1.43 % with a daily loss rate of 3.9%. A total of 22 aquatic hyphomycete species was found on moss during 20 wks. of stream exposure, with the numbers per sampling date fluctuating between 4 after one wk. and 16 after 8 wks. Ergosterol content of decaying moss reached a maximum of 373 μg/g dry mass. Spore production and ergosterol levels in live stream-collected moss (May to November) were less than 1% of the maxima of litterbag moss.

Processing of native and exotic leaf litter in two Idaho (U.S.A.) streams

The Russian olive tree (Elaeagnus angustifolia L.) was brought to the western United States from Eurasia during the early to mid-1900s, and has since become a common member of many riparian communities in Idaho. We compared leaf chemistry and in-stream processing of Russian olive leaves (exotic) and various species of native leaves in one hardwater and one relatively softwater Idaho stream. Measurements using air-dried leaves showed that Russian olive contained the greatest concentration of nitrogen, approximately 1.6% of the dry mass, whereas the native species each contained less than 1.0% nitrogen. The C/N ratio of Russian olive was <30, whereas the natives each had C/N ratios greater than 40. Results from the hardwater stream indicated no difference in 30-day loss of AFDM between Russian olive and the native leaves (dogwood and aspen). In the relatively softwater stream, the Russian olive leaves were processed significantly slower than the native leaf species (cottonwood). The results indicate that a replacement of native riparian trees by exotics, such as Russian olive, may result in slower rates of leaf processing in Idaho streams but that the effect may vary among streams. When comparing the processing of native and exotic leaf litter, initial nitrogen concentrations and initial C/N ratios of the leaves did not appear to be accurate indicators of relative decay rates.

Effects of Water Chemistry and Habitat on the Density of Young Brown Trout Salmo trutta in Acidic Streams

We examined the relationship between young brown trout ( Salmo trutta) density in lake tributaries, and water chemistry and habitat variables. The study was carried out during the autumn in three acidic, softwater river systems in western and southwestern Norway; Gaular and Vikedal (1987–1993) and Bjerkreim (1988–1993). The streams had mean calcium concentrations of 0.35 mg L-1 (Gaular), 0.52 mg L-1 (Vikedal) and 0.84 mg L-1 (Bjerkreim). The concentration of inorganic Al was generally low, with mean values of 8.40 (Gaular), 22.22 (Vikedal) and 43.36 μg L-1 (Bjerkreim). In multiple regressions that involved different water chemistry variables, brown trout density correlated best with calcium concentration and with a combination of calcium and pH; the Ca2+:H+ ratio. In Vikedal and Gaular, calcium explained 51 and 57%, respectively, of the variability in brown trout densities. Althoug alkalinity exhibited the best correlation with brown trout density in Bjerkreim ( r2=0.33), it was similar to that of the model that included all major ions plus pH. The Ca2+:H+ ratio had a larger effect for variability in brown trout density in Gaular (r2=0.66) than calcium alone. In Vikedal and Bjerkreim, the Ca2+:H+ ratio also correlated with brown trout density, but considerably less than in Gaular. The predictive power of habitat variables was much lower than that of water chemistry; the single most important factors were altitude in Gaular (r2=0.22), mean water temperature in Vikedal (r2=0.11) and depth SD (index of heterogeneity) in Bjerkreim (r2=0.07). Models that included both habitat and water chemistry variables showed that the density of young brown trout was predicted primarily by calcium concentrations in Gaular (r2=0.75) and Vikedal (r2=0.54), as opposed to pH in Bjerkreim (r2=0.25). Habitat had low effect in all three river systems (r2=0.01–0.04). The final model explained 86, 68 and 32%, respectively, of the variability in brown trout density in the three catchments. Thus, water chemistry variables seem to be factors that limit the density of young brown trout in acidic softwater streams.

The faunal communities of upland streams in the eastern region of Ireland with reference to afforestation impacts

Macroinvertebrates were sampled from forty-seven sites on upland soft water streams in eastern Ireland. Classification generated four recognisable faunal communities or site groups which differed in biological, physical and chemical character; these patterns were supported by ordination analyses. The environmental gradients which probably influenced water quality were broadly categorised into geology, distance from source or elevation and forestry. Faunal diversity and abundance were reduced in both high altitude and extensively afforested sites compared to moorland sites. Whereas, Plecoptera dominated the fauna at most sites, many taxonomic groups such as the Ephemeroptera and members of the family Elmidae were absent from high altitude and forested areas. The impact of afforestation was most evident at those sites which were located in forest plantations or were on catchments with extensive (>25%) closed canopy (>12 yr) afforestation. Low levels (<25%) of forestry in the absence of acid waters did not lead to impoverishment. This work reveals how plantation forestry in areas receiving only moderately polluted rain can be linked with acid waters and impoverished invertebrate communities.

The aquatic processing of sclerophyllous and malacophyllous leaves on a Mediterranean island (Corsica) : spatial and temporal pattern

Leaves of two species, alder (Alnus glutinosa) and holm-oak (Quercus ilex), were exposed in bags of two mesh sizes in two climatically contrasting sites of a Corsican softwater stream. Leaves were incubated both in winter and in summer for about 6 months. The field experiment was designed to determine the influence of both spatial (climate) and temporal (season) variations of temperature, as well as differences in the chemical and physical properties of sclerophyllous and malacophyllous leaves, on leaf decomposition rates. Comparisons were made between leaves colonized by macroinvertebrates and leaves protected by finemesh. In winter and summer, holm-oak leaves were colonized much less by macroinvertebrates than alder leaves. Spatial and temporal differences in leaf litter processing were mainly dependent on three factors (i) the chemical and physical properties of the leaves, (ii) the abundance of macroinvertebrates in the sediment and (iii) the temperature. The climatical pattern of temperature had a greater influence than its seasonal pattern. In contrast with many other studies, abiotic factors dominated over biotic factors in this study.