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The decomposition of dead organic matter is a major determinant of carbon and nutrient cycling in ecosystems, and of carbon fluxes between the biosphere and the atmosphere (1-3). Decomposition is driven by a vast diversity of organisms that are structured in complex food webs (2,4). Identifying the mechanisms underlying the effects of biodiversity on decomposition is critical (4-6) given the rapid loss of species worldwide and the effects of this loss on human well-being (7-9). Yet despite comprehensive syntheses of studies on how biodiversity affects litter decomposition (4-6,10), key questions remain, including when, where and how biodiversity has a role and whether general patterns and mechanisms occur across ecosystems and different functional types of organism (4,9-12). Here, in field experiments across five terrestrial and aquatic locations, ranging from the subarctic to the tropics, we show that reducing the functional diversity of decomposer organisms and plant litter types slowed the cycling of litter carbon and nitrogen. Moreover, we found evidence of nitrogen transfer from the litter of nitrogen-fixing plants to that of rapidly decomposing plants, but not between other plant functional types, highlighting that specific interactions in litter mixtures control carbon and nitrogen cycling during decomposition. The emergence of this general mechanism and the coherence of patterns across contrasting terrestrial and aquatic ecosystems suggest that biodiversity loss has consistent consequences for litter decomposition and the cycling of major elements on broad spatial scales., Biological diversity that directly influences litter decomposition exists at multiple trophic levels (4). This diversity includes plants that produce litter mixtures of varying quality, microbial decomposers and invertebrate consumers of [...]

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2008.16989.x Byline: Fabio Lepori, Bjorn Malmqvist Abstract: Despite long-standing research, the processes that drive community assembly remain poorly understood. We censused macroinvertebrate communities and measured flood disturbance in 17 Scandinavian mountain streams to assess the hypothesis that communities are shaped by stochastic processes under stable conditions, and increasingly by deterministic processes as disturbance becomes more severe. Each study stream was categorized as being stable (n=5), intermediate (n=7), or disturbed (n=5) depending on the severity of scouring floods. Following spring floods, the number of potential colonisers decreased with increasing disturbance, suggesting that disturbance filtered out species unable to cope with the stress involved. Communities at stable sites had the highest beta diversity, indicating that stochastic processes of community assembly were most important under the least disturbed conditions. In partial contrast with our predictions, the lowest beta diversity occurred between intermediate (not disturbed) sites, suggesting that increasing disturbance first enhances determinism but then rekindles stochasticity at severity levels beyond intermediate. Macroinvertebrate communities were shaped by deterministic processes, which recruit potential regional colonists depending on niche differences and disturbance conditions and by stochastic processes, which distribute the selected species randomly among individual localities. Although often considered opposing, stochastic and deterministic processes interact hierarchically, with relative strength modified by disturbance. Article History: Manuscript Accepted 30 September 2008 Article note: F. Lepori (falepori@warnercnr.colostate.edu) and B. Malmqvist, Dept of Ecology and Environmental Science, Umea Univ., SE-901 87 Umea, Sweden. Present address for FL: Dept of Fish, Wildlife and Conservation Biology, Colorado State Univ., Fort Collins, Colorado 80523, USA.

Abstract: We show that benthic freshwater communities of naturally acidic streams in boreal catchments differ depending on properties of the surrounding landscape. Although low pH usually is associated with negative [...]

Abstract: We assessed the biomass and stable-isotope composition ([[delta].sup.13]C and [[delta].sup.15]N) of consumers (aquatic insects and fish (Cottus gobio)) and potential food sources (detritus, biofilm, seston, algae, and mosses) in [...]

Different important features of aquatic experimental systems that affect the experimental approaches during the process of understanding the effects of biodiversity on the functioning of the ecosystem are presented. The multifarious aspects of biodiversity are discussed, which facilitate in understanding effects of biodiversity changes on the overall functioning of the ecosystem and assist in identifying the mechanisms involved.

The nature of the taxonomic richness of benthic invertebrates and breakdown rate of leaf litter in three naturally acid streams is examined. Leaf litter is the energetic basis of production in low-order streams and is therefore useful as a model process.

The suspension feeders are the most impressive ecosystem engineers. Bivalves suspension feeders have high individual filtration rates and promote the deposition of faeces and pseudofaeces.

FEEDING ANIMALS TRANSFORM ORGANIC MATTER INTO FECAL PELLETS, WHICH SINK OR ARE TRANSPORTED HORIZONTALLY BY CURRENTS; THESE FLUXES RELOCATE ORGANIC MATTER IN AQUATIC ECOSYSTEMS Think of trophic levels, and what [...]

Examines the effects of different ecological processes on larval blackfly in regulated and unregulated rivers in northern Sweden. Influence of the changes in water flow (hydraulic disturbance) on blackfly larvae; Analysis of the reduction of predation pressure and competition; Application of the results on conservation ecology.

The macroinvertebrate fauna of 23 springs in central Sweden was sampled. A total of 79 taxa was recorded, including three crenobiont, nine crenophilic, 33 lotic, 11 lentic and 21 ubiquitous taxa. Only eightwere non-insect taxa. Geological and hydrogeological maps were used to categorize each spring, resulting in eight glaciofluvial, 11 moraine and four limestone springs. Faunal composition and environmental factors showed an overall similarity among spring types, except for geographic position, the almost exclusive occurrence of crenobionts in glaciofluvial springs, and factors associated with high concentrations of calcium carbonate in limestone springs. Canonical correspondenceanalysis showed that the crenobiont caddisflies Parachiona picicornis (Pictet), Crunoecia irrorata Curtis were associated with high discharge and high summer temperature. Lotic taxa, including the stonefly nymph Isoperla grammatica (Poda), the caddis larvae Halesus sp. and the mayfly nymph Baetis bundyae Lehmkuhl, were associated with high discharge and low summer temperature, while many lentic and ubiquitous taxa, e.g. dytiscids, were characteristic of small springs. It is suggested that the dominance of insect taxa, and the restricted occurrence of crenophilic and crenobiont taxa, are consequences of the glacial history and/or the hydrogeological setting of springs. Also, the possible influence of `diffusive rarity' of C. irrorata and P. picicornis, is discussed. [ABSTRACT FROM AUTHOR]

1. Effects of flow regulation on abundance and richness of net-spinning caddis larvae (Hydropsychoidea; Trichoptera) were examined in fifty-two North Swedish rivers. Models based on conditions at unregulated sites were used to predict densities at impacted sites and the residuals, i.e. the differences between observed and predicted numbers, were used as measures of the effects. 2. Two broad categories of impacted sites were identified. Sites with regulated but unreduced flow often have reduced seasonal flow variation and slightly enhanced short term variation, while those with reduced flow usually have long periods of low and stable flow occasionally interrupted by short periods of violently fluctuating flow. 3. The abundance of net-spinning caddislarvae was significantly lower than predicted at both types of sites(reduction 30%), while richness was significantly reduced only at sites with reduced flow (reduction 20%). 4. A subsequent analysis of the relationship between the effects and variables altered by flow regulations, e.g. flow magnitude and flow variation, indicated that species richness was primarily affected by the occurrence of periods with zero flow, while negative effects of abundance were associated with high flow variability. 5. Significant negative effects on the abundance of individual. taxa. were observed for Cheumatopsyche lepida and Hydropsyche pellucidula at sites with regulated but unreduced flow. 6. Analyses of the relationships between the effects and regulation-related variables suggest that H. siltalai was significantly negatively affected by the occurrence of zero flow and that negative effects on Arctopsyche ladogensis were associated with flow reduction and high flow variability. [ABSTRACT FROM AUTHOR]

In this study biogeographic patterns and habitat relationships of freshwater Ostracoda were investigated in the Canary Island archipelago. Most data were collected from published studies, though also new data from Gran Canaria are presented. In all, 22 freshwater species arepresently known to the Canaries. Six species, viz. Ilyocypris bradyi, Cypris bispinosa, C. pubera, Herpetocypris chevreuxi, Heterocypris incongruens, and Sarscypridopsis lanzarotensis are new to Gran Canaria, the first two also being new to the Canaries in general. Testing the influence of a number of variables on faunal richness indicated only a weak association with island area. Distances between islands also proved not significant, and so did other properties of islands, including age, altitude and precipitation. This was in contrast to a comparison set of data comprising aquatic beetles. Like beetles, however, ostracods did not show a nested pattern, i.e. faunas of species-poor islands were not subsets of species-rich island faunas. By having low endemicity (endemic species lacking in the Canaries), the ostracodfauna resembled island fern floras. Both groups of organisms have tiny diaspores (diameter< 0.1 mm) and are extensively parthenogenetic suggesting similar dispersal and founder mechanisms. We identified a pattern (with one exception), where those species with distributions extending across several islands also had wider within-island distributions. Many species showed affinities to different habitats dependingon conductivity of water, altitude and habitat types: whether they were permanent or temporary, hypogean or epigean, or characterized by running or stagnant waters. [ABSTRACT FROM AUTHOR]