We explored the spatial and temporal variability of benthic macroinvertebrate communities (density, taxon richness, evenness and taxonomic composition) in a tropical Panamanian stream that is potentially affected by organic and chemical pollution resulting from human activities. As predicted, pristine headwaters of Site 1, located within the Altos de Campana National Park, showed the lowest macroinvertebrate densities, suggesting an increase in pollution-tolerant taxa at downstream sites located near human settlements and agricultural land. Moreover, Site 1 had higher accumulated taxon richness than downstream sites (except Site 5), although evenness was higher at Site 3. Density and taxon richness were higher and more variable in the dry season, while evenness was only higher in the dry season at Site 1. Multivariate analysis showed that the fauna responded to a natural longitudinal gradient, but there was also a strong water quality signal associated with human settlements. Community composition was related to abiotic variables commonly associated to pollution, such as alkalinity, dissolved solids, phosphates, and total organic carbon.

Using field experiments, we investigated the effects of fish carcasses (so called ‘food falls') on benthic fauna. We simulated food falls using freshly killed fish during two different seasons (spring and summer) in the littoral zone of a large, pre-alpine meso-oligotrophic lake in central Europe (Lake Constance, Germany). This study provides evidence that input in the form of fish carcasses may play an important role in nutrient dynamics within this ecosystem. The benthic communities in the vicitinity and underneath the food fall were strongly influenced by the food fall. The results show that this supply of organic matter has a significant influence on the relationships within the communities, which are clearly dominated by bacteria, followed by copepod nauplii, cyclopoid copepods, chironomids, and ostracods. Total decomposition was obtained between days 80 and 68 of the experiments. The food fall had a positively but not significant effect on meiofaunal assemblages in these experiments. Furthermore, the results showed a negative relationship between bacteria and meiofauna abundance, indicating grazing by the meiobenthos on the bacterial community. These findings support other studies that found that the meiofauna exerted a grazing pressure on the microbial community, where this process was important in the decomposition of carcasses. Moreover, this study shows the potential importance of fish carcasses in Lake Constance, where food falls may generate high abundances and diversity of the benthic fauna and support high bacterial activities in this littoral ecosystem.

Colonization of incubated wood samples by invertebrates and biofilm was compared between a lowland and an upland stream over a 15 month period. Invertebrate densities increased during the first weeks of incubation and then decreased to rather stable densities during the remaining investigation period in both streams. Within the first incubation weeks invertebrate numbers were significantly higher in the lowland stream. Higher dissolved nutrient concentrations and water temperatures accelerated initial epixylic biofilm development in the lowland stream. Lowest invertebrate numbers on incubated branches in the lowland stream coincided with increased discharge. Extreme low flows in the upland stream resulted in lowest invertebrate numbers on incubated wood during the study. Temporal patterns of biofilm and invertebrates indicated some interactions, but statistical significance was low, which might be caused by the variety of interacting effects. Additionally, invertebrate assemblages of in-stream wood samples were collected from four lowland and four upland streams to examine differences of epixylic invertebrate assemblages between the two stream types. Invertebrate densities were significantly higher on submerged wood from lowland streams than wood from upland streams. However, no clear differences in invertebrate assemblages found between the stream types. The study results show that introduced wood in lowland and upland streams is rapidly colonized by aquatic invertebrates and provided an attachment site for biofilms. Invertebrate numbers during the first two months of incubation significantly overestimate the invertebrate numbers found on resident in-stream wood in lowland and upland streams. Analyses of taxonomic composition of wood-inhabiting invertebrate assemblages from natural wood from lowland and upland streams revealed that each stream displayed a rather specific epixylic fauna.

This study investigates a phytophylous community of Chironomidae larvae on the submerged plant species Myriophyllum spicatum L. in a eutrophic lake (Lake Sakadaš, Danube floodplain area in Croatia) during summer 2004. This macrophyte species appeared for the first time in the lake in 2004, lasted approximately three months and was considered as a temporary habitat. The chironomid community was very abundant in the stands of this macrophyte species, which developed at three sites. The recorded species belong to three subfamilies: Chironominae (Chironomini and Tanytarsini), Orthocladiinae and Tanypodinae. Species composition varied in time, though Orthocladiinae with their representative Cricotopus sylvestris gr. dominated throughout the entire sampling period, accounting for approx. 60% of the total community. However, the presence of this species group experienced a marked drop to only 10% in September when Chironomini larvulae and Paratanytarsus sp. prevailed. Furthermore, the share of Endochironomus albipennis (Meigen 1830) in relation to other species was also consistently higher. NMDS ordination and cluster analysis separated three main colonization periods based on larval abundance. RDA analysis indicated the influence of environmental variables, especially Secchi depth, macrophyte dry weight, depth and water temperature, on chironomid community structure.

Cross-transplantations of Omphiscola glabra between two French departments (Haute-Vienne and Indre) were carried out to study snail settlement in these new sites during six years and to determine if this snail species was well adapted to its local parasites (Fasciola hepatica and Paramphistomum daubneyi). Local snails placed in new sites for each department were used as controls. In Indre furrows, the number of adults per population and the area of each habitat peaked on the third year post-introduction. Similar findings were also noted in the Haute-Vienne furrows occupied by local snails but peaks were only observed on the fourth year. In contrast, in Haute-Vienne sites populated by introduced snails, there was a progressive decrease in snail abundance and habitat area from the second year. The local O. glabra transplanted in Haute-Vienne kept their same degree de susceptibility to F. hepatica and P. daubneyi, thus demonstrating a good adaptation of these snails to their parasites. In other groups of transplanted snails, the first natural infections were only noted from the second or third year post-introduction and their prevalence progressively increased over time. Local adaptation of these latter snails to parasites would be more progressive in time and would stretch over several snail generations.

Collections of ostracods from various habitats in and around Lake Inari, Finnish Lapland, provide the first record of these crustaceans from Finland north of the Arctic Circle. From a total of 35 sites visited, 14 species were collected, out of which four appeared to be new to Finland: Fabaeformiscandona lapponica, Pseudocandona pratensis, Eucypris pigra and Paralimnocythere relicta. Two major assemblage groups were recognised by clustering classification and multi-dimensional scaling ordination, one dominated by Cyclocypris ovum, the second by Candona candida. Taxonomic diversity of the most assemblages was of expected range based on the inventory of 53 freshwater species of Finland.

The taxonomy of the enigmatic genus Adebrotus Lugo-Ortiz & McCafferty is reviewed in the present paper. The type-species, A. amazonicus Lugo-Ortiz & McCafferty, is redescribed based on nymphs from Northern Brazil. Adebrotus lugoi, new species, is described based on nymphs from Southeastern Brazil, significantly extending the distributional range of the genus. In the light of these new evidences, the generic concept of Adebrotus is improved.