New Findings of White Clawed Crayfi sh, Austropotamobius pallipes (Decapoda, Astacidae), and Peculiarities of its Spatial Distribution in Neretvica (Bosnia and Herzegovina)

At the territory of Bosnia and Herzegovina, Austropotamobius pallipes (Lereboullet, 1858) is present mainly in the Neretva basin, partly in the Una and Tsetina river basins (Trožić-Borovac et al., 2012). This species was registered at elevations from 180 to 1024 m a.s.l., but most habitats are located at elevations from 300 to 600 m a.s.l. Based on indirect data, one can state that more than 2/3 of the crayfish population in the Neretva basin is concentrated in the Neretvica basin. Our studies showed that the crayfish are very irregularly distributed in the Neretvica basin. The crayfish are almost absent at well-flushed habitats without CPOM (deposits of coarse particulate organic matter, e. g., fallen leaves), as well as at habitats with monotonous boulders or gravel-sand bottom. The study of the size structure of the crayfish population showed the presence of juvenile crayfish with a size of less than 5 cm in the Neretvica river course. The most balanced structure of the crayfish population represented by juvenile as well as adult species is observed in Gorovnik.

Trash Dance: Anthropogenic Litter and Organic Matter Co-Accumulate on Urban Beaches

Anthropogenic litter (i.e., trash, AL) on beaches has negative ecological and economic impacts. Beach AL is likely moved together with coarse particulate organic matter (CPOM, algae, leaves), but no previous studies have assessed AL and CPOM co-distribution. We measured AL and CPOM on four urban beaches in Chicago, Illinois, USA, along two transect types (pier-adjacent, non-pier adjacent) in which each has three habitats (upland, beach, strand line). As expected, AL and CPOM density were positively related across all transects. AL and CPOM were significantly higher adjacent to piers, and variable among habitats. Wood, leaves, and smoking-related AL were most abundant in beach and upland zones while glass and algal detritus were abundant at the strandline. Overall, AL and CPOM show ‘patchy’ distribution attributed to wind and wave movement toward accumulation sites. Beach CPOM is a hot spot of biological activity (e.g., microbes, invertebrates, birds). Therefore, mixing of AL and CPOM suggests organisms may be more likely to encounter AL in mixed accumulations. Efforts to reduce the abundance and biological impacts of beach AL will benefit from emphasizing organic matter accumulation sites.

Effects of tributary size on the resource supply and physical habitat at tributary junctions along two mainstem rivers

Tributary junctions are regarded as ecologically important due to unique habitat present; however, there is limited understanding of the drivers of habitat attributes at these locations. Using six sites across two mainstem rivers, we tested whether tributary size relative to main stem governs the strength and direction of response of substrate size, stream temperature, and nutrient and coarse particulate organic matter (CPOM) concentration. We found that only phosphorus and CPOM concentration showed a significant relationship with relative tributary size. Small tributaries contributed high concentrations, whereas concentrations in larger tributaries resembled the main stem. Often, tributary exports were enough to increase the resource concentration in the main stem by 40%. Substrate coarsened by ∼60% downstream of tributaries. Temperature asynchrony was observed, where tributaries contributed water between 2.8 °C cooler to 1.9 °C warmer than the main stem within one diel period. Our results highlight the importance of small tributaries for whole network functioning. However, large spatiotemporal variability revealed how habitat attributes are highly context-dependent in these locations and may be difficult to predict in both scientific and management settings.

Topography and Land Use Modulate Hydrological and Nutrient Export Dynamics in two Andean Streams

Fluvial dynamics are driven by multiple environmental factors and scales. Studies coupling hydrological and nutrient dynamics of Andean streams are almost nonexistent. We characterized two adjacent streams with contrasting drainage basins: Casa de Piedra, originating in a small mountain lake and running through a pristine landscape, and Gutiérrez, originating in a large piedmont lake and running through an anthropized landscape. Despite both drainage basins sharing geology and climate, we found that the streams presented contrasting hydrological and nutrient dynamics. Casa de Piedra had higher discharge flashiness with shorter response delays to precipitation. Interestingly, Gutiérrez’s hydrology was buffered by the upstream lake, but its nutrient exports were not. Differences observed in quality and timing of coarse particulate organic matter export and basal export levels of phosphorus and nitrogen could be explained by human activities affecting Gutiérrez but not Casa de Piedra. Moreover, nitrogen:phosphorus ratio indicates a possible future shift to phosphorus as the limiting nutrient as Andean basins become more densely populated. In summary, our annual basis study shows that even under a common geology and climate, stream dynamics of adjacent basins can be starkly different due to differences in topography and land use.

Feeding on the roof of the world: the first gut content analysis of very high altitude Plecoptera

The biology of Plecoptera from high altitude Himalayan freshwaters is almost unknown. Very few and sporadic studies have been devoted to these insects, and exclusively with a taxonomic approach. We provide information on the feeding of Capnia nymphs from three lakes localized above 4,800 m a.s.l. (NE Nepal). Nymphs from these high altitude lakes feed mainly on fine detritus, acting as collector- gatherers, with the accidental ingestion of mineral matter, mostly in larger specimens. It is likely that the harsh environmental conditions in our study area create an environment unfavorable to both the allochthonous input of coarse particulate organic matter (such as terrestrial leaves) and the autochthonous input related to aquatic primary productivity, so that these nymphs feed on small organic particles that originates mainly from the catchment.