Benthic community structure and ecosystem functions in above- and below-waterfall pools in Borneo

Waterfalls are geomorphic features that often partition streams into discrete zones. Our study examined aquatic communities, litter decomposition and periphyton growth rates for above- and below-waterfall pools in Ulu Temburong National Park, Brunei. We observed higher fish densities in below-waterfall pools (0.24 fish m−2 vs. 0.02 fish m−2 in above-waterfall pools) and higher shrimp abundance in above-waterfall pools (eight shrimp/pool vs. less than one shrimp/pool in below-waterfall pools). However, macroinvertebrate densities (excluding shrimp) were similar among both pool types. Ambient periphyton was higher in below-waterfall pools in 2013 (4.3 vs. 2.8 g m−2 in above-waterfall pools) and 2014 (4.8 vs. 3.4 g m−2 in above-waterfall pools), while periphyton growth rates varied from 0.05 to 0.26 g m−2 days−1 and were significantly higher in below-waterfall pools in 2014. Leaf litter decomposition rates (0.001 to 0.024 days−1) did not differ between pool types, suggesting that neither shrimp nor fish densities had consistent impacts on this ecosystem function. Regardless, this research demonstrates the varied effects of biotic and abiotic factors on community structure and ecosystem function. Our results have highlighted the importance of discontinuities, such as waterfalls, in tropical streams.</p

Confirmation of the hosts involved in the life cycle of an acanthocephalan parasite of Anguilla anguilla (L.) from Lake Piediluco and its effect on the reproductive potential of its amphipod intermediate host

A total of 37 European eels, Anguilla anguilla, collected from Lake Piediluco, Central Italy, and measuring 35 to 75.5 cm in total length (mean&plusmn;1 SD, 56.41&plusmn;10.89 cm) were examined, and their acanthocephalan infections assessed. Thirty-two (86.49%) eels were infected with Acanthocephalus rhinensis (mean&plusmn;1 SD, 67.38&plusmn;65.16; range, 1-350), a species that, purportedly, can be discriminated on the basis of a characteristic band of orange-brown pigmentation encircling the anterior end of the trunk. This feature, however, was not seen on any of the A. rhinensis specimens that were removed, either attached to the gut wall or free within the gut lumen, from infected eels. Approximately 40% of the eels were coinfected with the dracunculid swimbladder nematode Anguillicoloides crassus, while a single eel was also coinfected with eight specimens of a second acanthocephalan, Dentitruncus truttae. From the stomachs of two eels, 109 intact and partially digested specimens of amphipod Echinogammarus tibaldii (Pinkster &amp; Stock 1970) were recovered, 16 (14.6%) of these were infected with one to two cystacanths of A. rhinensis per host. From a sample of 850 E. tibaldii taken from the peripheral lakeside vegetation, 102 (12%; sex ratio, 1:1) gammarids were infected with one to two A. rhinensis cystacanths. Unparasitised ovigerous female E. tibaldii specimens had significantly higher numbers of eggs in their brood pouches compared with their infected counterparts (t-test, P less than&nbsp; .01)

Succession of algal communities in headwaters: a comparison of pine afforested and natural grassland streams

We evaluated changes in the succession process in benthic algal communities of an afforested stream by comparing them with those in a grassland stream through analysis of temporal changes in composition, structure and functional traits in a 3-month experiment. We hypothesized that sunlight intensity reduction as a result of streamside implanted tree shading reduces the succession rate and community physiognomic complexity. We selected two streams with different riparian cover (grassland and pine afforestation) for installation of unglazed tiles as artificial substrates. The tiles were collected from each stream after 23, 45 and 73 days of exposure. Afforestation produced changes in algal succession, with lower biomass, lower diversity at the beginning of the experiment, and an increase in the proportion of small, low-profile, tolerant, unicellular and stalked algae, coinciding with the predominance of Achnanthidium. However, the grassland stream contained a higher proportion of intermediate-size algae, as well as a larger proportion of high-profile algae, coinciding with the expected results. In the afforested stream, succession proceeded toward the dominance of low-profile species, that were tolerant of low-light conditions. However, in grassland streams with higher sunlight availability, high-profile algae prevailed without the displacement of tolerant forms. Overall, our results indicate that algal communities in afforested stream remain structurally simpler.Fil: Cibils Martina, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto; ArgentinaFil: Principe, Romina Elizabeth. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Márquez, Javier Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto; ArgentinaFil: Gari, Elena Noemi. Universidad Nacional de Río Cuarto; ArgentinaFil: Albariño, Ricardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin

The physico-chemical habitat template for periphyton in alpine glacial streams under a changing climate

ISSN:0018-8158ISSN:1573-511